Study On Soil Fertility Improvement And Yields Increasing Effects Of Straw And Biochar Returning To Field

Many studies had proved that straw and biochar returning to field could increase the number of soil macro aggregates significantly,increase the organic carbon content in aggregates,improve soil structure and then improve the soil fertility.However,the research data of under the Brown soil long-term positioning test condition and the fertilization practices of equal nitrogen,phosphorus and potassium were few.Further research is needed Compared with the variations of aggregates,total nitrogen,soil organic carbon and crop yields after long-term straw and biochar returning to field in this experiment.The experiment was designed to find a suitable way to improve Brown soil and increase crop yields.Brown soil of maize continuous cropping system and peanut continuous cropping system were selected in six-year field micro-plot experiment in Shenyang,Liaoning Province.Six treatments were established:control(CK),chemical fertilizer application(NPK),biochar application(B),biochar with chemical fertilizer application(BNPK),straw application(S)and straw with chemical fertilizer application(SNPK).Collecting the soil samples of 0?20 cm and 20?40 cm soil layers after maize and peanut harvested in mature period.The main results are as follows(1)Straw and biochar returning to field could decrease 0?20 cm and 20?40 cm soil layers soil bulk density,as well as increase soil porosity.The soil bulk density of 0?20 cm soil layer was significantly lower than that in 20?40 cm soil layer and the porosity was greater than 20?40 cm soil layer.Besides,BNPK treatment was better than SNPK treatment In addition to B treatment of peanut,the other different fertilization treatments could all improve the soil available nutrients content.The available nutrients content of 0?20 cm soil layer were higher than that in 20?40 cm soil layer(2)In the maize experiment and in the 0?20 cm soil layer,BNPK treatment and SNPK treatment could increase>1 mm,1?0.5 mm and<0.053 mm size aggregates content compared with NPK treatment,increase by 31.57%,21.22%,9.64%,50.28%,22.94%and 2.96%respectively.And the aggregates content of different sizes in 0?20 cm soil layer were higher than corresponding size in 20?40 cm soil layer.BNPK treatment and SNPK treatment decreased the content of 0.25?0.053 mm size aggregate significantly,reduced by 15.92%and 13.63%.BNPK treatment and SNPK treatment significantly increased the average weight diameter(MWD),geometric mean diameter(GMD)and 0.25 mm size aggregate(R0.25).The MWD and GMD of SNPK treatment were higher than BNPK treatment significantly.In the peanut test,BNPK treatment and SNPK treatment had the same effects on the distribution of aggregates in 20?40 cm soil layer with maize experiment results.In the 0?20 cm soil layer,the SNPK treatment increased the content of>1 mm size aggregate significantly,increased by 96.95%.Similarly,the SNPK treatment's MWD,GMD and R0.25 were higher than BNPK treatment.This indicated that straw with nitrogen,phosphorus and potassium chemical fertilizer was superior to biochar with nitrogen,phosphorus and potassium chemical fertilizer in improving the stability of soil aggregates(3)In different fertilization treatments,the total nitrogen and organic carbon content were the highest in>1 mm size aggregate and the content in<0.053 mm size aggregate were the lowest.In the maize experiment,BNPK treatment and SNPK treatment could improve the content of total nitrogen and organic carbon contents in different sizes aggregates of 0?20 cm soil layer.The additional range of total nitrogen content was 8.16%?28.72%and the organic carbon content additional range was 23.11%?52.89%.In 20?40 cm soil layer,in addition to<0.053 mm size aggregate of B treatment,the rest of the treatments could improve the soil aggregates total nitrogen content.Besides,in addition to the>1 mm size aggregate of SNPK treatment,the rest of the treatments could increase the organic carbon content of soil aggregates.In the peanut test,the total nitrogen content of different sizes aggregates in SNPK treatment were higher than that in BNPK treatment and the>1 mm size aggregate of BNPK treatment organic carbon content was higher than the SNPK treatment.The total nitrogen and organic carbon contents of most aggregates in 20?40 cm soil layer were less than 0?20 cm soil layer.The total nitrogen and organic carbon in soil were mainly supplied by 0.25?0.053 mm and<0.053 mm sizes aggregates.BNPK treatment and SNPK treatment could reduce the total nitrogen and organic carbon content of the 0.25?0.053 mm size aggregate significantly In the maize test,the BNPK treatment and SNPK treatment could promote the allocation proportion of total nitrogen and organic carbon content in macro aggregates,while in the peanut test,BNPK treatment improving the allocation proportion of total nitrogen and organic carbon in macro aggregates was greater than the SNPK treatment(4)BNPK treatment and SNPK treatment could increase maize yield significantly,increased by 22.20%and 5.94%respectively compared with fertilizer application.SNPK treatment could increase the yield of peanut,increased by 9.76%.The peanut yield of SNPK treatment had no significant difference with NPK treatment.The plant height,stem diameter and the CCI value of maize and the main stem height and the CCI value of peanut were higher than that of the CK treatment.The CCI value of maize in different growth periods were ranging from 11.3 to 53.0 and the CCI value of peanut different growth periods were ranged from 18.5 to 46.1In conclusion,the long-term straw and biochar returning to field could reduce the soil bulk density,improve soil porosity and available nutrients content,change the distribution of soil aggregates,promote the formation of macro aggregates,improve the soil structure,improve stability of soil aggregates and the content of total nitrogen and organic carbon,contribute to maize and peanuts increasing production.In improving the stability of aggregates,the effects of straw returning to field was better than biochar returning to field.In improving the content of total nitrogen and organic carbon in soil aggregates,biochar returning to field were better than straw back to the field.