| Fertigation by center-pivot can achieve the goal of automatic and precise water and fertilizer management,and can effectively improve crop yield and quality.However,there are losses of evaporation and canopy interception,risks of foliar burns,which greatly limit the development and application of fertigation irrigation technology for large-scale sprinklers,and it is still lack of suitable management parameters of fertilizer and irrigation and sprinkler irrigation for different crops.Based on the field application of fertilization and irrigation hydraulic performance,the study evaluates the uniformity of flow rate,installation height of sprinkler,moving speed percentage,the working proportion of diaphragm metering pumps.and the evaporation loss of fertilizer solution and nutrient was calculated.The suitable installation height of sprinkler and suitable diaphragm metering pump working ratio were proposed,the amount of evaporation evaporation loss of fertilizer solution and nutrients was quantified.According to the different sensitivity of winter wheat and summer maize,the maximum canopy interception and ammonia volatilization loss in different growth stages were tested.The total amount of water and fertilizer loss caused by evaporation,crop interception and ammonia volatilization was proposed.Based on the mechanism of water and fertilizer transportation and crop response,the optimal operation management mode of center-pivot fertigation system was proposed.The main conclusions are as follows:(1)The hydraulic performance test results show that the performance of the fertigation device on the circular sprinkler is stable,and the irrigation depth can be accurately controlled by adjusting the pivot rotation speed.When the sprinkler height is changed,the degree of the irrigation depth deviating from the standard height(1.5 m)increases as the the sprinkler height deviates from the standard height,and increases as the sprinkler travel speed decreases.When the sprinkler height is changed from 1.5 to 2.6 m,the radial irrigation correction Hermann-Haiin uniformity coefficient varies from 80%to 85%,and the sprinkler height can be increased according to the crop height change.When the circular sprinkler was fertilized and fertilized,the modified Herman-Hain uniformity coefficient CUF ranged from 78%to 86%,and the fertilizer type and fertilizer concentration did not significantly affect the uniformity of irrigation and fertilization.The uniformity of fertilization concentration depends mainly on the performance of the fertigation system.(2)The evaporation drift loss rate of solution fertigatied by center-pivot varies from 1.5%to 10.1%,and the average value is 5%.The nutrient loss rate calculated based on the principle of water balance and mass conservation varies from-9.6%-21.6%,with an average of 1.5%.The loss of water is generally greater than the loss of nutrients.According to wet-absorption method,the canopy interception of winter wheat and summer maize was 0.64 um and 0.58 mm,respectively.Fertilizer concentration had no significant effect on canopy interception capacity of winter wheat and summer maize.The the average nitrogen loss rate by ammonia accumulation in winter wheat and summer maize was 1.2%to 2.9%,and 2.8%to 11.3%,respectively.The ammonia volatilization loss rate decreased with the increase of nitrogen application rate,and higher solution concentration resulted in higher ammonia concentration.Compared with the ground irrigation,the accumulation of ammonia volatilization loss in sprinkler fertilization is low.The fertilizer solution loss of winter wheat and summer maize was about 6.5%～8.3%and 5.3%～8.0%respectively.While the nutrient loss of winter wheat and summer maize was 4.9%～6.7%and 5.0%～7.7%,respectively.Therefore,in order to reduce the fertilizer loss rate,it is unreasonable to excessively increase the number of sprinkler fertilization,for high-stalk summer maize,fertilizing by low concentration is more suitable.(3)Winter wheat yield,irrigation water production efficiency and nitrogen fertilizer production efficiency of sprinkler fertilization were significantly higher than that of ground irrigation,which may be related to foliar fertilizer produced by canopy interception of nitrogen fertilizer.The treatment fertigatied twice had higher leaf area index(LAI),dry matter weight,nitrogen uptake and leave relative chlorophyll content(SPAD),but the amount of increase was significantly reduced between the treatments fertigatied 1 and 3 times.When the same amount of nitrogen was applied,the yield,water use efficiency and partial fertilizer productivity increased with the increase of the number of spraying fertigation.These results verify the feasibility of applying the method of calculating the nitrogen fertilizer application rate based on the initial inorganic nitrogen content of the soil in the irrigation and fertilizer integration technology.From the perspective of increasing crop yield and reducing the loss,it is recommended fertiliazing during the growth period of winter wheat for 2 times.(4)A two-year summer maize experiment showed that solution concentration from a center pivot fertigation system had little effect on plant height,leaf chlorophyll fluorescence(CF),leave relative chlorophyll content(SPAD),but had a greater impact on leaf area index(LAI)and yield.When the solution concentration is 0.105%and 0.188%,faster LAI and SPAD increase rates and higher yields can be obtained.The higher yield and partial fertilizer productivityr can be obtained by the concentration of the fertilizer solution being 0.146%compared with the concentration of the fertilizer solution of 0.292%,which applied the same amount of nitrogen.In order to improve yield and reduce the loss of nitrogen,the concentration of nitrogen fertilizer solution should be 0.105%.When urea solution concentration is higher than 0.4%,the edge of the blade and the tip of the blade are burned.The critical urea concentration avoiding the leaf burn is about 0.4%. |
