Effects Of Different Fertilization Modes On Crop Spectrum,soil Physicochemical Properties And Respiration In Sorghum Field

Agricultural production impacts the hydrothermal conditions of the system by changing the soil physicochemical properties and the above-ground and underground biomass of the crop.These changes in environmental conditions will inevitably lead to changes in soil respiration and its relationship with environmental factors.Therefore,the greenhouse gas emissions from agricultural production cannot be ignored on global warming.Soil fertility is one of the most common methods to improve crop yield and maintain sustainable production in agricultural fields.It is of great significance for the sustainable development of agricultural production and low-carbon agriculture to understand spectral characteristics of the crops,physical and chemical properties of soils and soil respiration and its relationship with corresponding environmental factors under different fertilization models.Therefore,this study is based on the long-term positioning experiment of sorghum fertilization in Dongyang Experimental Base of Shanxi Academy of Agricultural Sciences.From 2016 to 2017,soil physical and chemical properties analysis,crop canopy spectroscopy and soil respiration rate?R_s?were studied under different fertilization treatments.And the corresponding soil temperature and soil moisture factor were measured,and the soil bulk density,total void content,field water holding capacity,saturated water content,soil mechanical composition,pH,activated carbon pool,and soil respiration were analyzed under different fertilization modes.And the relationship between soil respiration and environmental factors.There were five treatments included in the fertilization experiment,and they are?1?no fertilizer?CK,?;?2?only inorganic fertilizer?OPT?;?3?inorganic and organic fertilizer?OPT + M?;?4?organic fertilizer + straw returning to field?M+S?,and?5?inorganic + organic fertilizer + straw returning to field?OPT+M+S?.The treatment began in 2011,and it has been six years when the experiment began in 2016.The main research results could be summarized as follows.?1?Effect of the fertilization on physical and chemical properties of soil.Compared with the control,the fertilization treatment significantly reduced the soil bulk density of 0¹0 cm depth,increased soil total porosity of 0¹0 cm depth,soil saturated water content and field water holding capacity.The bulk density,total porosity,saturated water content and field water holding capacity of 10³0 cm depth did not have a significant effect.Also compared with CK treatment,the contents of clay increased by 0.07% for OPT treatment,and decreased by 0.39%,0.33%,0.44% for M+OPT,M+S and M+OPT+S treatments,respectively;M+OPT+S treatment significantly increased soil active carbon pool 1,but not significantly for soil active carbon pool 2;among the treatments the pH values sorted in order of size of M+S,M+OPT,M+OPT+S,OPT and CK.?2?The effect of fertilization on crop canopy spectrum.The spectral reflectance curves of different sorghum canopies were basically the same.During the same growth period,compared with CK,the red edge positions of the four fertilization modes were red-shifted,and the slopes of the red edge and the area of the red edge were different.The position of red edge,slope of red edge and area of red edge under different fertilization treatments are M+OPT+S > M+S > M+OPT > OPT > CK.It indicates that the application of inorganic organic fertilizer with straw application to treat crops is the best.?3?The seasonal dynamics of soil respiration and its relationship with environmental factors.Fertilization treatment did not change the temporal dynamics of soil respiration;soil temperature and soil moisture could explain the seasonal variation of Rs 14 96% and 6 ³7%,respectively.Fertilization treatment significantly improved the interpretation of soil temperature,and soil moisture did not have obvious difference;the sensitive band of Rs is 754 ⁹00 nm,which is significantly correlated with the index of Dred,Sred,?red and 12 plantings.The three-factor model with spectral characteristic parameters,T₁₀ and W₁₀ as independent variables has a higher determination coefficient R₂ than the two-factor and single-factor models.?4?The effect of fertilization on soil respiration.There was no significant difference between OPT and CK.Compared with OPT or CK,OPT+M,M+S,and OPT+M+S increased by 28.21³9.07%,47.86⁷5.96%,and 46.15⁵0.82%,respectively.It shows that applying organic fertilizer can promote soil respiration.Compared with CK,the soil respiration temperature sensitivity index Q₁₀ of OPT,M+OPT,M+OPT+S and M+S increased by 26%,39%,21% and 37%,respectively.It indicates that fertilization can increase the temperature sensitivity of soil respiration.The main factors causing the difference in R_s/Q₁₀/R₁₀ treatment were Shannon diversity index/soil bulk density /soil organic matter,which can explain 97.6%/78.2%/92.8% variation.Therefore,it is concluded that through different fertilization treatments,soil physicochemical properties of farmland ecosystems can be improved,sorghum growth can be promoted,and soil respiration rate can be increased.