Veld Conditions

1. INTRODUCTION

One very important factor in veld management is that the farmer should look at his veld and be able to assess its condition. Is it in good condition, or is it suffering from overgrazing, over burning or other practices which are bad management? This lecture gives you a method for assessing the quality of veld, and tells you how to fill in a Veld Condition Score Sheet.

2. PATTERN OF DETERIORATION OF THE VELD

The deterioration of natural grazing land through over-frequent burning or overgrazing – or a combination of these factors – usually takes place in the following order.

• An adverse change occurs in the species composition of the veld. The original stand of closely spaced, vigorous perennial grasses which provide an almost complete cover of litter between the grass bases deteriorates, frequently by reduction in the number of palatable species and a corresponding reduction in the total number of species present.

• The vigour of perennial grasses declines and many of the larger tufts die. Death commonly develops from the centre of the tufts outwards, often leaving charred stumps visible at the base of the tufts. Fewer seedlings of the desirable perennial species survive, while undesirable perennial and annual grass species increase in number.

• In consequence, the amount of litter and soil cover decreases, thus exposing the soil surface to excessive raindrop action; the soil surface becomes compacted and runoff and sheet erosion become evident. Litter is caught up between the grass tufts, forming alluvial deposits or litter fans.

• Water infiltration into the soil is reduced and further destruction of perennial grass species follows; the amount of bare ground increases, sheet erosion is accelerated and, on some soil types, erosion pedestals and erosion pavements develop. In locations favourable for the growth of shrubs and trees, woody vegetation begins to colonize the bare patches of ground.

• Patches of bare soil become larger, the soil surface becomes compacted, infiltration decreases further, and run off and erosion increase. Grass pedestals often become more obvious, the sides of the pedestals being sharply defined and vertical. Erosion pavements become more pronounced and, as the infiltration of rain water diminishes, the vigour of grasses is further reduced. Bush encroachment is accelerated; grasses at this stage are predominantly annual species. A further complication is provided by an apparent increase in the activities of harvester termites, whose importance increases as the productivity of the habitat declines.

• Run-off and the incidence of induced drought conditions continue to develop; sheet and gully erosion becomes more widespread and streams, once permanent, become intermittent.

• In the latter stages trees die, desert conditions develop and any thought of production based on the use of the natural grazing has to be abandoned. All too frequently, ranchers become aware of the seriousness of the problem only when reclamation measures have become excessively expensive. The bush has by this time taken over large tracts of natural grazing land, erosion is severe and available surface water supplies have been severely reduced.

The above sequence of degradation is probably familiar to all persons concerned with the application of sound veld management practices, but is repeated here to indicate that all the danger signs can easily be identified by those wishing to look “into” rather than “at” the existing veld grazing conditions.

Because of the extremely complex nature of the grass associations, existing methods of statistically analyzing veld conditions – in particular species composition and basal cover – are extremely tedious and beyond the capabilities of the average extension officer or farmer.

On the other hand, we have become so obsessed with the need for statistical proof of range trends, that we have been reluctant to take a very close look at veld conditions and have rather looked to a series of thumb rules to sort out the veld management decisions that face us.

The veld condition score sheet given in this lecture can be used as a check list of Range Characteristics. These must be observed by farmers and extension officers, as they will enable trends in veld condition to be assessed; deterioration can be observed at an early stage and corrective veld management practices applied.

3. THE VELD CONDITION SCORE SHEET

The Veld Condition Score Sheet involves a very subjective assessment of:

• Grass species composition;

• Basal cover;

• Plant vigour and forage production;

• Litter or plant residue;

• Soil compaction and erosion.

SITE SELECTION

Variations in grass communities occur within a single veld type – or within a single paddock – and the siting of survey positions therefore deserve particular attention.

It is recommended that three or four sites which are considered to be reasonably typical of the veld condition in a particular paddock should be selected rather than the selection of one site in each of three or four paddocks. Alternatively, specific communities considered to be sensitive or to reflect different stages in the plant succession may be selected, on the assumption that trends will show up sooner at these sites.

It is possible that certain sections of a camp could deteriorate through over-grazing due to proximity to water supplies, while other parts of the camp show no signs of deterioration. Thus proximity to cattle routes, water points and feed bins must also be taken into consideration in the siting of survey positions.

Because of the sometimes abrupt change from one community to the next within a single veld type, the range assessment site must be restricted to a radius of five-yards, and the centre point must be plotted very accurately.

A very quick method of recording these sites, is to plot the positions on an aerial photograph and to take the distance and compass bearing to a suitable bench mark, for example an easily identified tree, rock, or fence post. Fixed point photography is also a useful method of confirming that follow-up surveys are made at the same point.

The number of sites per camp, and camps per farm to be studied, will depend on the objectives of the survey and the time available to the extension officer.

4. GRASS SPECIES COMPOSITION

An essential pre-requisite before any attempt at judging condition and trend is concerned, is a good knowledge of the flora of the area. At least the principal species of the main vegetation types should be readily identified, and their ecological significance recognized.

The following list may be used as an aid in assessing the ecological significance of the species composition. This list classifies all the species into “decreasers”, “increasers” and “pioneer”, and should be useful in deciding which the climax constituents are. The word “climax” is used to denote the type of grass cover which develops under relatively undisturbed conditions and will remain fairly stable under light to medium stocking rates.

It is necessary to know the percentage that each species of grass contributes to the total and then to ascertain how far these figures differ from those of the “climax” or desired stable sub-climax vegetation. At each site the relative proportions of the various grasses within a five yard radius are estimated visually. While this is a very subjective assessment, different operators – provided that they can identify all the main grasses present whether in seed or not – should arrive at approximately the same proportions. The main grass species can then be subdivided into “decreases” – desirable species likely to decrease with heavy grazing pressure, “increasers” – intermediate species likely to increase with heavy grazing and “pioneer or invader species” – early successional species.

The following charts show the preliminary classification of grasses into the above categories. For grasses not shown on these charts Rattray’s bulletin on “The Habit, distribution, habitat, forage value and veld indicator value of the commoner Zimbabwean grasses” has a much more comprehensive list and should be used to decide in which category to place the grasses.

From the estimated proportions of the various grasses and the above classification, the species composition of the veld at the particular site can be scored in the following way: (see page 6)

5. BASAL COVER OR PLANT DENSITY

The use of a density index to evaluate range condition is a simple criterion which is easy to apply, but there is no information at present available to indicate what the maximum or optimum density of cover for any particular veld type should be. However, significant changes in density can be detected, by surveys repeated in the same locality every two to three years.

Since basal cover tends to vary between one per cent on poor sites to 12 per cent on relatively good sites. A large number of recordings with the random dart or step point methods would have to be made to obtain a reliable estimate of the basal cover. For the veld condition score card, a simple visual assessment of the basal cover is suggested.

This assessment is modified for annual or invader species since these plants seldom provide all year round protection to the soil surface.

Basal Cover		Points
Excellent	Cover is maximum for site and species. Plants are evenly and closely spaced with no bare areas.	9 – 10
Good	Cover is still good but there may be occasional bare spots or “skips”. These may or may not be covered with annuals or invader plants.	7 – 8
Fair	Cover thin and patchy with spaces filled by weeds or annuals, or density may be high if cover is made up of running or sod grasses or other close growing invader plants.	5 – 6
Poor	This may give a wide range of density depending on the number and kind of invader and other undesirable species	3 – 4
Very Poor	Very Sparse cover	1 – 2

6. PLANT VIGOUR AND FORAGE PRODUCTION

In judging vigour, characteristics such as plant size, leaf size, colour number and size of seed heads, root systems, and growth forms, age distribution of plants and, earliness of growth are considered. This will not be easy for the layman to assess. However, age distribution of plants, die back on the larger tufts, and the ratio of estimated carrying capacity to potential carrying capacity under the best possible management – including bush control – could be used as a guide to assessing plant vigour and forage production.

Here 1:8 was assumed to be the highest carrying capacity that could be expected from that particular area under the best management conditions including bush control.

If, for example, the highest carrying capacity that could be expected from an area was assumed to be 1:3 and the present carrying capacity was assessed at 1:5, the percentage of possible forage production would be 3/5 x 100 = 60 per cent. The veld would therefore be given a point score of 6 for forage production.

A brief description of seedling development age distribution of plants and “die back” on the perennial tufts must also be recorded on the veld condition score sheet.

7. LITTER AND PLANT RESIDUES

Litter protects the soil surface from erosion, reduces run off, controls ground temperatures and evaporation and forms a protective mulch for seedlings.

Even in the absence of fire or termite activity which prevent any accumulation of litter, a high proportion of the grass litter laid down during the dry season is lost through natural oxidization processes by the middle of the following rainy season. However, even temporary litter protection in the hot dry season and the early rainy season must be beneficial in reducing ground temperatures, evaporation and run off. Accumulations of plant litter are therefore considered to be indicative of an improvement in range condition, and the quantities present can therefore be rated in order to assess the condition class.

The table below shows the % of ground surface covered by litter or plant residue

		Points
Excellent	Abundant residue or litter, detached and evenly distributed. It should be made up both fresh and partly decomposed plant residues. Desirable grass species should make up most of the litter. 90 – 100 % litter cover	9 – 10
Good	Moderate amount of litter which may not necessarily be evenly distributed and may be partly made up from non forage species. 70 – 80 % litter cover.	7 – 8
Fair	Litter inadequate, scattered and very unevenly distributed. Undesirable plants and or invader will make up a moderate proportion of the litter. 50 – 60 % litter cover	5 – 6
Poor	Inadequate litter unless made up of residue from weeds, invaders of poor forage value and tree leaves. 30 – 40 % litter cover	3 – 4
Very Poor	Negligible grass litter cover – less than 20 % litter cover	1 – 2

8. SOIL COMPACTION AND EROSION

This is considered by some American technicians as the most important of all the criteria used for judging condition. It takes into account the amount of soil movement; effectiveness of plant and litter cover protecting the soil; degree of soil compaction; size and shape of erosion pedestals; presence or absence of alluvial deposits; gullies; erosion pavements and condition of run-off water. All these factors are used to determine the condition class.

Any indication of excessive run-off must be viewed with alarm, particularly in the low rainfall areas, since this reflects a marked reduction in the effective rainfall and therefore in potential forage production.

Where the topsoil horizon is extremely compacted or alternatively where there is a significant surface crust, run-off is likely to be excessive even though soil erosion may be slight. In such cases, the soil compaction and erosion rating would be lowered even though soil movement is not obvious.

Litter piling up against plants forming miniature alluvial fans is an early indication of run-off. These alluvial fans tend to become the starting point for erosion pavements. Soil is caught up behind the litter barrier while sheet erosion takes place immediately below, thus transforming the soil surface into a series of very small steps or pavements.

The incidence, size and shape of plant pedestals can also be used as an indication of unfavorable soil conditions. Pedestals can be formed by ants carrying soil up into the grass tufts, by soil being washed away from the base of tufts and by raindrop action, whereby soil particles are splashed up on to the leaves and subsequently washed down into the base of the plants. Where the pedestals are numerous and steep sided, and grass roots are exposed at the soil surface, water and soil loss has obviously been excessive.

Very muddy run-off water gullies, silt deposit in dams and streams, and an intermittent flow in rivers that were once considered to be perennial, are all indications of the seriousness of erosion in our grazing areas.

SOIL COMPACTION AND EROSION	Points
Excellent: No evidence of soil movement; plant cover and litter effective in
protecting soil; run off is clear, no piling up of litter behind plants; gullies – if	9 – 10
present – completely stabilized and healed.
Good: Soil movement slight but difficult to recognize; plant cover and litter appear
to be effective in protecting soil; plant pedestals few or sloping sided and stabilized;	7 – 8
alluvial deposits and gullies – if present – are nearly healed; some litter may have piled against plants forming miniature alluvial fans; no noticeable compaction.

	SOIL COMPACTION AND EROSION	Points
	Fair: Soil movement moderate, but definitely discernible. May be accelerated in
	some places but stable elsewhere; plant cover and litter effectiveness doubtful;
	considerable quantities of bare soil; many plant pedestals, some steep-sided;	5 – 6
	erosion pavement forming; occasional alluvial deposits and rills present; gullies – if present – not raw; soil compaction noticeable, but not excessive; run-off water murky.
	Poor: Soil movement advanced. Plant cover and litter definitely not effective in
	preventing soil movement. Considerable quantities of bare soil; plant pedestals	3 – 4
	numerous and steep sided; stony soils with well-formed erosion pavement; rills
	and alluvial deposits common; gullies – if present – raw sided, compaction
	common; run-off water muddy

9. ASSESSMENT OF RANGE TREND

An upward trend is reflected by the appearance of a high proportion of seedlings or young plants of desirable species. Perennial species either recolonise the bare patches or germinate in the dying tufts of less desirable species, e.g. Heteropogon contortus seedlings growing out of Microchloa kunthii tufts. In addition there may be a litter build up between tufts, with a reduction in erosion.

A downward trend is reflected by a high proportion of dead or dying tufts, high steep sided plant pedestals with roots exposed, and an increase in pioneer or invader species. Termite activity could be high. The soil surface would be exposed with no litter accumulation. In addition to the assessments of species composition, basal cover, forage production, litter or plant residue, soil compaction and erosion, a brief description of the tree/grass relationships must be included on the Veld Condition Score Sheet. Here the physiognomic type which indicates the general structure of the vegetation, the dominant tree species and bush encroachment or coppice development is recorded.

Finally, termite activity must be noted. Of the two main types of termites which damage the veld, the harvester, which works mainly during the day and appears through a small harvesting hole in the soil, does more damage than the type which builds ant heaps and works mainly at night.

10. SUMMARY

Veld deterioration is generally a slow process but, too frequently, extension officers and farmers become aware of the problem only when conditions become extremely critical and the rate of deterioration has accelerated. Most of the danger signs can be observed at a relatively early stage by those wishing to look “into” rather than “at” the existing veld grazing conditions.

The Veld Condition score sheet is designed to give extension officers and farmers a check list of characteristics to look for in natural grazing land so that where trends are downward, corrective measures can be adopted at an early stage, before expensive reclamation measures are required.

Where survey sites are accurately plotted repeat surveys every two to three years should be made to check trend assessments at these sites.

The relative importance of species composition as compared with the other veld condition characteristics can be argued. For convenience, the different characteristics have all been given a 1 to 10 point rating. It is also noteworthy that different characteristics influence each other. For example, poor basal cover could result in poor litter protection which results in increased soil compaction and erosion. This may provide an argument in favour of altering the point ratings for the different characteristics.

Finally, the Veld Condition score sheet could be used as a basis for farmer veld judging competitions.