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Accueil du site → Doctorat → Chine → 2005 → Accumulative Mechanism, Crop Utilization and Environmental Response of Nitrate in Soil Profile in Dryland on the Loess Plateau

Northwest University of Science and Technology (2005)

Accumulative Mechanism, Crop Utilization and Environmental Response of Nitrate in Soil Profile in Dryland on the Loess Plateau

Dang Ting Hui

Titre : Accumulative Mechanism, Crop Utilization and Environmental Response of Nitrate in Soil Profile in Dryland on the Loess Plateau

Auteur : Dang Ting Hui

Grade : Doctoral Dissertation 2005

Université : Northwest University of Science and Technology

Résumé partiel
The reseach, based on the question of overuse or irrational use nitrogen causing nitrateaccumulation in pursuit of higher crop productivity in dryland, explored the process of nitrateaccumulation and crop validity of virious depths’ nitrate in soil profile with the 15N isotopetraced technique and long-term position experiment, and investigated the situation of nitrateaccumulation in the Loess Plateau with the method of point-region combination by collectingsoil profile samples in the representative regions. The results were followings :(1) By investigating soil nitrate in 0-300cm profile in the representative regions of LoessPlateau, nitrate accumulating amount was in 1.0-353 mg/kg, average 27 mg/kg, C.V. 2.1 in0-300cm soil profile of total samples coming from representative regions’ orchard land andfarmland, in general orchard > farmland. Nitrate accumulating amount was in 1.2 – 54mg/kg,average 8.2, C.V. 1.3 in farmland and in 1.3 – 352 mg/kg,average 47 mg/kg,C.V. 1.7 in orchard, respectively. In the different land types, nitrate accumulation was seriousin highland, terraceland and plainland in orchard, and the amount would increase with thefertilization levels or planted years. In farmland, nitrate accumulating amount showed theorder of highland>damland>plainland>terraceland, but the differences were small. Becausethe water table in dam-land or plain-land is shallow, nitrogen rate-increase might bring soilnitrate accumulation as well as underground water pollution. The rainfall in Changwu countyis richer than one in others in Loess Plateau, so the result from Changwu showed the deepestdepth of nitrate accumulation was 240cm in farmland or 300cm in orchard land in LoessPlateau.(2) The result from long-term fertilization experiment showed that nitrate accumulationin soil was inevitable in long-term imbalance use or overuse nitrogen. Nitrate content,accumulating amount, accumulative ratio and accumulative depth in soil were correlated withtype of fertilizers’ mixture, rate-applying, every item would increase with the rate of nitrogen,but decrease with the rate of phosphorus. Organic manure had the role of reducing nitrateleaching to deeper depth, but it was not able to decrease the amount of nitrate accumulation insoil profile. The accumulative ratio was in 8.5%-31.0% in 0-200cm soil profile withtreatments of NPM>N>NP>M. The most accumulative ratio was 44.1% in 0-400cm soil inonly use nitrogen of 180 kg/hm2.(3) 15N isotope traced results in field experiment in the south of Loess Plateau showedthat nitrogen would have aftereffect in evidence, the total recovery of five crops planted oneby one was 44.1%-46.5%, the remnant N in soil was 22.4%-28.3%. it showed that the greatremnant-N in soil was mostly reason for nitrate accumulation formation. Wheat, cornmulching planting did not have the role of improvement to nitrogen use efficiency(NUE) infirst crop, but increased obviously remnant-N in soil. The remnant-N could be useed byaftercrop, total NUE in two season wheats increased by 16.6%. The great remnant-N wouldmove down in soil profile by the way of mass-flow in action of rainfall, it was main reason ofnitrate accumulation in soil profile.(4) In rainfed farmland the nitrate leaching, movement and accumulation are impactedby some factors such as crops, fertilization, water and soil types. The crops with deep rootsand high yield might use nitrate in big extent and amount, soil nitrate accumulation mightdecrease

Mots clés : nitrate accumulation in soil profile availability environmental response loess plateau

Présentation (Dissertationtopic)

Page publiée le 3 mai 2013, mise à jour le 22 avril 2018