Effects Of Controlled-Release Urea Combined With Straw Returning And Phosphorus And Potassium On Yield And Soil Fertility Of Wheat And Maize

Straw returning and controlled release fertilizer are effective ways to improve soil environment and increase crop yield.Straw returning(SR)was an effective method to improve soil physical and chemical properties.However,the effect of SR to soil on soil physical and chemical properties has not been studied combined with controlled release urea(CRU).Meanwhile,the combined application of common nitrogen(N),phosphorus(P),potassium(K)and controlled-release fertilizer has been suggested to increase grain yield.However,the interaction of P,K and N in maize(Zea Mays L.)-wheat(Triticum Aestivum L.)rotation system was seldom studied under CRU and SR condition.The effects of combined application of CRU,common urea and straw on crop yield,nutrient use efficiency and soil physical and chemical properties were of great significance to popularize controlled release mixed fertilizer and SR in wheat-maize rotation system.The effects of CRU and SR on crop yield,soil physical and chemical properties and nutrient use efficiency in wheat-maize rotation system were studied by long-term experiment in five years.Meanwhile,the nutrient use efficiency,crop yield and net income of wheat and maize rotation system in North China Plain were evaluated by "3414" experiment through an eight years' long term experiment,using common urea as control.At the same time,the interaction between crop yield and N,P and K fertilizer under controlled release mixed fertilizer was studied.The main results are as follows:1.The results showed that average 5-year yield of controlled release blending fertilizer combined with straw returning treatment(BBFS)of maize and wheat were all the highest,which was significantly higher 20.2% and 18.2% than that of soluble urea without straw returning treatment(SU)respectively.Compared with SU,BBFS treatment increased the content of total nitrogen,acid hydrolyzed nitrogen and soil organic matter,up to 27.7%,18.8%,14.8% and 10.3%,but reduced the soil electrical conductivity,soil total phosphorus and soil carbon nitrogen ration by 8.9% and 4.25.The ammonium N content of SU accounted for 27.9% of the total hydrolysable N,while that of BBFS and SU accounted for 32.4% and16.1%.Meanwhile,soluble urea with straw returning(SUS)and BBFS treatment significantly increased the p H value of soil from 7.14 to 7.40 and 7.38 compared with SU and effectivelyalleviated soil acidification.The BBFS treatment significantly reduced the bulk density of soil by 3.9% and increased the total porosity of soil by 3.4% compared to SU treatment.Also BBFS significantly improved the stability of soil aggregates and the content of large aggregates(>0.25 mm).Moreover,The NUE of BBFS in maize and wheat was significantly higher than that in SU treatment,and increased by 82.4% and 59.3% respectively.2.The maize yield of the CRU treatment was 10.9% higher than that of the common urea treatment when the controlled release urea mixed with the common urea treatment and the common urea treatment were treated with the same amount of fertilization.The maize yield did not decrease when the using CRU and soluble urea blend with N application rate half of SN2P2K2.The net return increased by 14.8% in the former as compared to that in the latter.The nutrient uptake by maize decreased in the order: N>K>P.Meanwhile,CRU could reduce the risks of yield decreasing associated with price fluctuations.By multiple regression analysis,the model of maize yields and fertilizer application rates based on CRU was established(R2=0.9726,P=0.009).The coefficients of NP and NK were synergistic,while PK was antagonistic.The interaction effects of two factors decreased in order to: NK>NP>PK.The trend was converse for nutrient uptake efficiency.In conclusion,balanced fertilization with use of a blend of CRU and soluble urea as N source increased maize grain yield and net returns.3.Controlled-release blending urea could significantly increase yield,net return,and fertilizer use efficiency.The yield of wheat treated with constant fertilizer of controlled release mixed urea was the highest,which reached 8324 kg/hm2 and was 14.6% higher than that of common urea under the condition of equal amount of fertilizer.Wheat plants without added N or P produced small or no yields received only 1910 kg/hm2 and 3346 kg/hm2,respectively.But for plants without K,yields were comparable to those fertilized with the element,up to 6966 kg/hm2.Use efficiencies were highest for N,lowest for K,with P intermediate(N>P>K).Considering economics,the use of CRU may reduce losses resulting from expenses and lost yields caused by price fluctuation.Using regression analyses of wheat yields and fertilizer application rates based on CRU(R2=0.9968 P=0.0001),the coefficients for nitrogen and phosphorus(NP)and for nitrogen,and potassium(NK)were synergistic,but the one for phosphorus and potassium(PK)was antagonistic.Interactive effects caused by these three sets of two factors decreased in the order: NP>NK>PK.Nutrient requirements needed for maximum yields were highest for N,lowest for K,and with P intermediate(N >P > K);this was the same order as their use efficiencies for these elements.Hence,fertilization with a blend of cru and soluble urea to supply N increased wheat grain yields andnet returns.The results of this experiment will provide technical support for the popularization and application of CRU combined with straw returning,and an effective method for improving the physical and chemical properties of local soil.