| Water and nitrogen are two major factors that affect the growth and development of wheat.With the promotion and application of integrated water and fertilizer technology in agricultural production in China,the regulatory effects of water and nitrogen on wheat production in China are more direct and frequent.However,there is still a lack of scientific and reasonable integrated water and fertilizer solutions in current wheat production practice.Excessive nitrogen application in irrigation not only reduces water and nitrogen utilization efficiency,but also increases production input costs,and even causes resource waste and environmental pollution.In order to give consideration to water and nitrogen use efficiency,soil fertility status and crop production efficiency,this paper takes winter wheat under sprinkler irrigation in the Guanzhong Plain of Shaanxi Province as the research object,with the goal of exploring a water and fertilizer integration scheme that conforms to local intensive production,through field experiments,four irrigation levels（W1:30 mm,W2:60 mm,W3:90 mm,W4:120 mm）and four nitrogen application levels(N1:150,N2:187.5,N3:225,N4:262.5 kg·hm-2)were set up,A total of 16 treatments were used to study the effects of water and nitrogen regulation and interaction on winter wheat growth and development,yield and components,nitrogen absorption and transfer,water and nitrogen use efficiency,soil fertility status and nitrate nitrogen residue under sprinkler irrigation.The main research findings are as follows:（1）Irrigation and nitrogen application after spring can significantly promote the accumulation of dry matter in the later stage of winter wheat growth and development.The maximum increase in dry matter from heading stage to maturity stage under W4N3 treatment is 15012 kg·hm-2.During the mature stage,the dry matter accumulation of wheat under W2,W3,and W4 irrigation conditions increased by 1514,2240,and 2228 kg·hm-2 compared to W1 irrigation,respectively;The dry matter accumulation of wheat under N2,N3,and N4nitrogen application conditions increased by 1288,2010,and 1514 kg·hm-2compared to N1nitrogen application,respectively.There is a significant coupling effect between irrigation and nitrogen application on wheat yield.Under W3N2 treatment,the wheat yield reaches a maximum of 9053 kg·hm-2,which is 27.9%and 16.1%higher than that of W1N1 and W3N1treatments,respectively.（2）The nitrogen accumulation in wheat grains during the mature stage showed a trend of first increasing and then decreasing with the increase of irrigation and nitrogen application.Among them,the highest nitrogen accumulation in grains was 197 kg·hm-2 in the W3N2treatment,which was significantly increased by 24.7%compared to the W1N1 treatment.Under the same irrigation level,increasing nitrogen application rate resulted in a significant decrease in nitrogen utilization efficiency of wheat,with the most significant decrease in nitrogen fertilizer productivity,with N4 nitrogen application decreasing by 34.5%-40.4%compared to N1 nitrogen application;Under the same nitrogen application level,an increase in irrigation amount leads to a decrease in water use efficiency.The water use efficiency of W4 irrigation decreases by 12%-15.9%compared to W1 irrigation.（3）Improving nitrogen application levels significantly increases the content of nitrate nitrogen,ammonium nitrogen,total nitrogen,and p H value in mature soil,while reducing the content of water-soluble carbon;Improving irrigation level significantly increases the content of water-soluble carbon and soil total phosphorus.Excessive nitrogen application or insufficient irrigation can lead to an increase in nitrate nitrogen residue in the 0-200 cm soil mass,with an average nitrate nitrogen residue of 199.3 kg·hm-2 under N4 nitrogen application conditions;The average residual amount under W1 irrigation is 194.1 kg·hm-2.Water and nitrogen regulation significantly promotes the growth of soil microbial biomass carbon and nitrogen from heading to maturity,and inhibits the decrease of microbial biomass phosphorus.During the mature stage,the microbial biomass of carbon,nitrogen,and phosphorus reached their maximum values in W3N3,W3N4,and W4N4 treatments,which were 20.5%,59.2%,and 52%higher than those in W1N1 treatment,respectively.There is a significant positive correlation between microbial biomass carbon entropy,nitrogen entropy,and phosphorus entropy.Microbial biomass entropy,soil nitrate nitrogen,and p H value significantly affect soil microbial biomass.（4）Path analysis shows that the direct regulation effect of absorption and accumulation on yield is the strongest,while the indirect regulation effect of water and nitrogen input on wheat yield is the strongest.Both are the main factors for achieving wheat yield increase.The comprehensive quality evaluation of soil nutrient status and yield under different water and nitrogen treatments showed that the W4N3 treatment had the highest comprehensive score of1.38,followed by W3N2（1.27）,W3N3（1.14）,W4N2（1.09）,W3N4（1.07）,W2N3（0.94）,and W4N4（0.58）.The above seven treatments were aggregated into one group,making them the optimal treatment set.To sum up,the level of irrigation and fertilization can significantly regulate the growth and development of wheat,as well as the soil nutrient status.Ensuring high dry matter and nitrogen accumulation is the main factor in achieving wheat yield increase.In the winter wheat production under sprinkler irrigation in Guanzhong area,it is recommended to irrigate 80-100mm in the whole growth period,and apply 180-220 kg·hm-2 of nitrogen in combination,which can achieve efficient synergy of water and nitrogen utilization,soil fertility and wheat production. |
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