agricultural production guidelines
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Veld in KwaZulu-Natal
Co-ordinated Extension KwaZulu-Natal Veld 3.2 1999
INTRODUCTION TO VELD MANAGEMENT PRINCIPLES
J M B Smith
KwaZulu-Natal Department of Agriculture
Grazing Systems
Veld Management Principles
There are numerous grazing systems including: continuous grazing, rotational resting, rotational grazing and rotational resting and grazing. Their applicability will depend on the veld type, veld condition, livestock system and level of management. Each of these grazing systems is described below.
Continuous grazing
One camp is allocated to each group of animals. Stocking rate should be conservative to reduce the pressure on the palatable species, but this inevitably leads to selective grazing and a deterioration in veld condition.Rotational grazing
More than one camp is allocated to each group of animals. More efficient utilisation of the herbage is possible with less selective grazing taking place because the herd now grazes in smaller sub-divisions. Fire can be introduced as a management tool. The grazing intensity can be regulated by adjusting the period of occupation.A number of different methods of applying rotational grazing have been developed, depending on the objectives of the grazing system. These are:
- Non-selective grazing (NSG). This system is also known as high utilisation grazing (HUG), where the herbage utilization in a camp is maximised. High stocking density and grazing intensity are used to force animals to graze even the unpalatable species. This is of applicability mainly in the sourveld.
- Controlled selective grazing (CSG)
. Also known as high production grazing (HPG). Stocking rate and grazing intensity are based on the response of palatable plants to grazing. Animals are not forced to graze the unpalatable plants, which eventually become moribund and die. This system was widely advocated for the mixed veld.. In this system animals remain in a camp for a short period to prevent grass plants being grazed more than once while the animals are in the camp i.e. during the period of stay. The grass is then allowed to recover, while the animals are in the remaining camps of the system (during the period of absence), before the next period of stay.
- Short duration grazing (SDG)
Flexible grazing system. In this system the area to be grazed is normally divided into four cells or blocks, each cell having a number of camps. One of the cells is rested (in rotation) each growing season in rotation and burnt in the spring of the following season. Camps in this cell then become the priority camps and are grazed whenever the desirable grasses are ready to be grazed, irrespective of the amount of forage in camps of the other cells in the system. Cell number two, which was burnt the previous year, receives second priority, while cell number three, which was burnt two years previously, would be priority number three in the grazing rotation. The fourth cell would be rested.
For a successful veld management system a number of principles should be applied. These are:
- Separate veld type units (VTU’s). Areas with different palatability and grazing potential should be fenced off separately. This will depend on aspect, slope, soil type and rainfall. Small areas of sourveld could be included in a sweetveld camp, but not vice versa.
- Grazing capacity. Stocking within the grazing capacity of the veld is one of the most important grazing principles. Failing to stock correctly irrespective of how diligently the other principles are applied, will lead to veld deterioration. Assessing the grazing capacity of each VTU will assist the farmer in deciding on an appropriate stocking rate for each VTU.
- Resting of veld
. Frequent, intense grazing reduces grass vigour and yield. In order to maintain the vigour of the veld, it is necessary to rest the vegetation at certain critical growth stages, irrespective of the type of grazing system. The frequency and duration of these rests will depend on the nature and condition of the veld, whether the veld is grazed by cattle or sheep or both. Normally, veld grazed by cattle should receive a full season's rest once in four years.
- Period of stay. The number of days stock are kept in a camp (the period of stay) should be controlled, so that grazing of regrowth during the period of stay and grazing intensity are reduced to a minimum. The period of stay would vary according to the stocking density, the veld type, quantity of grass available and the growth rate of the palatable grasses. The period of stay in a camp should be 5-7 days in the sourveld, 7-14 days in the mixed veld and 14-21 days in sweetveld.
- Period of absence. After grass has been grazed, it initially grows slowly before entering a rapid phase of growth. After this phase, growth slows down and reserves are replenished. As grass grows out, its quality deteriorates. This occurs rapidly in sourveld and more slowly in sweetveld. The period of absence, therefore, should be relatively short in sourveld and much longer in sweetveld. In sourveld this period should be 25-35 days, in mixed veld about 42 days and the sweetveld 56-70 days.
- Grazing cycle. The grazing cycle is the addition of the periods of stay and absence and is the time taken for a group of animals to graze through a set number of camps. The grazing cycle should vary according to the veld type, i.e. 30 days for sourveld, 56 days for mixed veld and 70 days for sweetveld. Ideally the grazing cycle should be flexible and adjusted according to the growth of grass.
The grazing cycle should be used to calculate the period of stay in a particular camp in the cycle, particularly if the sizes of camps, which have been allocated to a particular group of animals, vary. To calculate the period of stay for a particular camp using the grazing cycle as a basis, the following information is required:
A: the number of AU that can be carried in the camp i.e. the area (ha) of the camp divided by the grazing capacity (ha/AU) of the camp; and
B: the number of AU that can be carried in all the camps allocated to the particular group of animals excluding the rested camps. The period of stay is them calculated as:
the grazing cycle x A/B (where A and B are given above).
Prevent top hamper accumulation. Due to selective grazing, unpalatable residual herbage accumulates and becomes moribund. The use of supplementary licks would partly overcome the problem by stimulating the animals to consume more of the low quality herbage than they would have had the lick not been provided. Where the top hamper accumulation does occur the herbage should be removed by burning or mowing whenever it becomes necessary. A camp requires burning if more than half of the previous season’s growth remains after winter. This applies particularly to sourveld. Rested veld should also be burnt before the next grazing season commences.
- Bush encroachment. In the savanna areas, where bush is either encroaching or thickening up, preventative measures are necessary. This should take the form of a hot burn where herbage fuel is sufficient, and/or the use of browsing animals, or chemical control.
- Livestock ratio. To ensure better veld utilisation where cattle and sheep are grazed they should be run together in a ratio of at least 1 AU of cattle to every AU of sheep (approximately 5 sheep) or at a ratio which favours cattle.
- Stocking intensity in multi-camp systems. In the operation of a multi-camp system, in particular where the camps vary in size, it is necessary to ensure that the stocking intensity for all camps is similar. If this is not done the grazing pressure on the veld could be too severe and animal performance could suffer.
The stocking intensity refers to the number of Animal Unit (AU) days of grazing per hectare in a camp during the period of stay. The stocking intensity is calculated by multiplying the number of AU allocated to the camp, by the number of days they are in a camp, and dividing by the area of the camp. For example, where 100 AU graze a camp of 50 ha for a 10 day period of stay:
Stocking intensity = (100 AU x 10 days) over 50 ha
= 20 AU days/ha or 20 grazing days/ha per period of stay.
The grazing manager is often uncertain as to whether the period of stay, period of absence or grazing cycle should be kept constant with varying number of camps in a grazing system. The effect on the stocking intensity is very important, as is illustrated in the following example where 30 AU graze 120 ha of land using either 2, 4 or eight-camps. The grazing cycle should be 56 days and period of stay or occupation 14 days. The effects of maintaining either the period of stay, period of absence, or the grazing cycle constant is illustrated in Tables 1, 2 and 3.
The stocking intensity in the eight-camp system is too great and the animal performance will suffer. Animals would perform best in the two-camp system.
The stocking intensity is now greatest in the two-camp system and animals will perform best in the eight-camp system.
Table 1. Maintaining the period of stay (Days in) constant.
Number
of
campsDays
inDays
outGrazing
cycle
(days)Stocking intensity
(Grazing days per ha
per period of stay)2
4
8
14
14
14
14
42
98
28
56
112
7*
14
28
* 30 AU x 14 days/60 ha
When the grazing cycle is kept constant for the different number of camps in a system, the stocking intensity will be the same for each camp. However, in the example it is obvious that the period of stay in the two-camp system is too long. In the short term, however, animal production will be very similar for each camping system.
Table 2. Maintaining the period of absence constant.
Number
of
campsDays
inDays
outCycle
(days)Stocking intensity
(Grazing days per ha per period of stay)2
4
8
42
14
6
42
42
42
84
56
48
21*
14
12
* 30 AU x 42/60ha
Table 3. Maintaining the grazing cycle constant.
Number
of
campsDays
inDays
outCycle (days)
Stocking intensity
(Grazing days per ha per period of stay)2
4
8
28
14
7
28
42
48
56
56
56
14*
14
14
* 30 AU x 28 days/60ha