| Soil carbon,nitrogen and phosphorus are important indicators of soil fertility.A lot of research has suggested that the nutrients in deep layer soil play a key role in the improvement of crop yield.Soil has a great potential for carbon and nitrogen fixation in the deep layer.Therefore,it is very important to study the change characteristics of carbon,nitrogen and phosphorus cycling in soil profile under different fertilization in order to understand the sustainable production capacity and mitigate the greenhouse effect.This study is based on long-term experiment platform,with Red soil,Loess soil,Fluvo-aquic soil and Black soil as the research project.Soil organic carbon,total nitrogen,total phosphorus and organic phosphorus of 0-100 cm profile soil(20 cm for each layer)were measured at the year of 1990(initial)and 2013 under different fertilization practices.Change characteristics and response relationship of soil profile carbon,nitrogen and phosphorus was analyzed under differences site or treatments.The main results and conclusions are as follows:Compared with the initial of experiment,soil organic carbon storage of 0-100 cm soil showed a net release(in the Red soil and Black soil,average decreased by 13 %)and maintaining state(in the Fluvo-aquic soil and Loess soil)under 24 years no fertilization(CK treatment).Leisure measures can quickly promote soil organic carbon storage and soil organic carbon storage was increased by 34 %-70 % in the Red soil,Loess soil and Black soil(mainly increased in 0-20 cm).Soil organic carbon storage of 0-100 cm was also improved at different levels under application of chemical fertilizers and chemical fertilizers combined with straw.For the different soil layers,soil organic carbon storage of Red soil mainly increased in 40-100 cm and of the Loess soil,Fluvo-aquic soil and Black soil mainly increased in 0-40 cm.Under chemical fertilizers combined with organic fertilizer(including NPKM and high NPKM treatment),soil organic carbon storage was respectively increase by an average of 33 %,33 %,47 % and 84 % in the Red soil,Loess soil,Fluvo-aquic soil and Black soil of 0-100 cm(mainly increased in 0-40 cm soil in the four soils).Compared with the initial of experiment,soil total nitrogen in 0-100 cm soil showed a net depletion(in the Fluvo-aquic and Black soil,average decreased by 19 %)and maintaining state(in the Red soil and Loess soil)under application of no fertilization(CK treatment).Leisure measures quickly promote soil total nitrogen storage,and soil total nitrogen storage was increased by 20 %-70 % in the Red soil,Loess soil and Black soil(mainly increased in 0-20 cm).For the Red soil and Loess soil,soil total nitrogen storage were respectively increased by 28 % and 8 % under application of chemical fertilizers,but 25 % and 22 % under application of chemical fertilizers combined with straw(mainly increased in 40-100 cm for Red soil but in 0-40 cm for the Loess soil).However,for the Fluvo-aquic soil and Black soil,soil total nitrogen storage of 0-100 cm soil was decrease by an average of 6% under application of chemical fertilizer and no obvious change under application of chemical fertilizer combined with straw.Under application of chemical fertilizers combined with organic fertilizer,soil total nitrogen storage was respectively increased by an average of 47 %,28 %,18 % and 37 % in the Red soil,Loess soil,Fluvo-aquic soil and Black soil of 0-100 cm(mainly increased in 0-40 cm soil in the four soils).Compared with the initial,soil total phosphorus storage of 0-100 cm soil was depleted in different levels in the four type soil under application of no phosphate fertilizer(including CK,N and NK treatments).Leisure measures(Fallow treatment)can reduce the degree of phosphorus depletion of 0-100 cm soil in the Fluvo-aquic soil and Black soil.Application of chemical fertilizers with phosphorus(Including NP,PK,and NPK)could supplement phosphorus which was uptake by crop and soil total phosphorus storage of 0-100 cm soil was increased by 5 %-25 %.However,soil total phosphorus storage of 0-100 cm soil was increased 7 %-13 % in the Loess soil,Fluvo-aquic soil and Black soil under application of chemical fertilizer combined with straw.Under application of chemical fertilizers combined with organic fertilizer,soil total phosphorus storage was increased by an average of 10 %-75 % in the four type soil of 0-100 cm(mainly increased in 0-40 cm soil in the four soils).Compared with the initial of experiment,the soil organic phosphorus content and the ratio of soil organic phosphorus to soil total phosphorus was respectively increased by an average of 106 % and 15.5 percentage points in 0-20 cm and 20-40 cm soil layer of Red soil,but the ratio of soil organic carbon to soil organic phosphorus and ratio of soil total nitrogen to soil organic phosphorus was respectively decreased by an average of 47% for all fertilization and management measures.However,the soil organic phosphorus content and the ratio of soil organic phosphorus to TP in 40-100 cm soil layer is slightly decreased,but the ratio of soil organic carbon to soil organic phosphorus and ratio of soil total nitrogen to soil organic phosphorus was significantly increased by an average of 107 % for all fertilization and management measures.The ratio of soil organic carbon to soil total nitrogen was increased by 34 % only in the 40-60 cm soil layer,no significant changes in other soil layers.There was a significant positive linear correlation between soil organic carbon,soil total nitrogen and soil organic phosphorus in the upland red soil profile for all fertilization and management measures.The results showed that long-term different fertilization and management measures did not destroy the coupling relationship between carbon,nitrogen and phosphorus.There were significantly effects on the coupling response of carbon,nitrogen and phosphorus cycling in the upland red soil profile under the incompatible inputs of carbon,nitrogen and phosphorus and different tillage practices. |
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