| In order to explore the suitable irrigation method and the matching nitrogen application rate in rice production,using C Liangyou Huazhan as the test material,a nitrogen fertilizer application amount experiment and a water and nitrogen dual factor experiment were carried out.(1)In order to study the reasonable amount of nitrogen fertilizer application under flooding irrigation,a nitrogen fertilizer application amount experiment was first carried out:six nitrogen fertilizer gradients were set,0,90,135,180,225,270 kg/ha,and flooded irrigation management was used.(2)The nitrogen fertilizer gradient was set according to the results of the nitrogen fertilizer application amount experiment,and the water and nitrogen two-factor experiment was carried out:the experiment set two factors:irrigation water amount and nitrogen fertilizer level.Based on the amount of water used for flooding irrigation,four water treatments are set:W1(flooded irrigation,100%irrigation volume),W2(mild dry and wet alternate irrigation,66.7%irrigation volume),W3(moderate dry and wet alternate irrigation,33.3%irrigation volume)And W4(rain-fed,0%irrigation),Irrigation frequency of different water treatments is the same,and it is irrigated at the same time when the W1 water layer disappears.In the two-year test,the irrigation volume of each water treatment was respectively W1:2735.5 m~3/ha and 2759.5 m~3/ha,W2:2021.6 m~3/ha and 2110.5 m~3/ha,W3:1319.5m3/ha and 1387.5 m3/ha.Set six nitrogen fertilizer gradients,0,90,135,180,225,270kg/ha.The rice growth traits,yield and water and nitrogen use efficiency were studied.The main test results are as follows:1. Under flooding irrigation conditions,increasing the amount of nitrogen application can significantly increase the number of rice tillers,increase plant height and SPAD value,and significantly promote the accumulation of dry matter in the two dry matter accumulation periods of jointing stage-full heading stage and filling stage-mature stage.The accumulation of dry matter increases the leaf area of rice,thereby increasing the photosynthetic rate,which is conducive to the increase of grain yield.However,excessive nitrogen fertilizer application will cause serious greed of rice during the mature period and inhibit the accumulation of dry matter in rice.Under different irrigation treatments,increasing the amount of nitrogen fertilizer can significantly increase the number of rice tillers,plant height and leaf SPAD;The reduction of irrigation amount will reduce the maximum tiller number of rice tiller dynamics,and postpone the date of the maximum tiller number of rice.The W3treatment significantly reduced the plant height of the low nitrogen application rate,and the high nitrogen application rate compensated to a certain extent for the effect of the reduced irrigation amount on the plant height.Under W2 and W3 treatments,the SPAD value of rice leaves at the maturity stage of high nitrogen treatments was significantly reduced,indicating that alternate dry and wet irrigation treatments can improve the phenomenon of green and late maturity.2. Under different irrigation treatments,increasing the amount of nitrogen fertilizer application can significantly increase the dry matter accumulation of the above-ground rice.Compared with W1,W2 treatment is more conducive to the accumulation of dry matter in the shoots of rice at the maturity stage,and W3 and W4treatments inhibited the promotion of high nitrogen application on the accumulation of dry matter in rice.Under different irrigation treatments,with the increase of nitrogen fertilizer application,the nitrogen content in rice stems and leaves gradually increased.In the 2019 experiment,W4 treatment will significantly reduce the nitrogen accumulation in grains.Under the water treatments of W3 and W4,the application of nitrogen fertilizer exceeding 180kg/ha is not conducive to the accumulation of nitrogen in rice grains.3. Under different irrigation treatments,with the increase in the amount of nitrogen fertilizer,the effective panicle number of rice increased significantly,but it may lead to a decrease in the thousand-grain weight of rice.The rain-fed treatment resulted in a significant decrease in the number of rice grains and seed setting rate.Under different irrigation methods,there is a quadratic relationship between the amount of nitrogen fertilizer application and rice yield.The amount of nitrogen applied at the peak of rice yield under different water treatments is different,When the nitrogen application rate reaches 135kg/ha,continue to increase the nitrogen application rate.Different water treatments have a significant impact on rice yield.Continued application of nitrogen fertilizer under water deficit conditions will result in a significant decrease in yield.In the 2018 and 2019 trials,the output of N270 was compared with that of N135,W1irrigation treatment increased by 4.14%and 8.30%respectively,W2 irrigation treatment increased by 3.49%and 8.70%respectively,W3 irrigation treatment reduced by 7.87%and 9.17%respectively,The W4 irrigation treatment reduced 10.28%and12.44%respectively.4. The amount of nitrogen fertilizer and water treatment have a significant impact on the agronomic utilization efficiency of nitrogen fertilizer in rice.With the increase of nitrogen application rate and the decrease of irrigation amount,the agronomic utilization efficiency of nitrogen fertilizer decreases significantly.In the 2018experiment,compared with W1,the agronomic nitrogen utilization efficiency of W2,W3 and W4 were reduced by approximately 25%,23%and 49%,respectively.In the2019 experiment,compared with W1,the agronomic nitrogen use efficiency of W2,W3 and W4 was reduced by approximately 14.06%,27.97%and 27.04%,respectively.Both the amount of nitrogen fertilizer and water treatment have significant effects on the partial productivity of nitrogen fertilizer in rice.With the increase of the amount of nitrogen fertilizer,the partial productivity of nitrogen fertilizer decreases significantly.The partial productivity of nitrogen fertilizer of W4 treatment was significantly lower than other treatments.In the two-year experiment of 2018 and 2019,the partial productivity of nitrogen fertilizer of W4 was reduced by about 7.0%and 7.6%respectively compared with W1.Water treatment has a very significant impact on rice irrigation water use efficiency.With the decrease of irrigation water volume,irrigation water use efficiency increases significantly.Under W1 and W2 treatments,with the increase of nitrogen fertilizer application,irrigation water use efficiency increased significantly;Under the W3 treatment,there was a trend of first increasing and then decreasing.When the nitrogen application rate reached 180kg/ha,the irrigation water use efficiency reached the maximum.Under W2(mild dry and wet alternate irrigation)conditions,the application of180kg/ha nitrogen fertilizer is a better combination of water and nitrogen,which can reduce the irrigation volume by about 25%and obtain higher yields,and maintain high nitrogen fertilizer agronomic use efficiency,nitrogen fertilizer partial productivity and irrigation water use efficiency. |
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