Crop Water And Nitrogen Absorption And Utilization Of Research With The Technical Parameters Of The Best Irrigation Under Subsurface Drip Irrigation Conditions

Crop Water and nitrogen use and optimum irrigation technical parameters under subsurface drip irrigation Abstract Based on bare soil experiments and plant experiments, water and nitrogen use and optimum irrigation technical parameters were studied under subsurface drip irrigation. In bare soil experimemts, the effect of differrent lateral depth, initial water content, irrigation amount and emitter flow rate (adopted by emitter diametter and presure) on the distribution of water and nitrate in soil were tested respectively. Plant expriments including winter wheat, corn and cotton were engaged respectively in PVC pipe and soil colunm to probe how lateral depth and emitter flow rate affect water and nitrate distribution, further more, affect crop growth and yield formation through affecting the distribution of water and nitrate in root zone. On the basis of above experiments, the optimum irrigation technical parameters were gained, which can increase yield, save water and nitrogen resources and reliviate NO; pollution. The results showed: 1. SDI was superior to surface irrigation on the effect on crop shoot and root growth. SDI caused water depletion to a certain extent in surface soil on early stage. Following root elongation in deep soil, crop water status was improved and reproduction growth was promoted, thus better yield was gained. 2. On the premise of yield increasing, SDI raised water use efficiency of 30% and N use efficiency of 7.38-44.55% than surface irrigation. The optimum lateral depth of winter and corn gaining supreme WUE and yield was 4Ocm,and cotton, 50cm. 3. SDI caused a high concentration of nitrate nitrogen near emitter. As a signalling molecule, NO; ion stimulated both of lateral roots initiation and elongation within the nitrate-rich zone. It caused root length density to increase in middle soil and the distribution of roots in soil changed, and resulted the stronghly uptake of NO; near the lateral depth. Root lengh density was related with the uptake of NO3- closely, and R2=0.9506. 4. SDJ saved water greatly. The mechanism of its water-saving included that it restrained evaporation on soil surface, it proved the status of soil porosity, increased water-contained porosities arid decreased air-filled porosities in topsoil, it controled deep percolation greatly. 5. The factors affecting water transporation in soil had soil kind, soil compaction, lateral depth, initial water content, irrigation amount and emitter flow rate. In certain soil, emitter flow rate was the most important factor. When emitter flow rate raised, water transporation rate on horizonal direction raised, the distance of transporation increased on horizonal direction also, and the formation of weting circle changed greatly. 6. Emitter flow rate decided crop抯 utilization for water and nitrogen through affecting water and nitrate transporation and distribution in soil directly, and through affecting the distribution of crop roots in soil indirectly. When emitter flow rate raised, cotton water use efficiency and N use efficiency improved, but improved degree was not same under different lateral depth. Water use efficiency raised 4.88%, 8.09% and 10.28%,...