| Improving the utilization efficiency of water and nitrogen in paddy fields and exploring the high yield potential of rice has always been one of the hot issues in current research.These issues are particularly critical for addressing the problems of high water consumption and pollution associated with rice cultivation in China.To explore optimal water and fertilizer management strategies for high yield and efficiency in rice cultivation,a field experiment was conducted at the Hubei Irrigation Experiment Center Station from May to September 2021and 2022.The experiment set up two irrigation methods:continue flooding irrigation(CF,W1)and alternate wetting and drying irrigation(AWD,W2).There were 5 fertilization types:no fertilization(N0),traditional fertilizer(N1),slow-release fertilizer(N2),slow-release fertilizer:traditional fertilizer=7:3(N3),slow-release fertilizer:traditional fertilizer=5:5(N4),a total of 10 treatments.The effects of different irrigation methods and different fertilizer types on rice growth characteristics,dry matter and nitrogen absorption and accumulation were obtained by combining field physical experiments and model simulation in the course of the study.The Aqua Crop model was calibrated and verified using experimental data,and its applicability for predicting rice growth in the Zhanghe Irrigation District under different water and fertilizer conditions was evaluated.By simulating different irrigation scenarios,the optimal water management strategy was identified for different hydrological years.The main findings of the study are as follows:(1)During the middle and late stages of rice cultivation,N2 treatment led to higher plant height,tiller number,chlorophyll SPAD value,and leaf area index compared to N1 treatment(by 1.42cm,11.06%,3.35%,and 36.80%,respectively).These results suggest that slow-release fertilizer can effectively enhance and sustain rice growth characteristics in this stage.In the early growth stage,N3 treatment demonstrated higher plant height and leaf area index than N2 treatment by 1.73cm and 7.30%,respectively.During the regreen-to-tillering stage,the tiller number growth rate of the N3 treatment was higher than that of the N2treatment,while in the late growth stage,there was little difference between the two treatments.These findings suggest that the slow-release mixed traditional fertilizer(7:3)is more effective in promoting plant height,tiller number,and leaf area index during the early growth stage.Compared to the N2 treatment,the growth characteristics of N3 treatment were inferior,indicating that the slow-release mixed fertilizer(5:5)had a less favorable effect on rice growth characteristics.AWD irrigation method can reduce ineffective tillers and increase leaf area index,but it might also have a specific inhibitory effect on plant height.(2)Under N1 treatment,AWD could promote the accumulation of dry matter and nitrogen in the middle and late stages of rice growth,promote the transfer of nitrogen to grain,and increase the partial productivity of nitrogen fertilizer,nitrogen agronomic efficiency and nitrogen harvest index.The average value of dry matter and total nitrogen in the whole growth period of N2 treatment and N3 treatment was higher than that of N1 treatment,especially in the middle and late stages.The dry matter of roots,stems and leaves,the output and transformation index of stems and leaves,and the nitrogen utilization index were higher than those of N1 treatment,indicating that slow-release fertilizer and slow-release mixed traditional fertilizer(7:3)were more beneficial to dry matter and nitrogen accumulation in the middle and late stages of rice growth than traditional fertilizer,thus improving the output conversion rate and nitrogen utilization rate of stems and leaves.Appropriate slow-release blending ratio is beneficial to dry matter and nitrogen accumulation in rice.Compared to N2treatment,N3 treatment can increase dry matter and nitrogen accumulation during the early and middle stages of rice growth while maintaining a high level in the later stage.In contrast,the high proportion of traditional fertilizer in N4 treatment is not conducive to the accumulation of dry matter and nitrogen in the middle and late stages of rice growth,resulting in lower output and transformation rates of stems and leaves and lower nitrogen utilization compared to slow-release fertilizer.(3)The average yield of N4 treatment was 7.93%lower than that of N2 treatment,indicating that slow-release mixed fertilizer(5:5)had a poor effect on rice yield.The yield of N3 treatment was 8.28%higher than that of N1 treatment,and the yield was not much different from that of N1 treatment.Compared with N2 treatment,N3 treatment could reduce the fertilizer cost of 346.30 yuan/hm~2and reduce planting costs.The yield of AWD was3.26%higher than that of CF,and the water productivity of AWD was higher than that of CF.Therefore,AWD+slow-release mixed fertilizer(7:3)treatment is a cost-saving,high-yield and high-efficient rice water and fertilizer management model.N2 treatment can increase yield by 10.25%compared with N1 treatment.AWD+slow-release fertilizer treatment is a high-yield and high-efficiency water and fertilizer management mode for rice,which still has certain suitability.(4)Under various water and fertilizer treatments,the Aqua Crop model achieved The coefficient of determination(R~2)values(>0.9)for aboveground dry matter and canopy coverage,with the root mean square error(NRMSE)between 15.7%and 21.8%and Nash-Sutcliffe efficiency coefficient(EF)between 0.76 and 0.99.During the verification period,the mean R~2values were 0.922 and 0.974,and mean NRMSE values were 24.47%and15.08%,while the mean EF were 0.947 and 0.977,respectively.These results indicate that the Aqua Crop model is suitable for simulating rice growth and development under different water and fertilizer treatments in Zhanghe Irrigation District.Scenario simulation analysis under different hydrological years indicate that the lower limit of irrigation in wet,normal and dry years under AWD is 120%,120%and 100%of RAW,and the upper limit of irrigation is reduced by 20 mm on the basis of AWD(W2).The yield was the largest,7867kg/hm~2,6901kg/hm~2,7890kg/hm~2respectively,and the irrigation amount was the smallest,120 mm,180 mm and 330 mm respectively,which was the best water management mode. |
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