Crop Residues And Nitrogen Fertilizer Response On Green-house Gases,Physicochemical Properties And Crop Growth In Farmland

Extensive synthetic fertilizers are added to crop following crop cultivation throughout the world.The developing of holistic approaches to build a crop yield increased and sustainable wheat-maize cropping system with improved soil organic matter and nutrients is needed for future food security and improved ecosystems functioning.Addition of organic and inorganic material,such as crop straw mulch and nitrogen fertilizer in most soils is considered a strategy for sustainable agricultural production.We conducted a two-year experiment i n 2 0 1 5 2017.Factorial experiment with thee repeats,having split-plot arrangements,with the addition of different levels of straw mulch(S1:0,S2:half,S3:full kg ha^-1)in the main plot,and nitrogen rates（N1:0,N2:80%and N3:100%）of N in the sub plots.We have collected data regarding greenhouse gases emission（CO₂ and N₂O）,soil enzymes（soil urease,invertase,phosphatase,and catalase）soil physic-chemical properties（soil moisture,soil temperature,available nitrogen,available phosphorus）,soil carbon and its management indexes（soil organic carbon（SOC）,dissolved organic carbon（DOC）,labile organic carbon（LOC）,and particulate organic carbon POC）)net photo-synthetic rate and its characteristics,leaf SPAD value,crop growth leaf area,and yield and yielding attribute of soybean-wheat,maize wheat,and fallow-wheat cropping systems.To determine the changes in GHGs emission,the soil CO₂ and N₂O emission was studied at different crop growth stages for each crop during the two year of experimental period.The summer season showed an increasing trend of gases emission from sprouting to branching and then a decrease in emission was observed till maturity stage of soybean,while in winter season the emission was significantly decreased from seedling to over wintering stage but then a steep increase was noted till grain filling stage,however the decrease in emission was noted from grain filling to maturity stage of wheat.The increase of 13.3 and 46.8%of CO₂emission was observed in maize-wheat rotation compared with that of soybean-wheat and fallow-wheat.The emissions of CO₂ and N₂O were different in different rotation systems.The CO₂ emission showed to maize-wheat>soybean-wheat>fallow-wheat.The CO₂ emissions of maize-wheat system increased by 13.3%and 46.8%respectively compared with soybean-wheat and fallow-wheat system.The N₂O emission showed to soybean-wheat>maize-wheat>fallow-wheat.The N₂O emissions of soybean-wheat system increased by 4.5%and 99.9%respectively compared with maize-wheat system and fallow-wheat system.Similarly,the N₂O emission of maize-wheat system increased by 90.9%compared with the fallow-wheat system.The effects of straw mulching and nitrogen application on CO₂ and N₂O emissions were analyzed.Straw mulching and nitrogen application significantly increased the CO₂ and N₂O emissions of different crops at different growth stages.The average emissions and cumulative emissions of CO₂ and N₂O treated by S₃N₃ were the highest among treatments.For soybean-wheat system,the average emissions and cumulative emissions of CO₂ increased significantly by 6.40%and 6.52%（soybean）,6%and 6.75%（wheat）respectively,compared with S1N1treatment.The average and cumulative emissions of N₂O were 85.2%and 82.8%（soybean）,144.51%and 108.25%（wheat）respectively.For the maize-wheat system,the average CO₂emissions and cumulative emissions of S3N3 were treated.The S1N1 emissions increased significantly by 7.52%and 7.11%（maize）,8.25%and 9.31%（wheat）,and the average and cumulative emissions of N₂O were 72.55%and 78.44%（maize）,128.32%and 130.58%（wheat）respectively.For the fallow-wheat system,the average CO₂ emissions and cumulative emissions of S3N3 treated were significantly higher than those of S1N1 treatments.And 7.86%（wheat）,the average emissions and cumulative emissions of N₂O were 78.21%and 80.44%（wheat）respectively.Soil samples from four depths（0 10,1 0 20,2 0 30 and 3 0 40 cm）were collected and analyzed.Soil enzymes,such as Urease,Invertase,phosphatase,and catalase,were significantly higher in the S3 treatment than in the S1 treatment.Values were greater for the samples collected at 0 1 0 cm soil depth than those collected from deeper soil layers.Compared with S1,the regime S3 increase an average,Urease,Invertase,phosphatase,and catalase a t 0 4 0 c m s o i l d e p t h by 33.5,50.2,47.4,and 26.8%in soybean and 16.4,55.4,54.2,and 10.1%in wheat crop.Similarly,for maize 21.6,70.0,48.3,and 7.76%and for wheat16.1,29.2,39.3,and 9.61%increase were noted for S3 treatment compared with that of S1.Furthermore,S3 resulted 18.2,32.8,50.3,and 9.9%increase compared with S1 treatment in sole what cropping（fallow-wheat）.Additionally,soil higher 28.11,39.25%of urease,phosphatase were reported from maize compared with that of soybean,for wheat,activity of urease,invertase and catalase under maize-wheat rotation were high than other rotations.There were no significant difference between N3 and N2 treatment but however,the N3responded in the increase in soil Urease,Invertase,phosphatase,and catalase in the N3treatment compared with that of N1 treatment under maize-wheat cropping system than soybean-wheat,and fallow-wheat.Regarding soil nutrients such as AN,AP,SWC,and soil carbon pool（SOC,LOC,POC,and DOC）were increased by maize-wheat crop rotation compared to that of soybean-wheat and fallow-wheat crop rotation.An average 13.8,20.2,11.1,51.1,25.4,and 28.7%increase in AN,AP,SOC,LOC,POC and DOC were observed in 0-40 cm soil depth with full straw mulch（S3）compared with S1 treatment.Under soybean cropping,However 12.9,30.8,25.5,47.0,18.1 and 13.5%were noted in wheat cropping.The S3 treatment responded 36.4,25.8,32.8,45.5,27.6,and 18.3%in maize crop and 12.8,27.5,22.8,43.1,42.4,and 12.7%in wheat.Furthermore,sole cropping system showed 13.4,28.9,26.8,49.7,26.5,and 13.4%increase compared with that of S1.The increase in soil moisture content and decrease in soil temperature was noted under S3 treatment in different crop rotations.Similarly,N3 responded higher for the all soil properties,compared with N1 treatment.While N3 and N2 showed no significant differences among different variables,respectively.Additionally,the interaction effect of straw mulch and nitrogen rate responded significantly on soil carbon pool,Especially,S3N3 treatment significant increased content of LOC,DOC and POC under different crop rotation systems,respectively.Similarly as soil nutrients,the increase in soil C and its management indexes in maize-wheat cropping system were higher than soybean-wheat,and fallow-wheat cropping system.Full mulching（S3）significantly increased photosynthesis,stomatal conducatance,inter cellular CO₂ emission,transpiration rate,SPAD-value for soybean/maize/wheat crops compared with S2 and S1 treatments.Similarly,the greater leaf area,crop growth rate was noted for S3 treated plots.The yield and yielding attributes of soybean-wheat,maize-wheat and fallow-wheat cropping system showed better response under S3（full straw mulch）treatment.The same trend of increase was noted for nitrogen rates（N3）in crop physiology,crop growth and for yield and yielding components of soybean-wheat,maize-wheat,and fallow-wheat rotation.During 2015 and 2016,compared with S1,the regime S3 increase 8.35%and 9.40%biomass and 21.1%and 17.3%seed yield soybean,however,during 2015-16 and2016-17,the higher 16.2%and 14.0%biomass and 10.8%and 11.2%wheat grain yield was obtained by S3 treatment compared with that of S1 treatment（soybean-wheat rotation）.Furthermore,S3 reported more 9.1 and 25.4%biomass and 9.5 and 8.0%grain yield of maize compared with S1 during 2015 and 2016.Additionally,2015-16 and 2016-17,the S3treatment documented increase of 15.2 and 13.5%biomass and 10.5 and 10.7%grain yield of wheat,compared with S1（maize-wheat）.Similarly,the wheat biomass and yield was increased under fallow-wheat rotation（Sole wheat）by 17.4 and 14.6%and 12.1 and 11.4%during 2015-16 and 2016-17.The increase in biomass 57.5 and 55.9%and grain yield 36.6and 58.5%in soybean and wheat,75.6 and 29.5%biomass and 38.9 and 35.8%wheat grain yield was recorded under soybean-wheat cropping during 2015-16 and 2016-17 under N3treatment compared with that of N1 treatment.The increase in yield was reported with respect to increase in nitrogen rates（N3）,therefore,the same trend as soybean-wheat was recorded for maize-wheat and also for fallow-wheat crop rotation system.The principal component analysis showed that S3N3 and S3N2 responded higher score and rank value compared with that of other treatments at soybean-wheat,maize-wheat,and fallow rotations.These 2 treatments showed high levels in crop growth,soil physical and chemical properties,greenhouse gas emissions and other aspects,and had the trend of improving crop growth and physiological characteristics and improving soil physical and chemical properties.Additionally,the economics analysis resulted that S3N2 is economically beneficial with respect to net income as compared to S3N3 treatment under different crop rotation.Overall,S3N3 treatment and S2N2 treatment had promote a better relationship between soil respirations,soil biochemical properties,but in most cases,there was no significant difference between S3N3 treatment and S3N2 treatment in soil physical and chemical properties.In addition,the greenhouse gas emissions and nitrogen inputs of S3N3 were higher than those of S3N2 treatment.From the perspective of agricultural sustainable development and energy saving and emission reduction,S3N2 treatment has more yield and efficiency and environmental benefits than S3N3 treatment.Therefore,this study considers that the combination of straw returning and reducing 20%nitrogen application.S3N2 is suitable for sustainable development of agricultural production in Guanzhong area.However further study will be needed for the efficient utilization of N by focusing the mode and type of different straw application in semi-arid region of China.