Study On The Relation Between Winter Wheat Yield And Water-nitrogen And Its Interaction Modle On The Loess Dryland

Water and fertilizer are two key factors for agriculture productivity.They can't be separated in the agroecosystem; Resonable water-fertilizer interaction can promote crop growth. Arid climate is the main factor affecting agriculture sustainable development. It can increase yield by coordinating the relationship of water-fertilizer to obtain an ideal yield in case through improving water use efficiency under the condition of less soil moisture. Field expirement was carried out different irrigation system(6 irrigation levels with 75mm in each winter wheat growth stage)on the basis of 6 N levels(0kg/hm~2, 75kg/hm~2, 150kg/hm~2, 225kg/hm~2, 300kg/hm~2, 375kg/hm~2)in this dissertation, crop production function and crop water-N production function are established by analyzing the relationship among water-fertilizer-yield, the relationship between crop air exchange characteristics physiological index and environmental factors, the relationship between deep soil moisture characteristics and water production efficiency are analyzed.The application of CropSyst to the Loess dryland are also explored. The concltions are as followed,1. Water-yield relationship shows that the relationship of water consumption of winter wheat and its yield showed quadratic curve relation, yield increased with the increace of water consumption in low and high yield levels. When water consumption amount reaches a certain amount, the increase of yield goes down and reaches the highest in the condition of that water consumption is equal to water demand.The sequence of water deficiency sensitive stage of winter wheat is sowing-regreening stage>jointing-earing stage>earing-filling stage. Therefore irrigation before sowing can't be replaced in this region.2. Relationship between N and yield shows that the benefit of nitrogen fertilizer is closely related with the status of soil moisture, but same fertilization get different yield under the condition of different soil water status.Generally it displayed as, yield, increased yield and increased yield rate increases with the increace of fertilization under W5, W4 and W3 irrigation levels. The effeciency of the increace of yield is significant under W1 and W2 levels. But NCR(nitrogen contribution rate) and NUE (nitrogen utilization effiency) have the trend of decreasing with fertilization increased. The reasonable appalization amount of N fertilizer has a significant difference under different water supplication. Therefore irrigation amount determines fertilization amount for the effective use of fertilizer and environmental protection.3. The result of water-N-yield relationship shows that the improve of water and nutrient condition both can increase yield significantly, the effect of water is more than fertilizer and they have a significant interaction.N3(225kgN/hm~2)level can get the highest WUE and water-fertilizer interaction effect under different irrigation level, the following sequence is N2(150kgN/hm~2)level, N4(300kgN/hm~2)level, N5(375kgN/hm~2)level, N1(75kgN/hm~2)level. N3W4(225kgN/hm~2,300mm irrigation)combination get the highest yield(11087.7kg/hm~2)with the amount of 7441.4m~3/hm~2 water consumption and its WUE is 1.49kg/hm~2, the most WUE is 1.72kg/hm~2 and its water consumption is 4157.3m~3/hm~2, yield is 7150.6kg/hm~2.4. Water maginal benefit declined with the increace of irrigation, the WUE of 4 times irrigation is less than the other irrigation systems, the WUE of 2 times irrigation, 3 times irrigation is more than 1 time, 2 times seperatly and the yield increased, the water maginal benefit of 4 times irrigation is less than 3 times irrigation.When irrigation amount is 75mm, the water maginal benefit of winter wheat get the highest. The highest yield consumpted the irrigation amount of 225mm. The economical irrigation rang is from 75mm to 225mm.5. The result of water-N-crop growth relationship shows that yield composition such as spike rate, grain number and one thousand grain weight et al, increase with the increace of water supplication, the regulation effect of nutrient is not significant, the water-N interaction effect is different from each yield composition. It display as, spike rate and grain number have a significant promotion effect in the opposite of one thousand grain weight.The root distribute in 0-60cm deep mostly, 70% of the total root quatity. Root grow deeply with less irrigation even without irrigation in the result of enhancing WUE by improving the ability of absorbing soil moisture in deep soil layer, take 150cm depth of root for instance, the total quatity of root increase with the increace of soil drought(less irrigation frequency) before blossom.6. Daily water demand of winter wheat varies significantly during the whole growing period, the water demand curve has two top point, the first small top point appears at pre-winter tillering stage and the second big top point appears at booting to earing stage, and its water demand is 66% of the whole growth period, the critical stage of water requirement is at booting to earing stage.7. CropSys model can simulate yield precisely as well as aboveground biomass, and describe the effect of the light, temperature and water on crop growth more precisely than other conventional formulas.with easier operation.The calibration CropSys model can be used for simulating crop productivity on the Dryland, introducing crop variety and selecting the best agronomic measure.8. The integrated water production function for the dryland built by the quadratic water production function modle and the Jessen modle is as followes,...