Effects of straw mulching on photosynthetic characteristics and yield of intercropped maize

To deeply understand the effects of combined intercropping and straw mulching practices on crop yield improvement, a 2-factor filed experiment was carried out at the Red Soil Experimental Station of Jiangxi Agricultural University in Nanchang City, Jiangxi Province, China. The experimental design consisted of eight treatments (i.e., 2 × 4) with two planting patterns maize monoculture (M), maize/soybean intercropping (I) and four straw mulch levels 0 (S0), 4 000 kg·hm^-2 (S1), 8 000 kg·hm^-2 (S2) and 12 000 kg·hm^-2 (S3). The study mainly investigated maize leaf traits, leaf physiological characteristics, photosynthetic characteristics and yield to learn the effects of different straw mulching levels and intercropping patterns on various maize traits. The results showed that mulching and intercropping increased maize leaf length, leaf width and green leaf area per plant. The difference between mulching treatments (S2 and S3 treatments) and non-mulching treatment (S0) was significant at P < 0.05. Moreover, the effects of straw mulching on the studied maize traits were more significant than those of intercropping. While maize leaf water content was little influenced by intercropping, it was significantly influenced by straw mulching. Intercropping and mulching increased leaf nitrogen content. Compared with S0 treatment, S3 treatment increased leaf nitrogen content by 25.6% and 56.6% under M treatment, and 30.0% and 42.9% under I treatment respectively at grain filling and maturity stages. The difference between S3 and S0 treatments was significant. Mulching and intercropping increased chlorophyll content in maize leaves and the effects of straw mulching were greater than those of intercropping. However, the effects of mulching decreased with increasing levels of straw mulching. Both mulching and intercropping enhanced photosynthetic characteristics of maize ear leaf. Compared with M treatment, I treatment respectively increased photosynthetic rate, stomatal conductance and transpiration rate by 13.1%, 42.3% and 39.3% at grain filling stage and 46.8%, 31.2% and 24.5% at maturity stage under S0 treatment. Concurrently, intercropping respectively reduced intercellular CO^-2 concentration by 20.8% and 18.4% at grain filling and maturity stages of maize. The difference between monoculture and intercropping under S0 treatment was significant at P < 0.05. While maize yield was obviously influenced by both mulching and intercropping, the effect of straw mulching was greater than that of intercropping. The findings demonstrated that straw mulching and intercropping were critical for improving maize leaf traits, physiological characteristics and yield. However, the effect of straw mulching decreased with increasing levels of straw mulching, and the effect of intercropping was less obvious than that of straw mulching.