Research On Labor Saving And Reducing Fertilization Technology Of Spring Maize In Loess Plateau

In Loess Plateau,spring maize production had the problem of nitrogen fertilizer excessive,reduced N use efficiency,and labor input,etc.The development and application of slow/controlled release nitrogen fertilizer had effectively solved these problems.But the fertilizer efficiency of slow/controlled release nitrogen fertilizer was affected by many factors,such as fertilizer types,external environment(temperature,moisture,etc.).Thus,suitable selection and promotion of slow/controlled release nitrogen fertilizer varieties and fertilizer techniques should be companied with local conditions.Because film mulching significantly increased water content,temperature and yield,which was widely used in Loess tableland.But there was spatial differentiation in soil water-heat condition and nutrient transport beside or under film.The location of fertilizer would affect the nutrient release about slow/controlled release fertilizer with the absorption and utilization of nutrients by plants.To assess the effects of fertilizer sources,N rates,fertilization modes(split application,basal application only)and fertilization places(beside or under plastic film)etc on the growth and yield of spring maize,water and nitrogen utilization,nitrogen uptake and nitrogen release characteristics in the field of tested nitrogen fertilizer under rain-fed spring maize.The aim of the study was to provide a scientific reference for the reduced nitrogen rate and simplified practices of rain-fed spring maize in the Loess Plateau area.Two experiments were conducted in Changwu,Shaaxi,China,located in the south of the Loess Plateau.(1)A 2-yr field fertilization trial with no N application(N0);conventional fertilization(N225,split application,beside film),reduced application(N180,split application,beside film),reduced-basal urea(B-N180,basal application only,beside film);reduced sulfur coated urea was basal applied only(B-SCU,beside film and B-SCUi,under film);reduced controlled loss urea was basal applied only(B-CLU,beside film and B-CLUi,under film)etc,were performed during 2017-2018.(2)The fertilizers' nitrogen release trial with 6 treatments included: common urea applied beside film(Urea)and under film(Ureai);sulfur coated urea applied beside film(SCU)and under film(SCUi);controlled loss urea applied beside film(CLU)and under film(CLUi)etc,was conducted during 2018 growth season without maize.The results of the study are as follows:(1)Fertilizer sources,N rates and fertilization modes have significant effects on spring maize yield and yield cpmponents,economic performances,morphological indexes,water and nitrogen use,etc.Nitrogen reduction(20%)had no yield loss but increased profits,water and nitrogen use efficiency when choosed the suitable fertilizer sources and fertilization modes.The nitrogen accumulation and grain nitrogen accumulation of B-N180 and B-CLU with basal application only were equivalent with conventional application treatment(N225).But the harvest index was highest in B-CLU.Reduction of basal application only fertilization(except B-SCUi)to improve the agronomic nitrogen efficiency and apparent nitrogen recovery.(2)The dynamic changes of mineral nitrogen in different growth stages were affected by fertilizer sources and application,also,by the rainfall and rainfall distribution in the growing season.The residue and distribution of the soil mineral nitrogen were also affected by the above factors.In basal application only treatments,the common urea(B-N180)and the controlled loss urea(B-CLU,B-CLUi)were higher in soil mineral nitrogen content before the jointing stage of spring maize;the jointing-silking period,controlled loss urea(B-CLU,B-CLUi)and sulfur coated urea(B-SCU,B-SCUi)were higher in soil mineral nitrogen content.After spring maize harvest,conventional application(N225)0-200 cm soil mineral nitrogen residue was higher than basal application only treatments,among which B-CLU treatment had the least residue;and spilt application treatments were higher than basal application only treatments.The mineral nitrogen residual position of fertilization placed under film were shallower than beside film.(3)The plant height and leaf area index of rain-fed spring maize in the Loess Plateau increased rapidly during jointing-silking period.The accumulation rate of dry matter accelerated from the bell stage.The peak of nitrogen uptake was in the joint-bell period.However,the uptake of nitrogen in the early growth stages had an important impact on plant growth and yield formation.The controlled loss urea provided more mineral nitrogen for the spring maize before the bell stage,and its nutrient release law matched the local hydrothermal conditions and the growth law of spring maize.(4)The yield effect of fertilization placed beside film were better than those of placed under film with the beside-film planting practiceIn general,nitrogen rate reduction(20%)was feasible on rain-fed spring maize in the Loess Plateau area.Reduce 20% of controlled loss urea could maintain grain yield,improve N use efficiency and economic performance,and save labor,so it could be recommended to be used in the simplified and efficient fertilization practice of spring maize in the Loess Plateau and similar area.