Study On Limiting Factors To Winter Wheat-Summer Maize Productivity In Hebei Plain

Winter wheat(Triticum L.)-summer maize(Zea mays L.) double cropping system is the main cropping system in Hebei plain.On the basis of data from a large sample formal farmer households survey involving six counties-Gaocheng Xinji which represent the piedmont plains,Qvzhou Darning Shenzhou Ningjin which represent the Heilong-gang region,experts questionnaires survey and potential productivity estimation,this paper systematically analyzed the limiting factors to winter wheat-summer maize productivity,Aimed at objectively know the limiting factors and provide a scientific basis for research department , technical extension department and government.The main conclusions are as follows:1.Analysing the estimating results of winter wheat-summer maize potential productivity in typical counties of Hebei plain could draw the conclusion: Model assessment of photosynthesis-temperature potential productivity is 22916.6-26071.5 kg/hm~2,potential productivity of light,temperature and rainfall is 16860.5-18660.8 kg/hm~2.2.The maximum yield achieved in model research fields can regard as the technical potential's reference index in current winter wheat-summer maize cropping system, the yield of investigating farmer households is about 13462.5~14525.0kg/hm2, which only accounts for 66.9%—73.2% of the yield in model research fields.3.Analysing the limiting factors to wheat-maize productivity in technical dimension, major identified limiting factors include: Confusion in variety use;Poor tillage quality;Improper sowing density,there is the large seed rate on wheat and low density on maize;Untimely sowing;Application of manure is little, the proportion of fertilizer is severe unbalanced and the quantity is improper, the total input fertilizer of wheat and maize is about 557.66~900.09kg/hm2, N: P2O5: K2O=1:0.36:0.09,farmer households attach importance to wheat and put about 66.8%(N60.8% P2O5 85.1 %, K2O60.1%) of total fertilizer into wheat, compared with amount of applied fertilizer in model research fields(the total input fertilizer is about 828.75kg/hm2, N 468.75kg/hm2 , P2O5 211.25kg/hm2, K2O 148.75kg/hm2, N: P2O5: K2O=1:0.45: 0.32), most of the farmer households apply higher rate of nitrogen but potassium less;Insufficiency of irrigation facility, improper irrigation period;Lack comprehensive and correct knowledge aboutpest and disease;Based on the grading standards(high yield exceeding 15000 kg/hm2, middle yield 11250— 15000kg/hm2, low yield under 11250kg/hm2), middle yield accounts for 74.6% of the total households;The main techniques for maximizing wheat-maize yield in these districts are put forward.4.Analysing the limiting factors to wheat-maize productivity in social dimension, major identified limiting factors include: Unsatisfactory profitability, the average yield of wheat-maize double cropping is 13759.58kg/hm2, net productivity is 10245.9lyuan/hm2;Compared with cotton, Profit is only 75.3% of cotton.5.Analysing the limiting factors to wheat-maize productivity in economical dimension, major identified limiting factors include:The land management scale is too small, the farmers' enthusiasm for planting grain crops is low;Farmer households acquire technical information through non-formal channel, technical support system and extension couldn't bring into play support function;micro-controlling by the state policies also plays an important pole in affecting wheat-maize potential productivity.