Canopy microenvironment change of peanut intercropped with maize and its correlation with pod yield

Field trials of the single cropping of peanuts and broad-sown intercropping of maize and peanuts were conducted in 2015 and 2016. Changes in peanut canopy transmittance, light intensity, canopy temperature, and humidity after the podding stage under different planting modes were monitored, and the correlations between them and pod yield were analyzed. Our results showed that, first, compared with a peanut monoculture, maize/peanut intercropping significantly reduced the light intensity of the canopy, the transmittance of the top and middle canopy, and the average temperature of the canopy from 9:00 a.m. to 11:00 a.m., and increased the average humidity of the canopy. Second, peanut canopy light intensity exhibited a single peak curve on sunny days, and the canopy light intensity of monocultured peanuts was significantly higher than that of intercropping. The difference in light intensity between a monoculture and intercropping was greater in the morning (when light intensity increased) and the afternoon (when light intensity decreased), while the difference between the two values decreased at noon during the direct-sunlight period. The ambient canopy temperature of peanuts decreased under intercropping in the night and before and after noon, compared with monoculture, with an observed highest difference of 4.9℃. Intercropping increased the relative humidity of the canopy during daytime, with a recorded highest difference of 21.03%. Third, under experimental conditions, the canopy environmental temperature and illumination at the podding stage were positively correlated with peanut pod yield, while the canopy environmental humidity was negatively correlated with pod yield, especially at the podding stage. Multivariate linear stepwise regression analysis showed that the most important environmental factors affecting peanut yield were canopy illumination and circumferential humidity at podding stage, and canopy circumferential humidity at the full-fruit stage. Path analysis showed that, besides directly affecting yield, illumination had a high impact on peanut pod yield by affecting canopy environmental humidity, indicating that the positive effect of illumination on yield can be improved by coordinating the relationship between illumination and humidity under intercropping conditions. In this experiment, the decrease in canopy light intensity and transmittance of intercropping and the increase in canopy relative humidity of intercropping were the main climatic factors limiting pod yield. It is possible that the yield of intercropped peanuts could be increased by planting them from east to west, which will increase the effective illuminance of the canopy at 9:00-11:00 a.m. and reduce the relative humidity.