Effects Of Nitrogen Application And Plant Interaction On The Decomposition Of Soil Organic Matter

Nitrogen fertilizer could affect the decomposition of crop straw and soil organic matter.However,in general soil culture experiments,the existence of crops is often ignored.The effect of nitrogen fertilizer on the decomposition of organic matter is affected by crops.Therefore,a pot experiment was designed to compare the effects of different nitrogen application on the decomposition of plant residues and SOC in oats and no oats.The experiment was a two-factor experiment:nitrogen gradient?N0,N1,N2,N3 and N4?*crop level?no oat and oats?.Ten treatments were assessed:?1?N0+no oat;?2?N1+no oat;?3?N2+no oat;?4?N3+no oat;?5?N4+no oat;?6?N0+oats;?7?N1+oats;?8?N2+oats;?9?N3+oats;?10?N4+oats.We investigated the dynamics of various soil N pool?inorganic nitrogen,microbial nitrogen?and N uptake by oats,as well as the changes of N and C in the light fraction?density<1.8g cm-3?in the whole oats growing period,and ¹³C was used as tracer to study the decomposition of plant residues and SOC.The main results as follows:?1?during the whole growing period of oats,the content of inorganic nitrogen in the oat-free soil was significantly higher than that planting soil.?2?The mineralized amount of plant residue and soil organic matter in oat-free treatment was higher than that in planting treatment.The decomposition ratio of soil organic matter decreased gradually with the increase of N application in the 5treatments of planting,but the decomposition rules of 5 treatments without oats was not obvious.?3?The results of 13C/12C showed that the SOM and LFOM mineralized amounts of oat-free treatment were higher than that of planting treatments,whether from straw part or soil part.With the increase of N application,the decomposition ratio of light organic matter?LFOC?decreased gradually in the 5 treatments of planting,but the decomposition ratio of 5 treatments without oats was not obvious.?4?There is a significant positive correlation between the mineralization of light group carbon and light group nitrogen.It is shown that the decomposition of nitrogen and the decomposition of nitrogen are coupled in this experiment.The results of this experiment show that:1.Compared with non-plant growth,planting oats reduced the decomposition of crop straw and soil organic matter.It is suggested that the absorption of water and nitrogen by plants may affect the decomposition of crop straw and soil organic matter.2.Under the condition of planting crops,with the increase of nitrogen application rate,the mineralization of crop straw and soil organic matter decreased gradually.However,there was no significant difference in the mineralization of crop straw and soil organic matter among different nitrogen fertilizer treatments without planting crops.In oat treatment,with the increase of nitrogen application rate,the nitrogen competition between microorganisms and plants weakened,and microorganisms reduced the amount of organic nitrogen.The absorption and utilization of crop straw and soil organic matter were reduced.