Effects Of Nitrogen Fertilizer Application And Mulching On Grain Yield And Quality Of Spring Maize On The Loess Plateau

Maize is one of the most important food crops in China,while moisture and nutrients are the main factors limiting maize yield and quality in drylands.Mulching and nitrogen application,as the most effective yield enhancement measures in current drylands nowadays,also have their non-negligible drawbacks.Long-term use of common plastic mulch can lead to degradation of arable soil quality,and the residue will cause serious environmental pollution,while irrational nitrogen fertilizer application can also produce a series of resource wastage and environmental problems.Previous studies have mainly focused on the effects of N fertilizer transport and agronomic practices on maize grain yield,while the studies on grain quality have stressed on its response to nitrogen application,neglecting the effects of agronomic practices and their interaction with nitrogen application on maize grain nutritional quality.This study took spring maize in the dryland area as the research object,we investigated the effects of different N fertilizer application rates and types and mulching methods on the yield and grain quality,as well as the accumulation of above ground dry matter and nitrogen uptake,so as to determine the optimal N application rates and types and mulching methods in the area,thus providing a theoretical basis for high green yield and quality of spring maize in the dryland area.The main results are as follows.(1)Gravel mulching,degradable film mulching and plastic film mulching all could increase spring maize grain yield and crude protein content.Grain yield under gravel mulching was significantly lower than plastic film mulching.Degradable film mulching could keep grain yield and crude protein content of spring maize as the same level as that under plastic film mulching,and obtain higher N harvest index.Degradable film mulching could replace plastic film mulching to achieve high yield and quality of spring maize in the rain-fed area of Loess Plateau.(2)Nitrogen application,plastic film mulching and interaction of two factors significantly increased grain yield,dry matter accumulation and N uptake of spring maize.Under the same coverage conditions,when the nitrogen application rate was less than 250 kg/ha,the grain yield was positively correlated with the nitrogen application rate,and the grain yield,dry matter accumulation and N uptake were no longer significantly increased when the nitrogen application rate > 250 kg/ha.Under the condition of mulching,the grain yield and crude protein content reached a high level of 18.73 t/ha and 9.35%,respectively.The excessive nitrogen application was not conducive to the further improvement of grain yield and quality.(3)Traditional recommended topdressing practices,one-time application of a mixture of controlled and straw returning kept the high yield of spring maize,with 17.36 t/ha 17.19 t/ha and 16.71 t/ha,respectively.Meanwhile,the grain crude protein,crude fat and crude starch contents were 8.64%-9.21%,4.65%-5.32% and 75.98%-76.52%,respectively.Compared with the traditional recommended topdressing practices,the one-time application of a mixture of controlled and straw returning had no significant effect on the dry matter accumulation of spring maize,but significantly increased the pre-silking,post-silking and total N uptake.The one-time application of a mixture of controlled treatment maintained high yield and high quality of spring maize on the basis of simplifying the field N fertilizer management.The results of this study showed that degradable film mulching can achieve the same level of yield and quality as plastic film mulching in the rain-fed area of the Loess Plateau;higher grain yield and quality can be achieved by applying 250 kg/ha of N under mulching conditions;controlled-release fertilizer mixed with ordinary urea in one application simplifies N fertilizer management while achieving high grain yield and quality.