Arachis pintoi cover cropping increases drought survival of Citrus latifolia in an intercrop with Coffea arabica

Aims: Once rare, extended droughts are becoming more frequent in parts of the wet tropics, impacting rain-fed production of major commodities including citrus and coffee. We hypothesized that the dense, deep-rooted, perennial cover crop Arachis pintoi would keep soil cool and moist during drought, protecting young Citrus latifolia trees. Methods: We measured moisture (NDMI) and vegetation (gNDVI) index using Sentinel2 multispectral imaging. We also made ground measurements of leaf stomatal conductance, soil temperature, and soil aggregation. Results: A. pintoi cover cropped plots had significantly higher NDMI and gNDVI, lower soil temperature, and larger soil aggregate cross-sectional area, in particular when compared to bare soil. After a rain and in full sun, C. latifolia transpiration spiked in bare soil but not in A. pintoi cover cropped plots. Zero C. latifolia trees died from drought in full-sun, cover-cropped plots. Similarly, zero died in shaded, bare-soil plots. In contrast, 6 (of 27) trees in full-sun, bare-soil conditions died. Conclusions: A. pintoi appears to maintain soil conditions that are conducive to C. latifolia survival during the dry season. The effect appears to be mostly due to shading, as cover cropping becomes dispensable under partial tree shade. Remote sensing detected treatment effects despite small experimental plot sizes. The higher post-rain leaf transpiration suggests C. latifolia may contribute to soil drying in bare soil. Higher vegetation index and soil aggregation suggest cover cropping may provide additional long term benefits in soil carbon sequestration.