Differences In Resource Utilization Efficiency Of Double Cropping Multiple Cropping Patterns In Paddy Fields In Eastern Hubei And Its Impact On Soil Fertility

Eastern Hubei is an important region to produce grain with the dominated cropping systems of single and double season cropping rice in Hubei Province,China.However,the annual productivity and production benefit of crops are low in this region.It is of great significance to optimize the cropping system and explore the potential of crops to use temperature and radiation resources for the improvement of crop productivity and production benefit in Eastern Hubei.In this study,a long-term fixed experiment with 6multiple cropping patterns,namely,oilseed rape-maize(O-M),oilseed rape-rice(OR),oilseed rape-water-saving and drought-resistant rice(O-WDR),wheat-maize(WM),wheat-rice(W-R),and fallow-double season cropping rice(F-DR)was conducted for 4 consecutive years in Eastern Hubei.The annual productivity and production benefits,the utilization of temperature and radiation resources,and nitrogen(N)and phosphorus(P)fertilizers of crop,and the changes of N and P contents and balances in the soil of different patterns were tested.The soil microbial communities structures were also analyzed.The main purpose of this study was to provide theoretical basis for optimizing the double cropping patterns in the paddy field of Eastern Hubei.The main results are as follows:1.Among all multiple cropping patterns,oilseed rape-rice and wheat-rice cropping patterns had a high and stable yield;meanwhile,the oilseed rape-rice pattern had the highest annual production benefit,which was 196% higher than that of fallow-double season cropping rice pattern.2.Oilseed rape-rice cropping pattern had relatively higher utilization rates of temperature and radiation resources,but its utilization efficiency of temperature and radiation resources was at a medium level in all multiple cropping patterns.The N and P use rates and efficiencies of oilseed rape-rice and wheat-rice patterns significantly increased,compared with those of fallow-double season cropping rice pattern.The total uptakes,partial factor nutrient balance,and partial productivity of N and P fertilizers were significantly higher in the oilseed rape-rice and wheat-rice patterns than in the fallow-double season cropping rice pattern.3.The oilseed rape-rice cropping pattern was beneficial to the N accumulation and the reduction of N loss in soil;while,the oilseed rape-maize pattern was beneficial to the P accumulation and the reduction of P loss in soil.The loss of N and P in the soil of fallow-double cropping rice pattern was at a relatively high level.4.The soil bacterial community abundance and diversity in wheat-rice,oilseed rape-rice and fallow-double season cropping rice systems were significantly higher than those in other patterns.The relative abundances of bacteria related carbon(C)and N cycling in the soil of wheat-rice,oilseed rape-rice and fallow-double season cropping rice patterns were significantly higher than that in the soil of wheat-maize and oilseed rape-maize patterns with the highest values being found in the soil of oilseed rape-rice pattern.The relative abundances of bacteria related P cycling and biocontrol in the soil of oilseed rape-maize and wheat-maize patterns were higher than that in the soil of other patterns.5.The abundance and diversity of soil fungal communities were highest in wheat-rice pattern,and lowest in oilseed rape-maize and oilseed rape-rice patterns.Compared with fallow-double season cropping rice pattern,the oilseed rape-rice pattern significantly reduced the abundance and diversity of soil fungi,and increased the bacterial/ fungal ratio(B/F)in abundance.The relative abundance of pathogenic fungi including Gibberella,Alternaria and Coniochaeta significantly reduced in the soil of oilseed rape-rice pattern;while that of beneficial fungi including Mortierella and others significantly increased in the soil of wheat-rice pattern.In summary,compared with the local traditional fallow-double season cropping rice pattern,the oilseed rape-rice pattern had a higher and stable annual economic yield,good economic and ecological benefits,and was conducive to the transformation of soil from "fungal" to "bacterial" type;therefore,it has the application prospect to replace the local traditional double season cropping rice pattern in Eastern Hubei.