Effects Of Different Measures Of Controlling The Supply Of Water And Fertilizer On Nutrient Uptakes Of Winter Wheat And The Corresponding Mechanics

Water and nutrient deficiencies are two key factors of limiting the development of agriculture in the dryland. Many of the researches carried out have concentrated on how to apply water and nutrients effectively to achieve the goal of high yield, good quality and high efficiency. But we still have limited information about the effects of different measures of controlling the supply of water and fertilizer on nutrient uptakes, accumulations and translocation; the corresponding mechanics remain unclear. There are close relations between nutrient uptake, transport and crop yield, quality and water and nutrient use efficiency of crops. The methods of field experiment, simulation experiment and analysis were used to study the effects of the different measures (i.e., mulching, fertilization and irrigation) to control the supply of water and nutrients on nutrient uptakes, accumulations and translocation of winter wheat; and their relationship with the accumulations of dry matter and water use efficiency were also analyzed. The corresponding mechanics were evaluated through three aspects, i.e., the dynamics of nutrient and water in soils, root growth and physiological metabolizing indices. The main experimental results were shown as followirigs:The different measures of controlling the supply of water and nutrients affect the dynamics of N, P, K uptake and accumulation of winter wheat, which has a similar trend as the dry matter; and both of the nutrient uptakes and dry matter of winter wheat have a same shape as S curves, and could be fitted by the exponential regression equations. The occurrence of the maximum rate of nutrient accumulation is earlier than the maximum rate of dry matter. Irrigation and applying nitrogen can increase the rate of dry matter and nutrient uptake. The effects of different factors affected N, P, K uptakes is in the following order, applying nitrogen>irrigation>mulching.The amount and ratio of nutrient translocations from leaf to grains vary with the mulching, and the supply of water and nitrogen fertilizer, indicating that the different water-fertilizer control measures can regulate nutrient transport and distribution in plant.The amount and ratio of nutrient translocation is the highest in the treatment of combining of the water, nitrogen and mulch. Irrigation, applying nitrogen and mulching increase the quantity of nutrient transport from leaf to grains; and so does the percent of nutrient in grains. The effect of the application of nitrogen fertilizer is more significant. There is significantly positive interaction between applying nitrogen and mulching.Irrigation and mulching significantly increase the recovery of nitrogen fertilizer, nitrogen agronomic efficiency and nitrogen physiological efficiency. The effect of irrigation is more significant than that of mulching. The recovery of nitrogen fertilizer is highest in the treatment of combining the irrigation and mulching, the increased value of N-fertilizer recovery compared to the CK is more than 20%.Only irrigation or mulching has a limited effect on winter wheat yield, whereas applying nitrogen significantly increase the yield. Positive interaction is found between applying nitrogen and mulching.Applying nitrogen fertilizer significantly increases the NOa'-N content in soil. Without the application of N-fertilizer, mulching decreases the content of soil NOs'-N; when N-fertilizer is added mulching obviously increases the content of soil NOa'-N. This effect is especially obvious under lower soil water content. As the increasing of soil water content, the effect of nitrogen in increasing the content of NCV-N in soil becomes more significant. The combination of water, nitrogen and mulch produce remarkably positive interaction, and harmonize the supply of water and nutrients, which make a good environment for the crop growth and yield forming process.Mulching restrains the growth of wheat roots in early growth period in the treatment without N-fertilizer, while mulching improves the root growing when nitrogen is appli...