Abstract
The adoption of ISFM technologies such as maize-soybean intercropping system is being promoted as one of the options to address low soil fertility and crop productivity among the farmers of the central highland of Kenya. The purpose of this study was therefore to determine the effects of maize-soybean intercropping patterns on soil inorganic N, N uptake and soil chemical properties. The experiment conducted during 2012 LR and 2012 SR and it was arranged in a randomized complete block design (RCBD) with four replications. The treatments were four maize (M) – soybean (S) intercropping patterns (conventional=1M:1S; MBILI-MBILI=2M:2S; 2M:4S; 2M:6S) and two sole crops of maize and soybean, respectively. The results showed that at Embu during 2012 LR, at harvest the MBILI and 2M:4S treatments observed significantly (p=0.0525) the lowest N03- - N content (8.24 mg kg-1 and 9.15 mg kg-1, respectively); and at Kamujine during the same 2012 LR, at harvest the sole soybean treatment recorded statistically (p = 0.0301) the highest N03- - N content (8.24 mg kg-1). At Kamujine the sole soybean treatment recorded statistically (p=0.0131) the highest (12.84 mg kg-1) soil mineral N. The N uptake by maize and soybean was significantly affected by the intercropping patterns and it was positively correlated with soil mineral N, at both sites during the sampling period. During 2012 SR at Embu site, the MBILI treatment observed significantly the highest soil total N value of 0.05% (p=0.0530). The soil SOC was not significantly affected by the intercropping patterns at this location. The SOC was significantly affected by the intercropping and the conventional treatment recorded the highest value of 2.46%, p=0.0020. Key words: Maize-soybean, intercropping patterns, soil mineral-N, N-uptake, chemical soil properties, central highlands, Kenya.
Highlights
Soil fertility depletion in smallholder farms is the fundamental biophysical root cause for declining per capita food production in SSA (Mugwe et al, 2007)
The results showed that at Embu during 2012 long rain (LR), at harvest the MBILI and 2M:4S treatments observed significantly (p=0.0525) the lowest N03- - N content (8.24 mg kg-1 and 9.15 mg kg-1, respectively); and at Kamujine during the same 2012 LR, at harvest the sole soybean treatment recorded statistically (p = 0.0301) the highest N03- - N content (8.24 mg kg-1)
At Embu during 2012 LR, no significant differences were observed in soil nitrate – N content (N03- - N) as affected by the intercropping patterns during all the sampling periods, except at 12 weeks after planting (WAP) where the 2M:4S treatment observed significantly (p=0.0285) the highest N03- - N content (9.01 mg kg-1) than all other treatments, excluding sole maize treatment; and at harvest (20 WAP) where the MBILI and 2M:4S treatments observed significantly (p=0.0525) the lowest N03- - N content (8.24 mg kg-1 and 9.15 mg kg-1, respectively) than the sole soybean and conventional treatments, with 14.95 and 14.62 mg kg-1, respectively
Summary
Soil fertility depletion in smallholder farms is the fundamental biophysical root cause for declining per capita food production in SSA (Mugwe et al, 2007). Increasing pressures on agricultural land have resulted in much higher nutrient outflows and the subsequent breakdown of many traditional soil fertility maintenance strategies, such as fallowing land, intercropping cereals with legume crops, mixed crop-livestock farming, and opening new lands (Sanchez et al, 1997). It is necessary to adopt improved and sustainable technologies in order to guarantee improvements in food productivity and thereby food security (Landers, 2007; Gruhn et al, 2000) Such technologies include the use of integrated soil fertility management practices (ISFM) such as intercropping cereals with grain legumes as one of its main components (Mucheru-Muna et al, 2010; Sanginga and Woomer, 2009). Improved intercropping systems are part of ISFM technologies (Mucheru-Muna et al, 2010; Sanginga and Woomer, 2009) and in central highlands of Kenya the information is scarce regarding to optimum cropping pattern of maize-soybean intercropping system, and regarding to its effect on soil chemical properties
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