Abstract
A study was conducted to identify the most suitable intercropping arrangement in smallholder farms in Western Kenya. Biomass and N (nitrogen)-accumulation, N2 fixation and grain yield of maize and soybeans grown as intercrops at three planting densities were assessed. The study was conducted in four seasons. Three soybean varieties, Namsoy 4m, SC Squire and TGx1987-18F, were used in the experiment. Maize: soybean planting densities 1:1 (D1), 1:2 (D2), 1:3 (D3) as well as sole soybean (SS) and sole maize (SM) were tested. Higher biomass, N-accumulation, and N-fixed in the order 3.8 Mg ha-1, 260 kg ha-1 and 161 kg ha-1 respectively, were recorded in D3 with long maturing variety TGx1987-18F. Conversely, higher soybean grain yield < 2.4 Mg ha-1 was achieved by intermediate maturing SC Squire in D3. The highest maize yield in the intercrop was obtained in D1. N balance calculations indicated that planting TGx1987-18F resulted in an addition of 6 to 67 kg N ha-1, while SC Squire and Namsoy 4 m removed 3 to 89 kg N ha-1 when soybean grain was removed from the field. The differences in N balances between the intercrops depended on the N-fixed and the amount of N in harvested soybean and maize grain. Greater land equivalent ratio < 1.75 were obtained with SC Squire and Namsoy 4m in D2. We concluded that intermediate maturing soybean have multiple benefits for farmers in Western Kenya at 1:2 maize: soybean planting density provided that the practice is accompanied with good soil and crop management practices.
Highlights
Intercropping is regarded as an important practice to stabilize yield, improve crop production and environmental quality in regions with risk in production (Juma, Tabo, Wilson, & Conway, 2013; Vanlauwe et al, 2015)
This paper reports results of the study conducted in Western Kenya with the objectives to (i) assess biomass accumulation and nitrogen fixation of soybean varieties intercropped with maize at different planting densities, (ii) determine yields of maize and soybean intercropped at different planting densities; and (iii) assess the benefits of intercropping soybean and maize at different planting densities under smallholder farmers' conditions
N-accumulation and N-fixed was higher in D3 with the long maturing soybean variety TGx1987-18F, while higher grain yield was recorded in D3 with SC Squire, a variety with intermediate growth duration
Summary
Intercropping is regarded as an important practice to stabilize yield, improve crop production and environmental quality in regions with risk in production (Juma, Tabo, Wilson, & Conway, 2013; Vanlauwe et al, 2015). Rerkasem, Peoples, Herridge, & Bergersen, 1988; Waddington, Mekuria, Siziba, & Karigwindi, 2007). The reasons for increased production of intercrops are different length of vegetation period, various need for resources and different time of using those resources, suitable vertical arrangement of crops leading to better use of light and less intense competition for nutrients and water (Belel, Halim, Rafii, & Saud, 2014). Intercropping of legumes and cereals conserves natural resources and increase economic returns (Juma et al, 2013)
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