- Practical guidelines for the establishment of Old Man\'s Saltbush in Winter Rainfall Regions
|Last update: August 12, 2011 03:41:17 PM|
Practical guidelines for the establishment of Old Man’s Saltbush in Winter Rainfall Regions
INTRODUCTION TO OLD MAN'S SALTBUSH
Old man's saltbush (A triplex nummularia) is a greyish green shrub and is a well-known fodder plant in South Africa. It is indigenous to Australia, but is planted on a large scale worldwide. Although old man's saltbush is primarily a Mediterranean plant, it grows well in a wide variety of climates.
Since numerous articles on old man's saltbush have been published (see references), this guide will only briefly deal with aspects such as nutritional value, possible applications and carrying capacity. The object of this publication is to provide guidelines for the successful establishment of old man's saltbush in winter rainfall regions.
The nutrient value of old man's saltbush varies according to the method of sampling. As a general guideline, the crude protein content can be taken to be between 16 and 20 % while the total digestible nutrients (TDN) are in the vicinity of 40 %. Although the protein content is sufficient for ruminants in production, the TDN is not sufficient. Old man's saltbush should therefore be seen as a fodder mainly suitable for maintenance. In the case of animals in production, an energy supplement will be necessary for satisfactory results.
In winter rainfall regions small stock are usually under stress in the last weeks of pregnancy because of a lack of quality grazing. Despite the TDN being low, the introduction of old man's saltbush pastures during this critical period will result in a substantial improvement in feeding conditions.
ACCEPTABILITY TO RUMINANTS
The palatability of old man's saltbush varies greatly, depending on soil type: the higher the salt contents of the soil, the less palatable the plants. A high intake of salt (when drinking water also has a high saline content) limits the intake of old man's saltbush. It has, however, been established by Hoon & King (1993) that supplementation of American aloe (Agave) greatly increased the intake by sheep of old man's saltbush, resulting in increased performance. Although no scientific trials have been conducted, farmers have found that animals perform better on old man's saltbush when they have access to cereal straw or hay.
In areas where the salt content of soils is low, stock relish saltbush and intakes are high enough to obtain a moderate increase in body mass. When grazing is scarce, even the least palatable stands of old man's saltbush are utilised by ruminants without any apparent negative effects. However, breeds differ. If the saline content of the soil and drinking water is high, the intake of Angoras and Merinos can be low enough for the animals to die.
As a fodder plant old man's saltbush plays an important role by supplying a substantial amount of green material during the dry season. It is thus possible to move a large number of animals from the veld onto saltbush pasture. As it is only necessary to establish old man's saltbush once, it has a cost benefit in relation to most other pastures. The plant also has a low water requirement. According to De Kock (1980) old man's saltbush requires only 304 kg of water to produce one kg of dry material compared to lucerne that requires 750 kg. Old man's saltbush is thus capable of continuing production under relatively dry conditions.
Old man's saltbush can provide shelter during lambing or after shearing. It also provides shade i n summer.
ense stands of saltbush can be used to prevent wind and water erosion. On the West coast of South Africa wind erosion has been largely eliminated by planting old man's saltbush as windbreaks. At the same time these windbreaks, in combination with cereal residues, supply valuable summer grazing.
The old man's saltbush plants provide excellent firewood. The plant has the ability to regrow to its former size within a few months and can therefore be cut every second or third year, depending on regrowth and demand. As soon as stock has removed all the leaves from the branches, they can be harvested. Under favourable conditions the plants should reach their previous height within 8 months.
The carrying capacity of old man's saltbush depends largely on soil type, depth and rainfall. Under dryland conditions and a rainfall varying between 125 and 200 mm/year on the West coast, carrying capacities of between 700 and 2 800 sheep grazing days/ha have been achieved. Even at a modest 700 sheep grazing days/ha the carrying capacity of old man's saltbush is much higher than that of natural veld in the winter rainfall regions. On experimental plots on the West coast the carrying capacity of old man's saltbush was 10 to 20 times higher than natural veld on the same soil and with the same rainfall.
In Table 1 the carrying capacity of old man's saltbush is compared with that of various fodder crops. From Table 1 it is evident that the carrying capacity of old man's saltbush compares favourably with that of annual fodder crops. The daily gain on saltbush was lower, but the benefit of old man's saltbush lies in the low production cost, low water consumption and its hardiness.
PRACTICAL METHODS FOR PLANTING OLD MAN'S SALTBUSH
As has previously been stated, the main object of this guide is to provide guidelines for the successful establishment of old man's saltbush in the winter rainfall areas. The guidelines take the form of a recipe, to be implemented judiciously according to seasonal climatic conditions, soil types and long term rainfall means. This recipe is the result of many years' experience in the low rainfall areas along the West coast of South Africa and can be recommended with confidence for all winter rainfall regions with a rainfall of 125 mm/year or more. Establishment percentages of more than 95 % can, without exception, be obtained if the correct procedures are followed.
Originally the planting of old man's saltbush was a costly and time-consuming process for the following reasons:
The plants were propagated in plastic bags, making it difficult to transport them in large numbers. This problem was overcome when it was found that plants could be grown in seedbeds and transported in bundles in wet hessian grain bags. This makes it possible to transport up to 20000 plants in a normal pickup.
Initially all plants were watered at transplanting. This was, however, a labour intensive process and time consuming. A significant breakthrough was the discovery that planting could be highly successful without any watering as long as certain aspects, to be discussed later, were observed.
The transplanting itself was very labour intensive. In particular, farmers in the extensive sheep farming areas did not have sufficient labourers to plant on a large scale. Some farmers in the higher rainfall areas used mechanical rooibos tea planters, but the latter were not suitable for the lower rainfall areas. A special planter, cheap and relatively easy to build and that could plant the seedlings deeply enough, was developed, Two rows could be planted simultaneously and with only three labourers, 2500 plants/h could be planted. The development of this system has resulted in a dramatic increase in the establishment of old man's saltbush.
Foto: Salt bush planter
PRINCIPLES ON WHICH THE GUIDELINES ARE BASED
Seedlings must be hardy with preferably only one stem.
Soil preparation before planting must commence early in the rainy season, but planting should only start towards the end of the season. This latter fact is vitally important.
Soil preparation is aimed at the elimination of weeds and moisture retention.
Transpiration of the transplanted seedlings is limited by planting the plants as deep as possible. Only a small part of the plant must be above ground level.
The plants are not watered at all at planting.
With correct soil preparation enough water is retained to allow the plant to continue growing rapidly for several months, even without any rain.
PROPAGATION OF SALTBUSH SEEDLINGS
In order to obtain well-developed and hardy plants for transplanting in July to August, the seed can be sown in open seedbeds from October of the previous year, but not later than January. The ideal height of the plants at planting time is 20 to 25 cm.
The steps for propagating plants of the right type and quality are as follows:
Start preparing a fine seedbed in good time. Apply 3 kg of superphosphate/100 m2 at planting time or apply manure at least one month earlier.
The seed is soaked in water for 2 to 3 days to remove excess salts. After that the seeds are kept in a wet grainbag until the first white roots become visible. This usually takes another 2 days.
Where weeds and/or nematodes are a problem, it is important to fumigate the seedbeds beforehand with methyl bromide. No herbicide has yet been registered for saltbush, but in the case of grasses cycloxydim has given good results.
Make shallow furrows with the corner-edge of a spade and plant the seeds thickly in the furrows, approximately 1 kg seed/20 m2. The furrows must be about 8 to 9 cm apart. Flatten the soil with the back of a spade and wet thoroughly. In the case of light textured soils it may be advisable to compact the topsoil. This improves germination, as the compacted topsoil stays wet longer due to water moving up from the wet soil below.
Until the seed has germinated properly, the topsoil must never be allowed to dry out. Most failures with germination can be ascribed to the fact that the topsoil has dried out at some stage.
A dense stand of plants in the seedbed will ensure that the plants have only a single undivided stem each, which will make planting easier, especially with the saltbush planter. Plants that become too large can be topped. Plants that were sown early, can be pruned back repeatedly to a height of 20 cm.
Start preparing the strips where the plants are to be transplanted in good time. In the case of virgin soil, rich in shrubs and plant matter, it may be beneficial to start preparing the soil using a disk plough during the previous rainy season in order to give the organic matter enough time to rot. The first cultivation must take place just after the first winter rains to make sure that weeds are stimulated to germinate, and to improve water penetration and conservation.
Wait until good rain in July (m9re than 10 mm) and cultivate a second time as deep as possible. Start planting immediately in order to get the plants in while the soil is still wet. Under normal conditions, planting can continue for at least 5 to 6 days after rain.
The second cultivation is very important in order to get rid of weeds and to retain enough water. A lot of weeds will use all the moisture from the soil during the first dry period (usually in August). Thorough soil preparation will ensure sufficient moisture for the plants to grow quickly until late summer. The plants can then be grazed within a few months. With a clayey soil with a tendency to form clods, the upper soil must be cultivated as finely as possible to ensure maximum water retention.
Old man's saltbush can be planted up to late winter. The best results are often obtained with plantings in August and September. If the soil is thoroughly wet, there is no need for further rain. Soil that was cultivated and had no rain afterwards to compact it, stay wet longer. The plants keep on growing until late summer. A lot of rain in winter has no benefit, as saltbush does not grow in winter. For good results, the soil must retain water for the warmer months.
Do not plant too early. Planting before 15 July usually results in poor establishment and growth in the first year. The higher the rainfall in an area, the later planting should take place.
OTHER PRECAUTIONARY MEASURES
Loosen the plants with a garden fork before lifting them, while making sure that the roots are intact.
Keep the roots moist with wet bags. Make sure that the labourers are not careless,
Plant deep. Most of the leaves should be underneath the soil surface. The less plant protruding above the soil surface, the less water is lost through transpiration. Plants that are planted deep in moist soil do not need rain for a few weeks. If the soil has retained enough water, no further rain will be needed.
At planting, enough pressure must be applied to compact the soil around the roots. The pressure wheel of the planter may not be sufficient and it may be beneficial to compact the soil with a tractor. In the loose soil the plants do not bruise easily, even if the wheel happens to go over a part of the plant,
The plants should not be watered at planting, as this may cause the soil to compact which will result in it drying quickly.
Espacement will depend on soil depth and annual rainfall. With a rainfall of 150 mm or less, the number of plants/ha should not exceed 1 200. With a rainfall of more than 200 mm, up to 2 500 plants can be planted/ha on deep soils. A high winter rainfall will have little benefit, unless the soil is deep enough to retain a lot of water. The well-developed root system of old man's saltbush is of no use on shallow soils.
Good results are obtained where saltbush is spaced in such a way that cultivation can take place between rows.
The planting of small grain between rows is recommended as saltbush forms a good combination with crop residues. Oats can be left as foggage between the rows. The width of implements to be used must be taken into account when row spacing is planned. Cultivation between the rows prevents invaders from establishing among the saltbush.
Fig. 1, 2 and 3 show different spacing for different plant densities. With the spacing in Fig. 2 the plants in the narrow row should compete sufficiently to keep out invader shrubs such as Galena Africana, while cultivation between the wider rows is possible. Where poor growth is expected, a spacing where cultivation between all the rows is possible, will be best. The spacing in Fig. 3 is ideal in cases where a larger area is needed for small grain.
Very little is known about the feeding requirements and fertilisation of old man's saltbush. The plants react well to nitrogen fertilisation. On most soils no fertilisation is required. Where winter cereals are planted between rows, the saltbush inevitably benefit from the fertilisation. Old man's saltbush does not grow well at pH levels of less than 4,5 (KCI).
Contrary to general opinion it is not essential that all old man's saltbush should be pruned. However, when there are obvious signs that plants are getting unproductive, pruning may be beneficial. A rotary slashed can be used for pruning. Various patents for mechanical pruning are being tested.
In higher rainfall areas, on deeper soils and where plants are widely spaced, there is no benefit in pruning back old man's saltbush. The saltbushes sprout from the lower branches and the part of the plant that is out of reach of the sheep, stimulates the plants to grow strongly again within a short time. The plant material that is not utilised serves as reserve for times of drought or in case of late winter rains.
The success of this method of planting depends on the following aspects:
Use hardy plants
At least two cultivations are essential
Plant late in the season
Plant rows wide enough apart in order to be able to control weeds and invader plants effectively
Plant seedlings as deep as possible. Less than 40 % of the plant (excluding roots) need be above ground
The soil around the roots of the plants must be thoroughly compacted.
By following these guidelines closely successful establishment will be obtained.
DE KOCK, G.C. 1980: Drought Resistant Fodder Crops: International Symposium on Browse In Africa, Addis Ababa, 1980
HOON, J.H. & KING, B.R. 1993. Garingboomaanvulling vir Dorpers op Oumansoutbos, KarooAgrlc. 5(1):1933.
LE HOUEROU, H.N. 1981. The feed value of A triplex spp. 5p., Techn. Paper no 13, UNTF/Lib 18, FAO & Agric. Res. Cent., Tripoli, Libya.
LE HOUEROU, H.N. 1992: The role of saltbushes (A triplex spp.) in arid land rehabilitation in the Mediterranean Basin: a review. Argroforestry systems, 18: 107-148.
STEYNBERG, H. & DE KOCK, G.C. 1987: Aangeplante weidingstelsels in die veeproduksiestelsels van die Karoo en ariede gebiede. Karoo Agrlc. 3(10):1987.
Middelburg : Grootfontein ADI.