Limiting Factors Analysis And Designing For High Yield And High Nutrient Use Efficiency For Winter Wheat And Summer Maize In Smallholder Farmers Fields In The North China Plain

Exploring the green agriculture development has increasingly been becoming an urgent demand for ensuring food security and environment sustainability.In this study,we are aiming to identify the main limiting factors for achieveing high yield and high efficiency in agricultural production.By monitored farmers’field practices for two years,we quantified the yield gap and PPPN gap of smallholders in the North China Plain(NCP).We proposed an improved management practices(IP),which is based on farmers,production data,and evaluated by farmers in their fields.We discussed the potential methods to increase the adoption of technologied in order to achieve high yield and high resources use efficiency in agricultural production with smallholder farms in large scale.The main results were concluded as follows:1.The average yield of summer maize among smallholder famrers with intensive production system was 10.5 t ha-1.The maize highest yield was 14.2 t ha-1;the average yield gap(difference between average yield and highest yield)was 3.7 t ha-1.The PFPN of maize was 49.1 kg kg-1 and average PFPN gap(difference between average PFPN and highest PFPN)was 47 kg kg-1.In addition,51 percent of farmers’ fields belonged to low yield and low efficiency group(LL).The most imoortant limiting factor for the PFPN gap was due to unscientific fertilizer application.However,we did not find a dominat factor to explain the yield gap,while plant density had a relatively higher contribution.2.Summer maize yield and PFPN had a poor performance in stability.For instance,with maize yield,only 6.1 perccent of total fields’ yield had a stable high yield performance,and only 6.2 percent of total fields had a stable high efficiency.The yield with improved management system(IP)was 11.1 t ha-1,which was significantly high than the farmers’ conventional system(FP,9.4 t ha-1).Compared with the FP system,the IP treatment increased PFPN and economic benefits by 31.1 and 20.5 percent,respectively.Moreover,the IP treatment could reduce nitrogen surplus amount by 102.0,30.7 and 0.0 kg N ha-1 in the three separate field experiments.The reactive nitrogen(Nr)losses intensity was reduced 7.5,1.5 and 0.0 kg t-1,respectively.The important reasons for limiting improved key technologies adopt rate was farmers’ limited knowledge and lack of labors,followed by poor facilities,limited market and social economic factors.3.For the winter wheat,the average yield of smallholder farmers was 8.5 t ha-1,and the average PFPN was 31.6 kg kg-1.The average yield gap was 1.8 t ha-1.The average PFPN gap was 15.2 kg kg-1.There was a significantly positive relationship between yield gap and PFPN gap;In addition,60.7 percent of the total fields belonged to low yield and low efficiency group.The most important limiting factor for the PFPN gap was also unscientific fertilizer application,while there was not exist a dominant factor to explain the yield gap,soil nutrients and factors from sowing to harvest all could affect the yield gap.4.Winter wheat yield and PFPN in the two years were also poor stability,only 7.3 percent of total fields’ yield was belong to high yield group,and only 1.6 percent of total fields belonged to high efficiency group,and 22.8 percent belonged to stability low efficiency group,which indicated that the efficiency problem was important than yield.The improved management production system(IP)of winter wheat could achieve 9.0 t ha-1,which was slightly high than the farmers’conventional system(FP,8.4 t ha-1)with 7.1 percent increasing.Compared to the FP,the IP treatment increased PFPN and economic benefits by 35.6 and 20.2 percent,respectively.What is more,the nitrogen surplus amount of IP was only 9.0 kg ha-1,which was significantly lower than FP value(76.8 kg ha-1).And the IP treatment reduced Nr losses intensity by 43.0 percent compared with the FP treatment.However,the effects of IP treatment were different among different fields.The most important reason for limiting winter wheat key technologies adopt rate was due to the poor facilities,followed by farmers’ limited knowledge,limited market,social economic factors and lack of labors.