Combining modelling and experiment to quantify light interception and inter row variability on intercropped soybean in strip intercropping

Abstract

Taller crops affect the direct light interception and use efficiency of shorter crops in strip intercropping. Quantifying the light interception of shorter crops and optimizing it by manipulating the configurations could reduce lodging and produce a greater yield. Prior investigations have examined the instantaneous light interception of short-stature crops in intercropping. However, the direct quantification of daily light interception (DAI) and its inter-row variation in strip intercropping remains unclear. In this study, we developed a modelling approach to quantify the daily light interception of soybean plants in different arrangements of maize soybean strip intercropping and verified its accuracy by measuring photosynthetic active radiation (PAR) and phenotypic response (plant height, leaf area, biomass, and yield) to light. Treatments included five intercropping systems (1M1S represents one maize row intercropped with one soybean row, 2M1S, 2M2S, 2M3S and 2M4S represent two maize rows intercropped with 1–4 soybean rows, respectively, with the increase of soybean strip width) and two sole soybean cropping system (S40 and S50, soybean row distances of 0.4 m and 0.5 m, respectively), all plants were planted in east-west rows direction. Our results showed that the DAI calculated using the new model of the soybean canopy in intercropping was lower than that in sole cropping. At the grain-filling stage, the DAI at the soybean canopy increased from 29.3 MJ/m2 in 1M1S to 125.6 MJ/m2 in 2M4S. In 2M2S, 2M3S, and 2M4S, the DAI of border rows (soybean rows close to the neighboring maize row) on the north side were 1.37, 8.89, and 18.72 times higher than those of the border rows on the south side, respectively. DAI was significantly correlated with the measured instantaneous PAR and increased with an increase in soybean strip width. The measured plant height, leaf area, biomass, and grain yield of soybean across each row of each intercropping treatment exhibited a consistent trend with changes in DAI, and they were positively correlated with the soybean strip width. Soybean plants in rows with less light interception showed an obvious shade response: plant height increased, and leaf area, biomass, and yield decreased. This physiological response of soybean was caused by changes in light interception, confirming the accuracy of the model. The proposed light interception model and related physiological responses offer a quantitative approach and reference for understanding light competition in strip intercropping systems to design better strip configurations.