The Effect Of Water And Fertilizer On Crop Production And Its Physiological Mechanism

Since the importance of water and mineral elements for plant growth was discovered, human being have been trying to found the technologies and methods to raise plant productivity. Much effort was put in the effect of water and fertilizer on crop production. However, many results didn't consisted with each other. The researches on the mechanism of the effect of water and fertilizer on crop production were based on the condition of water stress. Less concentration was given to the water and fertilizer effect on winter wheat and summer (spring) corn production in different stage of crop growth. In this research, the effect of cooperation of water and fertilizer in different crop growth stage on crop development, water use efficiency and some physiological characteristics were discussed based on the field and potted experiments. The main results were as following:1.The result of simulated experiments didn't coincide with the field situation. The results of field experiments showed that fertilizer contributed more to crop yield than irrigation water. At the present water resources situation, the main way to increase crop yield and water use efficiency in most farmland of loess plateau was increasing nutrients supply. Enhancing the storage of rainfall during summer fallow period and raising soil water content before sowing were important factors to obtain high winter wheat yield. The key irrigation time was related to soil water content before sowing, precipitation during crop growing and the precipitation distribution etc. Both of winter wheat and summer corn has still great potential to increase yield and WUE.2.Crop straw mulching changed the effect of water and N fertilizer on crop production. The soil water condition became better because of straw mulching. It resulted in the decrease of effect of irrigation on wheat yield, the increase of effect of nitrogen fertilizer on crop yield. Without irrigation during wheat growing, the wheat yield under straw mulching depended on the amount of N fertilizer. When less N fertilizer was applied, the yield of wheat under straw mulching was higher than that under no mulching. In different amount of N fertilizer application, the effect of mulch on wheat yield was related to total irrigation water and the distribution of water in different growth stage.3.The effect of straw mulch on wheat root growth was related to the application of irrigation and N fertilizer. No irrigation or less irrigation water during wheat growth stage and appropriate amount of N fertilizer were the condition that straw mulch could improve root growth. The distribution of irrigation water in the stages of wheat growth also influenced the effect of straw mulch on wheat root growth. Wheat root dry weight (ROW) of No Mulch treatment increased then decreased while ROW of Straw Mulch treatment decreased continuously with the increase of the amount of irrigation water. There was also a trend that ROW of No Mulch treatment decreased continuously with the increase of the amount of N fertilizer. When straw was mulched on the soil, appropriate amount of N fertilizer (112.5kg/hm2 $. 150kg/hiTT) could improve wheat root growth while the more N fertilizer decreased ROW. Straw mulch changed the distribution of wheat root throughout the profile of soil. With the change of the supply of irrigation water, wheat aerial parts biomass increased when root biomass decreased, while aerial part biomass decreased when root biomass increased (we called it "one up-another down relationship"). No matter whether straw mulching was conducted, this was true. With the change of supply of N fertilizer, there was also the relationship between the wheat aerial parts and root biomass of No Mulch treatment. While wheat aerial parts and root biomass of Straw Mulch treatment increased or decreased simultaneously with the change of supply of N fertilizer.4.The development of corn was restrained, growth stage was delayed, the height, diameter, leaf area and biomass above ground decreased because of water stress. The effect of water s...