Yield Variation Analysis Focused On Winter Wheat Of Farmers On Drylands In Loess Plateau

In drylands of the Loess Plateau China,winter wheat production has been facing serious problems as huge amount of and widely distributed low-yielding fields and remarkable yield variations among farmers,therefore,it is of great importance to explore the key factors affecting the yield for the purpose of closing yield variations and increasing the average yield levels of winter wheat over wide.A survey on 372 farmers’ fertilizer application in winter wheat production with the collection and analysis of their 0-100 cm deep soil and plant samples in the corresponding fields was carried out in Shanxi,Shaanxi provinces,the typical dryland wheat producing areas of the Loess Plateau in Northwest China,to study the relationship between the dryland wheat yield variations and yield components,NPK uptake,utilization,cultivation,fertilization,as well as the main soil fertility factors.The main results were as follows:1.Significant differences were found for the wheat grain yield among lands of farmers in Loess Plateau.Observed winter wheat yields in the three provinces were in the ranges of 2529-8419,1344-8073 and 2984-7145 kg ha-1,respectively.The mean grain yield of winter wheat in farmers’ lands in Loess Plateau of China was 3815 kg ha-1,the average yield of the middle-and low-yielding groups were respectively 32 % and 57 % lower than that of the high-yielding farmer group.While the grain nitrogen(N)content of the high-yielding group was 7 % lower than that of the low-yielding group,but the phosphorus(P)and potassium(K)contents of wheat grain and N,P and K contents of straw(stem and leaf)showed no significant variance among the yield groups.2.The key measures to increase wheat grain yield are improving the biomass and harvest index by increasing spike numbers and kernel numbers in drylands of the Loess Plateau.In addition,for improving grain yield,not only more uptake of NPK nutrients should be made,but also the nutrient distribution to grain be enhanced.Moreover,for high-yielding group,the nitrogen and potassium requirement for per unit wheat production are less than that of low-yielding group.3.Traditional cultivation and film mulching cultivation have significant effects on winter wheat grain yield.Compared with traditional cultivation,the wheat yield under plastic film mulching cultivation increased by 9.4 %.High-yielding group was observed higher N and P application,and the difference of N application between high-yielding and low-yielding group is larger under traditional cultivation.Film mulching cultivation reduces the amount of N and P application,but improves the wheat yield.There is no obvious effect about K application under traditional cultivation.Differently,increasing K application is favorable to increase yield under plastic film mulching cultivation.4.Soil total nitrogen content is one of the main factors causing yield variation between traditional cultivation and plastic film mulching cultivation.Under traditional cultivation,the soil total nitrogen in 40-60 cm layer varied significantly among different yielding groups,average soil total nitrogen in the high-yielding group was 7.5 % and 18.6 % higher than in the middle-and low-yielding groups,respectively;while under plastic film mulching cultivation,total N in 0-20 cm soil showed significant difference among the three groups,and it was also 3.2 % and 14.2 % higher than in the middle-and low-yielding groups,respectively.The yield variation between traditional cultivation and plastic film mulching cultivation was not caused by organic matter content.5.The available P in 0-40 cm layer was an important reason for the yield variation under traditional cultivation,while under plastic film mulching cultivation yield variation was caused by soil available P in 0-20 cm layer.Soil mineral nitrogen cannot explain the wheat yield variation among lands of farmers in Loess Plateau.The relationship of soil available K in 0-40 cm layer with wheat grain yield was not significant,improvement of soil available potassium in deep layers below 40 cm is beneficial to increase gain grain yield under plastic film mulching cultivation.6.No significant difference was found for the 0-100 cm soil moisture content of different yield levels at winter wheat harvest in either cultivations,although that in 0-60 cm soil under the traditional cultivation was 11.3 %-23.1 % higher than that under the plastic film mulching cultivation.Soil pH is not the reason for wheat grain yield variation among lands of farmers.7.The key measures to narrow the farmers’ winter wheat yield variations and increase the local yield levels are to clarify the nutrient requirement and utilization of farmers winter wheat,regulate cultivation and fertilizer management,strengthen the management of soil water and employ water retention cultivations,reasonably increase the N and P fertilizer input,control the K fertilizer use in the middle-and low-yielding fields under traditional cultivation,increase P and K fertilizer application apart from stabilization of the N input in the middle-and low-yielding fields under plastic film mulching cultivation,elevate the organic fertilizer application to increase the soil organic matter content,water holding capacity and nitrogen supply capacity,and then enhance soil available P supply capacity in the middle-and low-yielding fields especially under the traditional cultivation.