Effects Of N Fertilizer Combined Biochar And Straw Amendments On Soil And Wheat NP Contents And N: P Ratio

Nitrogen and phosphorus ecological stoichiometry provides a new perspective for studying the material cycle and energy flow of crop-soil ecosystem.By studying the metrological relationship between main chemical elements such as nitrogen and phosphorus,it is possible to combine the different organic levels such as population,community and ecosystem togather,which is beneficial for reveal the mechanism between plant growth and the relationship with restrictive factors.This perspective can expand a new pattern to study the relationship between crop productivity and chemical elements in dryland crop communities.In this paper,we put the spring wheat-soil system of dryland farmland in Dingxi City of Gansu Province as the research object.By field experiments,the field experiment was conducted to investigate the effect of N0(no nitrogen fertilizer and biochar amendment,as CK),N50(50kg·hm-2·a-1,no biochar amendment),N100(nitrogen fertilizer 100 kg·hm-2·a-1,no biochar amendment),B(biochar 15t·hm-2),BN50(nitrogen fertilizer 50 kg·hm-2·a-1),BN100(nitrogen fertilizer 100 kg·hm-2·a-1,biochar 15t·hm-2),S(wheat straw),SN50(nitrogen fertilizer 50 kg·hm-2·a-1,wheat straw),SN100(nitrogen fertilizer 100 kg·hm-2·a-1,wheat straw)on the soil nutrient contents of dry farmlands.Finally we discussed the ecological stoichiometry characteristics of wheat and soil under different amendments,which proved for the theoretical foundation with scientific soil management and nutrient limitation of farmland and rational fertilization.The results of the study are:(1)The dryland farmland SOM,STN,STP,SAN and SAP distribution patterns under different nitrogen combined biochar and straw source material were significantly changed,especially the biochar combined with 100kg·hm-2 nitrogen fertilizer amendment,whose results showed that the amendment could increase the SOM,STN,STP and available nutrient contents,which is effectively beneficial for the cultivate soil fertility and promote the soil carbon,nutrogen and phosphorus storages.(2)Soil N: P analysis showed that the STN: P ratio was between 1.42 and 1.58,and the SAN: P ratio was between 1.08 and 1.29.As the SAN: P of biochar amendments are highest,so the soil about P uptake remains a high transfer rate,which extravagantly absorb P element.Compare with straw amendments,the soil SAN: P ratio also was higher than that of the straw.As the biochar was more able to promote the sufficient supply of N of the soil,so the SAN: P ratio was higher than that in straw.(3)The amendments of N adding with biochar and straw sources all resulted in the improvement of wheat N and P contents.Except for biochar and straw additions,other enhanced N content of wheat.Wheat P content of different organs behaved signfigent imparity,especially the P was significantly highest under the measure of biochar combined with 100kg·hm-2 N fertilizer,which further improved the nutrient availability of nitrogen and phosphorus.Carbon-fertilizer interaction significantly increased the SAN and SAN of soil,which further improved the nutrient effectiveness of the nitrogen and phosphorus and indirectly enhanced wheat N and P contents.(4)N: P ratio of wheat under different carbon and nitrogen sources showed that N: P ratio was between 19.49 and 22.52,in which the leaf N: P was between 16.61 and 22.36,stem P between 18.56 and 25.64,grain N: P between 18.35 and 21.68.The N: P ratio of different organs under different amendments showed that the N: P ratio of wheat in dryland farmland were fluctuated in a very small range under the additions of nitrogen combined biochar and straw amendments.Wheat N: P ratio behaved inherent stability,which consistent with the homeostatic mechanism hypothesis.(5)Correlation analysis showed that the correlation between P content and N: P ratio was the most significant in both wheat and organic plants,and the N: P ratio was higher than that of N,and the effective P content of the Loess Plateau is far lower than the national average content of available P,the wheat population in the study area may be limited by P element.(6)Wheat product analysis showed that biochar adding with 100kg·hm-2 N fertilizer and straw adding 100kg·hm-2N fertilizer significantly increased the wheat yield,compared with CK amendment,the leaf yield increased by 14.81% and 10.92%,respectively.The stem yield was 58.91% and 52.32%,and grain yield increased by 55.26% and 36.78% respectively.The interaction among different organic matters such as biochar and straw and N fertilizer can significantly improved soil effective nutrient contents,and thus promoted wheat root nutrient uptake,which is beneficial for accelerating wheat growth rate.(7)The treatments significantly increased the soil nutrient content and crop yields,while the treatments significantly increased the nutrient content,which promoted the uptake of nitrogen and phosphorus of wheat.Thus,they also reduced wheat N: P ratio.Considering the effect of 100 kg·hm-2N fertilizer adding with biochar behaved most obvious,therefore,it was most reasonable to utilize 100 kg·hm-2 N fertilizer for promoting farmland productivity sustainable development of region.