Establishment of a Mathematical Model for Mulberry Balanced Fertilization in Hilly Areas of Sichuan Province

In order to increase mulberry leaf yield and production efficiency in hilly areas of Sichuan Province through scientific fertilization,3414,a quadratic regression design for modern fertilization,was employed to simulate the regression relationship between mulberry leaf yield and major fertilizer elements including nitrogen(N),phosphor(P) and potassium(K) among which mulberry leaf yield was the objective function and N,P and K were the regulatory factors to fertilization level.As a result,7 types of three-factor,two-factor and one-factor quadratic effect functions to N,P and K fertilizer elements were established.The weight of fertilizer factors having optimum mulberry leaf yield from all types of functions was expressed as KPKPNPKNKNNP.And the weight of fertilizer factors having ratio of leaf yield to input was expressed as KPKNPKPNKNPN.Among them,the three-factor quadratic effect function(Y=20 313+0.25X1+43.48X2+34.47X30.01X12-0.14X22-0.06X32+0.05X1X2+ 0.02X1X3-0.07X2X3,X1,X2,X3 referred to N,P,K fertilizer factor respectively) was a model containing all factors,being a recommended fertilization design for mulberry field.Single factor effect analysis indicated that K fertilizer had the highest influence to mulberry leaf yield and ratio of leaf yield to input.Therefore,among all the simulation functions,the one-factor quadratic fertilizer effect function of K fertilizer factor(Y=25 002.27+44.728X3-0.084X32) produced the optimum leaf yield and highest ratio of leaf yield to input.The best fertilization design which used 600.00 kg/hm2 N,210.00 kg/hm2 P2 O5 and 254.33 kg/hm2 K2 O produced the highest leaf yield as 30 945.00 kg/hm2 and the ratio of leaf yield to input as 17.57.The optimum fertilization design after confirmation in productive practice would provide good reference for establishing high yield mulberry field in Sichuan hilly areas.