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Practical guidelines for the establishment of Old Man’s Saltbush in Winter Rainfall Regions

 

G Louw

 

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.

 

NUTRITIONAL VALUE

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.

 

POSSIBLE APPLICATIONS

 

CARRYING CAPACITY

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:

Foto: Salt bush planter

 

PRINCIPLES ON WHICH THE GUIDELINES ARE BASED

 

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:

 

TRANSPLANTING

 

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.

 

 

OTHER PRECAUTIONARY MEASURES

 

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.

 

SPACING

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.

 

FERTILISATION

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).

 

PRUNING

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.

 

IN CONCLUSION

The success of this method of planting depends on the following aspects:

 

By following these guidelines closely successful establishment will be obtained.

 

REFERENCES

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.

 

Published

Middelburg : Grootfontein ADI.