| The highland of Loess Plateau is a large grain production base in the Loess plateau.Spring maize is one of the main grain crops in this region.But the fertilization technology of spring Maize was single formed with basal and top dressing,labor input and fertilizer excessive,resulted in environmental pollution,resource waste residue and soil N residue.Slow or controlled release nitrogen fertilizer can promote crop growth,reduce nitrogen loss,increase yield and Nitrogen use efficiency,which is an important technology for reducing nitrogen fertilizer.A field experiment was conducted under film mulching conditions in the highland of Loess Plateau area,to study the effects of different slow or controlled release urea,applied by basal application with reduced rate,on grain yield,nitrogen use efficiency,nitrogen accumulation,inorganic nitrogen dynamics in top soil(0~40 cm)layers and morphological index in spring maize.This study aimed to assure the optimum type and application rate of slow or controlled release urea for spring maize production in this region with simplified and efficient fertilization techniques.This field experiment was single factor completely randomized design,Spring maize cultivar was Zea mays L.cv.Xianyu335.Experiment consisted of nine treatments: no Nitrogen application(N0),farmer conventional Nitrogen fertilization(application rate was 225 kg N?ha-1,N225),common urea Nitrogen reduction(application rate was180 kg N?ha-1,N180),and nitrogen rate reduction with six kinds of slow or controlled release urea(application rate was 180 kg N?ha-1),i.e.,resin coated urea(RCU),controlled loss urea(CLU),sulfur coated urea(SCU),urea formaldehyde(UF),polypeptide urea(PU)and stabilized urea(SU).Plant and soil(0~40 cm layer)samples were collected at different growing stages,for analysis of leaf area index,plant height,biomass,grain yield,plant N accumulation and soil inorganic N concentration.The main results are as follows:(1)Application of nitrogen fertilizer could affect the yield and its components of spring maize significantly.Nitrogen application significantly increased yield,grain number per ear,ear length and ear diameter,but had no significant effect on 1000 grain weight and harvest index.Application of N fertilizer significantly increased grainyield of maize by 28%~65% relative to N0.Compared with N225,N180 significantly decreased grain yield by 19.2%;Application of RCU,UF,PU and SU did not significantly decrease grain yield,while application of SCU and CLU increased grain yield by 4.5% and 2.7%,respectively.Slow or controlled release nitrogen fertilizer increased Agronomic nitrogen efficiency and nitrogen partial factor productivity significantly,the highest ANE was SCU and CLU.(2)Compared with the common nitrogen fertilizer,slow or controlled release nitrogen fertilizer increased the economic benefit.Compared with N0,nitrogen fertilizer treatments economic benefit increased 2526~6324 ￥·ha-1.All N treatments,economic benefit of N180(12669 ￥·ha-1)was the lowest.Compared with N225,N180 and UF decreased net income by 2051 ￥·ha-1 and 467 ￥·ha-1,respectively;slow or controlled release nitrogen fertilizer(except for UF)increased economic benefit by 347~1747 ￥·ha-1.Compared with N225,slow or controlled release nitrogen fertilizer increased economic benefit by 1584~3798 ￥·ha-1.(3)Compared with N0,the nitrogen accumulation of plants in nitrogen treatments was increased significantly by 59.32~90.07 kg N·ha-1.Compared with N225,there was no significant decrease in the slow or controlled release nitrogen fertilizer treatments.Compared with N180,the nitrogen accumulation of slow or controlled release urea treatments(except UF)increased significantly.The trend of grain nitrogen accumulation was consistent with the nitrogen accumulation of plants.Compared with N225,N180 reduced the N use efficiency by 4.39%;Each slow or controlled release urea(except UF)were significantly increase the N use efficiency by 2.26%~12.69%,and the highest of N use efficiency was SCU and CLU.(4)Inorganic N content in topsoil(0~40 cm)of different nitrogen treatments at different growth stages were significantly differences,soil inorganic N content at jointing stage of SU increased significantly;soil inorganic nitrogen content of RCU,CLU and SCU increased significantly at huge bellbottom stage;N225 soil inorganic N content increased significantly at silking stage.After harvest,the nitrogen treatments inorganic N content in 0~200 cm soil was increased in different soil layers.Among them,the inorganic nitrogen contentof N225 was higher than other treatments,it is highest in 60~100 cm soil layer.(5)Compared with N0,the application of common nitrogen fertilizer could significantly increase soil water consumption 22.4~27 mm;and soil water consumption of slow or controlled release N fertilizer had no significant increase.Compared with N0,nitrogen application significantly increased water use efficiency 4.06~11.24 kg·mm-1·ha-1.Compared with N180,the nitrogen use efficiency of slow or controlled release N fertilizer was significantly increased4.42~7.18 kg·mm-1·ha-1.(6)Compared with N0,nitrogen application could significantly increase the biomass,leaf area index and plant height at different growth stages of spring maize(except jointing).In mature stage,nitrogen treatments(except UF)were significantly higher than N180.The leaf area index of spring maize increased firstly and then decrease,the leaf area index of all treatments reached the highest value at silking stage.In summary,under the climatic conditions of the highland of Loess Plateau area,Slow and controlled release nitrogen fertilizer,such as CLU and SCU,applied by single application with reduced amount(reduced by 20%),can maintain grain yield,improve N use efficiency and economic benefits,and save labor costs.Therefore,it can be used as an option for simplified and efficient fertilization in spring maize production in similar areas in Loess Plateau. |
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