The Characteristics Of The Black Soil C:N:P Evolution Based On Ecological Stoichiometry

Studying the effect of long-term fertilization on soil organic matter and microbial biomass carbon-nitrogen-phosphorus stoichiometric ratio has important theoretical and practical significance for a deep understanding of soil organic carbon and nutrient cycling and their interaction process.Based on the theoretical methods of Ecological stoichiometry and a 26-years fertilization experiment in a cropland,we analyzed content and stoichiometric ratio of C,N,and P in bulk soil,soil organic matter,and microbial biomass under various fertilization treatments.At the same time,based on the boundary analysis method,Big Data analyzed the effects of different climate and fertilization measures on the characteristics and capacity of soil microbial biomass carbon and nitrogen in China.The results of long-term experiments showed that compared with Fallow,long-term application of chemical fertilizers(N,NP,PK,NPK)significantly reduced the soil C: N ratio,and the application of P fertilizer(fertilizer phosphorus and organic phosphorus)significantly reduced the soil C: P ratio and N: P.ratio.Long-term application of fertilizer P(NP,PK,NPK)significantly increased the microbial biomass C: N ratio.Under long-term straw return treatment(SNPK),soil phosphorus caused nutrient restriction to microorganisms.In addition,because the farmland soil microbial biomass carbon-nitrogen-phosphorus ratio has no internal stability characteristics,so the change of carbon,nitrogen and phosphorus in soil will directly lead to the change of microbial community structure,and then the stoichiometric ratio of carbon,nitrogen,and phosphorus in microbial biomass will change.Among them,soil organic carbon,available phosphorus and pH played a key role in the growth and development of soil microbial communities(Available phosphorus was helpful for the growth of bacteria,and pH had a more significant effect on fungi.).However,the C,N,and P ratios of soil organic matter are more affected by microbial biomass carbon,the amount of nitrogen taken away by crops,phosphorus taken away by crops,microbial biomass nitrogen,microbial biomass phosphorus and some microbial populations.There was no direct significant correlation between soil microbial C: N: P ratio and organic matter C: N: P ratio,but different microbial populations had significant effects on soil organic matter C: N ratio and N: P ratio.Long-term chemical fertilizer treatment lead to deterioration of the soil nutrient environment and was not conducive to the growth and development of microbial communities.The application of chemical fertilizers with organic materials(straw and organic fertilizer)had an important role in improving the soil microbial community diversity,microbial population content,and the stoichiometric ratio of organic carbon,nitrogen,and phosphorus.Result from big sample size statistics showed that the response coefficient(i.e.,the correlation slope)between SMBC and SOC,SMBN and TN was 24.6 and 28.7 under organic amendments,respectively,which were significantly higher than that under the management without organic amendments(18.3 for SMBC and 17.9 for SMBN).The median value of SMBC/SOC and SMBN/TN were significantly different among the four climate zones.The highest value of SMBC/SOC was 2.67% under temperate semi-arid and sub-humid zone(M2),followed by sub-tropical(S,2.44%)and warm humid zone(W,2.31%),the lowest value is 1.48% under temperate humid zone(M1).The sequence of SMBN/TN was W(4.05%)>M2(3.50%)>S(2.99%)>M1(1.92%).The range of SMBC/SOC and SMBN/TN were 0.35%-6.50% and 0.50%-9.72% under various fertilization conditions with no significant deference.Boundary analysis showed that the maximum response coefficient of SMBC to SOC and SMBN to TN were 26.4-31.9 and 46.4-50.4,respectively.The current averaged value was about 67.0% and 46.3% of the maximum value,respectively.Climatic conditions have a significant impact on soil microbial biomass capacity.Different fertilization managements did not significantly changed the SMBC/SOC and SMBN/TN,but the organic amendment can significantly improve SMBC and SMBN,which can be helpful for soil biological fertility improvement.