Insect-proof nets affect paddy field microclimate parameters and grain quality of different japonica rice varieties

Abstract

Insect-proof nets (IPN) are widely used to protect crops from invertebrate pests. The effects of IPN on the main microclimate parameters of paddy fields, as well as grain quality, were investigated for three japonica Oryza sativa L. varieties (Nanjing 44, Nanjing 45, and Suxiangjing 3) that are widely grown in China. The environmental temperature of IPN-treated fields increased slightly, whereas the maximum value of photosynthetically active radiation (PAR), daily cumulative PAR, and daily cumulative global radiation all decreased. However, the ratio of PAR to global radiation increased significantly, from 15.08 to 45.48%. Compared to the no insect-proof net (NIPN) treatment, the head rice percentage increased significantly for all three varieties; however, the chalky grain percentage, area and degree, and the amylose content all decreased significantly. The response of gel consistency, protein concentration, and the main parameters of the rapid visco analyzer (RVA) profile of rice starch to IPN treatment differed between varieties. The peak viscosity and breakdown were increased compared to the NIPN treatment, whereas the final viscosity and setback were decreased. However, no significant differences were found between the IPN and NIPN treatments. Furthermore, statistical analysis indicated no interaction between rice planting pattern (RPP) and rice variety (RV) for the rice grain quality parameters. These results suggest that IPN treatment improved rice grain quality for all japonica rice varieties studied, possibly due to the slight increase in environmental temperature and increased ratio of PAR to global radiation in IPN treated paddy fields.