Planted pastures can be divided into three distinct categories. Firstly, there are the pastures (more correctly, grass fallows) of nematode-resistant grasses such as Katambora Rhodes grass and Ermelo Love grass grown in rotation with tobacco crops. These are normally not fertilised and, after the initial flush of vigorous grass growth resulting from the nitrogen released when the soil is ploughed, carrying capacity is little greater than that of cleared veld.
Secondly, there are grass-only pastures to which nitrogenous fertilizer is applied. The productivity of these pastures depends on the level of fertilizer application and, if large amounts of nitrogen are used, can be extremely high. It has been found that the tufted grasses are unable to withstand heavy stocking rates but that the running grasses such as Star grass or Kikuyu grass are well adapted.
Thirdly, there are pastures in which the nitrogen needed for productivity is supplied not from the fertilizer bag but by fixation of nodulated legumes. This is a relatively exciting development in southern Africa, and much still remains to be learnt, but it appears to have the potential of profitably increasing beef production over large areas.
The following is a list of the grasses and legumes more commonly used for planted sub-tropical pastures in Central and Southern Africa. For the cooler, moister parts of South Africa, more temperate grasses and legumes are favoured, like ryegrass, cocksfoot, red clover, New Zealand White Clover.
|Giant Rhodes Grass
Katambora Rhodes Grass
|Cynodon Nlemfuensis var Robustus
|Silverleaf Desmodium (Legume)
|Ermelo Love Grass
|Glycine Wightii var Longicauda
|Cooper Glycine (Legume)
|Beit Lotononis (Legume)
|Stylosanthes Guianesis var
|Oxley Fine-Stem Stylo (Legume)
|Trifolium Semipilosum var Glabrescenes
|Kenya White Clover (Legume)
2. PASTURE GRASSES
KATAMBORA RHODES GRASS (Chloris gayana)
Chloris gayana (Rhodes grass) is indigenous throughout Africa, and shows preference for the moist (not water-logged) fertile soil of medium rainfall areas. Rhodes grass has proved to be a popular pasture grass and has been introduced into many countries with a tropical or subtropical climate. Two strains have proved successful in planted pastures: Katarnbora Rhodes and Giant Rhodes. The Katambora strain was originally collected near the Zambezi River above the Victoria Falls.
Katambora Rhodes grass is a soft leaved, fine stemmed, tufted, stoloniferous perennial. It is not as leafy as other C. gayana strains. It generally produces an open sward of about 60 cm in height but when in seed is taller, around a meter in height. Because of its stoloniferous growth-habit poor stands can improve and bare areas will be colonized. The seed-head consists of up to 20 digitately arranged spikes. Spikes are a rich brown colour. This grass sets seed readily and under good conditions yields of 500-600kg seed per ha are possible. The seed is extremely small with approximately 4 000 seeds per gram.
Katambora is readily established from seed and, because of its resistance to eelworm, is ideally suited as a ley in tobacco rotations under dryland conditions. Katambora has a reputation for poor persistence and reduced production levels after two or three seasons. This seems to be linked with sandy acid soils under cooler conditions. General indications are that the grass does best on fertile, medium textured soils where temperatures are higher and rainfall is good. It does not stand up to heavy continuous grazing.
Experimental evidence has shown Katambora to be productive under lower levels of nitrogen application. It could prove to be a valuable pasture grass when used in conjunction with tropical pasture legumes in lays
Katambora has generally been grown in tobacco rotations with little if any additional nitrogen fertilizer. Production without additional nitrogen is very low.
Growth can be increased slightly in tobacco rotations with applications of additional nitrogen, up to 150 kg ammonium nitrate per ha, provided this is withheld in the season before the ley is ploughed out.
This grass should be grazed rotationally throughout the growing season. Allowing the grass to grow out by resting during the growing season, or grazing as foggage in winter, produces relatively poor winter grazing.
As with all grass planted by seed, it is important to prepare a fairly fine, firm seedbed. Attention must be given to reducing weed competition. Seed can be sown at any time during the growing season but mid-season planting mid- January to February will give the best results in most areas. Rainfall is most reliable during this period and enables cultivation prior to planting to reduce weed competition. Seeding rate will depend on the quality of seed used general recommendations are 4-6 kg per ha drilled and 6-8 kg per ha broadcast. Seeding depth is 6-10 mm.
Undersowing the maize crop is a reliable method of establishment. The maize plant population should be reduced to about 38 000 plants per ha. The seed is broadcast on the soil surface after weed cultivation and when the maize is about 60cm high.
GIANT RHODES GRASS (Chloris gayana)
This strain of Rhodes grass was probably originally introduced from Tanzania. It is very similar to Katambora but more robust. Giant Rhodes originally attracted much interest but this declined when it was found to be a host to eelworm and therefore undesirable for use in tobacco rotations.
This is a leafier, and more robust perennial than Katambora. It too, is tufted and stoloniferous and when in seed will grow 1,5 to 2 meters tall. Seed in the bag may be lighter in colour but, nevertheless, very difficult to distinguish from Katarnbora.
Given the right management Giant Rhodes is generally persistent. Like Katambora, it prefers the hotter areas with a good rainfall and will grow on a wide range of soils. It is frost sensitive and has been known to die out in winter after severe frost. Seed is set later than Katambore. It is readily grazed by animals in the dry state and in this respect is preferable to Katambora
This is the same as for Katambora except that a slightly heavier seeding rate is recommended. One gram contains about 4 000 seeds. When drilled, about 6-8kg per ha are required and 8-10kg per ha broadcast. This is because Giant Rhodes generally has a lower pure seed content.
Where Giant Rhodes is grown in mixtures with legumes it is initially more competitive with the established legumes. Siratro will eventually grow well with this grass but competition must be watched in the early stages and the grass must be mown if it tends to grow too tall.
Experimental work has shown, that strains of Rhodes grass will often produce as much herbage as Star grass at lower levels of nitrogen application. They should therefore not be discounted when considering which grasses to choose for grass/legume mixtures. This is particularly true when less permanent pastures are required.
Giant Rhodes is sensitive to severe grazing, particularly in the early and late growing seasons. Management should therefore take the form of rotational grazing, giving particular attention to resting in the late growing season to maintain vigour. This form of management is more acceptable for Giant Rhodes, which produces foggage of fair quality, than for Katarnbora which does not.
STAR GRASS (Cynodon nlemfuensis)
A number of strains of Star grass are cultivated as pastures. It is not easy to distinguish between them and it is possible that many stands are in fact mixtures of two or more strains.
“Star No. 2” is the most common strain used. It has in the past been variously referred to as Cynodon plectostchyus and Cynodon aethiopicus, but is perhaps best considered as a strain of C. nlemfuensis var. robustus.
C. nlernfuensis var, robustus occurs widely from East Africa to Southern Africa and grasses selected from a number of wild populations which were grown research farms in Zimbabwe
There is no doubt that, of the Star grasses presently selected for propagation, Star No. 2 is the best for medium to high rainfall red-soil or sandveld areas.
Star grass is a vigorous perennial, with strong, rapidly growing stolons. A dense sward develops under conditions of high fertility and heavy grazing. It can be said to be similar to couch grass (Cynodon dactylon) but very much coarser and robust, and distinguished by an inflorescence of 3-20 spikes arranged in a common axis but not digitately as in C. dactylon.
Star grass will grow in high rainfall areas over a wide range of soil conditions. In the low rainfall parts of the country it will only become productive under irrigation. There is little doubt that peak productivity is achieved under highly fertile warm conditions such as are found on ‘red’ soil in high rainfall areas.
Under irrigation, Star grass does well during the warm summer: months but is susceptible to cold night temperatures when it will grow only very slowly. For this reason irrigated Kikuyu is often preferred because of its longer productive season.
As presently cultivated strains of Star grass produce very little viable seed, propagation is by runners.
These take readily under the right conditions, so very few establishment problems are encountered.
A number of methods are used to plant Starr Grass, It can be underplanted in maize, in which case it is usually done by hand in each alternate row after the last mechanical weed cultivation.
Star Grass runners can be chopped, mechanically, into short (20 – 25 cm) lengths which are broadcast over the land to be planted and then lightly disced in. This method works best during a rainy spell.
Star can also be planted by hand at spacings of approximately two meters, or closer if a rapid cover is required.
Another semi-mechanical means of planting is to lay runners in the open furrows during the ploughing operation, in such way that they are not too deeply covered when the plough comes round again. Desired row spacing can be achieved by varying the number of passes made by the plough between planting furrows.
Where possible, soil samples should be sent for analysis to indicate fertilizer requirement levels at establishment. Where Star is under planted in maize the nitrogen applied to the maize is generally increased by about 25 %. The object is to overcome the lower maize yields that would result from grass competition, and to help establish the grass.
Where the grass is to be established in open lands, phosphate (and potash if required) should be incorporated before planting. Single superphosphate is usually recommended at a rate 200 – 300 kg per ha under average conditions. Ammonium nitrate can be applied in fairly frequent dressings of 100 kg per ha once the grass begins to ‘take’. The amount applied (at this stage) will naturally depend on the total amount of nitrogen it is intended to apply to the pasture and the nature of the season. Where soil fertility is suspect the incorporation of some nitrogen before planting will promote more rapid establishment.
Under grazing conditions, two animal-related problems arise. The first is danger of prussic acid poisoning, particularly in the early summer when the grass is showing signs of wilting.
Secondly, ewes grazing Star Grass pastures have been shown to produce lambs suffering from goiter and skeletal deformities, particularly in autumn-born lambs. Lambs are either stillborn or die soon after birth. Calves from cows grazing Star Grass pastures are not so severely affected. A salt lick containing 0.3 % iodine, provided ad lib to animals grazing Starr Grass will overcome this problem. Alternatively, the iodine may be included at the same rate in concentrate rations where these are fed.
When grown on heavy soil under dryland conditions Starr Grass will produce best if nitrogen is applied at a rate of 350 kg per ha (1 000 kg ammonium nitrate per ha). At this level the grass grows vigorously enough to prevent the invasion of Sporobolus Pyramidalis which would otherwise degrade the pasture. Under sandveld conditions, Star Grass is not so productive, and will yield only about two-thirds as much herbage for the same amount of nitrogen as applied on heavy soils. On sandveld, where the applied nitrogen is more efficiently utilized and satisfactory levels of production are achieved, Star Grass is usually fertilized at a lower level of about 500 kg ammonium nitrate (175 kg N per ha). The economics of nitrogen application must be carefully evaluated and related to prevailing conditions on each particular farm.
Stocking rates on well established, highly fertilized pastures are in the region of 12 yearlings steers of approximately 200 kg live mass per ha. Grass production, and therefore stocking rate, will however, vary from season to season depending on rainfall.
Grazing should commence about three or four weeks after the rains start and usually continues until April. Rotational grazing of Star Grass pasture is not essential. Where rotational grazing is practiced, however the stocking rate can be increased by about 25 % if the grazing period is restricted to one or two days, followed by 15 days rest.
ERMELO LOVE GRASS (Eragrostis curvula)
Eragrostis curvula occurs naturally in the cooler sub-tropics of southern Africa, but it does occur in the tropics to a limited extent. Many strains of E. curvula are known but the Ermelo strain is one of the most leafy and popular. Although this grass is less palatable than most other grasses used for pasture production, its ease of establishment, productivity and persistence have made it popular and widely used in sub-tropical climates the world over. Because of ease of establishment and persistence, it is also widely used to Control erosion on road embankments. It is resistant to root-knot nematodes.
Love grass is a strongly tufted erect perennial. Old tufts can become very large, leaves are narrow and drooping, and crowded at the base of the plant. CuIms are up to 120 cm in height, the seed-head being a dark olive-green open panicle. Each spikelet contains several florets. The seed is held loosely in the florets and is thus usually sold ‘naked’; smaller quantities are therefore required for planting. One gram contains approximately 3 500 seeds.
Ermelo is best adapted to high rainfall (+ 700 mm) cooler sub-tropical conditions on sandy to sandy loam soil. There is some evidence to suggest that it is not as resistant to cutting or grazing when grown on heavy soils. It does not seem to do well under warm conditions. It is an unpalatable grass and where it has been grown with other grasses, cattle and sheep will select these in preference and leave the love grass almost ungrazed. High levels of nitrogen fertilizer application will slightly improve palatability, as will cutting to keep the grass short. Love grass provides very poor winter grazing, but makes excellent hay, which cures rapidly after cutting. It is most popular for hay.
Ermelo love grass starts growth very early in the season — before the rains start — and so can provide a useful early season ‘green bite’.
It does not seem to mix well with tropical legumes. This is due in part to the very wide palatability difference between legumes and the grass, especially as the love grass grows out. The result is that the legume component is very heavily grazed while the love grass is almost ungrazed.
Love grass is easily established from seed, provided the seed is not planted deeper than 5-10 mm. Seed is sown in a well prepared firm seedbed, during period of reliable rainfall. Rolling before planting is usually essential if the grass is established in an open land, and again after planting if the soil is dry. A shower of rain after planting is often sufficient to cover the seed and firm the soil around the seed. Because love grass seed is sold naked, i.e. without chaff, it is advisable to mix the seed with sand or sawdust to obtain sufficient bulk for sowing. Seed
should not be mixed with fertilizer, but a fertilizer distributor can be used to sow the seed.
Broadcasting is the most common method used at a seeding rate of 2 – 3 kg love grass seed per ha.
Like most grasses, love grass can be very successfully established by underplanting a maize crop. Here the seed is broadcast on the loose surface of the soil after the last mechanical cultivation of the maize.
Where the grass is not under planted the fertilizer is incorporated in the soil during land preparation. Soil analysis will indicate the correct rate of application. Under average conditions on sandveld, superphosphate is applied at a rate of 200 kg per ha. Potash is not normally needed. Nitrogen dressings are recommended after the grass begins to grow, unless the soil is particularly deficient, in which case earlier application is necessary. Where the grass is established under maize the fertilizer applied to that crop is usually sufficient.
If Ermelo love grass is to produce satisfactory growth, substantial amounts of nitrogen up to 500 kg per ha of ammonium nitrate—will have to be applied in three or four dressings during the growing season. In addition, the grass must be grazed intensively to keep the sward not more than about 25cm high. Palatability and feeding value will be low if the grass is allowed to grow out. If grown for hay, 2 or 3 cuts can be taken per season, with a total yield of about 8 tonnes hay per ha.
SABI PANICUM (Panicum maximum)
Sabi Panicum is the only strain of Panicum maximum to have been grown commercially in Southern Africa. P. maximum is indigenous to tropical and subtropical Africa, often appearing in abundance where the soil has been disturbed. This is associated with the conditions of high fertility which occur when nitrogen is released as a consequence of soil .disturbance. It is a shade tolerant plant and forms a valuable natural constituent of veld in medium and low rainfall areas. Nevertheless, high production will only be achieved in regions where the rainfall is in excess of 700 mm.
Sabi Panicum originated in the Sabi valley and became popular with farmers during the early 1960s. Because of its sensitivity to grazing in the late season and autumn however, its popularity declined and it is no longer commonly grown. Nevertheless, it is a very palatable pasture grass capable of good production at the lower levels of nitrogen application; it is therefore a good choice for inclusion in tropical-legume/grass-pasture mixtures. A more recently selected strain of P. maximum, has been found to be more productive than Sabi and more resistant to defoliation.
A tall, vigorous, tufted perennial difficult to differentiate from other strains of P. maximum. The plant is leafy in the younger stages but becomes stemmy if allowed to grow out.
The seed-head is an open panicle with the lower branches arranged in a whorl. Spikelets are purple or predominantly purple. Sabi Panicum is not a host of root-knot nematodes and can therefore be used in tobacco rotations.
Sabi Panicum will grow and do well on both sandy and heavier soils. It does best however under conditions of high rainfall and high fertility, with a warm climate and medium textured soils. It is a shade tolerant plant and will grow under trees. In the natural state P. maximum is often found in association with Acacia trees. This association has been attributed to high fertility and better moisture conditions (in dry climates) associated with shade from the trees; this is also possibly a result of the protection from grazing afforded by the Acacias.
Sabi Panicurn is sensitive to hard grazing during the summer and will not persist if grazed heavily for long periods. This applies particularly in the autumn/late summer period when the grass should be rested and then grazed in winter.
This grass has done well in the provision of winter foggage grazing. Steers have been shown either to maintain weight or to show a slight live mass gain in winter without supplements.
Sabi Panicum is fairly easily established from seed which is generally sold contained in the husks and may give the appearance of being fairly large. The actual seed is very small, there being about 4 000 seeds per gram.
Good land preparation and an even firm seedbed are required. The land should preferably be rolled before planting and care must be taken to ensure that the seed is not planted too deep. Patchy stands often result if the seed is broadcast on rough land and then rolled in, because many seeds will be buried too deeply. Also, as the seed is small, it should be sown during a period of reliable rainfall so as to provide better germination conditions. Seeding rates are 6 kg per ha drilled and 8-9 kg per ha when broadcast.
Response to nitrogen fertilizer is good at moderate (175 kg N per ha) levels. At this level on sandveld Sabi Panicum has often produced more herbage than Star grass. This grass is however, sensitive to grazing and therefore will not persist if grazed heavily for long periods. Resting from late January to May has been shown to encourage the grass to persist. Rotational grazing of the pasture would also help in this respect.
Fertilizer applications should be based on soil analysis, under average conditions annual dressings of 200kg per ha single superphosphate should be applied. Nitrogen application will depend on the use of the pasture. The practice has been to exclude nitrogen in tobacco rotations but small quantities of up to 150 kg per ha may be applied provided it is not applied in the year before ploughing out. Where the grass is included in a mixture with tropical legumes it should not be necessary to apply nitrogen except during establishment to get grass away When legumes are included in the mixture it will be necessary to give increased attention to the phosphate requirement. It is possible that potash may also be needed.
Sabi Panicum produces a good amount of seed, but seed in the panicle ripens unevenly, starting from the outside of the panicle and moving inwards. Ripe seed is easily shed; mechanical harvesting of seed is thus not feasible. Hand reaping of selected seed-heads and more than one reaping are thus required if good yields are to be obtained. As newly reaped seed has low viability it should be stored in a cool place for a year before planting.
KUKUYU GRASS (Pennisetum clandestinum)
Kikuyu grows naturally in the highlands of East Africa, occurring mainly at elevations between 1 700 and 3 000 meters where the rainfall is in excess of 1 000 mm. In these areas it is accepted as being an indicator of high fertility. It is reputed to have been introduced into the Republic of South Africa in 1910 by Mr. Forbes and by 1917 was being widely used as a pasture grass and for lawns. It has since been introduced into most countries with a humid sub-tropical climate. A number of strains are propagated, some of which produce viable seed.
Kikuyu is a low-growing perennial spreading by means of numerous long rhizomes and stolons with short internodes which root readily at the nodes. Ungrazed, it will form a loose sward up to about 800 mm high; under grazing, will form a dense mat or sward. Short horizontal or weakly upright leafy branches arise from the stolons. Flowering stems are very short. The inflorescence is not easily recognized, consisting of a spike of 2-4 florets, enclosed in the upper leaf sheath. Leaf blades are strongly folded in the bud, later opening out flat up to 130 mm tong and 6 mm wide—or slightly more— tapering to a sub-obtuse tip, sparsely and softly hairy. The ligules are a ring of hairs.
Kikuyu is summer growing and is best suited to cooler areas where soils are fertile and rainfall is above 1 000mm. In lower rainfall areas, it is often grown under irrigation.
Kikuyu makes excellent spring, summer and autumn growth and is usually dormant in winter. On frost-free areas it will make slow winter growth. Its early growth, starting in August and continuing production until late May, are reasons for its popularity as an irrigated pasture grass in preference to Star grass. Kikuyu is not as palatable as other pasture species but it is nevertheless taken readily by animals. Crude protein analyses of 23 – 25 % in young herbage are not uncommon. It withstands close grazing and trampling and is ideally suited as a permanent pasture. It can be difficult to eradicate in irrigated areas and in areas to which it is adapted.
Bloat problems have been recorded from pure stands of Kikuyu, and more so from Kikuyu/white clover mixtures. Toxic levels of nitrate nitrogen have been recorded from Kikuyu pastures, particularly where large amounts of nitrogen fertilizer are applied in one dressing. This has caused the death of cattle in a few cases.
Kikuyu is most commonly and readily established by means of runners. These can be planted successfully at any time during the summer period; weed competition can, however, be a problem during the rains. If Kikuyu is to be grown under irrigation, it can be established during the cooler months. Growth will initially be slow but as the weather warms up the established Kikuyu will begin to grow rapidly. Where it is planted as a mixture with Kenya white clover both could be planted in May. This will allow the clover to germinate and initially grow with little competition from the Kikuyu until temperatures begin to rise. Kikuyu can be established by planting at 1 meter spacings but closer spacings of 0.5 meter or even closer will ensure a quicker cover.
Fertilizer applications should be based on the results of soil analysis but will probably include a heavy initial application of lime, preferably dolomitic lime, and 250 to 500 kg single superphosphate per ha. Depending on the cropping history of the land involved, a precautionary application of 30 kg per ha zinc sulphate and 10 kg per ha fertilizer borate may be advisable to supply these minor elements. Nitrogen fertilizer can be applied to promote rapid grass growth when temperatures rise and the grass begins to grow. Two dressings, in September and October should be sufficient.
Experimental work has shown that rotational grazing does increase herbage production but that it is not easy to convert this into increased beef production. General recommendations have been for 10 to 20 paddocks, allowing grazing and rest periods of either 2 days graze and 18 days rest or 1 days graze and 19 days rest. Fewer paddocks can be used however, such as a 6 paddock system allowing a 4 day grazing period and a 20 day rest period.
Stocking rates will vary with the production level achieved in the pastures. This will largely be controlled by the amount of nitrogen supplied artificially to pure Kikuyu stands or naturally from clover, and any additional nitrogen applied in clover/Kikuyu mixtures. Where it is desirable, nitrogen can be applied to clover/Kikuyu mixtures to increase production. This should ensure a better grass balance in the sward and boost production. Initial stocking rates of 15 – 18 weaner steers per hectare can be achieved on highly fertilized Kikuyu pastures and 10 – 12 weaners on clover based pastures. Stocking rates with dairy cows will depend entirely on how long the animals are allowed to graze the pasture each day. Where animals graze the pasture for the whole day, stocking rates of up to8 cows per ha (depending on body size) can be carried, but should be reduced in the cooler winter months.
Annual fertilizer applications will be approximately Dolomitic lime: 500kg per ha in August.: if necessary
Single superphosphate: 450-500kg per ha split into two applications, one in August and one in January.
Nitrogen: up to 300kg per ha for pure Kikuyu stands, applied in equal monthly dressings; of up to 175kg per ha on Kikuyu clover mixtures, applied in smaller dressings as desirable.
INTORTUM (Desmodium intortum)
Desmodium intortum is indigenous to Central and South America but has been used as a pasture legume in a number of countries. In Australia the cultivar Greenleaf is grown mainly in costal southern Queensland and northern New South Wales, although it also grows well on plateau further-north, such as the Atherton Tableland.
Intortum is a trailing perennial legume which roots from the nodes rather more readily than Silver leaf. The stems are finer and less hairy and the internodes shorter than those of Silver leaf, so that lntortum is a more leafy plant. The dark green leaves do not have a silvery stripe along the midrib but often have purple or brown flecks on the upper surface.
The inflorescence is a raceme of deep lilac to purple flowers which appear only in late April or May. The pods, which contain 8 to 12 seeds, are dark brown when ripe and constricted between the seeds. Like the pods of Silver leaf, they adhere to clothing or to woolly-coated livestock. The seeds are orange to brown color and there are about 500 seeds per gram.
Intortum is adapted to a wide range of soil types and will even tolerate short periods of water logging. Like Silver leaf, Intortum is better adapted to cool, high-altitude conditions than Siratro but is not as drought-tolerant, especially in the seedling stage. For this reason Intortum is
probably best suited to areas above 1 200 m altitude with a rainfall of more than 800mm annually.
Intortum is defoliated by frost but is not killed.
Seeds of Intortum are not likely to require scarification before sowing. As the seeds are small, even by pasture legume standards, they must not be sown deeply—less than 1 cm deep on a well-prepared seedbed. Like those of Silver leaf, seedlings of Intortum are susceptible to drought and to weed competition so that weedy sites should be avoided.
Seeding rate is about 2kg per ha.
Inoculation with the correct strain of rhizobium is probably desirable as an insurance against nodulation failure on the sands, but does not appear to be necessary on the heavier soils.
Use and Management
Intortum is similar to Silver leaf in its management requirements but it appears less tolerant of grazing and of dry conditions. Because it is late-flowering and sets little seed, stands of Intortum do not thicken from the establishment of shed seed as do stands of Silver leaf. For this reason Intortum is less suitable for veld reinforcement and its main role is likely to be in sown pastures.
Like Silver leaf, Intortum produces a deep layer of organic material on the surface of the soil and this contributes to fertility when the pasture is ploughed.
Because Intortum flowers so late, frost usually occurs before the plants have set seed so that seed production is unreliable and seed yields are usually low. As a result, it is unlikely that large areas of Intortum will be grown specifically for seed production and seed is likely to be reaped mainly from rested pastures in favorable years. Because the Desmodium spp. is cross-pollinated, seed should not be reaped from pastures which contain both Intortum and Silver leaf.
Hand pulling of the pods as they ripen will probably continue to be the main method of reaping seed. After drying, the seed pods can be threshed in a slow-running hammer mill, as recommended for Silver leaf.
SILVER LEAF DESMODIUM (Desmodium Uncinatum)
Desmodium uncinatum is indigenous to Central and South America, usually at elevated sites. It occurs as far south as Uruguay and northern Argentina and as far north as Vera Cruz in Mexico. It is not common in tropical Brazil, being limited to an area of over 1,000m elevation at about 10°S. Nevertheless, the strain which was eventually called Silver leaf was sent to Australia from Brazil in 1944. It was tested in south-eastern Queensland and north-eastern New South Wales in the 1950s and early 1960s and was released for commercial use in 1962.
Silver leaf desmodium has a trailing, as distinct from a twining, habit. The stems, which are green when young and brown when older, are covered with short hooked hairs and trifoliate, and the leaflets are about twice as long as they are broad and have pointed tip. The main distinguishing feature of the leaves is the irregular silver marking along the midribs on the upper surface of all three leaflets.
The inflorescence is rather open, and the pale lilac to pink flowers, which age to pale blue, appear in late March or April. The pods are sickle-shaped, about 5 cm long, and are constricted between the seeds so that they readily break into single-seeded segments. The pods, which are covered with short hooked hairs, stick tenaciously to clothing or the coats of livestock. There are approximately 220 seeds per gram.
A seedling of Silverleaf develops more surface roots but a smaller tap root than seedlings of Siratro or stylo and tends, therefore, to be more susceptible to drought. Adult plants of Silverleaf develop thick tap roots up to 1 cm in diameter and, on friable soils, also root from the nodes.
Most of the pasture booklets say that Silver leaf “is adapted to a wide range of soils”. However, it does grow best on heavier, more fertile soils and seedling growth and survival are often poor on sands. .
Silver leaf is less drought-tolerant than Siratro and Fine-stem stylo and is recommended only for areas receiving at least 800 mm rainfall annually. Growth chamber studies and practical experience have shown that growth is retarded at temperatures above 30°C and Silver leaf is therefore recommended for cooler areas above 1 200m altitude. The foliage is killed by heavy frosts but the plants re-grow from the crown; light frosts cause defoliation without killing the stems.
Seed of Silver leaf is sold naked (not in the pod) and does not normally require scarification to reduce the hard-seed content. Inoculation with the correct strain of rhizoblum is probably desirable on sandy soils. Silverleaf seed should be sown on a firm seedbed and covered to a depth of not more than 1 cm. As the seedlings are particularly susceptible to weed competition, pastures should ideally be sown on relatively clean land. On fields known to be weedy the first flush of weeds should be killed before sowing the seed. Because it is relatively shade tolerant, Silver-leaf is especially suited for under seeding in a maize crop.
The seeding rate is about 3kg per ha.
Use and Management
Silver leaf is probably best grown in mixtures with grasses for summer or year-round grazing, although it can also be grown in pure stands for use in autumn. It mixes well with a range of grasses, including Star grass.
Cattle take Siler leaf once they become accustomed to it. As with all the twining/trailing legumes. Silver leaf can be killed by continuous close grazing, and trials in south eastern Queensland suggest that under set stocking, 0.6 ha per steer is about the maximum stocking rate at which these legumes will persist. Until more is known about the best ways of managing grass/legume pastures, graze pastures of Silver leaf rotationally and avoid frequent and severe defoliation, especially in the late growing season.
Although Silver leaf is self-fertilizing it is basically cross-pollinated and “tripping” by bees has been found to favour seed set. Silver leaf is a prolific seeder and seed yields of 300 kg per ha or more are common.
The seed pods are usually reaped by hand as they turn brown. The hooked hairs on the pods, which cause them to stick to clothing, also cause them to “clump” so that seed in the pod is difficult to handle. After reaping, the pods should be spread in the sun to dry, threshed with a slow-running hammer mill (1 400 r.p.m. using a large screen) and the seed cleaned with a groundnut winnower.
Seed can also be reaped with a combine harvester, though there is evidence that it may be preferable to mow and windrow the seed crop and then to leave it for a week to mature before threshing.
COOPER GLYCINE (Glycine wightii)
Glycine wightii (of which Glycine javanica is a synonym) is indigenous and widespread in Africa, occurring most commonly on the heavier soils. It has been used as a pasture species in a number of countries, including Australia where there are four registered glycine cultivars.
G. wightii is a vigorous twining perennial legume which can root from nodes in contact with the soil and also has a well-developed tap root, which results in a fair degree of drought tolerance. The stems and the underside of the leaves are hairy and the midribs on the lateral leaflets of trifoliate leaves are closer to the outer side than the other.
The inflorescence comprises a large number of small creamy-white flowers which may be flecked with pink or violet. The pods, which form characteristic clusters, are small (40 – 50 mm long), dark brown or black, covered with fine hairs and contain 4 to 5 of the dark brown seeds.
In Southern Africa Cooper flowers in late March or April. It can be distinguished from the other glycine cultivars by (a) its dense cover of hairs, which reflects the light and gives the plants a silver appearance (b) the characteristic asymmetric shape of the lateral leaflets and (c) the constrictions in the pods between each seed.
Like all glycines, Cooper is best adapted to heavy, fertile, well-drained soils. It has a reputation as a drought-tolerant cultivar. All glycines appear to do better in dry years as they are badly affected by leaf diseases during wet spells. It is unlikely that Cooper glycine can be grown successfully where the mean annual rainfall is less than 750 mm. Cooper seems better suited than Siratro to higher, cooler conditions.
There are approximately 140 seeds per gram of Cooper glycine and the recommended seeding rate is 3 to 4 kg per ha. Establishment methods are similar to those for Sirato.
The seedling growth of all glycines is generally slow, often coupled with delayed nodulation, so that it is particularly important to prevent severe weed competition smothering the legume seedlings.
As G.wightii is widespread in Africa, seed of Cooper should not require inoculation.
Use and Management
Cooper glycine is best used in sown pastures, rather than for veld improvement. Young stands of Cooper should be grazed leniently but established stands can survive close grazing. Australian experience suggests that glycine pastures should be grazed heavily in the early growing season and then rested, to allow a dense leaf canopy to develop, before being grazed again in the late growing season. As Cooper is defoliated by frost it does not provide good foggage grazing but it does provide a useful green “bite” before the start of the rains.
Cooper is not particularly palatable, although cattle take it readily during the late growing season.
Seed production of Cooper glycine has not proved easy and seed yields have generally been low. Flowering is relatively late so that in frost-susceptible areas seed-set is sometimes prevented by early frosts.
Seed is best reaped by hand; pulling off the pods as they ripen and spreading them in the sun to dry.
The pods do not shatter as readily as those of Siratro, for instance, and may need to be beaten to release the seeds. Seed can be separated from the chaff by sieving.
Glycine contains a high proportion of hard seed and treatment to reduce the hard seed content is recommended, commercial seed is mechanically scarified before sale; small amounts can be treated with concentrated sulphuric acid for 20 minutes.
BEIT LOTONONIS (Lotononis bainesii)
Lotononis bainesii was first recognized as a legume with pasture potential in Queensland, Australia. Seed collected at the Worcester Veld Reserve, Cape Pro-vince, South Africa, was introduced into Australia in 1952 but growth in the early trials was poor. It was subsequently found that Lotononis would inoculate only with a specific rhizobium not occurring naturally in Australian soils and it was only after this rhizobium was isolated in 1958 and plants were inoculated with it that Lotononis grew well. Miles lotononis was released as an Australian pasture cultivar in 1966.
L. bainesil is widely distributed in South Africa but is especially common in the Transvaal where its range extends from the misty Soutpansberg above Louis Trichardt to the lowveld near Barberton. It also occurs in Botswana and South West Africa but has not been recorded as growing wild in Zimbabwe.
Research has shown that Belt lotononis has resistance to root-knot nematode: Lotononis plants from various sources were established in pots, inoculated with nematode larvae and allowed to
grow for about three months. The roots were then washed free of soil and inspected. All plants not infected by the nematodes were transferred to the nursery. Seed was collected from these plants and the process repeated for three generations, by which time the population had developed a considerable degree of resistance.
Lotononis is a creeping prostrate perennial with shiny hairless stems up to 1,5m long. These stems root at the nodes so that the plants spread rapidly, especially on sandy soils. The leaves are trifoliate and the leaflets narrow, hairless and shiny. They vary greatly in size, being up to 5 cm long when the plants are growing vigorously. The inflorescence is a loose-ball of yellow flowers, carried well above the level of the leaves. The main flowering period is in September – October, with a subsidiary flush in March. The pods are about 1cm long and turn brown and split open as they dry. The seeds are very small and range in colour from yellow to almost black.
Lotononis is one of the most frost -tolerant of the sub-tropical legumes and plants usually have a few green leaves, even in the middle of the dry season. Lotononis grows following out-of-season rain, whereas most other pasture legumes and grasses remain dormant.
Lotononis usually starts growing in September, as the weather warms up, but the growth consists mainly of flowers. Rapid leaf growth only begins after the start of the rains. Ungrazed stands of Lotononis may grow as tall as 60 cm
In Queensland Lotononis is used mainly on the coastal alluvial sands. In Southern Africa, the establishment and spread has been most rapid on the sandy soils on sandy soils, the growth of Lotononis has been very variable, with high yields in one season sometimes followed by low yields the next. On heavier soils, establishment is slower but yields are rather more constant. Lotononis can tolerate a degree of water logging and has grown well on some vlei-margin sites where it uses moisture in the subsoil to make good early growth.
Lotononis is recommended for areas above 1 200m altitude receiving at least 750mm rain annually.
Seed of Lotononis is very small (about 3 300 per gram) and it must therefore be sown very near the surface. Broadcasting the seed on a firm, fine seedbed which has been rolled with a Cambridge roller and then covering the seed with a flat roller or by light brushing seems especially satisfactory. The recommended seed rate of Lotononis is 0,5 kg per ha, although even lower rates can be used when the Lotononis is mixed with other legumes.
Inoculation with the correct strain of rhizobium is essential for successful establishment of Lotononis.
Use and Management
Lotononis is best used in pastures which are to be grazed fairly hard in summer. If the pasture is allowed to grow too tall the low-growing Lotononis is often shaded out by the grass and disease can spread rapidly through a tall pasture during wet periods. Lotononis has not done well during wet seasons as it has been badly affected by disease. Australian experience, indicates that Lotononis is a useful pioneer legume and fills in gaps if a pasture is thinned by drought, fire or insect attack . For this reason the main role of Lotononis appears to be as a component in mixtures with one or more other legumes when sowing pastures which will be grazed during the growing season.
Seed is best collected in October and November as there is then little foliage to interfere with operations. Small amounts of seed can be reaped by hand, pulling off the clusters of pods as they ripen. Larger areas can be mown and the herbage spread on a tarpaulin or hard surface to dry. The pods shatter when dry and the seed can then be separated from the chaff by sieving. A combine harvester can also be used successfully for reaping large amounts of seed.
Australian estimates of seed yields average 56k kg per ha
Lotononis produces a high proportion of hard seed and this should be reduced before sowing. Mechanical scarification seems the most suitable method and all commercial seed is treated before sale.
SIRATRO (Macroptilium atropurpureum)
Siratro is unique among currently-used sub-tropical pasture legumes in that it is the only one which has been bred, rather than selected from naturally occurring material. Macroptilium atropurpureurn (of which Phaseolus atropurpureus is a synonym) is native to many countries in Central and South America but the two strains from which Siratro was bred were collected in Mexico.
Before the release of Siratro, M atropurpureurn had not been used as a pasture species.
Of the two parent lines of Siratro, one was prostrate stoloniferous while the other was more vigorous and produced greater seed yields. Dr Mark Hutton of the CSIRO Division of Tropical Pastures, Queensland, crossed these two lines and was able to combine the desirable features of both in the eventual cultivar Siratro but this involved a programme of continuing selection under grazing conditions spread over a number of years.
If Townsville stylo was the legume which got the
tropical pasture revolution going, it has largely been Siratro which kept it going. The popularity of Siratro is largely due to its versatility. In sub-tropical Australia, Siratro has proved adaptable to a wide range of soils and climatic conditions, and this adaptability has led to its success in many countries.
Siratro is a deep-rooted perennial with long trailing stems which root at the nodes or which can twine up tall vegetation. The trifoliate leaves are dark green slightly hairy on the upper surface and silvery green and very hairy on the underside. The lateral leaflets have characteristic lobes on their outer margins.
The flowers are purple, turning black with age, and up to twelve are borne on a single stalk, which projects above the level of the foliage. The main flowering period is in October-November with a subsidiary flush in March-April. The straight cylindrical pods are about 8cm long and split open (shatter) when dry. Each pod contains about 12 seeds, dark brown to black in colour.
The twining stems of Siratro enable it to grow over and smother weeds and small bushes. In pure stands Siratro may form a dense tangled mass of foliage about a meter high.
In frost-free areas Siratro may retain its leaves well into the dry season but in cold areas the leaves turn white and drop off before frosts are recorded. Severe frosts may kill the stems completely but new shoots develop from the crown at the onset of warm weather. Flowering shoots predominate and relatively little foliage is produced until after the start of the rains.
Siratro is adapted to a very wide range of soils, excluding only very poor sands and very heavy clays. It is probably the most versatile sub-tropical pasture legume in terms of soil requirements, but it cannot tolerate water logging.
Siratro grows best at higher temperatures and grows much less vigorously at relatively cool high-altitude sites. Siratro is recommended for areas below 1 500m altitude with a rainfall of at least 700 mm.
There are about 78 Siratro seeds per gram. This is comparatively large for pasture legume seed but, even so, Siratro should not be sown more than 1 cm deep. It can be sown broadcast on disced soil in veld improvement projects but drilling is always preferable to broadcasting, especially in stands intended for seed production, as weeds can then be controlled between the legume rows. Under seeding a maize crop is probably the best way to establish Siratro.
Seeding rate is 3-5kg for Siratro sown alone or 2-4kg per ha when sown with a grass.
Siratro nodulates readily with naturally occurring rhizobium on most soils in Central and Southern Africa so that inoculation is not likely to be necessary.
Use and Management
Siratro is best used as grazing during the growing and early dry season. Because it is defoliated by frost it is of little value as foggage grazing in the cooler areas. Siratro starts growth well before the start of the rains and can provide a valuable early green “bite” but grazing at that time reduces seed set and therefore seed reserves in the soil.
In Australia nearly all the experimental grazing of Siratro has been under set stocking and stocking rates greater than a steer to 0,6ha resulted in a decrease in density and the vigour of the Siratro plants. There are indications that this production is less severe under rotational grazing, especially with a long rest between grazings. However, because of the growth habit of Siratro it is inadvisable to graze the plants too short as this reduces the rate of re growth. The ideal seems to be to graze rotationally, preventing frequent or severe defoliation. This has the further advantage of allowing the plants to set seed and so augment seed reserves in the soil.
The flowers of Siratro are self-pollinated. The seed pods are borne well above the foliage and can be reaped easily by hand. The flowering period of Siratro is fairly prolonged, and to achieve maximum yields it is necessary to reap several times, taking on each occasion only the pods which are hard to the touch.
It is best to reap about every three weeks to prevent undue losses from pods shattering.
The seed pods should be spread in a shallow layer to dry and shatter, and they can then be separated from the seed by sieving.
Because flowering is spread over a fairly long period, reaping seed with a combine harvester collects only a proportion of the total seed set and yields therefore are low, averaging 110 to 170kg seed per ha. Hand reaping results in higher yields.
In Queensland it has been found that in the southern part of the state, where Siratro is widely grown as a pasture legume, seed yields are relatively low and fluctuate widely from year to year. In northern Queensland Siratro is grown successfully as a seed crop under irrigation in the dry season. The crop is irrigated once only and is then left to produce a flush of flowers. Three seed crops can be reaped in this way during the dry season and after the final one has been combined the shed seed is collected with a suction harvester. In this way seed yields of up to 1 000 kg per ha can be obtained.
Siratro commonly produces a high proportion of hard seed, especially in seed reaped by hand. All commercial seed is now scarified before sale: homegrown seed can be treated with concentrated sulphuric acid for 10 minutes or heated dry to 70°C for 6 hours.
Attack by bean fly maggot can greatly reduce the stand of Siratro seedlings. To prevent this, the seed must be treated with a suitable insecticide.
OXLEY FINE STEM STYLO (Stylosanthes guianensis var. intermedia)
This cultivar was collected by W. Hartley (an Australian Plant Introduction Officer) from sandy loam soil near Asuncion, Paraguay, in 1948. It was tested in Queensland and found to be well adapted to light-textured (usually granite) soils in a region with an annual rainfall of 700 to 1 250mm and subject to frosts (often severe) in winter.
Oxley is one of the four cultivars of Stylosanthes guianensis available in Australia but the other three (Schofield, Cook and Endeavour) are all strains of var, guianensis and are adapted to hotter, frost-free conditions in the wet tropics.
Fine-stem is a semi-prostrate perennial legume which does not root at the nodes. The stems are finer and the leaflets smaller, shinier and darker green than those of the other stylo cultivars. Fine-stem stylo forms a pronounced crown at or just below the soil surface. Consequently the stem bases and buds are protected and Fine-stem stylo is more tolerant of close grazing and of fire than the other stylos.
The flowers of Fine -stern stylo are bright yellow with fine red stripes on the standard. As it flowers under long-day conditions (and in this differs from the other stylo cultivars) flowers are borne throughout the summer months. Each inflorescence consists of a cluster of up to a dozen flowers, with the outside ones ripening first, so that each inflorescence is likely to contain seed of various stages of maturity and, quite likely, flowers and buds as well.
Fine-stem styo seems particularly adapted to granite sandy soils.
The minimum average annual rainfall for successful results with Fine-stem stylo is likely to be about 600 mm.
Although Fine-stem stylo will nodulate satisfactorily with native rhizobia on some soils, inoculation with the correct strain of rhizobium is recommended as an insurance against nodulation failure.
Fine-stem stylo is particularly suitable for veld reinforcement on virgin or reverted land. Soil disturbance before seeding is essential for good results and a disc harrow has proved to be a suitable implement. A reasonable tilth can be obtained with a single pass of the disc immediately after burning the top hamper under moist conditions, but two or even three diskings will be necessary if the soil is dry or if the stubble is left unburnt. The disced strips should cover one quarter to half of the total area.
It is important not to sow the seed more than 13 mm deep. A seed drill is ideal but seed can also be broadcast on freshly disced soil and then rolled in.
Seeding rate should be about 3kg per ha of disced strip.Fine-stem stylo can also be used on reverted land.
Use and Management
Veld reinforcement with Fine-stem stylo is best grazed in some form of rotational system. In the latter part of the wet season and during the dry season the stylo is selectively grazed and is likely to be harmed by continuous grazing. Stylo is easily shaded out if the associated grasses become too tall as happens if the veld is rested all summer and grazed in winter only.
The seeds in each inflorescence ripen in sequence and flowering occurs over the whole growing season so that at any one time only a small proportion of the total seed produced is being carried on the plant. Because of this, maximum seed yield is obtained by allowing all the seed to open and fall and then collecting it at the end of the season. On a small scale this can be done by hand, especially if plastic sheets or old fertilizer bags have been laid between the rows of plants. On a larger scale the seed can be sucked up by a machine like an overgrown vacuum cleaner and then separated from the trash and sand, or it can be reaped with a subterranean clover seed harvester which sucks up and cleans the seed in a single operation. Using these methods, seed yields of more than 1 000kg per ha are possible.
When buying Fine-stem stylo seed, one should ensure that it has been scarified. Hard seededness, may, however, remain a problem in home-grown seed and this can be overcome by treatment with concentrated sulphuric acid for 20 minutes or by soaking the seed in water at 55°C, also for 20 minutes. After treatment the seed should be allowed to dry thoroughly before it is rebagged.
KENYA WHITE CLOVER (Trifolium semipilosum var. glabrescens)
Kenya white clover is indigenous in upland grassland in Ethiopia, Kenya and Tanzania occurring at altitudes between 1 500 and 3 000 m. In appearance it is very similar to the European white clover (Trifolium repens) but it has a more strongly developed tap root and is therefore more drought-resistant. It is also
better adapted to acid and infertile soils than T. repens and the locally-selected cultivar has a degree of resistance to root-knot nematode.
Kenya white clover is a prostrate perennial legume with stems which root freely from the nodes. In grazed pastures individual clover plants intertwine, forming a dense mat. The leaves are trifoliate and in many plants there is a broad white mark along the midribs; a less common marking is a dark red inverted V.
The stems and flower stalks are covered with soft hairs. T he flower heads are similar to those of T. repens and contain about 20 flowers which may range in color from almost white to pale pink. The
flowers turn downwards when mature and the pods, which contain about 4 or 5 seeds, are brown when ripe. There are two main flowering periods, October-November and March-May.
Kenya white clover is best suited to the moist highland conditions.
The most important use of Kenya white clover is likely to be in irrigated pastures, where it mixes particularly well with Kikuyu grass.
Kenya white clover is very frost-hardy and if irrigated continues to grow, albeit slowly, right through the cold season.
There are about 1 000 seeds per gram and because the seeds are so small it is important not to sow them deeper than 1 cm. Seeds should be sown at the rate of 1.5 to 2 kg per ha, either in drills 30 to 50 cm apart or by broadcasting and rolling. Irrigated pastures are best established by planting Kikuyu grass in mid growing- season, cultivating to control weeds and then over seeding with clover in March- April or in August.
Strains of rhizobium effective on Kenya white clover do not occur naturally in Southern Africa soils so that inoculation with the correct strain of rhizobium is essential. This strain is not the same as that for European white clover.
Use and Management
In irrigated pastures Kenya white clover has combined particularly well with Kikuyu grass, forming a productive pasture which can stand heavy grazing and has a grazing season of about eight months of the year. If the pasture is, allowed to grow tall, the grass is apt to shade out the clover. Bloat has proved a problem on pastures containing Kenya white clover but the risk can be reduced by replacing susceptible animals and feeding a bloat preventative during danger periods. The main periods of risk appear to be October to December and in March,
Kenya white clover produces seed mainly during the short day conditions of the dry season. Pastures from which seed is to be reaped should be grazed flat in late February to give a short even re growth with the seed heads carried clear of the leaves. For small areas the ripe seed heads can be plucked by hand and later threshed with a slow-running hammer mill. Larger areas can be reaped with a combine harvester or the pasture mown when the seed is ripe, winnowed and then threshed when thoroughly dry. It should be possible to obtain two crops of seed during the dry season.
Seed yields should be of the order of 200-300kg per ha.
Kenya white clover contains a high proportion of hard seed and some form of seed treatment is advisable. Commercial seed is scarified before sale; small lots can be treated with concentrated sulphuric acid for 20 minutes.