Effects of techniques of paddy field production mechanization on occurrence of diseases, insect pests, weeds and yield of double-cropping rice

Abstract: Four patterns such as mechanized rotary tillage-mechanized transplanting method, mechanized rotary with cattle tillage-mechanized transplanting method, cattle tillage-mechanized transplanting method and mechanized rotary tillage-manual transplanting method were tested in order to investigate the effects of different plowing-transplanting methods on diseases, insect pests, weeds and yield of double-cropping rice. Results showed that major diseases, insect pests and weeds were sheath blight disease Rhizoctonia solani, Cnaphalocrocis medinalis, Monochoria vaginalis and Echinochloa crusgalli in early rice with four plowing-transplanting methods in no using pesticide areas, and sheath blight disease, C medinalis, rice planthopper (Sogatella furcifera and Nilaparvata lugens), M. vaginalis and E. crusgalli in late rice. Under the same conditions of fertilizer and water management, the sheath blight disease indexes of early and late rice were 8.25-13.31 and 17.60-23.10 at booting stage, 13.75-20.90 and 20.02-23.76 at milky stage, respectively, which was more serious using mechanized rotary tillage-manual transplanting method than that using mechanized rotary tillage-mechanized transplanting method, and more serious using cattle tillage-mechanized transplanting method than that using mechanized rotary tillage-mechanized transplanting method. The second generation of C. medinalis occurred seriously in early rice, and its curled leaf rates were 15.03%-16.67%. The fourth and fifth generation of C. medinalis in late rice occurred seriously, and its curled leaf rates were 29.67%-33.48% and 60.09%-65.45%, respectively. The occurrence difference of C. medinalis was not significant between four plowing-transplanting methods in early and late rice. The population density of rice planthoppers in late rice was low at early stage, 425-550 heads/100 clusters at full heading stage, 1200-1600 heads/100 clusters at milky stage, which was highest using mechanized rotary tillage-manual transplanting method, and lowest using mechanized rotary tillage-mechanized transplanting method. There were M. vaginalis, E. crusgalli, Sagittaria pygmaea, Euphorbia lathyris, Murdannia triguetra and so on in early paddy field, which M. vaginalis and E. crusgalli were the dominant species, 68.00% and 29.70% of the total grasses, respectively. There were M. vaginalis, E. crusgalli, Rotala indica, Euphorbia lathyris, Cyperus rotundus, Alternanthera philoxeroides and so on in late paddy field, which M. vaginalis and E. crusgalli were the dominant species, 69.60% and 17.40% of the total grasses, respectively. The weeds' density was highest in early and late paddy fields with cattle tillage-mechanized transplanting method, followed by mechanized rotary with cattle tillage-mechanized transplanting method and mechanized rotary tillage-mechanized transplanting method, and lowest with mechanized rotary tillage-manual transplanting method. Variance analysis indicated that there was no significant difference in the yield among four kinds of plowing-transplanting methods. The diseases, insect pests and weeds in early and late rice under different plowing-transplanting methods could be controlled effectively by applying appropriate pesticides during the early days of pest occurrence. The average yields were increased 10.00% and 7.88%, respectively. The study provided a reference for the extension of control technology on diseases, insect pests and weeds of double-cropping rice in paddy field production mechanization.