Effects Of Different Modifiers And Maize-peanut Rotation On Community Structure And Diversity Of Functional Genes For Nitrogen Transformation

Continuous cropping has become a common phenomenon in agricultural production because of the influence of cultivated land area and planting conditions.Most crops will appear continuous cropping obstacle after repeated cropping,which results in worse growth,lower yield and inferior quality of crops,seriously restricting the sustainable development of agriculture.This study was based on the field experiment of biochar and carbon-based fertilizer established by Shenyang Agricultural University in 2011.Five treatments were set up in the experiment:treatment 1（maize continuous cropping）,treatment 2（maize peanut rotation）,treatment 3（peanut continuous cropping）,treatment 4（continuous cropping with chemical modifier）,and treatment 5（repeated cropping with biological modifier）.Collection of soil and plant samples for the 2021 harvest for soil fertility,bacterial and fungal community structure and diversity,AOBamo A,nir S,nir K,nar G and other functional gene community structure and diversity,nutrient uptake and yield analysis.The results as follows:（1）The application of chemical modifiers and maize peanut rotation could significantly inhibit soil acidification and improve the content of soil organic matter and nutrients.Compared with peanut continuous cropping,corn peanut rotation had a prominent positive effect on the content of soil organic matter and total phosphorus,increasing by 24.50%and 108.16%respectively;the application of chemical modifier had a prominent effect on the increase of soil available nutrients,increasing by 19.91%～52.57%,and the application of biological modifier had a prominent effect on the increase of soil available potassium content,increasing by 18.18%.（2）Long-term rotation and application of different modifiers had different effects on the contents of soil microbial biomass carbon and nitrogen.Compared with continuous cropping of corn and peanut,the content of soil microbial biomass carbon and nitrogen in corn peanut treatment increased by 15.80%～81.88%;compared with peanut continuous cropping,soil microbial biomass carbon and nitrogen increased by 35.67%and 88.41%respectively.Compared with peanut continuous cropping treatment,the microbial biomass nitrogen content increased by 33.83%.（3）Long-term rotation and application of different amendments had no significant effect on bacterial Alpha diversity in rhizosphere and bulk soil.Long-term rotation increased fungal Alpha diversity in rhizosphere and bulk soil of peanut:compared with PC treatment,the rhizosphere diversity index of peanut increased by 26.54%～42.27%and bulk biodiversity index increased by 36.20%～51.09%under M-PR treatment.（4）Long-term rotation could significantly change the bacterial structure in rhizosphere soil of peanut,and the fungal structure of rhizosphere and bulk.Different amendments had no significant effect on the bacterial and fungal structure of peanut rhizosphere soil,but could significantly change the bacteria structure of bulk soil.For bacteria,the dominant phylum Proteobacteria was positively correlated with soil organic matter content.The relative abundance of Proteobacteria in rhizosphere soil was increased by 11.43%～16.49%in long-term rotation and different amendments.The relative abundance of Proteobacteria in bulk soil of peanut was increased by 25.27%after long-term application of biological amendments.For fungi,Basidiomycetes showed a negative correlation with soil organic matter content.The relative abundance of pathogenic fungi Basidiomycetes in peanut rhizosphere soil was significantly decreased under maize and peanut rotation.The abundance of fungi in M-PR was21.58%less than that in PC.（5）The Alpha diversity of nirK gene in peanut rhizosphere and non rhizosphere soil of long-term maize peanut rotation increased significantly by 108.51%and 122.92%;the Alpha diversity of amo A and nir S genes in rhizosphere soil decreased significantly by 15.48%～37.97%.The Alpha diversity of amo A gene and nir S gene between rhizosphere and bulk in peanut rhizosphere soil decreased significantly by 16.12%～76.82%;the alpha diversity of amo A gene bacteria in peanut bulk soil increased significantly.The Alpha diversity of amo A and nir K genes in peanut bulk soil increased significantly by 50.80%～65.37%.（6）Compared with peanut continuous cropping,rotation has no significant effect on soil NH₄⁺-N and NO₃^--N contents.The content of NH₄⁺-N in soil could be decreased significantly by applying amendments.Compared with PC treatment,the content of NH₄⁺-N in PCCA treatment and PCBA treatment decreased by 35.30%and 66.48%respectively.The content of NO₃^--N in soil treated with chemical amendments increased 42.06%compared with PC treatment.（7）Long-term rotation and application of different amendments significantly changed the community composition of bacteria carrying amo A,nir K,nir S and nar G genes in peanut rhizosphere and bulk soil.In peanut rhizosphere and bulk soil,the amo A gene carrying Nitrosovibrio increased 17.08%～184.40%,nir K gene carrying Bradyrhizobium increased19.81%～111.09%,the relative abundance of nir S carrying Thauera increased by 34.11%～96.03%,and that of Acidiphilium carrying nar G gene decreased by 66.90%～85.44%.（8）The long-term maize peanut rotation had the best effect on promoting nutrient accumulation in peanut pods,which increased by 39.29%～105.22%compared with peanut continuous cropping;the long-term application of chemical modifier had the best effect on the accumulation of nitrogen,phosphorus and potassium in peanut stems and leaves,which increased by 57.90%～31.09%compared with continuous cropping of peanut.The long-term use of corn peanut rotation and long-term application of modifier can improve the yield of peanut.The yield increase effect of corn peanut rotation is more significant,which is 61.09%higher than that of peanut continuous cropping.Different modifiers had significant promoting effects on flower production,but there was no significant difference between them.