Studies On Changes Of Nitrogen And Phosphorus In Surface Water And Soil Profile Of Paddy Fields Affected By Fertilization And Nutrient Management On Chengdu Plain

Nitrogen and phosphorus are essential elements of plant,in order to ensure that the high yield and quality crops,the soil need for added nitrogen and phosphorus fertilizer,but because the nutrient management was inappropriate,which caused the loss of nitrogen and phosphorus in paddy fields has become more prominent.Therefore,study on the dynamics of nitrogen and phosphorus in water and soil layer affected by fertilization on Chengdu Plain paddy field,it has an important reality meaning to fertilization reasonable,to control the loss of nitrogen and phosphorus in the paddy field and to protect ecology and environment.This study used by an independent irrigation system of field experiments,to study the effect of nitrogen and phosphorus content in surface water of sandy loam and heavy loam paddy field,leaching,crop yield and the change of the nitrogen and phosphorus content in vertical soil in Pengzhou and Guanghan by fertilization.The results showed that:1.In Pengzhou sandy loam,the total nitrogen mass(TN) in the surface water was closely correlated to the rates of nitrogen applied and followed a trend of TN at the elongation stage＞that at the tilleting stage＞that at the transplanting after nitrogen was applied.After basal fertilizer the maximum content of nitrogen in surface water of paddy field was 26%of the applied,and it was 52%after nitrogen applied at the tillering stage and the elongation stage.But in Guanghan heavy loam,because of the soil cracking and high clay content,the TN mass didn't linear correlation with the application rate,and after 1 day of the fertilization the TN mass in Guanghan surface water was lower than Pengzhou.2.There were similar dynamics of nitrogen and phosphorus in surface water after fertilization.TN reached its peak values 1d after fertilizer application,and ammonium nitrogen(NH₄-N) reached its peak values 2d after fertilizer application.TN and NH₄-N reduced to less than 50%4d later,after 7d they reduced to less than 20%.The change in concentration of nitrate nitrogen(NO₃-N) was different from TN and NH₄-N:it increased slowly and reached its peak values 4d after fertilizer application and then gradually declined.In addition,the concentration of TN and NH₄-N in surface water of Guanghan always lowers than Pengzhou experiment paddy field.It shows that different soils had different absorbability to different forms of nitrogen,and different nitrogen translates velocity.The concentration of phosphorus in surface water of paddy field reached its peak values 1～2d after fertilizer application,and reduced to less than 50%4d later, after 7d they reduced to less than 15%.In addition,some treatments' concentration of phosphorus showed increased after top dressing.3.After X-ray diffraction and infrared ray analysis,it showed that in pengzhou experiment field the major clay mineral was chlorite,illite and kaolinite,the minor clay mineral was amphibole,quartz and feldspar.These mineral and soil texture characteristic was the reason of this soil hard to engender crack,but water easy to leaching.So there's farmers turn the soil before planting to prevent leaching.In Guanghan experiment field the major clay mineral was illite,montmorillonite,halloysite and chlorite,the minor clay mineral was quartz and feldspar.These mineral and soil texture characteristic was the reason of this soil had high fertility,nutrient preserving and water supplying capability.Because this soil had several expend-type clay mineral,and had a lot of clay,it was easy to engender crack when drought.But there's farmers didn't turn the soil before paddy planting,thus the rate of leaching between 2.02～34.48 L/(m²s). So this paddy field needs turn before planting to prevent leaching.4.In Pengzhou sandy loam paddy field,the rate of nitrogen application was the major factor effect the yield of paddy,next was phosphorus.The yield of the treatments of complete applied nitrogen,phosphorus and potassium was increased 26.34%～27.66%than the treatment of halve rate of nitrogen application,and it was increased 8.75～9.69%than the treatment of no phosphorus.When we application the same rate of fertilizer,the affect to yield by different splitting application ratios of nitrogen was small.In addition,rate of nitrogen application would affect the amount of uptake by paddy,and applied signal fertilizer or decrease the application rate would affect paddy absorb anther element.In Puanghan zero tillage heavy loam paddy field,because of the leaching,the nitrogen splitting application ratios affect the yield.When we application the same rate of fertilizer,the nitrogen splitting application ratios are 3:7:0 was increased 4.68%and 5.93%than no base nitrogen application and halve rate of nitrogen application.There were significant differences between nitrogen and phosphorus uptake for rice grain and straw,but had no significant regulation.Even if it was leaching,but the yield was increased 14.18～31.06%more than Pengzhou,which showed basic fertility affect yield.5.In Pengzhou sandy loam paddy field,the concentration of TN,NH₄-N,NO₃-N,TP and AP were decreased with the depth in vertical soil,but the middle layer(20～40cm) to the bottom(40～60cm) was decreased slowly.Compare to pre-cultivation we could knows that,the concentration of NO₃-N decreased 8.31～10.58mg/kg than pre-cultivation,but the change of the middle layer and the bottom is small.The concentration of NH₄-N in surface layer was increased 6.95～12.31mg/kg than pre-cultivation;in middle layer and bottom increase slowly,between 1.43～7.81mg/kg.The concentration of TN in surface layer change small,but in middle layer it increased 0.05～0.11g/kg and decreased 0.01～0.10g/kg,and in bottom it was increased 0.04～0.08g/kg and decreased 0.01～0.05g/kg than pre-cultivation.The concentration of Olsen-P and TP changed small in vertical soil yet.In Guanghan heavy loam paddy field,there were NH₄-N,NO₃-N and AP leached,then the change character of NO₃-N and AP appeared as "S",in 40～60cm there concentration increased.The concentration of NH₄-N was no similar change between every treatment.The concentration of TN and TP were decreased with the depth in vertical soil.Compare to pre-cultivation we could knows that,the concentration of NO₃-N and AP were decreased in surface,second and third soil layer,and the decrease trend was lower with the depth increase.The concentration of NH₄-N was increased 0.37～6.11 mg/kg in surface,but below the surface it changed no regulation.The concentration of TN and TP had no change. 6.In Pengzhou sandy loam paddy field,to increase paddy field and to decrease the loss of nitrogen and phosphorus in the paddy field.We should deep plowing before paddy planting,and when we application the same rate of fertilizer(N₁₅₀P₆₀K₉₀(kg/hm²)),the nitrogen splitting application ratios are 3:7:0 was the best fertilization.In the fields of water management,we should be focused on 1～7d after fertilization,so as to avoid nitrogen and phosphorus runoff loss caused by rain and drainage.In Guanghan heavy loam paddy field,we should take the same nutrient management as Pengzhou,except cultivation (shallow tillage before paddy planting).