Effects Of Subsoiling And Controlled Release Urea On Nitrogen And Water Utilization Of Maize And Their Hormone Regulatory Mechanisation

In this study, two summer corn varieties with two cultivation systems and four nitrogenlevels, this research analysed the effects between Z958and D3of different treatments on yieldand yield components, photosynthesis, grain filling rate, the utilization efficiency ofnitrogen-water and the regulatory mechanism of endogenous hormone in summer corn. Theresults are useful to supply a principle and technology of high yield for summer corncultivation. The main results were as follows:1Effects on photosynthetic performance and yield of summer corn under differenttreatmentsThe controlled release urea could provide plenty of nutrients and significantly enhancethe LAI, Pn, gs and PNUE, extend the leaf photosynthetic time of maize after flowering, andwas better for more photosynthate accumulation of maize. The subsoiling was in favor ofpromoting the water absorption of maize by roots. Compared with other treatments, thesubsoiling and controlled released urea treatment significantly enhanced nutrients absorptionand utilization efficiency of maize and significantly improved photosynthetic performance ofear leaf after flowering in both varieties.Photosynthetic performance played a key role for the yield of maize. Improvingphotosynthetic performance could enhance the photosynthate accumulation of maize atflowering and was material basis of increasing yield. At the same cultivation system, the drymatter accumulation, the1000-grain weight and the yield at the controlled-release ureatreatments were higher than other normal urea treatments. Under the same nitrogen level,compared with rototilling treatments, the yield of subsoiling treatments were significantlyhigher than rototilling treatments in both varieties. The interaction treatments betweencultivation system and nitrogen level had highly significant effect on the maize yield and the1000-grain weight, and the interaction treatment between subsoiling and controlled-releaseurea treatment had the higher yield of maize than other treatments in both varieties. Comparedwith D3, the yield of Z958was higher than D3.2Effects on nitrogen and water utilization efficiency of summer corn under differenttreatmentsWater and nitrogen fertilizer play important roles in improving maize yields. Comparedwith normal urea treatments, controlled-release urea treatments results in more efficient N uptake by plants. In addition, controlled release urea can reduce environmental pollution bymatching nutrient release with plant demand. Subsoiling significantly increased the rainfallstorage capacity of soils. In addition, subsoiling may also promote water uptake by crop roots.Thus, the interaction between subsoiling and controlled release urea had the higherwater/nitrogen utilization efficiency than other treatments in two varieties. Compared with D3,the water/nitrogen utilization efficiency of Z958was higher than D3.3Effects on the AO activity and contents of endogenous of ear leaf and grain underdifferent treatmentsAldehyde oxidase (AO, EC1.2.3.1) catalyzes the final step of ABA biosynthesis and isexpressed in both leaves and grains. AO activity effect the ABA contents. The water/nitrogenutilization efficiency of maize both played important roles in plant AO activity. Thewater/nitrogen utilization efficiency of maize could restrain AO activity in ear leaf, but ingrain could enhance the AO activity. Thus, the interaction between subsoiling and controlledrelease urea restrained AO activity in ear leaf and enhanced AO activity in grain. Therefore,compared with other treatments, the interaction between subsoiling and controlled releaseurea favourable enhanced ABA biosynthesis in grain and restrained ABA biosynthesis in earleaf.The ABA content in the ear leaf and grain had large effect on Zr content in thecorresponding parts. Compared with other treatments, the interaction between subsoiling andcontrolled release urea restrained ABA content and enhance Zr content in ear leaf and ABAand Zr content during the middle grain-filling stage.4Correlation analysis between endogenous hormone and photosynthetic performanceand grain-filling rateThe present study demonstrated that the ear leaf photosynthetic capacity and grain-fillingrates were affected by the interactions between ABA and Zr content of the ear leaf andgrain.The ear leaf ABA content was significantly negatively correlated with the Pn, gs andPNUE. However, the ear leaf Zr content was highly and positively correlated with the Pn, gsand PNUE. In grain, both ABA and Zr were highly and positively correlated with grain fillingrate and the ear leaf Zr content was also highly and positively correlated with grain filling rate,but the ear leaf ABA content significantly and negatively correlated with grain filling rate.5The best treatment mode for summer cornThe interaction treatment between subsoiling and controlled release urea had the highestwater/nitrogen utilization efficiency than other treatments in two varieties. Regulation effectof ABA and Zr on physiological metabolism in both ear leaf and grain，the regulation effects of ABA and Zr on the improvement of photosynthetic performance and the increasing grainfilling rate were significantly correlated. Compared with other interaction treatments betweencultivation systems and the nitrogen levels, the interaction between subsoiling and thecontrolled released urea treatment significantly increased the photosynthetic performance, andits yield was the highest than others in two varieties. Compared with D3, the yield of Z958was higher than D3.