Effects of different fertilisers on rice resistance to pests and diseases

Abstract

A field experiment was conducted in Shanghai in 2013, to study the effects of different fertiliser applications on the occurrence of rice pests and diseases. The experiment included four treatments: a non-fertilised control (CK); rapeseed cake manure (CM) at a low (CML) and a high (CMH) rate; and a synthetic chemical fertiliser (CF). No pesticides were applied within the rice-growing season. The rice plants treated with CF grew tallest, and had higher contents of NH4+-N, NO3–-N, chlorophyll and soluble proteins than those in the other fertiliser treatments and CK. However, the incidence of leaf rollers (Cnaphalocrocis medinalis), stem borers (Chilo suppressalis) and planthoppers on the rice plants treated with CF was significantly higher than in the other fertiliser treatments and CK (P < 0.05). In particular, the incidence of stem borers in the plants treated with CF was about 10 times higher than in the other treatments and CK, and the density of planthopper populations on the plants treated with CF was 1.73, 1.42 and 3.04 times that on plants treated with CMH, CML and CK, respectively. The application of fertilisers increased soil microorganisms, and the effects of rapeseed cake manure on the increase in microorganisms were most significant. Numbers of soil bacteria, fungi and Actinomyces were the highest in soils treated with CMH. Application of rapeseed cake manure also significantly raised the activity of soil dehydrogenase. The CF treatment inhibited dehydrogenase activity but raised urease activity significantly. Average theoretical grain yields in treatments CML, CMH, CF and CK were 7.45 × 103, 8.85 × 103, 7.41 × 103 and 3.70 × 103 kg ha–1, respectively. The application of CF stimulated rice vegetative growth more effectively but finally led to lower grain yield due to higher incidence of pests and diseases.