Using crop and pest models for management applications

Models that simulate crop production systems are useful tools to aid in crop management. The manager can evaluate numerous management options quickly and select the options most suitable for his situation. The Florida Soybean growth model (SOYGRO) has been implemented with several user interfaces to meet specific management goals. These implementations include a gaming model (SOYGAME), a pest decision model (PESTDEC), an irrigation decision model (IRRDEC) and a strategy evaluation model (SICM). The crop model integrates the effects of weather conditions, crop management inputs and soil conditions on crop yield and the yield changes are reflected in the corresponding profit. Also described in the paper is an automated weather collection and reporting system for the acquisition and use of weather data.     

基于ORYZA2000的水量平衡要素和

在对水稻生产模型ORYZA2000充分验证的基础上，以2003年团林水肥耦合试验设计为背景，应用ORYZA2000模拟分析了不同施肥条件下传统淹灌和3种节水灌溉方式下的稻田田间水量平衡要素、产量以及水分生产率。结果表明，节水灌溉方式灌水量大大低于传统淹灌，其中无水层灌溉节水效果又明显优于沟灌，可靠性高，雨养灌溉虽然能最大限度的节约灌溉水量，但其应用取决于区域气候特点，应结合气候预测应用。水分胁迫可以增大不同施氮水平下稻田腾发量的差异，施氮可以减少株间蒸发，增加作物蒸腾，从而增加稻田腾发量和产量。     

基于SQL的智能灌溉专家系统优化设计

随着全球水资源的不断匮乏,节水形势越来越严峻。传统的灌溉技术缺乏对水资源的合理分配,导致水资源利用率十分低下,浪费现象较为严重,且不合理的灌溉模式对农作物生长也产生了一定的影响。为提高水资源利用率,保证农作物时刻具有所需的水分,基于SQL数据库技术,完成了智能灌溉专家系统的优化设计。通过分析专家系统的基本结构,建立了SQL数据库的E-R模型,并对智能灌溉专家系统的典型数据表(用户信息表、机具信息表、灌溉标准信息表和水泵信息表)进行优化设计。最后,对灌溉系统的实际灌溉情况进行试验,结果表明:基于SQL的智能灌溉专家系统可以根据农作物的生长所需合理分配水资源,使农作物具有适宜的水分环境,对大幅提高农作物产量和质量具有一定的实践意义。     

A real-time water allocation model for large irrigation systems

In this study a simulation model for real-time irrigation scheduling of water deliveries at the tertiary and secondary canal levels of large irrigation systems has been developed. The model is responsive to current season changes in weather and other variables. The irrigation scheduling of the subsequent week is found out at the end of each week by updating the status of the system with real time data up to that week and then by solving the model for the new conditions. The model is based on water balance approach for lowland paddy and a soil moisture simulation approach for determining the irrigation requirements of upland crops. Expected rainfall at different probability levels during the irrigation season was used based on past rain fall data and Leaky law. The model was applied to an irrigation system in Thailand for determining the required irrigation deliveries. Result of the application indicate that the model can be used for determining water deliveries in a real-time basis.     

基于实时气象信息的灌溉决策支持系统研究

基于实时气象信息的灌溉决策支持系统,是利用实时的气象信息结合灌溉预报模型,实现灌溉管理的自动化、智能化。详细介绍了基于实时气象信息的灌溉决策支持系统主要的数学模型、系统结构及功能。与现有的灌溉管理系统相比本系统在改进了灌溉计划的制订流程、增加了实时气象预报的灌溉计划修正功能,并提供智能的人工干预功能;此外,结合数据分析技术和灌溉管理的实际特点,利用回归分析方法解决由于极端天气或数据采集过程中引起的数据缺失及错误问题,提供灌溉决策的准确性。实际应用表明,系统具有较高的实用性和准确性,为灌区灌溉管理提供了科学手段及依据。     

攀枝花市蔬菜节水灌溉的实验研究

节水灌溉是以浇灌最少量的水得到最大经济效益的作物产量为目标,向农田人工补水的一种技术措施。除了满足作物需水要求外,灌溉还有调节土壤的温热状况、培肥地力、改善土壤深化性状等作用。在四川攀枝花市特定的自然气候条件下,采用滴灌和沟灌两种灌溉方法,对苦瓜和番茄进行灌溉对比实验研究。研究结果表明:滴灌较传统沟灌不仅能节约50%以上的灌水量,降低生产成本,而且可大幅度增加蔬菜产量,提高产品的商品性,减少环境和产品污染。     

Evaluating canopy temperature-based indices for irrigation scheduling

Summary Since the development of commercial versions of infrared sensors, they have been increasingly used to determine canopy temperature and schedule irrigations. However, some shortcomings of the technique have been identified, among them the sensitivity of canopy temperature measurements to weather fluctuations. Based on field and computer simulated data, an analysis of the suitability of crop water stress indices (CWSI's) developed from canopy temperature under variable weather conditions was done. Important day to day fluctuations of CWSI values determined using an empirical baseline (empirical CWSI) appeared common for nonstressed crops, particularly under low vapor pressure deficit conditions. These fluctuations generate uncertainty in the use of this empirical index to determine needs for irrigation. The use of an improved index (theoretical CWSI) requiring measurements of net radiation, soil heat flux and wind speed, and estimates of aerodynamic and canopy resistances reduced but did not eliminate these fluctuations. Results using a simulation model showed that the empirical CWSI provided late indication of irrigation needs, after some water stress has developed, which may limit its application for crops sensitive to water stress. These simulations also indicated that the theoretical CWSI was able to track the development of water stress and provide reasonable indication of irrigation needs. However, this result may not be fully realized in field applications where the determination of CWSI may be affected by various sources of variability which are not accounted for by the model.     

基于物联网技术的江西丘陵地区土壤墒情监测

针对江西丘陵地区作物种植分布广、监测点多、布线和供电困难等特点,利用物联网技术,采用高精度土壤温湿度传感器和智能气象站,建立土壤墒情监测系统,远程在线采集代表性地块土壤墒情、气象信息,实现墒情（旱情）自动预报、灌溉用水量智能决策和远程灌溉设备自动控制等功能。      

Real-time adaptive irrigation scheduling under a limited water supply

The problem of real-time irrigation scheduling under limited water supply is considered. The goal is to develop an irrigation operation policy which maximizes crop yields and is responsive to current season changes in weather and other variables. Because irrigation decisions are sequential and dependent on crop and soil water status, and also because crop yields can only be known at the end of the season, the decisions are arrived at by a two-stage process. In the first or the design stage, irrigations are planned for the entire season at weekly intervals using historical data and an optimal irrigation scheduling model. In the second stage, the decisions for the subsequent weeks are revised each week after updating the status of the system with real time data up to that week and solving the irrigation optimization model once again for the new conditions. Thus, each week an irrigation decision is made, the entire planning horizon is kept in view. The procedure is illustrated by application to a case study.     

Water user associations in Inner Mongolia: Factors that influence farmers to join

Irrigation districts in Inner Mongolia face problems that are familiar to irrigation areas around the world: shortage of water resources, poor management of water, inefficient use of water resources, and imbalance of financial revenues and expenditures. Water user associations have been promoted to address water supply problems and to encourage efficient water use. In this study, farmers from three distinct areas in Inner Mongolia were surveyed to determine their level of understanding of water user associations and the factors that affect their becoming members. A majority of respondents thought that water user associations were useful to safeguard farmers’ interests, to help reduce labour inputs and disputes about water, to reduce irrigation costs, and to promote efficient water use. The factors found to be most important were: (1) being a village cadre; (2) good state of health; (3) high degree of understanding about water user associations; (4) small percentage of the household in the labour force; (5) cropping income a high percentage of family income; (6) having had previous conflicts involving water use issues.     

Scheduling water application on drip irrigated sugarcane

Irrigation is necessary in order to produce sugarcane in semiarid south Texas, but water supplies are becoming increasing limited. Drip and sprinkler irrigation systems offer more precise water control than conventional furrow irrigation, but are more expensive. This study was conducted to evaluate four different methods (pan evaporation (E_pan), evapotranspiration (ET), auto-tensiometers, manual tensiometers) for determining the amount of irrigation water to apply, and three different frequencies of water application on sugarcane, in order to make the most efficient use of available water using subsurface drip irrigation. The study was conducted over three sugarcane seasons: the plant crop and two ratoon crops. The amount of water applied based on the different methods varied from year to year, with the ET method prescribing the most water in the first ratoon crop but the least amount in the second ratoon. This was probably caused mostly by differences in annual weather conditions. The more frequently water was applied, the larger amount any method tended to prescribe, since more frequent applications resulted in keeping the soil profile fuller, therefore providing less capacity to store rainfall when it occurred. Number of stress days as determined by calculating a stress coefficient based on ET and soil water balance indicated a large amount of stress in the first ratoon but almost none in the second ratoon crop. Direct soil water monitoring indicated much less stress than the calculated levels. Growth measurements and sugarcane yields showed that the highest water applications resulted in the best responses, regardless of the scheduling method used. All irrigation scheduling methods were effective, prescribing similar amounts of water for a given season. Direct measurement using tensiometers gives the most accurate assessment of field conditions, but is expensive and labor intensive. Automated tensiometers were not very reliable. Pan evaporation and ET are effective once they are properly calibrated by developing appropriate coefficients for a particular region. Pan evaporation has been used for a long time, but it is more difficult to obtain reliable data compared to ET data from automated weather stations.     

Making the user visible: analysing irrigation practices and farmers’ logic to explain actual drip irrigation performance

The actual performance of drip irrigation (irrigation efficiency, distribution uniformity) in the field is often quite different from that obtained in experimental stations. We developed an approach to explain the actual irrigation performance of drip irrigation systems by linking measured performances to farmers’ irrigation practices, and these practices to the underlying logic of farmers who operate these systems. This approach was applied to 22 farms in Morocco. Four sets of variables helped explain the gap between the actual irrigation performance and the performance obtained in experimental conditions: (1) farmers have agro-economic motivations or want to improve their social status, and for them, irrigation performance is at best an intermediate objective. (2) Irrigation performance is not a static value, but a rapidly evolving process, related to the (perceived) ability of farmers to change irrigation practices and renew irrigation equipment, but also to farmers’ aspirations. (3) The social network of farmers, supporting the introduction and use of drip irrigation, determines how farmers may share experience, information and know-how related to drip irrigation. (4) Today, there is no social pressure to irrigate carefully to save water; only the state explicitly links the use of drip irrigation to saving water. Making the drip user visible in research and policy studies would lead to more realistic assessments of irrigation performance and draw the attention of policy makers to the actual conditions in which drip irrigation is used, and as a consequence help incorporate ‘saving water’ as an objective for drip irrigation users.     

Institutional management regimes for pricing of irrigation water: the French model — lessons for India

In France, the River Basin Committees and Water Agencies are in-charge of managing water resources. However, many surface irrigation networks were initiated and operated by the Regional Companies and farmer syndicates exclusively for agricultural development in the southwest of the country. These are water institutions playing an active role in water management with an objective of cost recovery in order to improve the quality of irrigation services to the users. The implementation of various innovative institutional management approaches by these agencies have yielded a modest degree of success in addressing the crucial problems of the irrigation sector in terms of pricing water, cost recovery, financial viability and overall sustainability of the surface irrigation system. This study attempts to examine the relevance of the institutional management approaches of France to the Indian context. The institutional framework for setting the price of irrigation water is through negotiation between the management and the user representatives. The important lessons drawn based on the experiences of the French model include the granting of financial autonomy to the water institutions in order to recover operational and maintenance costs, participatory approaches of decentralised management, user involvement in the decision-making process, devolution of small-scale irrigation networks to the users for management and the promotion of effective and viable user associations with access to technical information relating to the use of irrigation technologies.     

Evaluation of surface irrigation system performance using System Dynamics (SD) approach

Various methods and criteria have been proposed and utilized for the evaluation of irrigation systems performance, which can be used for comparison of design conditions and irrigation systems performance. Surface irrigation systems should be paid more attention among all other irrigation systems due to their operation simplicity and high losses. In the present study, while describing main relationships of irrigation evaluation criteria of application efficiency, water requirement efficiency, Deep Percolation Ratio and Tail Water Ratio, a method based on SD will be introduced. Modeling of this approach has been done using VENSIM-DSS software. Model has been tested in a case study that included the modeling of a furrow in four irrigation status: current situation, full irrigation, deficit irrigation and finally deficit irrigation with optimized irrigation cutoff time and inflow into furrow. The results reveal the high capabilities of SD approach in modeling water resources and irrigation systems. Its user friendly and ability in transferring data to the data bank can introduce this approach and software as an applicable decision support system.     

节水灌溉稻田水碳通量日变化特征

为了揭示不同天气条件对节水灌溉稻田水碳通量日变化的影响,采用涡度相关系统对节水灌溉稻田水碳通量进行了连续监测,分析了不同天气条件下节水灌溉稻田水汽与CO_2日变化特征。结果表明:节水灌溉稻田各月阴天与晴天典型日内水碳通量变化趋势相似,阴天变化呈现多峰变化,晴天下变化较稳定。夜间和凌晨变化较小,差异也较小,白天差异较大。水稻全生育期各月阴天下典型日稻田水汽通量的峰值是晴天下水汽通量峰值的0.5倍左右。各月之间阴天和晴天的水汽通量在生育中期的八九月峰值均较大。节水灌溉稻田夜间以呼吸排放CO_2为主,白天以光合固定CO_2为主。7、10月阴天典型日稻田CO_2通量峰值是晴天峰值的0.5倍左右,而在水稻生长旺盛的八九月,两种天气条件稻田CO_2通量日变化多数时段偏差较小。     

关中地区气候变化对主要作物需水量影响的研究

用关中地区30个气象站41年气象资料,探讨了关中地区主要作物冬小麦和夏玉米需水量与相应生育期内气候因子的变化趋势,分析了气候变化对作物需水量的影响。结果表明:关中地区冬小麦需水量无一致变化趋势,净灌溉需水量(NIWR)呈增加趋势;夏玉米需水量呈不显著减少趋势,净灌溉需水量无一致变化趋势。气象因子影响顺序为,冬小麦:相对湿度>最高气温>日照时数>降水量>平均气温>风速,夏玉米:日照时数>相对湿度>最高气温>平均气温>降水量>风速。日照时数和风速引起冬小麦需水量的降低趋势在很大程度上抵消了相对湿度和最高气温引起的冬小麦需水量的升高趋势,而冬小麦生育期降水的减少是造成冬小麦净灌溉需水量增加的主要原因;风速和日照时数的降低趋势是导致夏玉米需水量减少的主要原因。关中地区秋冬春季向暖干发展,夏季除风速显著降低外,其它气象因子变化不大。     

Determination of spatial water requirements at county and regional levels using crop models and GIS: An example for the State of Parana,Brazil

Due to the competitive use of available water resources, it has become important to define appropriate strategies for planning and management of irrigated farmland. To achieve effective planning, accurate information is needed for crop water use requirements, irrigation withdrawals, runoff and nitrate leaching as a function of crop, soil type and weather conditions at a regional level. Interfacing crop models with a geographic information system (GIS) extends the capabilities of the crop models to a regional level. The objective of this study was to determine the irrigation requirements, annual runoff and annual nitrate leaching for the most important crops of the Tibagi river basin in the State of Parana, Brazil. The computer tool selected for this study was the Decision Support System for Agrotechnology Transfer (DSSAT) version 3.5 (98.0) and its associated crop modeling and spatial application system AEGIS/WIN. It was assumed that farms within the same county use similar management practices. To achieve representative estimates of irrigation requirements, the weather data from stations located within each county or the nearest weather station were used. A weighting factor based on the proportion of soil type and crop acreage was applied to determine total annual irrigation withdrawals, annual runoff and nitrate leaching for each county in the river basin. The model predicted outputs, including yield, irrigation requirements, runoff and nitrate leached for different soil types in each county, were analyzed, using spatial analysis methods. This allowed for the display of thematic maps for irrigation requirements, annual runoff and nitrate leaching, and to relate this information with irrigation management and planning. The maximum annual irrigation withdrawal, runoff and nitrate leaching were 22,969 m³ per year, 31,152 m³ per year and 1488 t N per year in the Tibagi river basin. This study showed that crop simulation models linked to GIS can be an effective planning tool to help determine irrigation requirements for river basins and large watersheds.     

Water scarcity, prices and quotas: a review of evidence on irrigation volumetric pricing

Underpricing of irrigation water is frequently identified as a primary cause of excessive use of water for irrigation. Higher prices are believed to have the potential to promote conservation. Changes in user behavior are predicated on a quantitative relationship between water charges and the volume use, but volumetric management is quite rare in practice. This paper reviews irrigation schemes that combine conditions of water scarcity and volumetric pricing, either at the bulk or individual level, and provides clear evidence that scarcity is almost invariably dealt with through the definition of quotas. In contrast to the large theoretical literature that has promoted price-based regulation as a key instrument of water demand management, it appears that prices are mostly used to regulate use at the margin, beyond the quota, rather than for rationing scarce water. This is an important role but one that falls short of efficiency pricing. The advantages and drawbacks of quotas are discussed, and an interpretation of why they are selected in practice is given.     

Evaluation of irrigation schemes for sugarcane in Sindh,Pakistan, using SWAP93

A computer simulation model, SWAP93, was used to simulate the soil water balance of sugarcane (Saccharum officinarum L.) over a period of 6 years, in order to develop an efficient irrigation scheduling scheme for Sindh, Pakistan. Given the limitations and inflexibility of the existing warabandi irrigation system, which does not allow on-demand irrigation, only irrigation depth and irrigation interval were varied in order to assess the best irrigation depth/interval combination for sugarcane production. Twelve irrigation treatments were simulated. These treatments were four irrigation amounts (900, 1200, 1650 and 1800 mm) and three irrigation frequencies (7, 10 and 15 days). Three seasons with rainfall totaling less than 20 mm were compared with three seasons of over 200 mm rainfall. Two approaches were used in assessing the irrigation schemes: yield parameters and water management response indicators. Treatment parameters (e.g. irrigation amounts, weather conditions, soil characteristics, etc.) served as input for SWAP93, actual transpiration was calculated and then used in a crop water production function to predict yield and water use efficiency. Additionally, water management response indicators were derived from model outputs, and used to assess the impact of the schemes on soil salinity and water logging. Both these indicators and the yield and water use efficiency indicated that a seasonal total of 1650 mm, applied at a 15-day interval was the best irrigation scheme for the region.     

民勤县主要作物优化灌溉制度制定及风险分析

根据由气象站和田间试验搜集到的民勤县各灌区1985—2008年间统计数据资料,建立了民勤县典型作物基于机会约束规划的优化灌溉制度模型,利用动态规划方法求解,制定出了几种典型作物在不同水文年的灌溉制度,其节水增产效果显著,并对其用水风险进行了分析。