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Sulfur Requirements of Cowpea and Implications for Production in the Tropics 1
Author(s) -
Fox R. L.,
Kang B. T.,
Nangju D.
Publication year - 1977
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1977.00021962006900020002x
Subject(s) - cultivar , vigna , legume , agronomy , tropics , grain yield , dry matter , yield (engineering) , soil water , biology , horticulture , ecology , materials science , fishery , metallurgy
Low S concentrations in rainwater and depleted organic matter reserves of soils are associated with S deficiencies in the seasonally dry West African savanna. The purpose of this study was to provide information on the internal and external S requirements of cowpea, a promising grain legume for tropical Africa. Three cultivars of cowpea [ Vigna unguiculata (L.) Walp.] were grown in pots in which seven levels of SO 4 ‐S were maintained in the soil solution. About 7 ppm S was required in the soil solution for 95% of maximum grain production for cultivars ‘TVu 76‐2E’ and ‘TVu 201‐ID’. Cultivar ‘Sitao Pole’ required about 2 ppm S in solution. The S contents of uppermost, fully expanded leaves at early flowering associated with 95% of maximum grain yield were 0.32% for Sitao Pole and 0.50% and 0.65% for cultivars, TVu 201‐ID and TVu 76‐2E respectively. The corresponding S content in the petioles was about 0.08%, 0.39%, and 0.42% respectively. Older leaves and leaf petioles accumulated S if it was supplied in excess of requirements. The S percentage of grain was 0.26% when yield was 95% of maximum. Sitao Pole accumulated S to a maximum of 0.36% when SO 4 ‐S was supplied at 45 ppm in solution. About 30% of the plant S was in the grain of plants adequately supplied with S and about 50% was in the grain when the S supply was moderately deficient. The N/S ratio of upper trifoliate leaves associated with 95% of maximum grain yield was about 10 at first bloom. At near maximum yield, cultivar TVu 201‐ID contained about 80 mg S per plant in the grain. Assuming (65,000 plants/ha) the S requirement for grain was about five times mean annual S in the rainwater of northern Nigeria. Sulfur fertilization of field grown cowpea in southern Nigeria was accompanied by a small (12%) but statistically nonsignificant increase in yield. Sulfur fertilization (20 kg S/ha) was required to give 0.26% S in the grain.