Comparison of soil water capture rates of irrigated sole versus intercropped Sorghum bicolor and Arachis hypogaea

A fundamental understanding of how intercrop systems capture and use water resources is crucial in providing the scientific basis of the advantage of mixed crops over sole cropping. The objective of this paper was to investigate how water management affects the temporal and spatial water capture ability of each crop in an intercrop system. Field experiments were conducted in 2 contrasting growing seasons on a level, welldrained loamy, Grossarenic Paleudult. Sorghum and groundnut, sown as sole crops and intercrops were subjected to 4 water treatments in 4 replications. The 4 treatments were: (1) Optimum irrigation, (2) deficit irrigation allowing 2 days of stress on sorghum, or (3) on groundnut, (4) rain fed. Sole crops were seeded in 30 or 60 cm rows at densities of 256000 (sorghum), 160000 (groundnut) plants/ha. In the intercrop, 2 rows of sorghum 30 cm apart, were alternated with 2 rows of groundnut 45 cm apart, resulting in densities of 157000 p/ha for sorghum and 102000 p/ha for groundnut. Daily and seasonal crop water use rates (ETC) of both crops in the mixture were slightly higher than in the corresponding sole crops in all but the rain fed treatments during the growth cycle in the drier year, with a seasonal increase in the intercrop ETC of 8.90, 8.21 and 8.78% relative to sole cropping in treatments 1, 2 and 3. The contrary was observed in the wetter year with a slight decrease in the mixture ETC of 2.47, 2.47 and 0.38% in treatments 2, 3, and 4. Likewise, intercropping increased the seasonal water capture efficiency by 8.47, 6.94 and 8.51% respectively in treatments 1, 2, and 3 relative to sole cropping during the dry year. The improved water uptake rate and efficiency of the intercrop system was attributable to the spatial and temporal complementarities and reduced competition between the component crops.Keywords: Water capture, sole crop, intercrop, spatial and temporal complementarities