Nutrient contents of Soyabeans: A Guide for sugarcane growers under fast track land reform programme [FTLRP] in Zimbabwe

Abstract

Soyabean biomass, stover and roots when incorporated into the soil can improve the organic matter and the carbon (C): nitrogen (N) ratio of the soil. Of its total N, 60-90% is translocated into the seed. This research was conducted on sandy clay loams of the lithosol group under the Zimbabwe soil classification system at The Zimbabwe Sugar Association Experiment Station (Z.S.A.E.S) in the South Eastern Lowveld, the leading sugarcane producing region in Zimbabwe. The objectives of this research were to: 1) analyse the nutrient content of the soyabeans under study, 2) assess the contributions of the various soyabean parts to soil fertility, 3) determine the liming potential of the soyabeans and 4) determine the forage potential of the two soyabean varieties as livestock feeds. The following parameters were measured: 1) nutrient composition of the vegetable and grain soyabeans, soyabean biomass 2) nitrogen fixed by both grain and vegetable soyabeans. Vegetable soyabeans (variety S114) and grain soyabeans (variety Storm) were used for this study. Vegetable soyabeans had higher nitrogen, phosphorus and potassium while grain soyabeans had higher calcium and magnesium. This shows that vegetable soyabeans as a nitrogen fixing crop have Plural? the potential to ameliorate soil fertility. However, grain soyabeans seem to have better liming potential than vegetable soyabeans. Forage Storm can improve the magnesium and calcium constituency of livestock while vegetable soyabeans can influence the phosphorus content. The two elements are critical to lactating cows and young stock. The crops have high levels of calcium and magnesium, which are the critical elements for the improvement of soil pH. Interestingly, high nitrogen (N), phosphorus (P) and potassium (K) contents were observed in grain soyabeans. These nutrients in grains are not returned to the soil as the grains are sold as a commercial crop. The economic benefits of growing soyabeans accrue from the nutrients that remain in the leaves, petioles, stems and shells that are ploughed into the soil during land preparation.

Keywords: soil fertility, soyabeans, smallholder farmer

African Journal of Food, Agriculture, Nutrition and Development, Volume 13 No. 2 April 2013