Testing pearl millet and cowpea intercropping systems under high temperatures

With the potential threat of more frequent climate extremes putting semi-arid crop production in jeopardy, there is a need to establish more climate resilient cropping practices. Intercropping is often practiced by farmers in semi-arid regions and is perceived as a risk reducing practice. However, there is little knowledge of how and to what extent it can be a viable option under future conditions. As testing a complex adaptation strategy in controlled environments is difficult, conducting field experiments in the dry season offers opportunities to test cropping systems under extreme but real-world conditions. Consequently, a field trial was run in semi-arid India over a two-year period (2015 and 2016) in the dry and hot (summer) season. These trials were set up as a split split-plot experiment with four replicates to assess the performance of simultaneously sown sole versus inter cropped stands of pearl millet and cowpea, with two densities (30 cm and 60 cm spacing between rows-both with 10 cm spacing within rows), and three water treatments (severe stress, partial stress, and well-watered) applied with drip irrigation. Results showed that intercropping pearl millet led to a significantly lower total grain yield in comparison to the sole equivalent. Pearl millet's highest yields were 1350 kg ha(-1) when intercropped and 2970 kg ha(-1) when grown as a sole crop; for cowpea, 990 kg.ha(-1) when intercropped, and 1150 kg ha(-1) as a sole crop. Interestingly, even when maximum daily temperatures reached up to 42.2 degrees C (on Julian day 112 in 2016), well-watered, pearl millet produced reasonable yields. Cowpea yields were often lower than 1000 kg ha(-1). Only under the highest irrigation treatment (well-watered) sole cropped, low density were yields of 1150 and 1110 kg ha(-1) achieved in 2015 and 2016, respectively. We conclude that successful intercropping systems must be highly specific to conditions and demands. More research would be needed to identify suitable cowpea genotypes and planting densities that could allow for higher intercropped pearl millet yields.