Water use efficiency and productivity of dryland grain sorghum and cowpea intercrops in distinct semi‐arid conditions

An intercropping system is one of the traditional practices adopted under dry conditions due to its ability to utilize resources efficiently. There is limited information on water use efficiency (WUE) and water equivalent ratio (WER) of grain sorghum ( Sorghum bicolor )‐cowpea ( Vigna unguiculata ) intercrop grown in different agroecological regions of the semi‐arid Limpopo province of South Africa. A no‐tillage field experiment arranged in a randomized complete block design with four replications over two growing seasons, 2018/2019 and 2020/2021, in two distinct regions, Syferkuil and Ofcolaco of the province, was established to assess the water productivity of sorghum‐cowpea intercrop. Four grain sorghum cultivars, Enforcer, Avenger, NS5511, and Titans were intercropped with two different cowpea densities of 37,037 and 74,074 plants ha −1 . The results from Syferkuil revealed that for grain sorghum, the cultivars Enforcer and NS5511 exhibited higher crop WUE when grown with 37037 plants ha −1 compared to 74074 plants ha −1 density, resulting in approximately 31% and 8% increase, respectively. For cowpea, 74074 plants ha −1 density cowpea in an intercropping system resulted in higher crop WUE of 3.22 kg ha −1 mm −1 , 6.85 kg ha −1 mm −1 compared to 37037 plants ha −1 density, with 1.18 and 5.05 kg ha −1 mm −1 in 2018/2019 and 2020/2021 cropping seasons, respectively. Similar results were observed at Ofcolaco, where Enforcer intercropped with 74074 plants ha −1 density accumulated the highest crop WUE. For cowpea, high crop WUE was observed with the intercrop cowpea means of WUE of 9.61 kg ha −1 mm −1 and 3.57 kg ha −1 mm −1 under 37037 plants ha −1 and 74074 plants ha −1 , respectively. The intercropping system resulted in high water productivity compared to sole, as indicated by WER greater than 1.0 for all the treatments. Intercropping enforcer or ns5511 with 37037 plants ha −1 cowpea density maximized sorghum WUE, whereas high cowpea density maximized cowpea WUE. All intercrops treatments achieved WER of > 1.0, indicating a higher advantage over the sole system.