ISSN:
1573-0867
Keywords:
Nitrogen
;
phosphorus
;
potassium
;
organic matter
;
fallow
;
forecasting
;
fertilizer requirement
;
Sierra Leone
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract The quantities of nitrogen, phosphorus and potassium supplied by an ‘average’ African soil cleared from bush fallow, assuming no losses, were approximated. Values ranged from 23 to 120 Kg N ha−1, 1.8 to 12 Kg P ha−1, 47 to 187 Kg K ha−1, depending on type of fallow, length of fallow, drainage and extent of depletion of native supplies. Additional amounts of 4 to 5 Kg N ha−1, 4 to 6 Kg P ha−1 and 14 to 20 Kg K ha−1 are obtained from the ash. Using crop nutrient removal data and approximate efficiencies of native and fertilizer N, P and K, fertilizer requirements at the reconnaissance level were estimated for selected target yields. For newly cleared uplands at cropping/fallow ratio of 2:7, N fertilizer requirements for cassava (30 t ha−1), maize (4 t ha−1), and sweet potato (16 t ha−1), were 138, 98, 42 kg ha−1 respectively. Wetland rice (4 t ha−1) required 55 kg N ha−1. Corresponding P fertilizer requirements for cassava, maize, sweet potato, upland rice (1.5 t ha−1) and ground-nut (1 t ha−1) were 190, 80, 30, 30 and 16 kg P ha−1 respectively. Wetland rice required 83 kg P ha−1. Substantial residual values of applied P are to be expected. Cassava required 60 kg ha−1 of K on newly cleared land. In soils of lowered nutrient status higher N, P, and K fertilizer requirements were indicated for all crops. Land use data from Sierra Leone were used to illustrate how the total quantities of N, P and K fertilizers in a country in the forest zone of Africa can be approximated. Fertilizer needs in Sierra Leone were in decreasing order P 〉 N ≫ K. N, P and K requirements were estimated to be 10,000 t, 20,000 t and 4,000 t respectively. The nutrient balance sheet method described in this paper is a useful tool to estimate the order of magnitude of fertilizer requirement at selected target yields for countries in Africa.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01050271
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