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Lanzhou University (2014)

Effects of Plastic Mulch on Soil Nitrogen Cycling and Fate of Fertilizer Nitrogen in Field-grown Maize at a Semiarid Site


Titre : Effects of Plastic Mulch on Soil Nitrogen Cycling and Fate of Fertilizer Nitrogen in Field-grown Maize at a Semiarid Site

Auteur : 刘小娥;

Grade : Doctoral Dissertation 2014

Université : Lanzhou University

A new cultivated pattern of two ridges and their furrows covered by plastic film has been widely applied in dryland farming systems, for its significant effect on increased yields and income in the semiarid Loess Plateau of china. Plastic mulch effect on the interaction between film fully-mulched ridge-furrow cropping and maize growth on temperature and moisture, soil nitrogen content, soil nitrogen cycling and the fate of fertilizer nitrogen in croplands has received limited attention. Four treatments were evaluated in2011and2012 :(1) no mulch+no crop planting ;(2) mulch+no crop planting ;(3) no mulch+crop planting ; and (4) mulch+crop planting. Narrow and wide ridges were alternated in all treatments and maize (Zea mays L.) was seeded in the furrows only for the crop-planted treatments. Main results as follows:1. Compared with no mulch, the presence of mulch in both the2011and2012cropping seasons consistently increased soil temperature by2.7-3.3℃in the0-20cm soil layer over the course of the whole experiment under no maize planting, whereas it increased by2.6-3.3℃in the first two months of the season only under maize planting. This showed that no increase in soil temperature in the later growth stages in mulched maize-planted fields was due to the interception of solar radiation by the crop canopy. In2011, mulch increased soil water storage (in the0-100cm depth) by19-40%and conserved100mm more rainfall in the0-170cm depth over the whole experimental course compared with unmulched treatment under no maize planting, However, soil water storage was higher in mulched treatment in the early two and half months but was similar in the remaining months under maize planting, and that a15%higher amount of water loss happened in mulched treatment than in unmulched treatment under maize planting. In2012, soil moisture dynamics under the four treatments were different from those in2011because of residue effects and higher precipitation. In2012, soil water storage was higher in mulched treatments than in unmulched treatments throughout the experimental course, regardless maize planted or not. Compared to no mulch, mulch increased grain yield and water use efficiency by70-72%and57-77%, respectively, over the two experiment years. The results suggest that, in addition to increased soil temperature during the early growth stages, increased transpiration under mulch contributes to increased grain yield and water use efficiency compared with no mulch.2. Two months after urea application, total NH3-N volatilization in unmulched fields (30-34kg ha-1) was ten times that in mulched fields. Over five months of maize growth, soil N in the0-15cm was mineralized in the first three months but immobilized in the later two months. N mineralization rate was generally unaffected in the first one month but stimulated by mulch in the middle two months ; N immobilization rate was reduced by mulch in the last two months, compared with no mulch. Maize planting increased soil N mineralization mainly in the peak growth compared with no maize planting. Total N mineralized over season was201-309%greater in mulched than in unmulched soils and12-114%higher in maize-planted than in non-maize-planted soils, indicating that soil N mineralization was stimulated by the improved soil hydrothermal conditions under plastic mulch compared with no mulch. The reduced ammonia volatilization and stimulated N mineralization were responsible for the increased soil N content and uptake by maize under mulch compared with no mulch. Our results demonstrate that plastic mulch prominently changes N cycling in croplands.3.15N isotope traced results in field experiment showed that In2011, in-season maize use efficiency of fertilizer N was23%under no mulch and19%under mulch, that is, a19%decrease under the latter than under the former (P<0.001). In2012, maize use efficiency of residual labeled N (%of N from labeled N in aboveground biomass in2012over labeled-urea N applied in2011) was10%under no mulch and16%under mulch, an increase by63%under the latter than under the former (P<0.001). The cumulative maize N use efficiency (%of N from labeled urea in aboveground biomasses of2011and2012over labeled N applied in2011) was similar in non-mulched (34%) and mulched plots (36%)(P>0.05).

Mots clés : Plastic mulch; soil temperature; soil water; ammonia volatilization; nitrogen mineralization; soil mineral nitrogen; fertilizer use efficiency; the fate offertilizer nitrogen;

Présentation (CNKI)

Page publiée le 16 novembre 2017