Yield and inter-specific interactions in maize/chickpea intercrop under different application rates of P in irrigated sierozem along the Yellow River in Northwest China

The effects of application of different rates of phosphorous on rhizospheric soil processes and yield of maize and chickpea under mono-cropping and intercropping systems were studied in irrigated low Olsen-P sierozem along the Yellow River in Northwest China. The results show that zero (P0) or 40 kg·hm^-2 (P40) P application of maize/chickpea intercrop gives LER (land equivalent ratio) of biomass and grain yield less than 1.00. This implies intercropping disadvantage at P0 or P40, which is mainly due to reduction of chickpea yield. At P application rate of 80 kg·hm^-2 (P80), biomass and grain yield LERs are greater 1.00, implying intercropping advantage.Yield of intercropped maize is 3%, 12% and 19% higher than that of mono-cropped maize at P0, P40 and P80 respectively. Yield of intercropped chickpea at P0 and P40 are significantly lower than that of mono-cropped chickpea. Aggressivity of maize for water, nutrients and other resources is stronger than that of chickpea (A_mc>0) during the co-growth period of two crops. The dynamic curve of chickpea growth indicates that the aggressivity is more significant under P0 and P40 treatments. Harvest index (HI) of intercropped maize is higher than that of mono-cropped maize, and that of intercropped chickpea is less than that of mono-cropped at different P levels. There is no indication that intercropping chickpea enhances organic P utilization by maize. Acid phosphatase activity for intercropped chickpea at P0 is lower than that for the mono-cropped. No advantage is noted under intercropping at P0 and P40. However intercrop advantage is observed at P80.