Nitrogen Use Efficiency Relates With Soil Fertility In Fluvo-aquic Soil

Nitrogen is one of the most important plants available nutrients and is the most crucial crop yield-limiting factor in the agricultural field.Sustaining soil organic carbon?SOC?is of primary importance in terms of cycling plant nutrients and improving the soil's physical,chemica,and biological properties?Rasool et al.2008?.SOC is an important index of soil quality because of its relationship with crop productivity?Lal 1997?.The present study carried out during 2016-2017,aim to get a relationship between NUE and soil fertility under five N application rates in winter wheat and summer maize cropping system.The soil treatment during both wheat and maize were five various soil fertility levels?very low,low,medium,high,and very high?based on soil fertility index.The treatments were replicated four times in a randomized complete block design?RCBD?at Zhengzhou,Henan province.The results showed that higher soil fertility levels?high and very high?offered significantly high crop yield(41-44%and 98–105%,N uptake(47%and 116-123%,NUE?18-23%and 12%??P<0.05?compared to very low fertility level in both seasons?wheat and maize?.This may indicate that long-term incorporation of organic amendments under present condition provides enough nutrients to make the nutrient supply non-limiting.In both seasons?winter wheat and summer maize?,the relationship between grain yield of wheat and soil fertility levels was significantly positive observed by the equation(y=a*?1-exp?-b*x??(Grain yield=17.67(1-exp^?-5.85x?)R²:0.85.and P-value 0.0002),respectively?Figure 3-9?.Similar relationship was observed between ¹⁵NUE and soil fertility levels(y=a*exp^?b*x?,R²:0.90 and P-value0.002),respectively Figure 3-11.The significant and positive relationship was observed between grain yield of maize and soil fertility levels by growth equation?y=y0+a*b^x?=y=22.75+?2.962*29.569?^x,R²=0.91,P<0.05?Figure 4-8?.The relationship between NUE and soil fertility was significant by exponential growth equation(y=a*exp?b*x?=y=46.41?exp?^0.82x,R²=0.96,P=0.0006),respectively?Figure 4-9?.Indicated that increase the addition of long-term organic material to the soil to increased SOC content resulted in increases the N synchronization between soil and plant.Higher soil fertility?Higher SOC?which results in increases the utilization and supply of nutrient by rapid mineralization lead to increase the quality of soil structure,enhanced the supply of soil organic material potentially increases soil microbial activity and soil N availability,ultimately reducing the dependence upon chemical N fertilization.Optimal soil nitrogen management is vital to crop production and environmental protection.There has been an increasing interest in the application of organic amendments to attain sustainable agricutlural in China which is highly associated with a wealth of data from long-term experimental sites exhibiting continuous long-term application of inorganic and organic fertilizers including NPK,compost,manure,and straw as well which have shown promise to increased crop yields and soil quality specially of soil organic carbon contents.The third an incubation study was conducted using Fluvo aquic soils with five different fertility levels and the N mineralization potential?NPM?,and mineralization rate constant?k?was quantified at35°C under optimum soil water conditions.Higher soil fertility levels offered significantly higher k?P<0.01?,ranging from 0.118 to 0.327 week^-1,but not NMP.The significant positive correlation between k and soil microbial biomass carbon and N suggested more organic N inputs could potentially enhance soil N mineralization.The consistency in NMP across treatments suggested its dependence on inherent soil properties rather than fertilization management.Nitrogen mineralization during wheat and maize growing seasons was estimated to be 0.03–04(g kg^-1)and 0.03–0.06(g kg^-1),respectively.A unit increase in the N mineralization rate enhanced the nitrification rate up to 3-fold.There was a coupled trend between fixed NH₄^+,and mineralized N.Results suggested NH₄⁺fixation was crucial for balancing NH₄⁺–N mobilization and immobilization,which should be considered in future research.Additionally,Optimizing the nitrogen application rate can increase NUE in relation to soil fertility.However,the optimal N rates vary substantially when different targets such as maximum yield or maximum economic benefits are considered.Nitrogen?N?mineralization is a central soil process because it controls the supply and magnitude of mineral N to plant.Mineralization is crucial for estimating N availability,exogenous input quantification,and associated environmental impacts.Nevertheless,the processes of microbial immobilization and mineralization ammonium fixation and its release are crucial factors in finding N retention and supply yet the effect of organic amendments on ammonium fixation and release is dependent on quality and quantity as well as the timing of organic amendments.Moreover,there was a coupled trend between fixed NH₄^+,and mineralized N.results suggested that NH₄⁺fixation was crucial for balancing NH₄⁺-N mobilization and immobilization,which should be considered in future research.The relationship between NUE and N mineralization,non-linear during wheat?y=a*exp?b*x??+c*exp?d*x?,R²=0.98,P=0.006);?y=a*exp?b*x?,R²=0.99,P=0.0007?,respectively?Figure 3-12and 3-14?;(y=a*(1-exp^?-b*x?),R²=0.95,P=0.0006);?y=a*exp?b*x?,R²=0.988,P=0.0017?respectively?Figure 4-10 and 4-12?;while non-significant relationship was observed between NUE and N mineralization potential?Figure 3-13 and 4-11?respectively,revealed that higher soil fertility levels offered significantly higher k?P<0.001?,but not nitrogen mineralization potential.Further revealed that positive correlaton betewwn k and soil microbial biomass carbon and N suggested more organic inputs could potentially enhance soil N mineralization.The consistency in NMP across treatments suggested its dependence on inherent soil properties rather than fertilization management.However,lower soil fertility levels?very low,low and medium?and higher N application rates led lower N use efficiency increased the risk of N to be dispersed in environment which may involve in environmental pollution.However,it is important to avoid extra usage of mineral fertilizers and organics,as they increase production cost and could not elevate the crop yield which ultimately destroys farm land environment.It can be proposing that an enhanced supply of soil organic material potentially increases soil microbial activity and soil N availability,ultimately reducing the dependence upon chemical N fertilization.Optimal soil nitrogen management is vital to crop production and environment protection.This study proposed that an enhanced supply of soil organic material potentially increases soil microbial activity and soil N availability,ultimately reducing the dependence upon chemical N fertilization.