In recent years late spring rains and prevailing drought conditions have put many livestock farmers under severe pressure, especially those who have relied on post-harvest crop residues in combination with natural grassland (veld) to carry their stock. Reductions in maize planting and additional losses in dry matter from veld due to drought conditions have resulted significant deficits in fodder flows. In the light of the above, consideration should be given to the establishment of permanent pastures on marginal lands. This would serve several purposes, including the conservation of the top soil by ensuring permanent ground cover, and also provide a source of early grazing in spring with the additional potential to harvest several cuts of hay during the summer months to ensure a fodder bank for winter. Eragrostis curvula( E. curvula) also known as “Weeping Love Grass” and “Oulandsgras” was one of four grass species that was selected as a result of the international recognition of the importance of grassland productivity and soil conservation, and is one of the most important pasture grasses in South Africa. E. curvula is easy to establish and generally persists longer than many other species. It has been used with great success for grazing, hay production, a lay pasture after pototo and tobacco production and has played an important role in the prevention of soil erosion by stabilisation of road verges and disturbed soil. There are numerous cultivars available in the market some of which include Ermelo, Agpal, Umgeni, PUK E3, PUK E436 and American Leafy. E. curvula is a tufted subtopical grass with an extensive root system which helps build soil structure. It will survive in areas receiving 400 -1000 mm of rainfall per year and can tolerate soil acid saturations in excess of 70%. It typically grows from September through to March as seen in Graph 1: A well managed pasture may yield four cuts per season if the prevailing conditions are condusive to growth while in drier areas one or two cuts may be achieved. E. curvula yield is a function of rainfall, temperature and nitrogen application and may vary due to geographic location ranging from an excess of 12 tons /ha in the northern areas of the Eastern Cape, Midlands and Northern Kwa Zulu Natal and the cooler areas in eastern Mpumalanga, 6-8 tons/ha in the Free State, 8-10 tons/ha in Gauteng and tapering to 4-6 tons/ha in the western regions of the country. Dry matter yields in excess of 14 tons per ha are attainable with a good fertilization program; even with erratic rainfall, reasonable dry matter and protein yields are attainable, as shown in Graphs 2 – 4 below: Application of N determines dry matter production and improves palatability; additionally, adequate potassium (K) is essential to ensure high yields are maintained. E. curvula is an efficient forager of K, it is important to carry out regular soil tests to ensure that soil K-levels are not ‘mined’ in high production pastures which will result in significant losses in production. Furthermore, when planning N applications take into…
AFRIKAANS: Maak Ammoniumsulfaat deel van jou bemestingsprogram Specific applications of Ammonium Sulphate may serve as an important source of Nitrogen (21% N) and Sulphur (24%S), for crop production. Ammonium Sulphate can generally be regarded as a suitable supplemental source of nitrogen (N), which can address all Sulphur(S) requirements. Under specific conditions the use of Ammonium Sulphate can result in higher grain yields compared to other N-sources when used as the primary N-source. Before planting Large quantities of Ammonium Sulphate can be broadcast before planting under Centre Pivot Irrigation, especially when soil pH is high and where considerable quantities of plant residues are incorporated in the soil. The volatilization of Ammonium Sulphate is relatively low compared to other N sources, however volatilization can be significant under alkaline conditions and therefore Ammonium Sulphate should rather be incorporated. The application of Ammonium Sulphate as the main source of N before planting could result in higher grain yields compared to other N-sources under specific conditions (Figure 1). Possible reasons for higher yields obtained with Ammonium Sulphate compared to other N-Sources as in Figure 1: Wheat response to S due to S-deficiency in the soil. Less leaching compared to other N-Sources. Under strong alkaline conditions the greater acidifying effect of Ammonium Sulphate can enhance the uptake of other plant nutrients. In Plant Mixtures All N in Ammonium Sulphate is in the ammonium (NH4+) form while most crops prefer a combination of both nitrate (NO3–) and ammonium. Furthermore the conversion of ammonium-N to nitrate-N is usually very slow when band placed. Relatively small amounts of Ammonium Sulphate are incorporated in some granular and liquid plant mixtures to increase the sulphur and ammonium content. Extra ammonium in the plant mixture will accordingly reduce leaching of N in the plant mixture. The application of Ammonium Sulphate as the only source of N in plant mixtures is not recommended. After planting Large quantities of Ammonium Sulphate can be broadcast after planting as the main N-source, either through spreading or Centre Pivot applications. As previously indicated soil incorporation is preferred. The practice of applying up to 100kg Ammonium Sulphate/ha over maize plant rows directly after planting serves as an insurance against possible leaching losses of N in plant mixtures and an effective way of meeting all crop S requirements. The band placement of large quantities of Ammonium Sulphate as the main source of N after planting is not recommended. Mixtures of LAN and Ammonium Sulphate in a ratio of 75% LAN : 25% Ammonium Sulphate (marketed as KANAS by some local fertilizer suppliers) combines the optimal benefits of both products and contains 26.25% N and 6% S. This ratio of N : S closely resembles the requirement of many crops, with the added benefit that the N is applied in both the ammonium and nitrate forms. Similarly AS is mixed with Ammonium Nitrate Solution to provide a liquid product called Ammonium Sulphate Nitrate (ASN) containing 18% N and 2.4% S. Relatively large quantities of either KANAS or ASN may be…
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Dr Neil Miles consulting soil scientist
Neil Miles is a consulting soil scientist based in Mount Edgecombe. Prior to entering into consultancy, he spent 28 years with the KZN Department of Agriculture, as a research scientist and research manager, followed by 10 years in research and advisory work with the South African Sugarcane Research Institute (SASRI).
Neil played a leading role in the development of both the Cedara Fertilizer Advisory Service and SASRI’s Fertiliser Advisory Service (FAS). His PhD, through the University of Natal, focused on the nutrition of intensive pastures. Neil’s particular interests are soil health and the nutrition of crops and pastures.
Contact Neil: email@example.com