Effect of water and fertilizer coupling optimization test on water use efficiency of rice in black soil regions

How to improve the water use efficiency of rice in black soil regions was studied. The black soil region in paddy fields was chosen as the research object. The research showed the fertilizer coupling mathematical model with N,P,K,irrigation water( W) and water use efficiency( WUE),which was set up under the condition of controlled irrigation with quadratic D- 416 optimized saturation design. The results show that the decending order of single factor' s influence on the WUE was N,K,P and W. All the interactions between N&P,N&K,N&W,K&P,P&W and K&W on the WUE were raised initially,and when reached a certain value,they began to decline. The decending order of each interaction on the WUE was K&P,K&W,N&K,N&P,P&W and N&W. When the WUE was targeted within 1. 8- 2. 5 kg / km^3,an optimized proportion plan was obtained in the 95% confidence interval,i. e. N 87. 76- 103. 32 kg / hm^2,K_2 O 52. 37- 66. 53 kg / hm^2 and P_2O_536. 80- 46. 71 kg / hm^2. Furthermore,the late tillering of the soil moisture content was 70. 07%- 72. 57% of the saturated moisture content.

Optimal control algorithm of fertigation system in greenhouse based on EC model

Two new control algorithms based on MSP430 microcontroller unit(MCU)were developed to improve the performance of a fertigation system controlled by the electrical conductivity(EC)value of an irrigation nutrient solution in a greenhouse.The first algorithm is incremental proportional-integral-derivative(PID),and the second one is a two-stage combination algorithm(PID+fuzzy).With an improved multi-line mixing Venturi tube,several sets of experiments were conducted for a fertilizer absorption test under two conditions,namely,various suction lines and different EC target values settings.Under the first condition,with an EC target value of 2.0 mS/cm and opening of various suction pipes,the steady-state times are 186 s,172 s,134 s,and 122 s corresponding to the opening of one to four suction pipes,respectively,for PID+fuzzy control.The corresponding values are 220 s,196 s,158 s,and 148 s for incremental PID control.Under the second condition,four suction pipes are opened with different target EC values of 1.5 mS/cm,2.0 mS/cm,and 2.5 mS/cm,and the shortest response time and the minimum overshoot were obtained for PID+fuzzy control when the target EC value is 1.5 mS/cm,which are 96 s and 0.18 mS/cm,respectively.While the corresponding values are 112 s and 0.4 mS/cm,respectively for incremental PID control.The two control strategies can adjust the EC value to the target value for real-time control,but the combination control algorithm can be implemented more rapidly,accurately,and steadily with a small overshoot compared with incremental PID control.The combination algorithm(PID+fuzzy)control strategy also possesses better properties for automatic fertigation control in greenhouses than the incremental PID control strategy,the combination algorithm provides an optimal way of water and fertilizer management for crops in greenhouses which will contribute to water and fertilizer saving.

Optimizing water-saving irrigation schemes for rice(Oryza sativa L.)using DSSAT-CERES-Rice model

Rice is one of the major crops in China,and enhancing the rice yield and water use efficiency is critical to ensuring food security in China.Determining how to optimize a scientific and efficient irrigation and drainage scheme by combining existing technology is currently a hot topic.Crop growth models can be used to assess actual or proposed water management regimes intended to increase water use efficiency and mitigate water shortages.In this study,a CERES-Rice model was calibrated and validated using a two-year field experiment.Four irrigation and drainage treatments were designed for the experiment:alternate wetting and drying(AWD),controlled drainage(CD),controlled irrigation and drainage for a low water level(CID1),and controlled irrigation and drainage for a high water level(CID2).According to the indicators normalized root mean square error(NRMSE)and index of agreement(d),the calibrated CERES-Rice model accurately predicted grain yield(NRMSE=6.67%,d=0.77),,shoot biomass(NRMSE=3.37%,d=0.77),actual evapotranspiration(ETa)(NRMSE=3.83%,d=0.74),irrigation volume(NRMSE=15.56%,d=0.94),and leaf area index(NRMSE=9.69%,d=0.98)over 2 a.The calibrated model was subsequently used to evaluate rice production in response to the four treatments(AWD,CD,CID1,and CID2)under 60 meteorological scenarios which were divided into wet years(22 a),normal years(16 a),and dry years(22 a).Results showed that the yield of AWD was the largest among four treatments in different hydrological years.Relative to that of AWD,the yield of CD,CID1,and CID2 were respectively reduced by 5.7%,2.6%,8.7%in wet years,9.2%,2.3%,8.6% in normal years,and 9.2%,3.8%,3.9% in dry years.However,rainwater use efficiency and irrigation water use efficiency were the greatest for CID2 in different hydrological years.The entropy-weighting TOPSIS model was used to optimize the four water-saving irrigation schemes in terms of water-saving,labor-saving and high-yield,based on the simulation results of the CERES-Rice model in the past 60 a.These results showed that CID1 and AWD were optimal in the wet years,CID1 and CID2 were optimal in the normal and dry years.These results may provide a strong scientific basis for the optimization of water-saving irrigation technology for rice.

Effects of water and nitrogen coupling on growth,physiology and yield of rice

Water and nitrogen fertilizer are two essential factors for quality and yield formation of rice.Experimental study was carried out to investigate the effects of water and nitrogen fertilizer coupling on yield-related factors,such as growth(height),physiological indicators(chlorophyll and leaf area index(LAI))and yield composition indicators(productive panicles,thousand grain weight and total grains per panicle).Results showed that,the height difference under two irrigation regimes was not significant,and it showed no difference until the tillering stage(p>0.05).The water control method for controlled and mid-gathering irrigation(CMI)was favorable for nutrients converting to rice grain.Meanwhile the height difference for CMI and conventional irrigation(CVI)was the biggest at 80 d after rice transplantation.Variance analysis showed the effect of fertilization on height was significant(p<0.05).With organic fertilizer application,it could control plant growth and promote the nutrients converting to the panicle.The change curve of LAI was similar to chlorophyll content.Organic fertilizer application could not only promote chlorophyll content and LAI,but also delay leaf fading and promote yield.Nitrogen fertilizer factors showed significant difference on rice yield,compared to irrigation regimes showing no significance.Considering the irrigation and fertilizer factors together,the interaction was significant.The descending orders for the effects of water and nitrogen on rice yield were fertilizer,water and fertilizer,water.Regression analysis showed that the productive panicles and total grains per panicle of rice were extremely significant on rice yield,and the direct effect of total grains per panicle on yield was greater than that of productive panicle.This study results could provide theoretical basis for water and nitrogen management to improve rice production.

Mechanism of water savings and pollution reduction in paddy fields of three typical areas in southern China

Field irrigation and drainage regulation and fertilization application could affect water utilization and pollution transportation in a paddy field.In this study,representative rice-producing areas of Zhejiang Province in southern China were selected to study the effects of different field water level control(conventional irrigation and drainage W0,controlled irrigation and drainage W1 and W2)and different fertilization methods(2 times of fertilization F2 and three times of fertilization F3)on water irrigation quantity and consumption of rice,rice growth,water utilization,and pollution reduction.Results showed that field water level control had a great effect on irrigation quota in growing period rather than that in soaking period,and irrigation quota for W0 was 37.0%-71.7%higher than that for W1 and W2 in the whole growth period of rice.Although the upper limit of rain storage was greatly increased by W1 and W2,on the contrary,the yield under W1 and W2 was 0.4%-2.1%higher than that under W0.Water consumption,water leakage,and evapotranspiration were 16.63%-34.4%,39.97%-60.8%,and 9.40%-31.53%lower under W1 and W2 than those under W0,respectively,while it showed no significant changes under W1 and W2.Rainfall use rate and WUEI(water use efficiency of irrigation)under W1 and W2 had been significantly improved by 8.20%-129.58%and 31.58%-201.61%compared to W0.The contribution of nitrogen and phosphorus loss from surface water accounted for 90%and the total pollution load of total nitrogen(TN),NO_(3)^(-)-N,NH_(4)^(+)-N and chemical oxygen demand(COD)were 20.0%-63.4%,21.8%-66.3%,21.5%-63.8%,and 21.4%-46.5%lower for W1 and W2 than that for W0,respectively.Meanwhile,compared to F2,dispersed fertilization(F3)was beneficial to increase the yield and decrease pollutant load.Additionally,the path of IRA→NH_(4)^(+)-N→COD and IRA→WCA→WUE_(I) presented partial remediation effect,and the effect size was 23.6%and 38.1%,respectively,the path of IRA→WUE_(I)→WUE_(ET) presented a full remediation effect,and the path of IRA→WCA→WUE_(ET) presented suppression effect.