Coupling Effects Of Water And Fertilizer Supply On The Utilization And Movement Of Residual Nitrate In Soil Under Partial Root-Zone Irrigation

Partial root-zone irrigation (PRI) could save irrigation water without significant yield reduction. A large number of researches about the coupling effects of water and nitrogen fertilizer supply on plants growth and its impacts on nitrate movement under PRI have already been conducted. However, for the vegetables normally applied more fertilizer, there is a lack of researches about the coupling effects of fertilizer (including nitrogen form and phosphate supply) and water supply on vegetable growth,and nitrate movement down soil profile in greenhouse protected soil. This research is carried out to explore the response of vegetable plant (tomato) growth, the utilization and movement of residual nitrate down soil profile by applying labeled nitrate (K15NO3) to different layers of a greenhouse protected soil. This research would provide a theoretical basis for improving water and fertilizer use efficiency in vegetable production and reducing the nitrate leaching and thus reducing the risks of environmental pollution. This research is conducted in a greenhouse using tomato as plant material..The results show that:The first test sets up three factors, they are phosphorus(non-phosporus),the methods of irrigation(normal irrigation and alternate partial root-zone irrigation) and the marked nitrogen is buried in15cm or45cm from the surface. Set the experimental treatment by combination.The result shows that:under any irrigation method,the crop’s biomass under the phosphorus treatment is significantly higher than the non-phosporus treatment, at the same time,it improves the crop’s utilization and the absorptive amount of residual nitrogen in soil. Compared with normal irrigation treatment,alternate irrigation treatment can save water by34.33%-38.81%. However, its total biomass is equal to91.78%～95.59%of the normal treatment. At the same time, between the two treatments, there is no significant difference of the PRI’s utilization and uptake amount of the residual nitrogen in soil. Phosphorus affects the migration of the residual nitrogen in shallow soil. Under the alternate irrigation treatment, the migration distance of15N, which is marked in the position of15cm or45cm in soil from surface, is less10cm than the treatments of normal irrigation.The second test sets up three factors as below:the methods of irrigation(normal irrigation, alternate partial root-zone irrigation and deficit irrigation), different nitrogen(NO3-N and NH4-N) and the different marketed position of15N (15cm or45cm from the surface). The result shows that:the crop’s biomass which is applied with NO3-N is significantly higher than which is applied with NH4-N under PRI, at the same time, it improves crop’s utilization and uptake amount of the residual nitrogen in soil. Compared with normal irrigation treatment,PRI can save water by34.31%. The total biomass which is applied NH4-N under PRI is equal to92.1%～98.4%of the normal treatment. It also can improve the utilization and uptake amount of residual nitrogen in soil under the treatment of NO3-N under PRI, while the treatment of deficit irrigation reduced significantly. To the15N marketed in the position of15cm,it migrates15cm under PRI, while the distance of migration is35cm under the normal irrigation, and the distance of migration is5cm under the treatment of deficit irrigation. For the15N which is marked in the position of45cm in the soil from surface, the distance of upward migration of treatment of PRI is5cm, while the distance of downward migration of normal irrigation treatment is5cm,besides the distance of upward migration of the deficit irrigation treatment is15cm.The third test sets up two factors,they are the methods of irrigation(normal irrigation, alternate partial root-zone irrigation, fixed irrigation and deficit irrigation), and different nitrogen(NO3-N and NH4-N),what’s more, the15N is buried in110cm. The research shows that:under any irrigation method,the crop’s biomass which is applied NO3-N is significantly higher than which is applied NH4-N. The total biomass of the treatment of NH4-N under PRI is equal94.08%to the normal treatment, while the total biomass of the treatment of NO3-N under PRI is equal 89.91%to the normal treatment, besides,these two treatments can save water by34.31%, For the treatments of fixed and deficit irrigation,the amount of the crops reduced significantly. Under different nitrogenous fertilizer treatments,the crop’s utilization and uptake amount of the residual nitrogen in deep soil showed the following regulation from big to smallin turn as follows:alternative irrigation, normal irrigation,fixed irrigation,deficit irrigation.