The Effects Of Fertilization On Soil Environment And Maize Growth Under Ridge And Furrow Rainfall Harvesting System

Shortages of water resources and low soil fertility are two key factors that limit crop production in the semi-arid region of the Loess Plateau.The ridge and furrow rainfall harvesting?RFRH?system is used widely in the rain-fed areas of northwestern China as an effective tillage measure for improving the rainfall use efficiency and crop yield in dryland farming areas.In order to explore the effects of the RFRH system on soil environment,further improve and expand the application of the RFRH system in dry farming areas,and to excavate its increasing yield potential,we conducted field fertility gradient experiment in Pingyang County in Ningxia for 5 consecutive years?2012?2016?.The field experiment included two planting models of the ridge and furrow rainfall harvesting planting and traditional flat planting?T?,four different fertilizer rates(no fertilizer,N:P at 150:75 kg ha^–1,N:P at 300:150 kg ha^–1,and N:P at 450:225 kg ha^–1).The main results are as follows:1. Effect of fertilization on soil water?1?At the same fertilization level,R treatments?RH,RM,RL,and RN?could significantly increase the 0?200 cm soil water content?SWC?and soil water consumption?ET?,and significantly reduce water consumption strength and crop water consumption coefficient?WUC?.Compared with corresponding T treatments,the SWC of R treatments increased by 5.8%?H?,6.1%?M?,6.3%?L?,and 6.4%?N?,the ET increased by 1.7%?H??1.1%?M??3.1%?L??1.8%?N?,and whereas during the sowing?VT stage was reduced by 27.9%?H?,39.6%?M?,29.2%?L?,and 39.4%?N?,and the WUC decreased by 17.3%?H?,20.1%?M?,19.5%?L?,and 24.6%?N?.?2?Under the RFRH system,SWC and WUC decreased with the increase of fertilizer application.Compared with the no fertilizer?N?treatment,SWC of fertilization treatment decreased by 15.9%?RH?,13.3%?RM?,and 10.5%?RL?,and WUC decreased by 165.9%?RH?,179.8%?RM?,and 171.1%?RL?.The ET,water consumption intensity of maize water sensitive period?V8?R3?,and soil water use efficiency?SP?all showed an increasing trend with the increase of fertilizer application rate.Compared with the RN,the ET of fertilization treatment increased by 6.5%?RH?,5.4%?RM?,and 3.6%?RL?,the water consumption intensity of maize water sensitive periods increased by 20.4%?RH?,20.2%?RM?,and 16.2%?RL?,and SP increased by 37.6%?RH?,39.1%?RM?,and 36.6%?RL?.2. Effect of fertilization on maize growth?1?Compared with T treatments,the RFRH system could significantly increase the plant height,stem diameter,leaf area,dry matter,ear grains,and 100-kernel weight,thereby significantly increasing maize grain yield and biological yield.Under two planting methods,the ear length,ear grains,100-kernel weight,and biological yield and fertilization rate showed parabolic relationship?P<0.05?.When the amount of fertilization reached a certain value,ear length,ear grains,100-kernel weight and biological yield would no longer increase or even decline.?2?Compared with corresponding T treatments,the grain yield of R treatment increased by 11.9%?H?,12.8%?M?,14.0%?L?,and 15.1%?N?;WUE increased by 9.0%?H?,10.3%?M?,10.2%?L?,and 13.5%?N?;RUE increased by 11.5%?H?,13.9%?M?,15.0%?L?,and 15.3%?N?,respectively.Under the RFRH system,compared with RN,the grain yields of RH,RM,and RL increased significantly by 49.5%,51.5%,and 49.8%;WUE increased by 45.5%,48.2%,and 47.6%;RUE increased by 49.5%,51.8%,and 50.1%,respectively.?3?Rainfallduring the maize growth period,fertilizer rates,and their interaction had significant effects on the grain yield,WUE and RUE,and fertilization effect was greater than water effect.Regression analysis showed that the grain yields with the maximums of13689.1 kg ha^-1 under N:P at 265.0:132.5 kg ha^-1 in the RFRH system,and reduced by20.8%compared with the optimum fertilization of conventional flat planting(320.0?160kg ha^-1).WUE with the maximums of 30.0 kg mm^-1 ha^-1 under N:P at 420.0?210 kg ha^-1in the RFRH system.Compared with traditional flat planting,the WUE with maximum of the RFRH system increased by 17.5%,while as the optimum fertilizer application rate increased by 11.9%.3. Effect of fertilization on nutrient uptake and fertilizer utilization efficiency?1?Compared with T treatment,the nitrogen accumulation in R treatment increased by15.7%?H?,21.9%?M?,21.4%?L?,and 31.1%?N?,the phosphorus accumulation increased by 41.5%?H?,19.1%?M?,18.2%?L?,and 16.7%?N?.Under the RFRH system,compared with RN,the nitrogen accumulation of RH,RM,and RL increased significantly by 66.5%,66.8%,and 60.5%;the phosphorus accumulation increased by 66.2%,62.6%,and 55.7%.?2?Compared with T treatment,the nitrogen fertilizer use efficiency?NUE?,physiological use efficiency?NPE?,and harvest index?NHI?in R treatment increased by10.7%?H?,4.5%?M?,and 4.9%?L?,respectively.The phosphorus fertilizer use efficiency?PUE?,physiological use efficiency?PPE?,and harvest index?PHI?in R treatment increased by 23.5%?H?,4.5%?M?,and 7.2%?L?,respectively.NUE/PUE and NPE/PPE both decreased significantly with the increase of fertilizer application rate,while the NHI/PHI increased first and then decreased.?3?Compared with T treatment,the contents of organic matter?SOM?,nitrate nitrogen?NO₃-N?and available phosphorus?AP?of R treatment at 0?40 cm soil layer increased by1.0%,13.1%,and 7.5%,respectively.The SOM,NO₃-N and AP increased with the increase of fertilizer application rate.4. Effect of fertilization on greenhouse gases emission?1?This three-year observational study showed that N₂O cumulative emission increased linearly with the fertilization rate.Compared with T treatment,the cumulative N2O emissions from the RFRH system decreased by 8.7%?H?,9.5%?M?,9.3%?L?,and-2.7%?N?,respectively.Under the two planting model,SWC and NO₃-N were significantly positively correlated with the N₂O emission flux,and SWC was the key variable that affected the N₂O emission flux in the RFRH system.The RFRH system significantly improved the soil water and temperature conditions in the maize rhizosphere to promote growth,increase the grain yield,and reduce the nitrate nitrogen content in the soil.As a result,the RFRH system significantly reduced the total N₂O emissions.?2?Compared with T treatment,the cumulative emissions of CH₄ during the growing period of the RFRH system decreased by 12.3%?H?,9.9%?M?,12.3%?L?,and-10.9%?N?.Under the RFRH system,the cumulative emissions of CH₄ from fertilization treatments were reduced by 37.9%?H?,33.4%?M?,and 24.5%?L?compared to RN treatments.CH₄cumulative emission increased linearly with the fertilization rate?R:R²=0.793,P<0.0001;T:R²=0.220,P=0.124?.SWC was the main decision variable for CH₄ emissions from the RFRH system.?3?Compared with T treatment,the global warming potential?GWP?and greenhouse gas intensity?GHGI?decreased by 7.7%?H?,7.8%?M?,9.0%?L?,and 34.4%?H?,26.9%?M?,43.7%?L?,respectively.With the increase of fertilizer application rate,GWP increased linearly.When the application rate of N:P was 200:100 kg ha^–1,the GHGI of RFRH system was the lowest,which was 35.9%lower than that of T treatment.5. Effect of fertilization on soil microbial community diversity?1?The changes in the soil nutrients?AP?SOC?TN?NO₃-N?DOC?DON?and moisture?SWC?significantly affected the relative abundances of bacterial phylum Actinobacteria,Proteobacteria,Gemmatimonadetes,Latescibacteria,Firmicutes,Bacteroidetes,and Acidobacteria?Gp17 and fungal phylum Ascomycota,Fusarium,Zygomycota,Basidiomycota,Glomeromycota,and Chytridiomycota.The combined application of nitrogen and phosphorus reduced the fungal diversity and altered the community composition.The combined application of nitrogen and phosphorus reduced the diversity and altered the composition of fungal communities.Compared with T treatment,the relative abundances of the bacterial phylum Acidobacteria,Verrucomicrobia,Latescibacteria,Chloroflexi,Candidatus Saccharibacteria,and Euryarchaeota were significantly increased,while the bacterial phylum Gemmatimonadetes and fungal phylum Basidiomycota,Chytridiomycota,Glomeromycota,and Glomeromycota significantly reduced relative abundance.?2?Compared with T treatment,the richness index?ACE and Chao1?and diversity index?Shannon-Wiener and Simpson?of RFRH system were not significantly different.With the increase of fertilization rate,the number of OTU,richness and diversity of soil microbial were all reduced.?3?Increasing the N:P fertilizer rate had potentially negative impacts on nutrient cycling in the soil and it enhanced the relative abundance of the known plant pathogenic bacterial genus Pseudomonas?Streptomyces?Bacillus and fungal genus Fusarium,thereby demonstrating the possible negative effects of excessive fertilization on the stability of soil ecosystems under RFRH system.These findings suggest that the RFRH system is an effective tillage measure for reducing N₂O emissions.When the N:P fertilization rate was 200:100?265:132.5 kg ha^-1,which contributes to sustainable high grain production and low environmental pollution,and had a high yield(13458.7?13689.1 kg ha^–1)and WUE(27.8?30.0 kg mm^–1 ha^–1)levels and lower GWP and GHGI values(0.117?0.121 kg CO_2-eq kg^–1).