Resistance changes and effectiveness experiment of increasing yield of rice with mixed planting under mechanical transplanting

Abstract: In recent years, growing crops in mixtures has become an important element of sustainable agriculture and organic farming. Mixed cropping is especially popular in parts of Asia. Rice is one of the most important crops in China. Rice is cultivated in a quarter of the arable land in China and supports more than half of its population. Pests and diseases are the main limitations in rice production. It was reported that the rice yield loss due to pests and diseases exceeds 20%. Available insecticides are currently used for the control of rice pest. Mixed planting of different rice varieties is an effective strategy to control weeds, diseases and pests, but it is difficult to extend at large scale because of the complicated operating. Until now, a lot of researches focus on intercropping, but few studies about completely mixed planting have been reported. Meanwhile, along with the development of the agricultural industrialization and modernization, rice mechanized transplanting will replace the traditional transplanting by hand in our country, and the economy and technology conditions for developing rice mechanized transplanting are also maturing day after day. The mixed planting becomes easy to carry out using mechanical transplanting model. The experiment was conducted in China National Rice Research Institute experiment station in 2013, and two rice varieties, i.e. Shenliangyou 5814 and Zhongzheyou 8, which had similar plant height and growth period and different resistance, were used in this experiment. Five patterns including 100:0, 70:30, 50:50, 30:70, and 0:100 mixtures (by plant number) of Shenliangyou 5814 and Zhongzheyou 8 were adopted to evaluate the effects of mixed planting on rice growth and yield. The experiments were laid out in a split-plot design: contrast test of five mixture patterns was in the main plot, and that of non-pesticide and pesticide was in the sub-plot. The results showed that: the mixed planting significantly improved rice yield and the resistance to weeds, disease and pests. In all mixed planting patterns, mixed pattern of 50:50 had the best resistance to weeds, disease and pests, and the weeds biomass decreased by 13.1% and 54.1%, and sheath blight index decreased by 79.5% and 27.1% compared with planting patterns of 100:0 and 0:100, respectively. The lodging rate of rice decreased with the increasing of Zhongzheyou 8 mixture rate. The yields of rice in five mixture patterns without pesticide application decreased by 32.6%, 31.3%, 26.9%, 27.4% and 28.8%, respectively, compared with those of corresponding treatments with pesticide application. So the rice mixed planting was an effective management to improve rice's resistance to weeds, pest and disease, and it could reduce the input of pesticide. The mixed planting pattern can improve rice tiller development and leaf area index, especially at tillering stage. Mixed planting could promote nutrient transformation, and promote nutrient accumulation in the grains. Compared to the monoculture planting patterns (i.e. 100:0 and 0:100), the yield of rice in mixture pattern (50:50) increased by 12.8% and 7.0%，respectively, and the grain filling percentage increased significantly. This study indicated that the fitting rice mixture pattern combined with mechanized transplanting could reduce production input and improve rice yield and quality. More research is needed to do, such as the fitting variety for mixed planting, the production technology for getting high yield.