1. TYPES OF MAIZE

Maize was the main food crop of the American Indians. It was the basis for the ancient civilisations which they set up in South and Central America long before Christopher Columbus reached America.  It continues to be the backbone of world agriculture and ranks equally with wheat and rice as a ‘staff of life’ all over the world.  Maize also continues to have a significant influence on humans world-wide and even more so in Africa, where it has become the staple food item.  Columbus brought maize seed back to Spain on his return voyage in 1493. As the most productive of all cereals its cultivation spread rapidly around the world in the early part of the 16th century following the trade routes of the Portuguese.  It was probably during this time that maize was first introduced into Africa.


In South Africa, maize is by far the most important grain crop and is grown under a variety of environments and conditions. Approximately 8 to 10 million tons of maize grain is produced annually in South Africa on approximately 3.5 million hectares of land. Half of this harvest is used for human consumption. Maize is also used widely for animal feeds in the meat, dairy and poultry industries and, in its processed forms, in the manufacture of starch and oil products and biofuels. A recent development is the use of popped popcorn in place of synthetic granules as packing material in crates. This serves as an environmentally friendly material that breaks down naturally, prevents pollution and is even edible.


The largest areas of maize are planted in the Free State (35%), North West (30%) and Mpumalanga (15%) provinces.

Maize belongs to the genus Zea and its botanical name is Zea Mays.  There are at least five types of maize, including the following:

  •     Popcorn:  This is essentially a small-kernelled flint type and is usually considered to be the most primitive of the present types of maize. The kernels may be either pointed (rice type) or round (pearl type). Advanced varieties bred for high popping expansion have very thick skins. Popcorn is consumed directly as a confection rather than a staple food.
  •     Flint or flour types:  These have a hard endosperm and are almost impossible to grind by hand when dry.  The kernels may be softened by boiling and then wet grinding them into a dough called masa, which can then be re-dried as a flour.  Flinty maize has a good germination and can be stored longer. These types are most commonly used by the dry milling industry as they produce more of the popular high quality and high value white maize products required by the market.
  •     Dent types:  This is a structural compromise between the flinty and flour types with a marked indentation on the top of the seed which varies with genetic background.  The sides of dent maize are flinty while the centre core is floury.  These varieties are considerably softer than the flinty types and can be easily ground by hand when dry. They are commonly grown for daily human food requirements in Africa and are consumed fresh as ‘green mealies’.
  •     Sweetcorn:  In these varieties there is a sugary gene which prevents or retards the normal conversion of sugar into starch during development of the endosperm. As a result the dry sugary kernels are wrinkled and glossy.
  •     Pod corn:  This is more of an ornamental type. The major gene involved produces long glumes which form part of the flowers enclosing each kernel individually. This also occurs in many other grasses.

The maize varieties which are produced in abundance are the flint, flour and dent types.  These are white maize types and are mainly milled and used for human and livestock consumption. Yellow maize is used primarily for animal feeds, but has recently gained popularity in some areas for green mealie consumption. Maize is a versatile plant and can grow under almost any conditions. The diagramme below shows the main areas or localities where maize can be grown in South Africa.

Figure 1: Maize production regions of South Africa

Source: Agricultural Research Council-Grain Crops Institute

1.    Western region                                                                                                  ■  Dryland                                 

2.    Moderate eastern region                                                                              ▲ Irrigated

3.    Cold eastern region

4.    KwaZulu-Natal region

5.    Irrigation  – warm region

                           – cold to temperate region

6.    Eastern Cape

2. CHOICE OF CULTIVARS

Hybrid: a new form of plant or animal resulting from a cross between organisms that have different genotypes   Cultivars: a variety of a plant that has been developed under cultivation and that does not occur naturally in the wild   Yield: the quantity of a crop or a product produced from a plant or from an area of land   Adaptability: the ability to change (or be changed) to fit changed circumstances  

There is a wide range of hybrid maize cultivars available to growers in South Africa, each with their own characteristics. The farmer should be careful to select the cultivar that best suits his climatic and soil conditions, as well as his practical requirements. The following guidelines assist with cultivar selection:

  •     Establish the suitability of a new cultivar before replacing an older, proven cultivar;
  •     Spread your risk by using a selection of cultivars with different growing season lengths instead of relying on one variety;
  •     Choose cultivars with a wide adaptability i.e. the potential to increase expected yield in favourable conditions while guaranteeing acceptable yields in adverse conditions; and
  •     Review your cultivar choice annually, at the end of each season.

Advice on cultivar choice is available from the Agricultural Research Council – Grain Crops Institute (ARC-GCI) in Potchefstroom, PCI Agri, cooperatives and commercial seed companies.

The following factors will influence your choice of cultivars:

  •     Yield potential and adaptability: Because of the wide variety of conditions underwhich maize is produced in South Africa it is vital that the cultivars chosen should be adapted to the specific conditions of your area;
  •     Length of growing season: This will vary between areas and be dependent on prevailing climatic conditions. The length of the growing season is calculated as the period in days from planting to flowering (sexual maturity) and physiological maturity (dry dough stage after full seed set). It is important to select a cultivar with a season length to match the rainy season of your area;
  •     Disease resistance: Cultivars should be selected according to their levels of resistance or tolerance to the diseases prevalent in your area;
  •     Lodging: The inability of the maize plant to remain upright under the weight of the crop load and local wind conditions. Cobs which are lying on the ground are more susceptible to insect and mechanical damage and are more difficult to harvest. Plant breeders have developed varieties which are less susceptible to lodging, but differences between cultivars still exist; and
  •     Prolificacy: The potential of a cultivar to produce more than one ear or cob perplant. This characteristic is linked to the adaptability of the cultivar and is useful in situations where it is necessary to plant low populations per hectare.

DRYLAND AND IRRIGATED MAIZE

Maize cultivars are grouped according to their season length:

GROUPDAYS TO FLOWERING
 COOL AREASWARM AREAS
Ultra shortLess than 70Less than 60
Short70 to 7560 to 65
Medium75 to 8065 to 70
Long80 to 8570 to 75
Very longMore than 85More than 75
Dryland farming: an agricultural technique for non-irrigated cultivation of land. For example, maize grown without irrigation but reliant on rain   Irrigated: to supply water to land to allow plants to grow, by channels, pipes, sprays or other means  

The value of being able to group the cultivars is that the farmer can choose between varieties, depending on the length and timing of the rainy season in his area.

Maize grown under dryland conditions represents the greater proportion of maize grown in South Africa. The practice here is to rely entirely on the normal rainfall distribution pattern for the moisture requirements of the crop.  The choice of hybrid cultivar becomes extremely important for maize growing under these conditions.  Knowledge of local climatic conditions is essential.  For example, one would grow a late maturing variety in an area which has a short growing season.  Similarly, it would be unwise to grow an early maturing variety in an area which has a relatively long season.

Irrigated maize can produce high yields but tends to become specialised and is an expensive investment when one considers the basic requirements of an irrigation system.  Irrigation can either be flood irrigation which is the cheapest way of applying the water but also the most inefficient. Overhead sprinklers and centre pivot irrigation are more efficient but expensive in terms of the capital required for installation of the system. This is in addition to the energy (electricity) requirements to ensure enough pressure for the system to work. For irrigation, the soil/water and soil/plant relationships together with plant/water relationships are extremely important.

The following guidelines from the ARC-GCI give the essential steps in terms of full irrigation of maize which is normally done using overhead sprinklers or centre pivots:

  •     Usually irrigate thoroughly before planting.  Wetting the entire soil profile will ensure that irrigation can be delayed for up to 30 days after planting. This practice promotes the development of a deep root system. The water requirement is low at the early stage of development.
  •     Once the crop is established, irrigation should be applied regularly to prevent water stress. However, waterlogging has adverse effects on maize yield and crops should not be over irrigated.
  •     One week before the maize plant flowers, irrigation frequency must increase to approximately every 7 – 10 days. The crop is very sensitive to water stress at this stage.
  •     From approximately 35 – 40 days after flowering, the irrigation rate can be decreased. The final irrigation is done once the plant reaches physiological maturity, approximately 60 – 70 days after flowering.
  •     Once the maize is physiologically mature no more irrigation is required.

In some areas of southern Africa, most notably Zimbabwe and Mozambique, maize is grown out of necessity in vlei areas in order to take advantage of the early green mealie market. These are areas bordering on rivers or drainage areas which normally comprise deep sandy soils with high moisture content. Under normal conditions we would not use vlei areas for fear of creating an erosion hazard.  However, it is possible, and only under very special conditions that maize should be grown in vlei areas.  If it is your intention to grow maize in such areas this should be undertaken with the expert advice of extension workers in the field.  Generally, the recommendation is not to grow maize in vlei areas.

3. MAIZE SEED

This refers to maize which is grown specifically for seed and differs from maize grown for commercial grain. It has already been mentioned that there are a number of hybrid varieties available which have been developed by highly skilled researchers and plant breeders to fulfil the requirements of the industry. This process is designed to continually provide new hybrids that will give increased yields and are resistant to major pests and diseases. It is these varieties that are produced under different conditions which are referred to as ‘seed’.

We know that to be able to propagate a crop we need seed and that if we take seed from the maize crops that we planted this year and plant them next year, there will be notable differences in the uniformity of the crop and the final yield when compared with a crop which was grown from certified hybrid seed.  The seed used in the former situation is referred to as advanced generation seed in which the genetic makeup is not the same as in the hybrid seed. For this reason we are obliged to use certified hybrid seed if we intend producing good quality maize with a high level of production.

Plant breeding: the art and science of changing the genetics of plants in order to produce desired characteristics  

Maize seed is grown from identified and carefully selected parent plants which have beenbred over a long period and satisfy specific positive genetic requirements.  The parents consist of identified males and females which are initially grown separately, in order to bulk up seed stocks, then later planted in close proximity to cross pollinate and produce hybrid seed from the female plants.  This hybrid seed is then sold to the commercial maize-grower who will purchase it as certified hybrid seed and plant it to produce the hybrid commercial grain that will meet his needs.

The above shows that the maize seed we use today goes through a lot before arriving at our farms.  This is summarised in the figure below:

Figure 2: Maize Seed Production

The method of seed production is complicated and highly scientific and it would take up unnecessary time trying to explain it.  However, it should be noted that the use of hybrid seed is always recommended in all areas where maize is grown.

 

4. MAIZE FOR SILAGE

Silage: a fermented, high moisture fodder which can be stored and is fed to (ruminants) cattle. The whole green maize plant is used, not only the grain. Silage is normally stored in sealed pits or silos  

Maize grown specifically for silage is different from maize grown for grain.  The difference is not in the variety grown but in the plant populations and fertilisation used.  When maize is grown specifically for silage production we are interested in obtaining a high output of forage or chopped maize. At the same time, we are looking for a variety which will stand up in the land as a lot of sophisticated machinery is used in harvesting the maize, and if the crop is lying on the ground it will represent a loss. Generally yellow maize is more commonly used for silage due to its high nutrient content.


The plant population one should aim for is between 50 000 and 70 000 plants per hectare.

The best time to harvest the crop is at physiological maturity.  A simple method to determine physiological maturity is to wait until the leaves on the maize plant have died from the bottom up to the cob but must still be green and alive above the cob.  The average yield to be expected if the crop has been successful is about 50 tonnes per hectare of chopped maize.

The fertilizer application rates vary according to soil types.  This is high and should be around 450 kg of ammonium nitrate (34.5% nitrogen) per hectare.

There are several varieties recommended for the production of silage, each with its own characteristics. Detailed information is available from seed suppliers in each area. 

1. CLIMATE, SOIL AND NUTRIENT REQUIREMENTS

Maize is a summer crop and is generally not grown where mean daily temperatures are below 19°C.  Maize seed will germinate in soil temperatures as low as 10°C, but faster and more reliable results will occur at temperatures between 16°C and 20°C, where germination should take place within 5 – 6 days. Consistent temperatures above 32°C will have an adverse effect on crop yield, particularly during the flowering stage. Maize is susceptible to frost during the growth stages and a frost free period of 120 – 140 days is necessary during this time.

Soil:  A mixture of mineral particles, decayed organic matter and water. Topsoil contains chemical substances which are leached through into the subsoil where they are retained. Without care, soils easily degrade; losing the few nutrients they possess and become increasingly acid or sour   Nutrients: A substance that an organism needs to allow it to grow, thrive and reproduce e.g. carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. Plants obtain their nutrients from the soil, while humans and other animals obtain them from their food, including plants    

Commercial maize crops require between 450 mm and 600 mm of water during the growth period and a healthy plant will have consumed roughly 250 litres of water by the time it reaches maturity. Research has shown that approximately 10 – 16 kg of grain are produced for every millimetre of water used, illustrating the importance of water in the efficient production of maize.

Maize can be grown in a wide range of soils with varying success.  The heavy textured soils (sandy clay loams and heavier), which are inherently high in fertility are considered the most suitable.  However, with the recommended applications of fertilizer, good maize yields can be achieved with the lighter textured soils under reasonable climatic conditions.  Heavy soils have a higher water holding capacity; they require more water or rainfall to reach this capacity and can then retain moisture for much longer.  They are, therefore, able to sustain growth for longer. Maize is sensitive to waterlogging and poorly drained and badly aerated soils should be avoided.  In such areas the crop should be grown on ridges to ensure good drainage. The ideal soils for optimum maize production are those with a clay content of between 10% and 30%.

It has been found that poor maize growth in reasonable rainfall conditions can be attributed to deficiencies in the major nutrients.  Consequently, increased use of artificial fertilizers has produced remarkable increases in yields, particularly for lighter soils which have proved capable of yielding well provided sufficient nutrients are supplied.

The most important major nutrients are nitrogen, phosphorus and potassium, normally abbreviated using their chemical symbols: N, P and K. 

Nitrogen is a key part of proteins required throughout the growing period, as proteins and enzymes play a major role in growth and development.  Nitrogen can be a limiting factor and if this is the case there is a marked reduction in yield.  When nitrogen is applied at optimum levels, there is a significant increase in yield for a wide range of soils.  However, the time of application is important.  The first application of nitrogen occurs when the initial application compound of N P K is applied, but the amount applied here is small.  This is followed by one or two applications of top dressing while the plant is growing. 

The first application is best applied at approximately knee height and then again just prior to sexual maturity. The timing of these applications is critical.

Phosphorus in the form of phosphate is an important element in the early growth and development of the plant although it is taken up during the plant’s entire life.  Most of our soils are low in phosphates and it is essential that the land be taken up to a minimum level every year and if possible improved. This indicates that phosphates are essential and should be applied as a matter of course every year.  This forms part of the basic application of fertilizer. 

Potassium is vital in the growth and development of the maize plant and very important where maize is grown continuously on the same land.

2. FERTILISATION

The selection of the right fertilizer and the correct amount to be applied for your particular circumstances should be based on:

  •   Correct and reliable soil analysis;
  •   History of the farm;
  •   Soil types; and
  •   Advice of from the extension specialist in the area.
ARC-GCI: Agricultural Research Council – Grain Crops Institute  

Information regarding the assessment of these critical factors is available from ARC-GCI in Potchefstroom, PCI Agri and local extension officers.

The plant’s efficient use of nutrients will be negatively affected if the soil is extremely acidic or alkaline. An effective liming programme should be conducted based on the results of the soil analysis together with the fertilizer programme.

With regard to the application of soil nutrients, the national calibration programme is based on the relationship between nutrient element concentrations existing in the soil and relative yield, while focusing on maximising profits in relation to fertilizer costs. Some of the key guidelines are summarised below:

2.1   MACRO NUTRIENT ELEMENTS

NITROGEN (N)

  •     Planned yield in tons per ha:    2    3 4 5  6 7 8
  •     N-application in kg of N per ha:
  •     Western areas*             15   25    35   65   95
    •     Eastern area               20   40    60   80   100    120    140

*NB: For sandy soils <10% clay, add 20kg N per ha and for loam sand soils between 10 – 15% clay, add 10kg N per ha to these amounts


Remember that these figures represent kg per ha of the nutrient required. The actual amount of fertilizer applied would depend on the ratio of nitrogen in the compound mix.

Nitrogen deficiency results in pale, light-green or yellow-green foliage in young plants.

Later in the growth stages the older leaves show premature yellowing in a characteristic inverted V-shape on the leaf.

Kernels at the tip of the ear will also be missing leaving a stubby end.

Source: Iowa State University Extension

Nitrogen fertilizers should ideally be placed in a band 50 mm to the side of the seed row and 50 mm below the seed. Climatic factors and residual soil nitrogen levels will determine the amounts to be applied at planting and as a follow-up top dressing. Depending on the chosen row width, application rates at planting should not exceed the following amounts:

  •     0.9 m rows: not more than 40 kg N per ha
  •     1.5 m rows: not more than 30 kg N per ha
  •     2.1 m rows: not more than 20 kg N per ha

The combined application of nitrogen plus potassium should not exceed 70 kg, 50 kg and 30 kg per ha for the respective row widths. It is acceptable to apply larger amounts but the bands should then be placed 70 mm to 100 mm to the side and below the seed.

PHOSPHOROUS (P)

Phosphorous is generally less mobile in the soil than nitrogen and application recommendations are normally based on a gradual process of upgrading the soil concentration over a number of years.


Deficiency symptoms normally seen in the young plants and most noticeable under cool and wet conditions are typified by dark green leaves with reddish-purple tips and margins.

Source: Iowa State University Extension

Phosphorous should be placed in bands at 50 mm to the side and 50 mm below the seed.

POTASSIUM (K)

Potassium deficiency is initially evident in the lower leaves which show yellow or necrotic margins extending to the upper leaves. The prevalence of stalk rot under potassium deficiency conditions leads to an increase in lodging in mature plants. Kernels become smaller towards the tip of the cobs and gradually disappear resulting in a sharpened appearance.

Source: Iowa State University Extension


Potassium is usually applied in bands at planting in a fertilizer mixture, 50 mm to the side and 50 mm below the seed.


Depending on the chosen row width, application rates at planting should not exceed the following amounts:

  • 0.9 m rows: not more than 40 kg K per ha
  • 1.5 m rows: not more than 30 kg K per ha
  • 2.1 m rows: not more than 20 kg K per ha

As previously mentioned, the combined application of potassium and nitrogen should not exceed 70 kg, 50 kg and 30 kg per ha for the respective row widths.

2.2   MICRO NUTRIENT ELEMENTS

Most of the essential micro nutrient elements are applied as a part of a macro element fertilizer mixture.

MAGNESIUM (Mg)

Magnesium deficiency is usually associated with soil acidity and can be recognised by yellow to white steaks between the leaf veins, with bead-like necrotic spots within the streaks. The application of dolomitic lime or magnesium-bearing fertilizer mixtures will rectify the deficiency.

ZINC (Zn)

Plants showing zinc deficiency exhibit light streaks between the leaf veins from base to tip, while the leaf margins, mid-rib and tips remain green. These symptoms tend to appear in cool, overcast conditions but will disappear rapidly when the sun begins to shine.

BORON (B)

Boron deficiency will adversely affect pollination and the cobs will be malformed with an uneven distribution of kernels.

You should now be familiar with the basic requirements of fertilization. Serious mistakes can be made at this vital stage of fertilization, which will only become evident in the final crop.

3. LAND PREPARATION

Soil tillage, or soil structure management, is the foundation of any crop production system and the biggest cost factor in maize production.

The timing of ploughing the land in preparation for the crop of maize will normally depend on the previous crop.  However, ploughing should be carried out as early as possible in order to kill weeds and grasses, conserve moisture, reduce costs and allow for maximum decomposition of plant residues in time for the following crop.  It is imperative that bare land is ploughed as soon as possible after the end of the rains, as it becomes increasingly difficult to plough when the soils start drying out.

Successful land preparation for the production of maize seeks to:

  •     Loosen the soil and allow freedom of root development;
  •     Make a seed bed for successful germination and establishment of the crop;
  •     Increase the depth in which the fertilizer and residues are mixed in the soil;
  •     Use methods which preserve the tilth and soil structure as far as possible;
  •     Conserve moisture and increase subsequent rainfall penetration;
  •     Control and destroy weeds, pests and diseases;
  •     Produce the required soil conditions at minimum cost. Overworking ruins the soil resulting in soil capping, compaction and increased difficulty in tillage the following year;
  •     Produce a seedbed which is 250mm deep. This should be altered periodically in order to prevent the forming of a plough pan, which will affect root penetration;
  •     Apply minimum tillage techniques as recommended as these reduce labour and machinery costs.  These techniques lead to better water retention, reduced soil erosion and a reduction in soil compaction; and
  •     Ensure crop rotation, which is vital for :
  • Maintaining soil productivity;
  • Controlling soil erosion; and
  • Disrupting disease and insect life cycles.

TILLAGE SYSTEMS

Erosion: The wearing away of soil or rock by rain, wind, sea or rivers or by the action of toxic substances. Grass cover provides some protection against soil erosion  

The standard tillage systems in use for maize production are categorised according to the amount of soil disturbance they cause.

CONVENTIONAL TILLAGE

Ploughs, disc harrows and various mechanical cultivators are used before, during and after planting. Most of the crop residue is incorporated into the soil, initially leaving the surface bare. The advantages of conventional tillage techniques are the effective removal of weeds and the disruption of insect life cycles. Disadvantages include high machinery and fuel costs, potential soil and wind erosion, and possible damage to the soil structure by overworking.

      Source: Mississippi crops                                                      Source: Precision tillage

 

CONSERVATION TILLAGE

There is minimal soil disturbance through the limited use of chisel ploughs and in-row rippers. The intention is to leave as much of the previous crop’s stubble behind on the ground as possible, as a mulch to conserve moisture and protect the soil surface. The careful use of chemical herbicides further reduces mechanical tillage operations during the growth cycle.

Source: eorganic.info                                                             Source: ucanr.edu

Stubble: The short stems left in the ground after a crop such as wheat or oilseed rape has been cut   Mulch: An organic material used to spread over the surface of the soil to prevent evaporation or erosion e.g. dead leaves or straw   Humus: The fibrous organic matter in soil, formed from decomposed plants and animal remains, which makes the soil dark and binds it together   REDUCED OR MINIMUM TILLAGE

The only soil disturbance is during planting, and is limited to the planting strips, generally accepted as being not more than 15% of the soil surface. This practice leaves large areas of the soil surface covered with crop stubble, or mulch.

The advantages of minimum tillage are the control of wind erosion, weeds and insect pests although water erosion is difficult to manage. Machinery and fuel costs are also reduced. There is, however, a possibility of leaf diseases being carried over from one crop to the next via the crop stubble.

NO-TILL

Soil is only disturbed to a relatively shallow depth in the planting row and then left undisturbed until harvest. This method enhances the humus content of the soil and encourages beneficial soil organisms. The infiltration and retention of rain and irrigation water are improved. Other advantages are the control of wind and soil erosion, very low machinery and fuel costs and quicker adaptation to the optimum planting date.


Disadvantages include increased herbicide costs and risk of insect and disease carry-over. Possible compaction of the soil is also a risk. Planting machinery needs to be specially adapted to operate in no-till conditions.

Source: deere                                                               Source: eiard.org

Land preparation is perhaps one of the most important and expensive exercises in the maize growing process. If it is not done correctly it can be costly because of a reduced crop yield.

CONSERVATION AGRICULTURE

Residues: There are two types of agricultural crop residues:   Field residues are materials left in an agricultural field or orchard after the crop has been harvested. These residues include stalks and stubble (stems), leaves and seed pods   Process residues are materials left after the crop is processed into a usable resource. They include husks, seeds, bagasse, molasses and roots  

Conservation agriculture is aimed primarily at the maintenance of soil health in order to ensure consistent high yields. It is based on the following principles:

  •     Minimal disturbance of the soil throughout the growing season through the use of conservation tillage or no-till techniques
  •     Maintenance of adequate soil cover through the use of crop residues, preferably over 30% of the surface
  •     Application of an effective crop rotation programme in order to replenish soil nutrients and encourage soil organisms. Legumes are vital in such a rotation
  •     Strict control of vehicle, tractor and machinery traffic, especially on soils prone to compaction

Grazing of the crop residues by livestock can be introduced into the conservation agriculture system; however, the danger of soil compaction on moist soils should be taken into account.

Weed control through the judicious application of herbicides is a vital component of the conservation agriculture system. The inclusion of a herbicide resistant cultivar in crop rotation will assist significantly in the control of weed populations.

1. PLANTING

Germination: The beginning of the growth of a seed, resulting from moisture and a high enough temperature  

Planting of the maize crop should begin as soon as ground water and soil temperatures are adequate for good germination. Planting should be timed to ensure that the heat and water sensitive flowering stage of the crop does not coincide with the mid-Summer dry period common to most of the maize growing region.

General guidelines for planting are as follows:

  •     Cooler eastern areas: beginning  October to first week November
  •     Central regions: last week October to mid- November
  •     Drier western areas: last two weeks in November to mid-December

Planting outside the optimum period will reduce the production potential of the crop.

                                                    Source: usoonpatrol.org                                                 Source: williamsonsinperu.blogspot

 

ADVANTAGES OF EARLY PLANTING

Early planting of the maize crop offers the following benefits:

  •     Increase in growing season and grain-filling period; 
  •     Advancement of the important pollination period which may enable the crop to avoid pollination during the mid-season droughts experienced in this country;
  •     Potential to benefit during October and November when plant growth is most rapid, if moisture supply is adequate;
  •     Formation of a more robust root system if the cob develops before the main rains; and
  •     Assistance with weed control.

Seed requirements will vary according to the size of seed and method of planting, but it can generally be assumed that a 50 kg pocket of seed will be sufficient for two hectares. This is an average figure and more accurate information should be obtained from the local extension officer and commercial seed supplier. 

PLANT POPULATION AND ROW WIDTH

The number of plants per hectare (plant population) is more important than the specific row width, which can vary between 0.91 metres and 2.1 or 2.3 metres, between rows under dryland conditions. Narrow row widths will generate higher plant populations which are well suited to the higher rainfall areas where greater yield targets are expected.

The planting pattern that is normally recommended is one that will facilitate weed control. Modern machinery used to plant seed can be calibrated to plant a pre-determined plant population.

The objective in planting maize is to get a good stand (plant population). Poor yields are often attributed to poor stands and it is vital to achieve an even distribution of the desired population when aiming for high yields. 

The following guidelines are important in helping to achieve good stands:

  •     Soil characteristics and the control of soil crusting on susceptible soils, mainly the sandier soils;
  •     Efficiency of land preparation;
  •     Efficiency of the planting operation whether performed by hand or  machine;
  •     Condition, adjustments and speed of operation of planting machines;
  •     Quality of supervision given to the planting operation;
  •     Quality of seed used;
  •     Efficiency of pest and disease control;
  •     Minimum destruction of seedlings during cultivation operations; and
  •     Compaction of soil around the seed.


Under normal conditions planting depth will play an important part in successful germination. It is recommended that the seeds be placed at a depth of between 50 mm and 100 mm depending on the type of soil with planting depths shallower in heavy soils than sandy soils. It is important to obtain uniform planting depth and uniform tilth to ensure even germination over the entire land.

RAIN PLANTING

The farmer should be prepared before the first good rains and be ready to plant as soon as the soil moisture conditions are suitable i.e. when the soil is sufficiently moist to germinate all the planted seed. A good rule of thumb is that 25 mm of rain should have fallen in 24 hours.

DRY PLANTING

The land is fully prepared and planted before the rains to ensure an early start and release labour for other operations. This method has an element of risk as a small amount of rain might fall, which could be sufficient for germination but not for early establishment. This method should be employed only where rainfall is reliable.

2. WEED CONTROL

It is essential that all competition from undesirable plants is reduced to a minimum as yield potential will decrease if weeds are allowed to become established. Weed control is critical during the first 6 – 8 weeks after planting because weeds will compete with the crop for valuable water and nutrients during this vital growth stage. Weeds that are present during harvest may hinder the harvest process, pollute the grain with unwanted seeds or taint the maize seeds with their emissions. Weeds include all plants that are growing in the same land on which the maize has been planted.

MECHANICAL WEED CONTROL

Methods include the use of tractor-drawn implements which are restricted to the early stages of growth before the plants grow too tall. Hand weeding with hoes or badzas is effective but labour intensive. This method of weed control is widely used in this country but, to be successful, has to be repeated which may not be possible where large areas are under cultivation.

Source: lternet.edu

CHEMICAL WEED CONTROL

Chemical weed control is becoming more popular as more farmers realise the importance of keeping maize crops free of weeds. The chemicals used for weed control are called herbicides.

Source: nps.gov


The decision whether or not to use herbicides should be made in consultation with the farmer’s extension specialist or chemicals consultant and should consider the following:

  •     Major weed types on the farm;
  •     Rainfall pattern;
  •     Yield potential;
  •     Cost of mechanical control compared to chemical control;
  •     Implement capacity;
  •     Soil types – land classes;
  •     Crop rotation programmes; and
  •     Clay and silt content.

The herbicides can be applied by hand, by a tractor-powered sprayer or, in the case of large planted areas, by air.

For effective weed control throughout the season a minimum of two herbicide applications is generally recommended. The control of grass weeds in maize, which is a grass itself, is a major challenge. A disadvantage is the season-long germination of grasses.

Early season grasses can be controlled by pre-emergence graminicides (grass herbicides), such as acetochlor, atrazine and metolachlor, either singly or in combination.

Late germinating grasses may still cause problems and may be controlled by mechanical weeding or the split application of graminicides.

Some perennial grasses, such as Cynodon dactylon and wild sorghum are difficult to control chemically, with glyphosate being the best option.

Chemical options for pre-emergence broadleaf weed control include acetochlor, atrazine, cyanazine and metolachlor, and mixtures of these chemicals.

Post-emergence control for grasses is limited, with metolachlor and topramezone being the best options.

Post-emergence broadleaf control is provided with atrazine, acetochlor, terbuthylazine, cyanazine and combinations of these herbicides, plus 2,4D amine on its own.

The local extension specialist or chemical company should be consulted regarding the correct herbicides to apply and their application rates.

CULTURAL PRACTICES

The farmer can significantly reduce the weed pressure in his maize land by ploughing during winter or early spring, destroying the growing weeds. Wider row widths at planting will assist with mechanical weed control and effective crop rotation will also help to reduce the weed population.

3. DISEASE CONTROL

Plant diseases can decrease the yield and quality of the maize crop, as well as cause toxicity to humans and animals who consume the end product. Diseases of maize are caused mainly by fungi, bacteria or viruses.

Disease control strategies revolve mainly around the following primary practices:

  •     Plant resistance: use of cultivars specially selected and bred with resistance to specific diseases;
  •     Chemical control: application of registered fungal and bacterial remedies. Economic considerations come into play;
  •     Cultural practices, including soil tillage techniques, crop rotation using non-host crops, adjustment of planting dates to avoid favourable environmental conditions and control of stress in the crop; and
  •     Biological control: through the judicious use of biological agents under scientific supervision.

The most prevalent diseases affecting maize in South Africa are outlined below.

BACTERIAL STALK AND WHORL ROT (ERWINIA CHRYSANTHEMI AND ERWINIA CAROTOVORA)

Prevalent in maize grown in high rainfall areas or under irrigation, stalk rot causes lodging and whorl rot causes the growth tip of the plant to die, preventing further growth.

Control measures include selecting well-drained soils and preventing mechanical damage to maize plants during cultivation. Excessive application of irrigation water should be avoided especially during the hotter parts of the day.

Figure 1: Bacterial stalk rot

                           Source: Washington State University                                                  Source: CIMMYT 

BACTERIAL LEAF STREAK (XANTHOMONAS CAMPESTRIS)

This results in premature browning and drying of leaves leading to a reduction in grain weight. Little information is available and research is under way to find ways to counter this disease. Removal of crop residues and volunteer seedlings after harvest has been recommended but there are presently no registered fungicides available to control the disease.

Figure 2: Bacterial Leaf Streak

Source: no-tillfarmer

NORTHERN CORN LEAF BLIGHT (EXSEROHILUM TURCICUM)

This is one of the most common and widespread maize leaf diseases in South Africa, particularly in the KwaZulu-Natal region. It develops under warm humid conditions and the best control measure is to plant a resistant cultivar.

Figure 4: Northern corn leaf blight

Source: Pioneer Hi-Bred

Figure 5: Early lesion on leaf caused by Northern corn leaf blight

Source: Pioneer Hi-Bred (2010)

Figure 6: Lesions on leaves caused by Northern leaf corn blight

Source: Pioneer Hi-Bred (2010)

GIBBERELLA EAR AND STALK ROT (FUSARIUM GRAMINEARIUM SPECIES)

This is widespread across the South African maize producing areas and yields toxins which are harmful to humans and livestock. The disease is best controlled by the planting of resistant cultivars. Other methods of control include avoiding high density planting, crop rotation using non-host plants, early harvesting to avoid lodging, removal of infected plant debris, control of insect vectors such as maize stalk borer and low moisture levels during grain storage.

Figure 9,10 and 11: Gibberella ear rot

Source: Pioneer Hi-Bred (2010)

Figure 12: Gibberella stalk rot

Source: Pioneer Hi-Bred

Technical information regarding diseases and control measures in specific areas is available from ARC-Grain Crops Institute in Potchefstroom or the local extension officer.

4. PEST CONTROL

INTEGRATED PEST MANAGEMENT

A practical system of crop protection, incorporating chemical and biological control, in-bred plant resistance and cultural practices, to protect the crop by suppressing insect populations and limiting their damage to below economic threshold levels. In other words, the pest numbers are low enough that the damage they cause does not translate into economical losses for the farmer. Skilled advice regarding the combination and implementation of pest control strategies is available from the ARC-GCI in Potchefstroom.

CHEMICAL CONTROL

The application of pesticides is the most common form of pest control practiced in South Africa. Before embarking on a pesticide spray programme, the farmer should consider:

  •     Will the pest cause economic damage?
  •     Is there an alternative to chemical control?
  •     At which growth stage or infestation level should the pest be controlled?
  •     Which pesticides are registered for controlling the specific pest?
  •     How should the pesticide be applied?

BIOLOGICAL CONTROL

Natural control of pests will occur where predator species are encouraged and protected by the use of insecticides that are environmentally friendly and only toxic to the target organism.

PLANT RESISTANCE

The planting of specially bred pest resistant cultivars has both short- and long-term benefits. In the short term, the damage caused by specific pests is limited and economic threshold limits are usually not reached or exceeded. In the long term, the pest populations will be suppressed and stabilised below economic threshold levels.

 

CULTURAL PRACTICES

Pest populations will be suppressed by cultural practices which are harmful to the specific pest. These include winter tillage, timely weed control and the removal of volunteer maize plants, correct cultivar choice and the correct choice of planting dates.

 

NEMATODE CONTROL

Plant-parasitic nematodes are present in all of South Africa’s maize producing regions and cause damage to the root systems of the maize plant. A gradual reduction in yields over a number of seasons is usually the only indication of a nematode infestation. The high cost of nematicides makes the economic justification of chemical control difficult, particularly in dryland maize, where results have been erratic. Registered nematicides include carbosulfan, carbofuran, and terbufos.

Soil and root samples should be sent to ARC-GCI for analysis to determine the levels of nematode infestation in the soil and obtain their recommendations for the treatment of the problem.

Several nematode groups have been identified in South Africa but the two most notable are:

  •     Root-knot nematodes (Meloidogyne species); and
  •     Lesion nematodes (Pratylenchus species).

While complete eradication of the nematode population in a particular field is economically impossible, the main objective of a nematode management programme is to keep the numbers of nematodes below economic threshold levels.

Pests of maize, which have been recorded, include those listed in the table below.

PEST
Maize stem borer Source: push-pull.netThe larvae are dark brown, becoming paler with age. They cause serious damage to the crown of the growing plant and normally infect the plant prior to sexual maturity.  They are also known to tunnel into the cobs and feed on the kernels. Chemical control using pesticides containing alpha-cypermethrin, fenvalerate, chlorpyrifos, deltamethrin, endosulfan, carbosulfan, lambda-cyhalothrin and cypermethrin, is available.
Chilo borer Source: arc.agric.za  Creamy white larvae with four rows of dots along the body. Cause the same damage as the stem borer. Chemical control using deltamethrin, endosulfan and lambda-cyhalothrin.  
Maize snout beetle Source: marysrosaries  Small brownish beetles that feed on the leaves of young plants. There are several species harmful to maize plants.  They are controlled by using chemicals at planting and by crop rotation.
Cutworm Source: Pioneer Hi-Bred  These damage the young plant just after germination.  The best control measure is to keep the land clean 4 – 6 weeks before planting. Pesticides registered include alpha-cypermethrin, deltamethrin, endosulfan, fenvalerate and lambda-cyhalothrin and cypermethrin.
African armyworm Source: arc.agric.zaThis is a leaf-eating caterpillar which feeds on members of the grass family. Since they normally appear in large numbers they can inflict serious damage. Chemical control when outbreaks occur, has been successful.  
African bollworm Source:portal.organic-edunet.eu  Three longitudinal dark bands separated by pale ones are characteristic of these larvae, which eat large holes through the whorl leaf roll, but prefer the cobs. They also cause significant damage to the silks of the young ears. They can be controlled by chemical applications of pesticides containing alpha-cypermethrin, deltamethrin, endosulfan, lambda-cyhalothrin, methomyl and cypermethrin.

Various insects prey on these maize pests, including wasps, parasitic flies, earwigs and beetles and it is useful for the farmer to be able to distinguish the beneficial insects from the harmful ones.

All of the problems discussed in this module are highly specialised and a wise farmer will adopt the following policy:  When in doubt – call the specialist. It is, however, helpful for him to have a basic knowledge of the insect pests affecting his crop.

You should be able to recall from this module the concepts involved in planting, cultivation and weed control. Problems of disease control and pest control are also important and the farmer should know where to seek technical assistance. Farmers should be continually aware of these yield-reducing factors.

5. PRODUCTION MANAGEMENT GUIDLEINES

ARC-GCI has provided the following summary of management guidelines as a handy stage-by-stage reminder for maize farmers:

GROWTH STAGE 0: FROM PLANTING TO SEED EMERGENCE

  •     The seedlings will emerge above ground level between 6 – 10 days after planting in warm moist conditions. The optimum temperature should be between 20°C and 30°C and the moisture content should be at 60% of the soil capacity.
  •     The seeds should not be planted too deep as they will take longer to emerge and may begin to develop under the surface and die off.
  •     Fertilizer should not be placed too close to the seed row to avoid burning of the primary roots.

 GROWTH STAGE 1: FOUR LEAVES UNFOLDED

  •     A new leaf will unfold almost every third day, with the growth point still below the surface.
  •     Tasselling initiation occurs at this stage.
  •     During this tender stage the young plants are susceptible to damage by wind-blown sand, hail and frost although the growth point will still be protected by the soil covering.
  •     Waterlogging will damage the underground growth point and should be avoided.
Tillers: a shoot of a grass or cereal plant, which forms at ground level in the angle between a leaf and the main shoot. True stems are only produced from the tillers at a later stage in the plant’s development  

    Cultivation close to the plant row should be avoided so as not to disturb the young root growth, thereby stressing the plant.

GROWTH STAGE 2: EIGHT LEAVES COMPLETELY UNFOLDED

  •     The leaf area increases 5 – 10 times and the stem mass increases 50 – 100 times during this stage.
  •     Ear initiation has commenced and side tillers are beginning to develop below the surface.
  •     The growth point is now between 5.0 and 7.5 cm above the surface of the soil.

GROWTH STAGE 3: 12 LEAVES COMPLETELY UNFOLDED

Nodes: A point at which lines or pathways intersect or branch; a central or connecting point  

    The tassel in the growth point is developing rapidly. Lateral shoots bearing cobs develop from the sixth to eighth nodes above the ground. The potential number of seed buds on the ear has already been determined.

  •     Efficient water and nutrient management is critical during this stage as deficiencies will adversely affect the final size and yield of the ears.
  •     Plants damaged below the growth point will not recover.

GROWTH STAGE 4: 16 LEAVES COMPLETELY UNFOLDED

  •     The stem is lengthening rapidly and the tassel is almost fully developed. Silks begin to develop and lengthen from the base of the upper ear.
  •     Hot soil surfaces will affect the development of the lateral prop roots.
  •     Water and nutrient deficiencies will negatively affect silk development and the number of kernels per ear.
  •     Hail damage will be detrimental.

GROWTH STAGE 5: APPEARANCE OF SILKS AND POLLEN SHEDDING

  •     All leaves are by now completely unfolded and the tassel is visible. The lateral shoot bearing the main ear has almost reached maturity. The plant’s demand for water and nutrients is high during this period.
  •     Planting dates should be chosen to ensure that favourable growing conditions occur during this time. Water supply is vital to avoid stress through wilting during pollination.

Starch: a substance composed of chains of glucose units, found in green plants   GROWTH STAGE 6: GREEN MEALIE STAGE

  •     The ear, lateral shoots and bracts are fully developed and starch begins to accumulate in the endosperm.
  •     The cobs are ready for harvest as green mealies.

GROWTH STAGE 7: SOFT DOUGH STAGE

  •     Grain mass continues to increase and sugars are converted into starch.
  •     Silage making may begin at this stage.

GROWTH STAGE 8: HARD DOUGH STAGE

  •     Sugars in the kernel disappear rapidly. Starch accumulates in the crown of the kernel and extends downwards.
  •     Denting of kernels begins and this is the right stage for silage making.

GROWTH STAGE 9: PHYSIOLOGICAL MATURITY

  •     The kernel reaches its maximum dry mass and a layer of black cells develops at the base of the kernel. The grain is now physiologically mature and only the moisture content needs to be reduced before the crop may be harvested.
  •     Moisture content should be regularly monitored so that harvesting can begin as soon as possible below 14% to reduce grain losses.

GROWTH STAGE 10: BIOLOGICAL MATURITY

  •     The grains will dry out to below 14% moisture content during this stage. Under favourable drying conditions, the moisture content will be reduced by approximately 5% per week up to the 20% level, after which the process slows down.

1. CROP ESTIMATION

It is useful for the farmer to have an idea of the approximate size of his maize crop in order to help with his harvest and storage planning and to calculate his expected income.

A handy method of estimation, provided by the Agricol Agronomy Catalogue for 2012, is as follows:

  •     Six weeks after flowering, pick 30 cobs from different locations in the field;
  •     Count the number of kernels per cob, by multiplying the number of kernels per row by the number of rows on the cob;
  •     Add the total number of kernels together and divide by 30 to give the average kernels per cob;
  •     Multiply this average number of kernels per cob by the number of plants per hectare. This will give the approximate number of maize kernels per hectare;
  •     Multiply the number of seeds per hectare by 0,3 (average kernel weight in grams) and divide by 1000; and
  •     The answer should be the total kilogrammes of maize that you can expect to produce per hectare.

2. HARVESTING

Let us assume that we have grown the crop successfully and now remove it from the land and bring it in. This is probably the most important stage because we want to collect all we have harvested with as little wastage as possible, so therefore the more efficient the method the better the result. The farmer should choose the method which is most efficient for his means and that costs the least.  The maize crop should also be taken off the land at the correct time, which is approximately 200 days after planting, when the moisture content in the grain has reached about 13%. Crops can be removed earlier but would have to be dried. Sophisticated drying machines may mean mechanical problems.

There are two basic methods of harvesting maize: hand harvesting and mechanical harvesting.

HAND HARVESTING

There are three main methods of hand harvesting:

The first method involves cutting the entire plant off at ground level while green and stacking them in ‘stooks’ to assist with the drying process. Once dry, the cobs can be picked and shelled, or the entire plant including the cob can be used for animal feed

The second method involves removing the cobs from the plant and placing them in bags. These are taken to the edge of the land for collection by a tractor and trailer and transported to the Sheller which should be as close as possible.

Alternatively, the tractor and trailer can follow the harvesters who throw the cobs into the back of the trailer. To ensure that the cobs are not thrown over the trailer, a `bang-board’ is constructed in the trailer. This is a frame which is erected lengthwise over the middle of the trailer over which a hessian blanket (e.g. hessian bags sown together) is placed. When the cob is thrown against this bang-board it falls to the bottom of the trailer

The main hand harvesting team should be followed by a team of ‘gleaners’, who harvest what has been left behind and pick up cobs which have not landed on the ‘bang-board’ trailer. These cobs are placed in bags and left in groups on the land to be collected at the end of the day.

                                                    Source:iaea                                                                                            Source:iaea

This method of harvesting has a number of limitations and should be restricted to farms and smallholdings where small areas of maize are grown as it is so labour intensive. There are variations on this method but the best method is the one that retrieves most of the cobs from the land. 

 

MECHANICAL HARVESTING 

Maize is normally left in the field to dry out to a moisture content of between 12.5% and 14.0% before mechanical harvesting. This method is recommended for farms where large areas of maize are grown and involves the use of combine harvesters. These are highly sophisticated and expensive machines, which remove the cob from the plant and shell the grain off the cob. The grain is then transferred into a bulk trailer driving alongside. This method is highly efficient and the amount of maize left in the land is between 4 and 5%. Combine harvesters can be towed behind a tractor or self-propelled.

Source: wikipedia

3. HANDLING AND STORAGE

Regarding the situation where the maize has been shelled off the cob; even with hand harvesting the grain can only be removed efficiently through mechanical means.  There are a number of machines, both simple and sophisticated which can be acquired for this stage of handling. The clean grain can be handled in one of the following ways:

  •    Bagging: a lot of manual labour is required and the maize is placed in hessian bags which are stitched up. This method is recommended for farmers who are handling small crops and do not have bulk-handling facilities

                                        

  •     Bulk handling:  the maize is shelled mechanically and the clean grain is stored in bins above or below ground level. When the bins are full the farmer transports the grain to the bulk handling centres or grain silos. On arrival of the bulk handling transport trucks, the grain is augured into the truck from the bins. The auger is a mechanical tool designed for lifting the maize seeds from the bins below ground into the bulk trucks

The next stage is the storage of maize on the farms where it has been retained for livestock consumption or any other purpose:

  •     Storage in bags: This is the simplest method but requires a large floor area for storage. It must be completely waterproof to ensure there is no spoilage through moisture. It is important to remember that maize can be stored successfully at 12,5% moisture

Source: pages.kiva

  •    Bulk storage:  This is an economical method requiring little or no floor space. The grain is stored either in concrete or galvanized iron bins. The bins are an inverted cone shape with the outlet at the vent rim of the cone. Again, the system has to be waterproof. This method makes for easy movement of maize

An important aspect of maize storage is the precaution which should be taken to avoid damage by insect pests, namely, weevils, maize moths and flour beetles. These pests can easily destroy large quantities of maize if allowed to infest the stored crop and expert technical advice should be sought regarding chemical control methods.

                          Source: tomcradit                                                                                                Source:lickr

4. MARKETING

After years of price control by the Grain Marketing Boards, the South African maize market was deregulated in the late 1990s after which the South African maize producer became exposed to the global supply and demand effects on maize prices. To create a South African market that transmits global and local influences into a formal maize price, the South African Futures Exchange (Safex) was developed and bought out by the Johannesburg Stock Exchange in 2001. This futures market, by way of the market’s ‘invisible hand’ (supply and demand), sets the market prices for maize in South Africa.

Farmers either on their own or through brokers can adopt a number of different strategies depending on their type of operation. The marketing strategies available to the maize farmer include:

  •     Harvest and store the crop in co-operative silos for sale when the price is higher than at harvest time. This is the more conventional approach but storage and transport costs need to be taken into consideration;
  •     Forward contracts agreed pre-harvest, leaving the farmer vulnerable to price fluctuations;
  •     Harvest and store in silos on the farm, which is a flexible but capital intensive option that is normally only available to the large commercial farmer;
  •     Harvest and store in silo bags which is a new method of storage, being cheaper than silos, but not without the risk of loss or damage to the stored grain;
  •     Hedge risks on Safex futures and options preferably with the advice of a professional broker. Farmers use this as a hedging mechanism to secure a certain price for a certain amount of their maize but will not benefit if the price increases;
  •     Sell maize on the spot market and buy futures. The spot market means selling your crop on the day of harvest at the going price on that particular day;
  •     Use maize as animal feed and sell the animals;
  •     The ‘one third’ strategy, where the farmer splits his crop between futures contracts, animal feed and the spot market, thereby spreading risk; and
  •     Small scale growers normally sell their maize directly through forward contracts with millers or at the spot price to the millers.

Due to government subsidies to farmers in USA and Europe, the global grain market remains extremely volatile and this combined with fluctuating exchange rates and the usual weather anomalies, has the combined  effect of exposing unsubsidised South African farmers to a great deal of uncertainty and risk. This shows the importance of using the best possible marketing advice and strategies available.

              Source: kawambwafarmersdfa.blogspot                                         Source: jeffreyandkristinleeinrwanda.blogspot

MAIZE MARKET VALUE CHAIN

Source: Department of Agriculture (2012)