Management of established pasture

Gideon Jordaan, Eastern Cape Province, Department of Agriculture, PO Box 284, Cradock, 5880

INTRODUCTION

The introduction of established pasture in goat farming can only be economically successful if it is accompanied by objective and healthy planning and a high standard of management. Established pasture that is tackled too hastily is certainly one of the quickest ways to financial ruin.

An important requirement for the successful implementation of established pasture is to determine the needs of the flock under normal conditions and then to address them in the most economical and practical way; in other words, do thorough fodder flow planning. To do a meaningful fodder flow planning needs an objective evaluation of the potential of the pasture in that specific situation. A solid basic knowledge of production and management practice of pasture is therefore the foundation for everything else.

In terms of established pasture, management includes the following – and not in any order of priority:

  • Resource survey – water, soil, machinery, etc.
  • Decide on a method of utilisation or purpose
  • Choice of crop
  • Establishment
  • Fertilisation
  • Irrigation
  • Grazing

 

Utilisation or purpose

Although it is sometimes said that pastures are used or should be used to stabilise extensive stock farming, it is in fact used to make a bigger profit; there are only different ways of approaching it:

The first approach is to keep more stock

The main disadvantages are:

  • higher capital costs
  • in cases of drought, there is an increase of vulnerability.

The biggest advantage is that this concept sounds good and that it can accomplish a quicker turnover.

 

The second approach is to use pastures to wean more kids

Advantage

  • smaller capital input
  • more robust farming that will survive drought more easily

 

Both these systems can be used to benefit from better marketing opportunities.

Generally speaking, the most economical way of implementing established pastures is to help the farmer wean more kids; in other words, to address seasonal feed shortages (excluding droughts), especially problems of quality.

Many reasons can be provided for feed shortages, but in the greatest part of this country, with an average rainfall of 250 mm, it is particularly a shortage of quality (energy intake) that occurs among ewes that kid during winter and spring.

 

Fertilisation

The economy of established pastures is largely influenced by fertilisation. If one remembers that the fertilising costs of an irrigated grass pasture can literally amount to 40% of the total annual costs, it is clear that the wrong choice can lead to great economic loss.

 

Fertilisation before establishment

A good starting point is to analyse the soil. If such results are available, it is possible to correct deficiencies before establishment.

 

Gypsum or lime

This is the best time to effectively apply gypsum or lime if the soil needs these minerals. Gypsum must be administered at least 6 weeks before planting. An analysis of the soil is necessary to determine the gypsum or lime needs in the soil.

 

Phosphorus (P)

Serious P-shortages cannot be fixed after establishment and soil analysis is therefore necessary. There are reasonable differences among species as regards their ability to take up P and thus their soil P need. It is common knowledge that legumes require a higher soil-P status than grasses.

The P-status of soil under irrigation should be:

  • 20 mg/kg for grass
  • 30 mg/kg for legumes and mixes

 

The reaction to P is normally most notable during times of stress, such as cold weather. This is an important fact as the stock load during such times is restricted by low feed supply. It is essential for the P status of the soil does not impact negatively on the plant growth.

P is also important for legumes and effective N-bonding. It not only affects the DM production of the mix, but also the rough protein content as well.

 

Potassium (K)

The soil in traditional goat farming areas does not normally have K deficiencies, but sometimes a cation imbalance can result in K not being readily available. This must be identified in a soil analysis so that it can be corrected. Potassium deficiencies occur regularly in areas with a higher rainfall (more than 700 mm).

 

Fertilising for maintenance

Phosphorus (P)

Ideally soil analysis should be done annually to determine the P-supplement. If this is impossible, the supplements can be calculated by looking at the amount of plant material that was produced the previous season. When the pasture was used for grazing, 70% and 80% of the extracted P will be replaced into the soil via animal urine and faeces. For any other loss, it is recommended that 40% of the extracted P be replaced artificially. A certain amount of P is also released through mineralisation.

The following table applies to pastures with different production levels (0,3% P)

  Grass Mixtures Legumes
6t DM/ha 7kg/ha 10kg/ha 12kg/ha
15t DM/ha 15kg/ha 20kg/ha 25kg/ha

 

 

Potassium (K)

Almost all the K that plants extract from the soil is excreted by the animals and returned to the soil when the pasture is used for grazing. In our area it is seldom necessary to apply K artificially. When hay is cut, about 15 kg K/ton hay is removed from the soil, necessitating regular soil analysis.

 

Nitrogen (N)

From a fertilising perspective, N fertilisation has the single greatest effect on the production of grazing and its rough protein content. Unfortunately N soil analyses are not undertaken regularly; a rather conservative approach to nitrogen fertilisation is therefore essential. A very useful guide is that pastures need about 30 kg N per ton DM produced. Irrigated pastures (15-18 t DM/ha) therefore require 450 - 540 kg N/ha. Dry land pastures (production potential of 6-8 DM/ha) require 180-240 kg N/ha.

Fortunately an average of 120 kg N/ha is annually replaced into the soil by the mineralisation of organic material and effectively recycled through animals grazing there. The contribution by legumes is less under dry land conditions, probably an effective 60 kg N/ha annually. Grass grazing and a grass clover mix that both produce 8 t DM/ha will need 120 kg N and 60 kg N/ha respectively. Dry land grass pastures will annually need between 60 and 120kg N/ha for optimal production, while a grass clover mix annually needs between 0 and 60kg N/ha.

It remains difficult to determine the level of N fertilisation, so it is necessary to monitor the grazing production to determine if the desired goal has been achieved. The annual number of N applications and their distribution are determined by various factors, among which are feeding needs, growing season and the desired production. The application normally varies between 50 and 75 kg N/ha at a time. Pastures utilise N best during the peak growing season. Do not apply N during June / July – all you will gain is a little better quality.

It is important to realise that, even though fertilisation is the most expensive part in the production of established pastures, it cannot simply be ignored or excluded. Consult an expert in this field applying too little or too much fertiliser; too little fertiliser can also be a waste of money.

 

Irrigation

Considering that there is a large number of commercial goat flocks in the more arid regions of South Africa, it is necessary to give attention to the irrigation management of grazing.

Proper irrigation just after sowing plays an important role in the efficient germination and establishment and therefore on the subsequent production of irrigated grazing. For newly sowed or established grazing, sprinkle irrigation is the best method because the fine seeds and young plants have a lesser chance of being washed out; when more than 25 mm is applied, as usually happens in flood irrigation, it is unnecessary and in fact a waste of water. The amount of water applied during irrigation can only be accurately managed by sprinkle irrigation. Highly productive grazing, such grass clover grazing, usually needs approximately 800 to 1 200 mm of water per ha per year.

Where flood irrigation is used, approximately 30% more water must be applied to realise the same amount of production. This amount varies according to the improvement in the effectiveness of the system. To cultivate the best grazing effectively with flood irrigation, the beds must be short (100-150 m) and narrow (10-12 m) with a relatively steep slope.

There are big differences in the effectiveness with which plants utilise moisture. The following is a guideline of the effective water utilisation of grazing crops (ml water / gram dry material):

  • Lucerne 750
  • Underground clover 550
  • Rye-grass 450

 

 

Frequency of irrigation

The correct way of irrigation is to irrigate when 50% of the available moisture in the effective root zone has been extracted and then again up to field capacity. Most grazing plants have shallow root systems and therefore the effective root depth is taken as 30 cm; this means the irrigation frequency can become high. When irrigated grazing is used directly by animals, it is necessary for timing irrigation and grazing so that there is enough time for the soil to dry before grazing. Wet soil is subject to compaction because of tread action - direct damage of plants because of treading and therefore a higher loss of plant material. The following simplified schedule explains this:

  SPRINKLE FLOOD
AUTUMN 25mm/week 50mm/2 weeks
WINTER 25mm/week 50mm/3 weeks
SPRING 25mm/week 50mm/2 weeks
SUMMER 50mm/week 50mm/week

This schedule works very well when a 21-day resting period between grazing is allowed.

All intensive grazing (in fact, all plants) sacrifices vegetative growth or production if it suffers moisture stress.

 

Grazing

The fodder value of grazing is mainly determined by two factors, namely the nutritional value and intake. Animal intake must be high for effective pasture use. Intake is influenced by the following factors, among others:

  • The animals’ grazing habits - election
  • grazing time
  • number of bites
  • Acceptability of the grazing - physical characteristics
  • chemical characteristics

All the plant characteristics above that can have a positive impact on intake occur in strong, growing plants. Management is basically the farmer’s actions to ensure vigorous growth in grazing; in other words, fertilising, irrigation and grazing.

 

Utilisation after establishment

Established pastures must not be used too soon after establishment, but in the case of fast growing kinds (yearlings) it can be a disadvantage to wait too long. A guideline is to graze high producing pastures six to eight weeks after establishment. A golden rule is to treat established pastures to the best advantage as possible in the early stadium.

Utilisation can be used in one of two ways:

1. Permanent grazing

The result of permanent grazing depends on the type of animal used, the stock load and the species composition of the grazing. The chances of success on permanent grazing are better with cattle and goats than with sheep, and on single species rather than mixed grazing. A major problem with permanent grazing is selective grazing that can lead to lower grazing production and the intrusion of unwanted plants. The creation of established pasture is a costly process and thus maximum returns must be aimed at. This is why permanent grazing is not recommended.

 

2. Rotation pastures

Rotation pastures is the most common system used on established pastures. The rate of rotating high producing pastures should be quick, with relatively short grazing and rest-periods. Grazing periods can be between 3 to 7 days with resting periods of 20 – 30 days. This means that at least 4, but preferably 8, camps should be provided per flock.

Rotation pastures has numerous advantages for established pastures. It creates an opportunity for using higher stock density to combat selective grazing and to obtain more complete utilisation. It offers an opportunity to reserve certain camps for hay and silage in times of overproduction. The rest-periods give plants a chance to recover well after heavy defoliation. However, beware of making the rest-periods too long; it may be detrimental since it can lead to a loss of quality, while great losses can be incurred by trampling in long grazing.

A more intensive form of rotation pastures is strip grazing. Strip grazing entails temporarily fencing off strips of pasture with electrified fencing. Stock is then limited to a small section of pasture until it has been adequately utilised before moving the animals on to a next strip. Animals are frequently kept for only part of the day in such a strip. Strip grazing is thus a very intensive form of rotation pastures that requires effective management and continuous attention and interest. Strip grazing can render a very high animal production from irrigated pastures. Because animals are prevented from roaming around, wasted energy and waste due to trampling are minimal.

Cradock Experimental Farm March 2008

 

References

Dannhauser CS. 1991. Die Bestuur van Aangeplante Weiding in die Somerreënvaldele. Pietersburg: Review Drukkers.

Dickinson EB, Hyam GFS & Breytenbach WAS. 1990. (eds.) Die Kynoch Weidingshandleiding. Wendywood: Keyser Versfeld.