Field microclimate and yield for proso millet intercropping with mung bean in the dryland of Loess Plateau, Northwest China.

Abstract

Based on the ecological environment features of Loess Plateau, we examined field microclimate characteristics and yield of four different intercropping patterns for proso millet (P) and mung bean (M) including 2:2, 4:2, 4:4, 2:4. The results showed that, compared with monoculture, intercropping increased plant height, leaf area index (LAI) and chlorophyll content (SPAD) of proso millet in its late growth stage, while LAI and SPAD of mung bean decreased due to the shade of the high proso millet. Mung bean appeared spindly growth for a while by increasing the plant height. Moreover, upper canopy illumination and air temperature during grain filling stage of proso millet decreased under intercropping conditions, but relative humidity substantially increased. These changes regulated soil temperature and light leakage, which decreased under intercropping systems, and thereby led to a cold and wet ecological environment. Poor atmospheric and light conditions formed a relative closure growth environment for mung bean, which suppressed its growth. The panicles, spike length, grain mass per plant and 1000-grain mass of proso millet under 2P2M, 4P2M, 4P4M and 2P4M treatments was significantly increased by 7.5%-45.0%, 2.2%-12.2%, 35.4%-94.0% and 2.3%-4.7%, respectively. This caused a 5.6%-20.7% increase of yield than the mono-culture. The branch number, pods per plant, grain mass per plant and 100-grain mass in mung bean were decreased under different intercropping treatments, and the yield was significantly reduced by 34.8%. Land equivalent ratios (LER) of each intercropping pattern were all greater than 1. Among them, LER of 2P4M was the maximum (1.86), and 2P4M treatment held relatively reasonable composite configuration. Our results suggested that 2:4 ratio of proso millet/mung bean intercropping patterns performed better than other ratios on the Loess Plateau.