Effects Of Different Corn Planting Densities On Soil Moisture And Yield In Rainfed Farming Land Of North-east Of China

Maize is one of the three major grain crops in the whole world. The planting area is already 2.735×104 hm2 at present. Three northeast provinces are the main grain production area and the important commodity grain base of maize in China. In 2009, planting area and yield of maize all accounted for over 60% of the total planting area and yield of cereal in Liaoning. At present, maize production in various regions is still led by the rainfed agriculture. This paper studies on making full use of rainfall and improving water use efficiency of maize in rainfed agriculture.It is great significance for easing the shortage of agricultural water resource in China, increasing the maize yield and guaranteeing the national food security.This paper make a case of Shenyang city, study on effects of different corn planting densities on soil moisture and yield in rainfed farming land of North-east of China. By 2009-2010 two years test, soil water, plant growth status, and yield are observed, which are under different planting densities. The related meteorological data need to be observation and collection.,Analyze soil moisture change trend under different planting densities and tillage depths in the whole growth period and in different growth periods. In typical weather, analyze soil moisture along soil profile change trend. Based on water balance equation it need to seek out corn evapotranspiration under different plant density. Using the meteorological data to calculate reference crop evapotranspiration and seeking out the crop coefficient of different densities. Calculate for precipitation use efficiency and water use efficiency. The main conclusions as follows.(1) Wave variation of soil moisture has a close relationship with rainfall and evaporation. There is a lot of rain between June and July, so soil moisture fluctuation frequently. Step into September to the corn harvest period, soil moisture is in smooth gradual cut phase. Planting density has a certain influence on distribution of soil water storage area. In maize root distribution area,20-40cm-layer soil moisture of T3 (55500/hm2) change most, soil moisture of T1 (40500/hm2) change minimum. In plenty of rainfall and consecutive drought time, soil moisture of 20-40cm depth can has most around 10% difference. Under various planting densities, soil moisture content in 20-40cm consumption up mostly in drought. This place is the main soil water storage area and water consumption of maize root area.(2) During whole growth stage, soil moisture fluctuation trends general same in shallow tillage area and the deep tillage area, but the fluctuations affected by factors such as precipitation, evaporation and plant transpiration effect are different in the different growth period. Comparison of before and after rainfall (33 mm), soil moisture of shallow tillage area had increased 2%-3%, and deep tillage area had increased 2.2%-5.4%. Deep tillage area can save more rain than shallow tillage area, which played "soil reservoir" storage effect. In a continuous drought, soil moisture is nearly the same at first, but with the soil depth increased, soil moisture of shallow tillage area significantly reduced.10 days later, difference in reducing up to 1.1%, and maximum difference has reached 2.6% after 20 days. Compared with shallow tillage area, soil moisture of deep tillage area had declined more slowly.(3) Leaf area per plant declined with the plant density increasing, but community's leaf area and the leaf area index increased with the community leaf area and the leaf area index increase. Plant height, stem diameter and yield components changed little under different plant densities. In this experiment, the most suitable density of new variety LiaoDan527 is about 3200 to 3335 per 667 m2, which can get the highest yield.(4) According to long series precipitation frequency analysis calculation, precipitation frequency is 83.43% in 2009, which is partial drought year. Precipitation frequency is 9.98% in 2010, which is partial flood year. T2 is the maximum water requirement in shallow tillage area, which is 373.3mm. The maximum required water period is spike formation stage, and Kc in elongation stage is maximum. T2 is the minimum water requirement in deep tillage area, which is 439mm. The stage required water situation for:elongation stage> spike formation stage> seedling stage> maturity stage, rendering a section unimodal curve, and Kc in elongation stage is maximum. Crop required water of deep tillage area is bigger than shallow tillage area. Crop coefficient is about 0.65, in shallow tillage area, and it is about 0.8 in deep tillage area. T2 had highest precipitation use efficiency in 2009, which is 4.08kg·m-3.M2 (3335/667m2) had highest precipitation use efficiency in 2010, which is 1.75kg·m-3. T2had highest water use efficiency in 2009, which is 3.02kg·m-3. M2 had highest water use efficiency in 2010, which is 4.53kg·m-3, which is 1.60kg·m-3.