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Effects of Intercropping on Soybean N2‐Fixation and Plant Composition on Associated Sorghum and Soybeans 1
Author(s) -
Wahua T. A. T.,
Miller D. A.
Publication year - 1978
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/agronj1978.00021962007000020018x
Subject(s) - intercropping , agronomy , sorghum , biology , dry matter , monoculture , nitrogen fixation , weed , cultivar , dry weight , bacteria , genetics
Sorghum ( Sorghum bicolor (L.) Moench) and soybean ( Glycine max (L.) Merrill) are being intercropped in the tropics so that crops more effectively utilize water; there is better weed control, and soil fertility is improved. A field experiment was conducted to determine the effects of sorghum‐soybean intercropping on soybean N 2 ‐fixation and plant composition of both crops. The soil was a Flanagan series, a fine, montmorillonitic, mesic Aquic‐Argiudoll. Soybeans were intercropped with tall and semi‐ dwarf sorghum cultivars at 16 population densities from 1.38 to 33. plants/m 2 . Soybean N 2 ‐fixation was estimated by acetylene reduction. Various plant parts were analyzed for present N. Nitrogen‐fixation by soybeans grown with tall sorghum was reduced 99% due to reduction in number of nodules per plant (77%), weight per nodule (50%), and specific nodule activity, SNA, (96%). Soybean dry matter and seed percent oil were also reduced by 87 and 8%, respectively. Soybean percent seed protein and leaf N were unaffected by intercropping. Soybeans grown with semi‐dwarf sorghum fixed 2.64 times more N than plants in monoculture but produced 40% less dry matter and 3% less oil in seed. Percent seed protein and leaf and stem N of soybeans were unaffected by intercropping. The increase in N 2 ‐fixation was probably due to increases in number of nodules per plant (62%) and SNA (364%). Possible involvement of allelopathy, NO 3 ‐ absorption, delayed senescence, and inter‐ specific mechanical support was considered. Protein yield of intercropped tall and semi‐dwarf sorghum was reduced by 15 and 71%, respectively. Only in the dwarf cultivar did intercropping increase percent seed protein by 15%. Sorghum grain oil was unaffected by intercropping.