| Fertilization technology is an important measure to ensure high-yield of crops,high use efficiency of fertilizer and the protection of environment.Vegetable is a main source of many various nutrients for human body,its soil tests and fertilizer technology researches have attracted wide attention.According to the regularity of fertilizer requirement for vegetable,properties of soil for fertilizer and fertilizer effect,the fertilization implementation can achieve the purpose of to be high-yield,high-quality,efficient and environmental,also the sustainable development of vegetable industry has a very important significance.Lettuce as one of leafy vegetables is widely 'cultivated in Chongqing.At present,there is a lack of systematic research about the nutrient condition in the soil in which lettuce grows.In this paper,we adopted field trials,laboratory analysis and mathematical statistics method,to study the soil nutrient content and characteristics by "3414" trials of 38 lettuces which respectively coming from Jiulongpo,Shapingba and Bishan in Chongqing,at the same time,established a index about the nutrient abundance and deficiency in soil and recommended the optimum fertilizer dosage Results is showed bellow:1.Establishing logarithmic equations of lettuce relative yield and soil nutrient by 38 "3414" experiment.Soil available nitrogen,deficiency:y = 32.7431n(x)-66.636(R~2 =0.545);no fertilizer:y = 31.6391n(x)-82.884(R~2=0.541).Soil available phosphorus,deficiency:y = 12.4961n(x)+40.872(R~2=0.551);no fertilizer:y =11.7431n(x)+ 28.772(R~2=0.497).Soil available potassium,deficiency:y =23.6931n(x)-22.668(R~2=0.529);no fertilizer:y = 14.6981n(x)+ 0.3849(R~2=0.521).Soil nutrient index was divided into 5 grades(very deficient,low,medium,higher,abundant)according 60%?75%,75%?90%,90%?95%and>95%grade scale of "soil testing and fertilizer technical specifications".Soil available nitrogen grades were<47.8mg/kg,47.8?75.6 mg/kg,75.6?120 mg/kg,120?139 mg/kg.?139 mg/kg.Soil available phosphorus grade were<4.62 mg/kg,4.62?15.3 mg/kg,15.3?51.0 mg/kg,51.0?76.1 mg/kg,?76.1 mg/kg.Soil available potassium grades were<32.8 mg/kg,32.8?61.7mg/kg,61.7?116mg/kg,116?144mg/kg,?144mg/kg.2.Ternary quadratic regression,dualistic and quadric regression and mono-quadratic regression equation were used to analyzing the experimental result of lettuce"3414".Optimum fertilizer amount calculated with marginal effect.Taken the ternary quadratic regression equation as the principal,dualistic and quadric regression and mono-quadratic regression equation was supplement.The regression equation of soil nutrient and optimum fertilization amount:available nitrogen y =-238.21n(x)+1399.1(R~2=0.548),available phosphorus y =-47.341n(x)+274.92(R~2=0.510),available potassium y =-168.1ln(x)+ 1013.9(R~2=0.577).The classification of lettuce soil nutrient,nitrogen:>477kg/hm2,367?477kg/hm2,259?367kg/hm2,224?259kg/hm2,?224kg/hm2,scope 224-477kg/hm2,phosphorus:>199kg/hm2,147?199kg/hm2,89?147kg/hm2,70?89kg/hm2,?70kg/hm2,scope 70?199kg/hm2,potassium:>418kg/hm2,316?418 kg/hm2,215?316 kg/hm2,181?215 kg/hm2,?181 kg/hm2,scope 181?418 kg/hm2.Phosphorus recommend fertilizing amount was contained in design of experiments,nitrogen and potassium recommend fertilizing amount need adjust for them slightly extrapolation.3.Dividing yield levels into high,medium and low according to "3414"experiments yield.The nutrient of nitrogen,phosphorus and potassium uptake scope was 66.8?100kg/hm2,8.88?12.2 kg/hm2,89.2?116 kg/hm2 respectively.The average amount and average content of nitrogen,phosphorus and potassium has the same regular:K>N>P and variation of NPK was K>P>N in same level.The average content of N,P,K in lettuce were not obvious in high,medium,low yield levels,but the average amount of N,P,K in lettuce change significantly:high>medium>total>low.The change was same that nitrogen,phosphorus and potassium uptake in total and medium level.It was approach of lettuce uptake nutrient,ratio were:1:0.12:1.16,1:0.13:1.18,1:0.13:1.34 per 1000kg in high,medium and low yield..Regression analysis about lettuce absorption amount and yield showed that the regression model reached extremely significant level(p<0.01)in different level.The determination coefficient of medium level was biggest(0.608),the others were lesser.4.Results of nutrient efficient:AE(Agronomic efficiency of applied fertilizer)of nitrogen,phosphorus and potassium were all the highest in the low yield level.AE was the highest(49.4?99.2kg·kg-1)and RE(Apparent recovery efficiency of applied fertilizer)was the lowest(6.6%?12.5%)of phosphorus.The biggest SCR(Soil contribute rate)(82.9%?96.9%)was potassium.PE(Physiological efficiency of applied fertilizer)was not regular pattern of nitrogen,phosphorus and potassium in all yields levels. |
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