| The effect and mechanism of different fertilization patterns on?rainfall-crop yield-soil quality-soil microbes?was studied in the typical dark loessial soil areas of the Longdong loess plateau,which will provide scientific basis for efficient utilization of water and fertilizer resources in upland fields,optimal management of soil quality,and sustainable improvement of soil productivity.The study,based on the long-term fertilization experiment established in Pingliang City,Gansu Province in 1979,was carried in 2015-2017 by investigating the long-term meteorological and experimental data during 1979-2017.There were six treatments,including:no fertilizer(CK),single chemical nitrogen fertilizer(N),nitrogen-phosphorus fertilizer(NP),straw+nitrogen-phosphorus fertilizer(SNP),single organic fertilizer(M)and organic fertilizer+nitrogen-phosphorus fertilizer(MNP).The main objectives of this study were to:1)analyze the effect of long-term fertilization under the winter wheat-spring maize rotation on crop yield and its stability and sustainability,fertilizer contribution rate to yield(FCR),rainfall use efficiency(RUE)and water use efficiency(WUE),and the relationships among the yield,fertilization patterns and precipitation;2)analyze the changes of soil physical,chemical and biological characteristic,and evaluate the soil quality by using minimum data set method;3)Canulate the basic soil productivity and its contribution rate to yield by using the DSSAT-CERES-Wheat model and clarify the relationships among the contribution rate to yield of basic soil productivity and soil fertility factors;4)analyze the community structure and diversity of soil bacteria,archaea and ammonia-oxidizing bacteria and archaea related to nitrogen cycling and their key functional gene characteristics by using high-throughput sequencing technologies,i.e.Illumina Miseq and Roche 454 GS FLX Titanium System,and clarify the relationships among the soil microbes and soil fertility factors.The main conclusions were as follows:(1)Under the long-term winter wheat-spring maize rotation in the Longdong loess plateau,the yield,the stability and sustainability of yield,the contribution rate of fertilizer to yield,rainfall use efficiency and water use efficiency(WUE)of crops were significantly improved by both the combination use of NP fertilizers with straw returns and manures.Compared with N treatment,the yields of winter wheat under SNP and MNP treatment significantly were increased in all the dry,normal and wet years by 140%?151%?113%?174%and 70.6%?102%,the yields of spring maize were increased by 69.5%?99.9%?91.1?104%and 105%?127%,respectively.The FCR,RUE and WUE of winter wheat under SNP and MNP treatment significantly were increased in all the dry year by 197%?204%?153%?165%and 81%?82%,The FCR,RUE and WUE of spring maize were significantly increased by 172?217%?71%?99%and 77%?118%.Those of winter wheat were significantly increased in all the normal year by 749%?843%?118%?180%and 152%?227%,those of spring maize were significantly increased by 1451?1543%?91%?104%and 104%?91%.Those of winter wheat were significantly increased in all the wet year by 84%?520%?73%?105%and 57%?109%,those of spring maize were significantly increased by 40?44%?104%?125%and 136%?158%.The variation of interannual precipitation was the main factor affecting the yield stability and sustainability.The precipitation did not effect on the stability and sustainability of winter wheat yield significantly,but on spring maize.The stability and sustainability of winter wheat yield significantly were improved in all the dry,normal and wet years by both the combination use of NP fertilizers with straw return and manure.However,the stability and sustainability of spring maize yield were improved with the rainfall increased.(2)Under the long-term winter wheat-spring maize rotation in the Longdong loess plateau,the basic soil productivity and its contribution rate to yield of the long-term different fertilizations showed a fluctuating upward trend.The basic soil productivity of long-term no fertilizer and single nitrogen fertilizer were significantly decreased at the rate of 0.23%and 3.03%per year,whereas that of both the combination use of NP fertilizers with manure and single manure were increased at the rate of 2.70%and3.82%per year.No significant differences in the basic soil productivity of both the combination use of NP fertilizers with straw returns and NP fertilizers were found.The contribution rate to yield of basic soil productivity under the straw or manure combined with NP fertilizers significantly were higher than single nitrogen fertilizer,single manure and NP fertilizers.Soil organic carbon was a key soil fertility factor that affects the improvement of basic soil productivity.(3)Under the long-term winter wheat-spring maize rotation in the Longdong loess plateau,it was an important measure to supple soil nutrient,enhance soil biological fertility and improve soil quality using the straw or organic fertilizer combined with chemical fertilizer managements.Compared with the beginning of the experiment,the soil bulk density(1.5?10.8%)and the proportion of soil microaggregates(40.7?56.8%)in topsoil were significantly reduced by applying single nitrogen fertilizer,manure,straw or manure combined with nitrogen and phosphorus fertilizers.The soil p H was increased(0.04?1.54%)by applying single nitrogen fertilizer,manure,straw combined with nitrogen and phosphorus fertilizers,whereas the soil p H was decreased(0.5%)by applying manure combined with nitrogen and phosphorus fertilizers.The content of soil organic carbon(40.0?108.7%),total nitrogen(0?55.3%),total phosphorus(20.0?59.3%),available nitrogen(34.4?103.3%),available phosphorus(106.3?561.5%)and available potassium(145.0?206.7%)were significantly increased by applying straw or manure combined with nitrogen and phosphorus fertilizers.The activities of urease(8.2?47.5%),sucrase(16.1?62.7%)and alkaline phosphatase(12.0?65.5%)were significantly increased under the straw or manure combined with nitrogen and phosphorus fertilizers treatments in 2017,relative to in 1989.After 39 years of continuous fertilization,the content of microbial carbon(20.9?199.2%)and nitrogen(18.5?259.0%)were significantly increased under the manure combined with nitrogen and phosphorus fertilizers treatment.Based on the soil quality linear model,the soil quality index was calculated and ranked as MNP(0.66)>M(0.57)>SNP(0.49)>NP(0.30)>N(0.27)>CK(0.19).(4)Soil bacteria under the different fertilizations was consisted of 38 phyla,157classes,297 orders,541 families and 1062 genera.Proteobacteria and Firmicutes were dominant bacteria at the sowing,flowering and harvest stages of winter wheat in all treatments,which the relative abundance of those were 33.8%and 31.9%at the sowing stage,39.4%and 17.3%at the flowing stage and 19.5%and 57.5%at the harvesting stage,respectively.Bacillus,other and lactococcus were dominant bacteria at the sowing,flowering and harvest stages of winter wheat in all treatments,which the relative abundance of those were 18.3%,10.7%and 8.2%at the sowing stage,39.4%,20.6%and 4.8%at the flowing stage and 36.0%,12.5%and 15.8%at the harvesting stage,respectively.The diversity,abundance and uniformity of soil bacteria under the combination use of NP fertilizers with straw return and manure at the sowing stage were higher than no fertilizer,single manure and NP fertilizers,whereas those of them significantly decreased at the flowing and harvesting stage.The content of available potassium and ammonium nitrogen in soil significantly affected the composition of soil bacteria before sowing.(5)Soil archaea under the different fertilizations was consisted of 5 phyla,23classes,40 orders,47 families and 57 genera.Euryarchaeota and Thaumarchaeota were dominant archaea at the sowing,flowering and harvest stages of winter wheat in all treatments,which the relative abundance of those were 26.3%and 71.5%at the sowing stage,21.2%and 77.3%at the flowing stage and 57.1%and 41.0%at the harvesting stage,respectively.Other and uncultured?archaeon were dominant archaea at the sowing,flowering and harvest stages of winter wheat in all treatments,which the relative abundance of those were 70.6%and 24.1%at the sowing stage,76.6%and 20.0%at the flowing stage and 41.6%and 52.2%at the harvesting stage,respectively.The abundance of soil archaea under the combination use of NP fertilizers with straw return,NP fertilizers,single manure and single nitrogen fertilizer at the sowing stage were higher than no fertilizer and NP fertilizers,whereas those of them significantly decreased at the flowing and harvesting stage.No significant difference in abundance of the combination use of NP fertilizers with manure at the sowing stage,whereas the diversity and uniformity of soil archaea in all treatments significantly increased at the harvesting stage.The content of available potassium and p H in soil significantly affected the composition of soil archaea at the flowing stage.(6)The diversity of ammonia-oxidizing bacteria was significantly affected by Long-term different fertilizations,but was not significant to the ammonia-oxidizing archaea.The abundance of arch-Amoa gene in topsoil was significantly higher than that of bacteria(1-15 times),and it was significantly correlated with soil total nitrogen and available nitrogen,while the abundance of amo A gene was not significantly correlated with nitrogen components.The effects of crop growing period and fertilization on ammonia-oxidizing function of bacteria were greater than those of archaea.In summary,both the combination use of NP fertilizers with straw returns and manures are two effective fertilization strategies to guarantee the sustainable and efficient crop production under the long-term winter wheat-spring maize rotation in the Longdong loess plateau.The yield,the stability and sustainability of yield,the contribution rate of fertilizer to yield,rainfall use efficiency and water use efficiency of crops are significantly improved by both the combination use of NP fertilizers with straw returns and manures.However,further optimization in fertilization details is required in term of precipitation years.Our results showed that the contribution rate to yield of basic soil productivity were improved due to the soil nutrients and soil quality increase.On the other hand,the content of available potassium,NH4-N?NO3-N and p H in soil was significantly affected by long-term different fertilizations,which determined the diversity,abundance and uniformity of soil bacteria,archaea and ammonia-oxidizing bacteria. |
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