Effects Of Different Mechanical Sowing Methods On Growth, Yield Andeconomic Efficiency Of Wheat

To meet the demands of yearly mechanization and light-duty production, mechanical sowing, integrated with mechanical and agronomic technologies in soils at different moisture levels, has been a heated research topic in recent years. This study was conducted on the experimental sites of Rugao, Xinghua, Donghai, and the Experimental Farm of Jiangsu Provincial Key Lab of Crop Genetics and Physiology during the two wheat growing seasons from 2012 to 2014. Different wheat sowing machines, including Type 2BG-6A drilling machine, broadcasting machine, and ribbon-drilling machine, were tested, with artificial broadcasting as the control treatment. The effects of different mechanical sowing methods were studied on grain yield, net economic efficiency, seedling growth, population quality, canopy microclimate, accumulation of nutrient elements, and physiological activities of flag leaves. This study provided theoretical support for the system innovation of key wheat cultivation technology. The main results were as follows:1. Higher grain yield, lower input cost, and higher net efficiency were determined in the treatments of mechanical sowing methods than in the treatment of artificial broadcasting on all experimental sites. The grain yield was the highest in the treatment of mechanical drilling provided sowing date and soil moisture were suitable. Mechanical broadcasting or mechanical ribbon-drilling had higher grain yield when sowing was late and the soil was high in moisture content or clay percentage. The net efficiency was higher in all the mechanical treatments as compared with artificial sowing. Mechanical sowing not only decreased production cost but also increased net efficiency. The grain yield of the treatments with different mechanical sowing were linearly correlated with economic efficiency. Mechanical sowing should be adjusted according to the specific sowing conditions. Specifically, mechanical drilling should be used if sowing date and soil moisture are suitable. Mechanical broadcasting or mechanical ribbon-drilling should be used when sowing was late and soil was high in moisture content or in clay percentage.2. Sowing quality, which varied greatly in soils with different moisture contents, was significantly affected by mechanical sowing methods. When soil moisture was at suitable level, higher emergence percentage, lower rate of sparse plantation, uniform seedling emergence, and higher dry weight per plant were obtained by mechanical drilling. At high soil moisture content levels, seeding depth varied greatly, the rate of seedling establishment was greatly reduced, the rate of sparse plantation was significantly higher, and dry weight per plant was greatly reduced. When mechanical broadcasting was used, the seeding depth was low and uniform, the emergence rate and dry weight per plant were high. In the treatments of mechanical ribbon-drilling, the seeding depth was high and uniform, but the rate of leaf emergence was slow, and the seedlings were long and low in dry weight per plant.3. Compared with mechanical broadcasting, wheat seedlings in the treatments of mechanical drilling and mechanical ribbon-drilling grew more slowly, the accumulation of biomass at early growth stages was decreased, but moderate population was achieved with more effective tillers and higher percentage of ear-bearing tiller, and more dry matter accumulation after anthesis. For the treatment of mechanical broadcasting, strong seedlings were easily developed and high amount of biomass was accumulated before jointing, but there was a large number of ineffective tillers and high LAI at booting stage, resulting into inadequate biomass accumulation after anthesis and low percentage of ear-bearing tiller. 4. Different sowing methods had significant effects on nutrient absorption of wheat plants. After booting stage, the nutrient accumulation was high in the treatments of mechanical drilling and mechanical ribbon-drilling as compared with mechanical broadcasting. Compared with mechanical drilling and mechanical ribbon-drilling, the absorption and accumulation of nitrogen and phosphorus in the treatment of mechanical broadcasting was significantly higher during over-wintering and at joint stage, and premature senescence of wheat plants occurred at late growth stages. There was a scattered distribution between grain yield and nutrient accumulation at the early and middle stages. The grain yield was linearly correlated with nutrient accumulation at anthesis stage and mature stage. The nutrient absorption ability in different mechanical sowing treatments were dependent on sowing conditions. When the soil was high in moisture content, seedlings didn’t grow well, which affected the nutrient absorption at middle and late growth stages.5. There was higher light transmittance in the treatments of mechanical drilling and mechanical ribbon-drilling as compared with the treatment of mechanical broadcasting. The interlayer-temperature in the treatments of mechanical drilling and mechanical ribbon-drilling were higher and closer to natural temperature as compared with mechanical broadcasting and artificial sowing. The declining rates of SPAD readings between 14 and 28 d after anthesis and net photosynthesis were significantly lower in the treatments of mechanical drilling and mechanical ribbon-drilling as compared mechanical broadcasting. The senescence process was accelerated in the treatment of mechanical broadcasting. In the treatments of mechanical drilling and mechanical ribbon-drilling, the activities of SOD, POD, and CAT of the flag leaves at anthesis were positively and linearly correlated with grain yield, but the content of MDA was negatively and linearly correlated to grain yield.6. In grain nutritional and processing quality, there were significant difference between mechanical broadcasting and mechanical drilling and ribbon-drilling, but no significant difference was determined between mechanical drilling and mechanical ribbon-drilling. The grain bulk density and sedimentation value in the treatment of mechanical broadcasting method were higher than those in the treatments of mechanical drilling and mechanical ribbon-drilling. The contents of protein and wet gluten in the treatment of mechanical broadcasting were lower than those in the treatments of mechanical drilling and mechanical ribbon-drilling. The peak viscosity, through viscosity, and final viscosity in the treatment of mechanical broadcasting were significantly higher than those in the treatments of mechanical drilling and mechanical ribbon-drilling.