Research On The Effects Of Inorganic-organic Fertilizer Incorporation Under Rice-wheat Rotation System In Hubei Province

In this study,three years of field experiment was carried out in Jingmen,Hubei province,under a rice-wheat cropping system subjected to different fertilizer regimes in two seasons(May and October).Five treatments with randomized block design of four replicates were designed as follows:no fertilizer(CK),100%traditional fertilizer(100F),100%recommend fertilizer(100C),on the basis of 100C treatment,20%chemical nitrogen replaced by organic fertilizer,with same phosphate and potassium(80C+20M)and on the basic of 100C treatment,reduce 20%nitrogen chemical fertilizer and 20%nitrogen replaced by organic fertilizer,while phosphate and potassium remained the same(64C+16M).The purpose of this study was to investigate the effects of pig compost and chemical fertilizers combination on the crop yields,nitrogen use efficiency,soil nutrients,enzyme activities,and soil microbial community.The main results obtained are listed as follows.1.The 100C and 80C+20M treatments,both could keep rice and wheat production stable and maintain the productivity of rice-wheat rotation system when compared to CK treatment.Compared to chemical fertilizer,organic fertilizer combined with nitrogen fertilizer can promote the nitrogen recovery efficiency(REN),the partial productivity of nitrogen(PFPN)and the agronomic N efficiency(AEN).2.In the rice season,the soil organic matter(SOM)content,soil available phosphorus(Olsen-P)content and the urease activity were significantly increased in 80C+20M and 64C+16M treatments.While in wheat season,all of the soil nutrients,soil urease and invertase activities were significantly increased in 80C+20M treatment.We also detected seven kinds of soil enzyme activities using a new method of labeled substrate MUB-microplate fluorimetric assay.The results showed that,fertilization had a certain extent inhibition effects on the rice soil extracellular enzyme activities.In addition,a strong inhibition from chemical fertilizers and a weak inhibition from organic manure fertilizer were found.Fertilization promoted several kinds of extracellular activities in wheat season,but inhibited soil a-glucosidase and ?-cellulase activities.Furthermore,the soil urease activity,invertase activity and ?-xylosidase activity all had a significant correlation with the yield of rice and wheat.3.In the rice season,the results of real-time PCR showed that fertilization increased the copies number of soil bacteria,ammonia oxidizing microbes(AOA and AOB)and nitrogen-fixing bacteria(nifH).The copy numbers of soil bacteria and nifH gene in 80C+20M treatment were the highest,and the number of AOA and AOB were the highest in 64C+16M treatment,indicating that organic fertilizers combined with chemical fertilizer had a strong effect on soil functional bacterial.In the wheat season,the copy numbers of soil bacteria in 100F treatment were the highest,and the number of nifH gene,AOA and AOB in 100F treatment was the highest,indicating that chemical fertilizers had a great effect on soil functional bacterial.Correlation analysis showed there was a significant possitive correlation between the numbers of AOA,AOB,nifH and crop yield,indicating that these three N-cycling related gene had a significant effect on rice and wheat production.4.We used Illumina MiSeq technology to analyze the soil bacterial community by sequencing 16S rDNA V4 region,detail results showed that short-term fertilization had less effect on soil bacterial diversity.There were nine dominant groups(more than 1%relative abundance in phylum level)invesgated in all soil samples,including Acidobacteria,Bacteroidetes,and Proteobacteria,etc.At the genus level,Gemmatimonas was the dominant group in wheat and rice season.Considering class and genus level dominanted in rice and wheat season,we can conclude that organic manure combined with chemical fertilizer significantly changed the soil community composition.There are some correlations between the relative abundance of soil dominant bacterial groups and soil chemical properties.In particular,the amount of soil bacteria had a significant positive correlation with soil nutrient(r=0.240,p<0.001),especially with SOM and pH.Furthermore,there is a significant positive correlation(p<0.01)between soil bacterial community and the cropping system,and the correlation between soil bacterial community and fertilization was also significant(p<0.05).In summary,80C+20M treatment has significant advantages in increase of crop yield,optimizing the yield components,improving nitrogen use efficiency,and it also showed positive impact on soil fertility,soil functional bacterial population and soil bacterial composition etc.Overall,our present study preliminary reached the target of reduces 20%nitrogen fertilizer under organic and chemical fertilizer combined application.