Deficit irrigation management for rice using crop growth simulation model in an optimization framework

Optimization of irrigation water is an important issue in agricultural production for maximizing the return from the limited water availability. The current study proposes a simulation–optimization framework for developing optimal irrigation schedules for rice crop (Oryza sativa) under water deficit conditions. The framework utilizes a rice crop growth simulation model to identify the critical periods of growth that are highly sensitive to the reduction in final crop yield, and a genetic algorithm based optimizer develops the optimal water allocations during the crop growing period. The model ORYZA2000, which is employed as the crop growth simulation model, is calibrated and validated using field experimental data prior to incorporating in the proposed framework. The proposed framework was applied to a real world case study of a command area in southern India, and it was found that significant improvement in total yield can be achieved by the model compared to other water saving irrigation methods. The results of the study were highly encouraging and suggest that by employing a calibrated crop growth model combined with an optimization algorithm can lead to achieve maximum water use efficiency.     

Simulating Phenology,Growth and Yield of Transplanted Rice at Different Seedling Ages in Northern Iran Using ORYZA2000

Rice crop growth and yield in the north Iran are affected by crop duration and phenology.The purpose of this study was to calibrate and validate the ORYZA2000 model under potential production based on experimental data for simulating and quantifying the phenological development,crop duration and yield prediction of rice crop influenced by different seedling ages.In order to calibrate and validate the crop parameters of ORYZA2000 model,a two-year field experiment was conducted under potential growth conditio...     

Simulation and Validation of Rice Potential Growth Process in Zhejiang Province of China by Utilizing WOFOST Model

Since the pioneering work in the 1960s, substantial progress has been made in crop growth simulation both in developing and applying models. Crop growth simulation integrates the knowledge of computer science, phytophysiology, agroecology, agrometeorology, soil science, agronomy and systems, combines the plant and environmental factors, and describes quantitatively the dynamic relation between crop growth, development, yield formation and environmental techniques [1]. WOFOST (World Food Stu…     

水稻发育期模型的比较

通过对CERES-rice、ORYZA2000、RCSODS、RiceGrow等模型中发育期模型的比较与分析,揭示了这些模型在发育速率对温度的响应模式、发育期阶段划分与参数设置、日长效应模式的差别,分析了累积生长度日、发育生理日及发育速率的关系。研究表明,4个模型的发育速率对温度的响应模式基本一致;CERES-rice、ORYZA2000、RiceGrow在基本营养生长期和籽粒灌浆期参数设置一致,而在光敏感期虽然都有3个参数(发育速率、临界日长、日长效应系数),但CERES-rice和Rice-Grow中各有一个参数固定,穗发育期CERES-rice和RiceGrow均没有引入新参数,而ORYZA2000则引入新参数;CERES-rice、RCSODS和ORYZA2000的日长效应模式基本一致,而与RiceGrow差异较大。RCSODS中的发育期模型阶段划分较为简单,参数较少;ORYZA2000模型最为通用,但参数较多,且仅根据发育期资料无法唯一确定。     

运用WOFOST模型对浙江水稻潜在生长过程的模拟与验证

通过2001～2003年在金华市和2004年在杭州市的水稻田间试验,应用WOFOST模型对浙江水稻潜在生长进行了模拟和验证。对于常规晚稻秀水11和杂交晚稻协优46,用2001年和2002年的试验数据作参数校正,得到一套参数后,用2003年试验数据作模型验证;对于单季稻两优培九,则以2004年试验数据用于校正,2003年的用于验证。通过对几种水稻品种模拟结果的综合分析,主要结论如下： WOFOST 模型可以成功地用于浙江主要水稻品种潜在生长过程的模拟,可以较好地分析浙江水稻的生长过程和产量潜力。由WOFOST模型计算得到浙江中部地区连作晚稻的生产潜力为8100 kg/hm2左右,中稻为9300 kg/hm2左右。目前两种水稻的实际平均产量分别为模拟产量的78%和70%。判断结果表明,有必要对目前水稻中、后期的田间管理措施进行重新审视。     

稻田应用“水肥一体化”的现状、问题与思考

水肥一体化技术是在灌溉的同时将肥料混合施入土壤的集灌溉和施肥于一体的技术。发展和应用水肥一体化技术不仅可以达到节水省肥的目的,还是实现农业精确定量、智慧管理的重要途径。本文概述了水肥一体化在国内外的研究进展和水肥一体化中滴灌等技术在设施栽培以及玉米、棉花等作物生产中的应用现状。对滴灌技术在水稻中应用存在的成本高、环境不友好、品种适应性差等问题进行了分析,并提出对应的沟渠改造、加强滴灌管道建设、垄畦栽培结合、水肥药一体化和筛选新品种等解决方法。本文为水肥一体化在水稻栽培中的应用提供了参考,探索了水肥一体化水稻栽培未来的方向。     

Estimation of paddy water productivity (WP) using hydrological model: an experimental study

Water productivity (WP) expresses the value or benefit derived from the use of water. A profound water productivity analysis was carried out at experimental field at Field laboratory, Centre for Water Resources, Anna University, India, for rice crop under different water regimes such as flooded (FL), alternative wet and dry (AWD) and saturated soil culture (SSC). The hydrological model soil-water-atmospheric-plant (SWAP), including detailed crop growth, i.e, WOFOST (World Food Studies) model was used to determine the required hydrological variables such as transpiration, evapotranspiration and percolation, and bio-physical variables such as dry matter and grain yield. The observed values of crop growth from the experiment were used for the calibration of crop growth model WOFOST. The water productivity values are determined using SWAP and SWAP–WOFOST. The four water productivity indicators using grain yield were determined, such as water productivity of transpiration (WP_T), evapotranspiration (WP_ET), percolation plus evapotranspiration (WP_ET+Q) and irrigation plus effective rainfall (WP_I+ER). The highest value of water productivity was observed from the flooded treatment and lowest value from the saturated soil culture in WP_T and WP_ET. This study, reveals that deep groundwater level and high temperature reduces the crop yield and water productivity significantly in the AWD and SSC treatment. This study reveals that in paddy fields 66% inflow water is recharging the groundwater. There is good agreement between SWAP and SWAP–WOFOST water productivity indicators.     

Effects of water management and organic fertilization with SRI crop practices on hybrid rice performance and rhizosphere dynamics

A field experiment was conducted to investigate the effects of intermittent versus continuous irrigation, together with different degrees of organic fertilization, on the growth and yield of hybrid rice, looking also at the functioning of the rhizosphere as this is a key element affecting crop performance. The crop management practices employed generally followed the recommendations of the System of Rice Intensification (SRI). The aim of the research was to learn how water management and organic fertilization together would affect crop outcomes. Under intermittent water application as recommended with SRI management (aerobic irrigation, AI), grain yield increased by 10.5–11.3%, compared to standard irrigation practice (continuous flooding, CF). The factor that contributed most to higher yield was increased number of grains per panicle. It was seen that under the range of organic fertilization treatments evaluated, intermittent irrigation compared with CF promoted greater dry matter production and higher leaf area index (LAI) during the main growth stages. Also, the combination of intermittent irrigation and organic material applications significantly increased soil redox potential (Eh), compared with CF, and also the numbers of actinomycetes in the rhizosphere soil. Actinomycetes were evaluated in this study as an indicator of aerobic soil biota. It was seen that with intermittent irrigation, the application of organic material improved the functioning of the rhizosphere and increased yield. However, these results based on 2 years of study reflect relatively short-term effects. The effects of longer-term water management and soil fertilization regimes should be also examined, to know whether these effects continue and, if they do, whether they become greater or less.     

Evaluation and application of ORYZA2000 for irrigation scheduling of puddled transplanted rice in north west India

Water-saving technologies that increase water productivity of rice are urgently needed to help farmers to cope with irrigation water scarcity. This study tested the ability of the ORYZA2000 model to simulate the effects of water management on rice growth, yield, water productivity (WP), components of the water balance, and soil water dynamics in north-west India. The model performed well as indicated by good agreement between simulated and measured values of grain yield, biomass, LAI, water balance components and soil water tension, for irrigation thresholds ranging from continuous flooding (CF) to 70 kPa soil water tension.Using weather data for 40 different rice seasons (1970-2009) at Ludhiana in Punjab, India, the model predicted that there is always some yield penalty when moving from CF to alternate wetting and drying (AWD). With an irrigation threshold of 10 kPa, the average yield penalty was 0.8 t ha⁻¹ (9%) compared with CF, with 65% irrigation water saving, which increased to 79% at 70 kPa with a yield penalty of 25%. The irrigation water saving was primarily due to less drainage beyond the root zone with AWD compared to CF, with only a small reduction in evapotranspiration (ET) (mean 60 mm).There were tradeoffs between yield, irrigation amount and various measures of WP. While yield was maximum with CF, water productivity with respect to ET (WP_ET) was maximum (1.7 g kg⁻¹) for irrigation thresholds of 0 (CF) to 20 kPa, and irrigation water productivity (WP_I) increased to a maximum plateau (1.3 g kg⁻¹) at thresholds ≥30 kPa.Because of the possibility of plant stress at critical stages known to be sensitive to water deficit (panicle initiation (PI) and flowering (FL)), treatments with additional irrigations were superimposed for 2 weeks at one or both of these stages within the 10, 20 and 30 kPa AWD treatments. Ponding for two weeks at FL was more effective in reducing the yield penalty with AWD than ponding at PI, but the biggest improvement was with ponding at both stages. This reduced the average yield loss from 9% (0.8 t ha⁻¹) to 5% (0.5 t ha⁻¹) for AWD with thresholds of 10 and 20 kPa. However, maximum WP_I (1.1 g kg⁻¹) was achieved with an irrigation threshold of 20 kPa combined with more frequent irrigation at FL only, but with a greater yield penalty (8%). Thus the optimum irrigation schedule depends on whether the objective is to maximise yield, WP_ET or WP_I, which depends on whether land or water are most limiting. Furthermore, the optimum irrigation schedule to meet the short term needs of individual farmers may differ from that needed for sustainable water resource management.     

Performance of direct-seeded rice under various dates of sowing and irrigation regimes in semi-arid region of India

Rice (Oryza sativa L.) is the most important staple food crop in the southern region of Asia, and Indian subcontinent being one of the major producers. Production of conventional transplanted rice requires a large amount of irrigation water, labor, and energy. The scarcity of irrigation water has encouraged farmers to adopt an alternative rice production system, i.e. the direct-seeded rice (DSR), which is proposed to be farmers’ friendly with a potential to save water. Our study reports the performance of DSR with respect to yield and water expense efficiency based on different irrigation regimes and dates of sowing. A field experiment was conducted in the semi-arid region of northern India during the rainy season of 2011 with two treatment combinations (dates of sowing: 15th May and 5th June and three irrigation regimes: irrigation scheduled at irrigation water-to-cumulative potential evapotranspiration; IW/CPE ratio of 1.0, 1.5 and 2.0) in a completely randomized design. We found statistically higher water expense efficiency of DSR sown on 5th June as compared to DSR sown on 15th May without any significant differences in growth and yield. A significant yield difference between DSR grown with irrigation regimes of IW/CPE 1.0 and 1.5 and DSR grown with irrigation regimes of IW/CPE ratio 2.0 were observed. The DSR grown with irrigation regimes of IW/CPE ratio of 1.5 resulted in significantly higher water expense efficiency than the one with IW/CPE ratio of 2.0. Obtaining a higher yield of DSR under scarce irrigation water might be a trade-off between optimum water use and maximum yield avoiding excess ground water exploitation in sub-tropical semi-arid regions of India. Our study suggests that sowing time and irrigation regimes are two important aspects of “rice production” to attain “win–win” solution. Thus, strategic and judicial use of irrigation water with management of sowing time could potentially escalate the rice production in water scarce regions of India.     

Possible causes of yield failure in tropical aerobic rice

Aerobic rice is a water-saving rice production system for water-short environments with favorable soils and adapted, potentially high-yielding varieties that are direct dry seeded. Soils remain aerobic but supplementary irrigation is applied as necessary. In the dry season of 2004 and 2005, a water by N experiment was set up at the location “Dapdap” in central Central Luzon, Philippines, to explore water and N management strategies in aerobic rice. The experiment was laid out as a split-plot design on a loamy sand soil with three water treatments (irrigation twice per week, once per week, and once in two weeks with modifications) and 5 N levels (0–200 kg ha⁻¹). Average seasonal soil moisture tension ranged from 9.2 to 20 kPa but yield hardly responded to the treatment combinations and ranged from 0 to 2 t ha⁻¹. In addition to trial-specific parameters, root knot nematodes and micronutrients (2005) were monitored. Galling of roots due to nematodes was assessed through a rating scale of 0–5, with 0 = no galling and 5 = >75% of the root system galled. The degree of galling reached a level of 5 at flowering and harvest in 2004, and 3 at tillering and 4 at harvest in 2005. Results of a plant tissue analysis at mid-tillering for Fe, Mn, and Zn showed on average values above critical levels; individual replicates, however, indicated deficiencies for Mn. In addition to actual field observations, we used simulation modeling (ORYZA2000) as a tool to estimate attainable yield under actual water conditions and N inputs to explore how yield failure set in. Simulation results matched observed values for total above-ground biomass and leaf area index quite well when no N was applied. When high rates of N (200 and 165 kg ha⁻¹) were applied, simulated values matched actual field data only until about the panicle initiation stage; afterward, observed values remained below the simulation. We interpreted this as evidence that growth-limiting factors other than water or N affected the crop from this growth stage on. Observations made in the field on root knot nematodes and micronutrients suggested that these two factors, especially root knot nematodes, may have been major constraints to crop development in this experiment.     

主要节水灌溉方式对水稻根系形态生理的影响

水稻是耗水第一大作物。发展节水栽培对稻田水分高效利用和缓解我国水资源短缺具有重要意义。水稻根系是吸收水分和养分的重要器官，也是多种激素、氨基酸和有机酸合成的重要部位。水分管理措施的改变会直接或间接引起根系生长发育发生改变，从而影响水稻地上部生长发育和产量形成。本文综述了干湿交替灌溉、控制灌溉和覆盖旱种对水稻根系形态和生理特性的影响，提出了今后节水灌溉下水稻根系的研究重点，以期为改善水稻根系形态生理和高产节水栽培提供理论依据。     

Numerical simulation on effect of irrigation conditions on water temperature distribution in a paddy field

Water management methods regulate water temperature in paddy fields, which affects rice growth and the environment. To understand the effect of irrigation conditions on water temperature in a paddy field, water temperature distribution under 42 different irrigation models including the use of ICT water management, which enables remote and automatic irrigation, was simulated using a physical model of heat balance. The following results were obtained: (1) Irrigation water temperature had a more significant effect on paddy water temperature close to the inlet. As the distance from the inlet increased, the water temperature converged to an equilibrium, which was determined by meteorological conditions and changes in water depth. (2) Increasing the irrigation rate with higher irrigation water amount increased the extent and magnitude of the effects of the irrigation water temperature. (3) When total irrigation water amount was the same, increasing the irrigation rate decreased the time-averaged temperature gradient effect over time across the paddy field. (4) Irrigation during the lowest and highest paddy water temperatures effectively decreased and increased the equilibrium water temperature, respectively. The results indicate that irrigation management can be used to alter and control water temperature in paddy fields, and showed the potential of ICT water management in enhancing the effect of water management in paddy fields. Our results demonstrated that a numerical simulation using a physical model for water temperature distribution is useful for revealing effective water management techniques under various irrigation methods and meteorological conditions.

     

Assessing crop management options with crop simulation models based on generated weather data

The efficient use of crop simulation models is an effective complement to experimental research. Long-term weather data obtained at a specific site are normally required for the application of these crop simulation models to help determine alternate management practices and associated decisions. Stochastic weather generators sometimes are used to complement or substitute historical weather data. The objective of this study was to evaluate the suitability of weather data generated by the weather generators WGEN and SIMMETEO as input for crop simulation models in order to determine the best option(s) among a number of different crop management practices. Five locations across Iran representing different climates were selected. The wheat, maize, and soybean models of the Decision Support System for Agrotechnology Transfer (DSSAT) were applied in this study, using 30 years of observed weather data and 90 years of weather data generated by WGEN and SIMMETEO. Simulated grain yield using either observed weather data or weather data generated by WGEN and SIMMETEO in response to various ‘experimental’ factors, e.g., cultivar selection, planting date, planting density, irrigation threshold, and change in precipitation under irrigated and rainfed conditions were compared. The statistical evaluation was based on t, F, and Kolomogrov-Smirnov (K-S) tests. The average of the percentage rejected tests was 20% and the parameter estimation method had no impact on the number of rejected tests. Irrespective of some significant differences between simulated yield based on observed weather data and those based on weather data generated by WGEN and SIMMETEO, a similar conclusion could be drawn about the best cultivar, planting date, plant density and irrigation threshold and response to changes in the amount of precipitation. Based on the results of this study it can be concluded that for many crop model applications where only relative estimates or determination of the best management option(s) rather than absolute values are required, weather data generated by either WGEN and SIMMETEO are accurate and sufficient.     

主要节水灌溉方式对水稻根系形态生理的影响

水稻是耗水第一大作物。发展节水栽培对稻田水分高效利用和缓解我国水资源短缺具有重要意义。水稻根系是吸收水分和养分的重要器官,也是多种激素、氨基酸和有机酸合成的重要部位。水分管理措施的改变会直接或间接引起根系生长发育发生改变,从而影响水稻地上部生长发育和产量形成。本文综述了干湿交替灌溉、控制灌溉和覆盖旱种对水稻根系形态和生理特性的影响,提出了今后节水灌溉下水稻根系的研究重点,以期为改善水稻根系形态生理和高产节水栽培提供理论依据。     

Future potential impacts of climate change on agricultural watershed hydrology and the adaptation strategy of paddy rice irrigation reservoir by release control

This study is to assess the climate change impact on the temporal variation of paddy rice irrigation reservoir water level from the future evaluated watershed inflow, and to suggest an adaptation method of the future reservoir water level management for stable water supply of paddy irrigation demands. A 366.5 km² watershed including two irrigation reservoirs located in the upper middle part of South Korea was adopted. For the future evaluation, the SLURP model was set up using 9 years daily reservoir water level and streamflow records at the watershed outlet. The average Nash-Sutcliffe model efficiencies for calibration and validation were 0.69 and 0.65, respectively. For the future climate condition, the NIES MIROC3.2 hires data by SRES A1B and B1 scenarios of the IPCC was adopted. The future data were downscaled by applying Change Factor statistical method through bias-correction using 30 years past weather data. The results of future impact showed that the future reservoir storages of autumn and winter season after completion of irrigation period decreased for 2080s A1B scenario. Considering the future decrease of summer and autumn reservoir inflows, the reservoir operation has to be more conservative for preparing the water supply of paddy irrigation, and there should be a more prudent decision making for the reservoir release by storm events. Therefore, as the future adaptation strategy, the control of reservoir release by decreasing in August and September could secure the reservoir water level in autumn and winter season by reaching the water level to almost 100% like the present reservoir water level management.     

Modeling of continental-scale crop water requirement and available water resources

The relationship between agricultural water demand and supply has been of interest to government decision makers and scientists because of its importance in water resources management. We developed a water cycle model for eastern Eurasia that can estimate water requirements for crop growth and evaluate the demand–supply relationships of agricultural water use on a continental scale. To produce an appropriate water cycle, the model was constructed based on small drainage basins. To validate the model performance with respect to simulated runoff, which is here considered as the available water resource, we compared our outputs with those of other models and with observed river discharges. The results show that this model is comparable to other models and that it is applicable for the evaluation of water cycles at continental scale. We defined two types of crop water deficits (CWDs) as indicators of agricultural water demand. These were formulated by considering the physical processes of crop water use; we did not include water consumption that is dependent on cultivation management practices, such as water losses in irrigation systems. We assessed the reliability of our indicators by comparison with indicators from other studies and with published statistics related to agricultural water use. These comparisons suggest that our indicators are consistent with independent data and can provide a reasonable representation of water requirements for crop growth.     

灌溉模式与施氮量交互作用对水稻产量以及水、氮利用效率的影响

【目的】研究不同水、氮管理模式对水稻产量以及水、氮利用效率的影响,以期为水稻高产与水、氮高效利用提供理论依据和技术参考。【方法】大田试验于2015-2016年在浙江富阳进行,供试品种为三系籼型杂交稻天优华占。设置常规灌溉(CI)和干湿交替灌溉(AWD)两种灌溉模式,同时设置低氮(LN,80 kg/hm~2)、中氮(MN,160kg/hm~2)和高氮(HN,240 kg/hm~2)3种施氮水平。【结果】灌溉模式与施氮量对水稻产量以及水、氮利用效率有显著互作效应。与CI相比,AWD抑制无效分蘖,分蘖成穗率提高8.1%~10.7%;提高抽穗期至成熟期的光合势(LAD)与群体生长率(CGR);促进根系下扎,10~20 cm根层根系生物量增加了24.4%~32.3%,同时提高了结实期根系活性;促使茎鞘中非结构性碳水化合物(NSC)向籽粒中运转;且AWD在160 kg/hm~2(中氮)施氮水平下可显著提高产量与水、氮利用效率,为本研究最佳的水、氮运筹模式。【结论】通过适宜的水、氮运筹可充分发挥其互作效应,提高水稻产量与水、氮利用效率。     

A model for explaining genotypic and environmental variation in vegetative biomass growth in rice based on observed LAI and leaf nitrogen content

The objectives of this study are to propose a model for explaining the genotypic and environmental variation in above-ground biomass growth via photosynthesis and respiration processes from transplanting to heading for different rice genotypes grown under a wide range of environments, and to identify the physiological traits associated with genotypic difference in the biomass growth based on model analysis. Cross-locational experiments were conducted with nine different rice genotypes at eight locations in Asia covering a wide climate range under irrigated conditions with sufficient nitrogen application. The crop growth rate observed during the period from transplanting to heading ranged from 3.4 to 19.4 g m⁻² d⁻¹ among the genotypes grown at the eight locations. About one-third of the data sets were utilized for model calibration and the remaining sets were used for model validation. An above-ground biomass growth model was developed by integrating processes of single leaf photosynthesis as a function of stomatal conductance and leaf nitrogen content, growth and maintenance respiration and crop development. To rigorously examine the validity of this process model, measured data were input as external variables for leaf area index (LAI) development and leaf nitrogen content per unit leaf area. The model well explained the observed dynamics in above-ground biomass growth (R² = 0.95*** for validation dataset) of nine rice genotypes grown under a variety of environments in Asia. The model simulation suggested that genotypic difference in the biomass growth was closely related to the difference in the stomatal conductance and leaf nitrogen content, as well as to LAI. This paper proposes the model structure, algorithms and all parameter values contained in the model, and discuss its effectiveness as a component of a more comprehensive model for simulating dynamics of biomass growth, LAI development and nitrogen uptake as a function of genotypic coefficients and environments.     

Yield and water productivity of rice–wheat on raised beds at New Delhi, India

Permanent raised beds are being proposed for the rice–wheat system in the Indo-Gangetic Plain to increase its productivity and to save water. It is not clear whether reported water savings in rice arise from the geometry of the beds per se or from the particular water management that keeps the soil in aerobic conditions and that can also be applied on flat land. Moreover, little research has been reported on direct seeding of rice on raised beds and on the effect of raised beds on the subsequent wheat crop. In this paper we compare the yield, input water (rainfall and irrigation) use and water productivity of dry-seeded rice on raised beds and flat land with that of flooded transplanted and wet-seeded rice, and analyze the effects of beds on the subsequent wheat crop. The experiment was conducted in 2001–2003 at New Delhi, India.

Rice yields on raised beds that were kept around field capacity were 32–42% lower than under flooded transplanted conditions and 21% lower than under flooded wet-seeded conditions. Water inputs were reduced by 32–42% compared with flooded rice, but could also be accomplished with dry seeding on flat land with the same water management. Reduced water inputs and yield reductions balanced each other so that water productivity was comparable among most treatments. Wheat yield was 12–17% lower on raised beds than on flat land with conventional (20 cm) row spacing. Neither wheat nor rice on raised beds compensated for the loss in rows by extra tillering or leaf growth at the edges of the rows. There was no carry-over effect of type of land preparation in rice on the growth and yield of the subsequent wheat crop. Further research on raised beds should focus on the selection of suitable rice and wheat varieties, soil health issues such as nematodes and micro-nutrient deficiencies, weed control, bed stability and long-term carry-over effects from one crop to the other.