Advances in Soil Fertility Research in Sudan
Keywords:Soil fertility, fertilizers, organic fertilizers, Salinity, Sudan soils
The objective of this article is to review the previous national researches directed to correct soil fertility status. Many field experiments were conducted to detect the responses of different crops to different fertilizers types. As early as 1911, pioneers realized that nitrogen is very low, due to low organic matter, hence, nitrogen was considered as the main yield-limiting factor. Since then, fertilizers research focused on the rate, amount, type and time of application of nitrogen fertilizers. First, nitrogen sources cotton crops was ammonium sulfate but, later, in 1960’s replaced by urea for its economical merits. Scientists noted the high correlation between the high response of crops to fertilizers and other agricultural inputs as protection, thinning, irrigation and time of sowing. Wheat yield increased significantly by nitrogen fertilization which was most affecting by time sowing. In rainfed area, sorghum responded well to added nitrogen but this response depends on sorghum variety. In early 1960’s, phosphorus fertilizer was introduced in Gezira Scheme in form of Triple Super- Phosphate (TSP). Crops like cotton, wheat, sorghum and sugarcane responded well to phosphorus fertilization. It worth mentioning that many successful attempts were made to substitute imported TSP by local partially acidulated rock phosphate which presents in abundance in Sudan. Early studies showed no response to potassium fertilization to cotton crop but recently many crops such as; potato, sugarcane, sweet potato, and banana were responded well to added potassium. Little data of any, on calcium and magnesium nutrition. Sulphur fertilizer addition in Sudan is low, they received less attention. Although microelements contents in Sudanese soil is very low, they received less attention in Sudanese agriculture. Organic soil fertility management was the concern of many scientists. A Number of field experiments were conducted using different manures to increase soil organic matter, biological activity and nutrient availability. It was found that application of sewage sledge and irrigation canal sediment combined with fertilizer nitrogen a useful practice in amelioration of poor-quality arid soils. Incorporation of crop residues was found essential to sustain soil fertility and crop production. The low productivity of salt-affected soils was studies by many researchers. Results of such researches indicated the short irrigation intervals as one of the best measures to increase yield significantly of such marginal soils. Other obtained the highest grain yield of wheat by application of chicken or farm yard manure grown ridges of sodic soil in Gezira. However, the findings of the research trials cited in this article indicated that most crops responded positively to the fertilizer’s application, which is evident of poor fertility of Sudan soils. In view of the results of number of field fertilization experiments, it is advisable to adopt the policy of adding both organic and inorganic fertilizers to crop for soil fertility conservation to increase yield and, hence, better sustainable agriculture development.