Biological and water-use efficiencies of sorghum-groundnut intercrop

In order to compare water-use efficiency of sole crops and intercrops, 2 experiments were conducted in 2 consecutive years with sorghum (Sorghum bicolor L. Moench) and groundnut (Arachis hypogaea L.) on a loamy, Grossarenic Paleudult. In a randomized block, split-plot design, sorghum (SS), groundnut (GG), sorghum/groundnut intercrop (SG) were subjected to 4 replicates of 4 water managements as main treatments (trt): (1) Optimum irrigation, (2) deficit irrigation allowing stress on sorghum, or (3) on groundnut, (4) rainfed. All crops were seeded in rows at a density of 256000 (SS), 160000 (GG), 256000 + 160000 (SG, year 1), 157000+102000 (SG, year 2) plants/ha. Soil water status was monitored and ET calculated all over the growing seasons. Dry matter (DM) and grain yields (GY) were determined at physiological maturity for each crop. Sorghum GY was very high, ranging from 3.55 (trt 4) to 8.03 (trt 1) Mg/ha in sole crop, and from 2.71 to 6.27 Mg/ha in intercrop. Groundnut GY was very high in sole crop (3.76 to 6.54 Mg/ha), but was very depressed in intercrop (0.13 to 3.26 Mg/ha). Mean Total Land Equivalent Ratio (TLER) was 1.14 for DM and 1.11 for GY, showing a 14 and 11% advantages over sole cropping. But these advantages disappeared when the amount of water used was taken into account in the Total Land Water Use EquivalencyRatio (TLWUER). The overall mean TLWUER were 1.01(irrigation) and 0.99 (seasonal ET) for DM, 0.98 and 0.96 for GY, indicating no advantage of intercropping over sole cropping. Nevertheless, based on water use ratios, intercropping was more water use efficient than sole crops. The contrasting results between the TLER and TWUER may imply that the yield advantage of intercropping was not attributable to its overall improved water use ratio but rather to its higher seasonal water use.Key words: Intercropping, Biological efficiency, Water use efficiency, TLER, TLWUE