Green Gram-sorghum Intercropping: Effects on Crop Microclimate, Competition, Resource Use Efficiency and Yield in Southeastern, Kenya

Abstract

A better understanding of cereal-legume interactions could improve the implementation of intercrop systems for cropping intensification. These interactions affect crop microclimates and the efficiency of utilizing growth resources such as water and nitrogen. In this study, four morphologically contrasting green gram varieties with close phenological ranges were intercropped with the sorghum, Seredo in Katangi and Mwala in southeastern Kenya during the short rains experimental season in 2022. The four green gram varieties were the tall N26 and dwarf types KS20, Karembo, and Biashara. The intercrop arrangements were: double alternate rows of sorghum and green gram (double row), single alternate rows of sorghum and green gram (single row), and single crops of each green gram variety and sorghum as control. Treatments were laid out in split plot design with intercrop arrangement as main plots and green gram variety in subplots. Intercropping reduced soil temperature, canopy temperature, vapor pressure deficit, and crop water stress index. For green gram, overall Water Use Efficiency (WUE) and Nitrogen Use Efficiency (NUE) was lower under intercropping by 2.6 kg ha-1 mm-1 and 1.65 kg kg-1, respectively compared with sole crop. Intercropped sorghum reduced WUE by 3.5 kg ha-1 mm-1 and NUE by 1.9 kg kg-1. Intercropped sorghum reduced the yield by 26% and green gram by 23%. However, the yield decline was significantly higher under single row (1.1 t ha-1) than double row crop arrangement (0.6 t ha-1). Variety N26 out-yielded the other green gram varieties, irrespective of crop arrangement. Green gram yield was driven by an increase in WUE and NUE while soil and canopy temperatures were dependent on vapor pressure deficit. However, these trait associations and temperature alterations were weak in sorghum yield determination. While intercropping promotes crop intensification, this study demonstrates that double-row intercropping could be more efficient than single-row in enhancing green gram-sorghum complementarity for increased grain yield, WUE, NUE, and the regulation of crop microclimate. This study recommends that double-row intercropping with variety N26 of green gram improves yield in dryland areas of Kenya. Further research is recommended for other green gram and sorghum varieties and intercropping configurations not used in this study.