The evolution of smallholder irrigation policy in Zimbabwe: 1928–1986

Voluntary smallholder irrigation schemes in Zimbabwe were launched in 1913 as a means of famine relief and subsequently to settle black farmers displaced from designated areas for white commercial farmers. In 1928 the colonial government inaugurated a programme to provide services to existing smallholder schemes and to assist in developing new schemes. This process eventually led to the erosion of farmer participation in planning, development and financing of smallholder schemes. Since 1928 the smallholder schemes have been heavily subsidised, a pattern that continues today. Currently about 3.4% of the land under irrigation is farmed by small holders who pay about 11% of the costs of irrigation operation and maintenance; the remaining 89% is subsidised by the government. More smallholder irrigation development is currently being planned. The government has made loan funds available to groups on the basis of financial viability, but to date this fund has not been significantly utilized by smallholders. In essence, smallholder irrigation development is being constrained by problems that have plagued smallholder schemes since 1928.Abbreviations AGRITEX Agricultural Technical and Extension Services - ARDA Agricultural and Rural Development Authority - DERUDE Department of Rural Development - NFIF National Farm Irrigation Fund - Z$ Zimbabwe Dollar     

基于模糊几何加权模型的灌区水资源优化配置

针对农业水资源优化配置中多目标赋权的不确定性问题,以黑龙江省绰尔屯灌区为研究区域,构建了基于模糊几何加权法的灌区水资源优化配置模型,把多目标规划问题转化为单目标非线性问题,得到了不同权重下不同生育期的灌区水资源最佳配置方案,并通过灌区综合能力评价体系进行比选.结果表明：通过与线性多目标模糊规划模型的对比,模糊几何加权模型可以根据实际情况对不同目标的权重进行调整,得出该条件下的灌区水资源最佳配置方案;当灌水量权重为0.3和经济权重为0.7时为最优方案,水稻产值为8 245万元,分蘖期、拔节期、抽穗期、乳熟期的灌水量分别为1 154.56万、779.12万、539.45万、336.57万m³.验证了模糊几何加权法在灌区水资源优化配置的可行性应用,为灌区农业水资源高效利用提供参考方案和决策支持.     

滴灌水肥耦合技术在西北干旱区作物栽培中的应用

水分和养分是影响作物生长发育的关键因素,明确作物需水需肥规律及其交互作用有助于农作物优质高产栽培。我国西北干旱区水资源极端匮乏,滴灌水肥耦合技术可以准确而均匀地将水肥施用于作物根部。对滴灌水肥耦合技术的优点及其对西北干旱区作物的影响研究进行了综述。滴灌水肥耦合技术通过扩大水分和养分在作物根区的运移范围,有利于作物对水分和养分的汲取和利用,实现节水省肥增产调质的目标。滴灌水肥耦合技术的优点为提高农作物水肥利用效率、促进农作物优质高产栽培、减少田间劳动力和有利于健康绿色可持续农业的发展。      

An analysis of the water management performance of small holder irrigation schemes in Zimbabwe

This paper analyses the water management performance of small holder irrigation systems in Zimbabwe. The government and farmer managed systems are compared in terms of their ability to match desired with actual water supply. Desired supply is defined as crop water requirements adjusted downwards by rainfall where relevant. The Theil measure of accuracy of forecasts is used to calculate the error committed by each system in trying to match water supply and demand. The analysis shows that, everything else being equal, the farmer managed system performs better than the government system in matching supply and demand. This means that the farmer managed systems should be encouraged for future small holder irrigation development in Zimbabwe.     

河南省烟区灌溉水全盐量和氯含量状况

通过对河南省烟区 135 3个灌溉水样分析表明 ,全省烟区灌溉水全盐量平均为 380 .1m g/ L,氯含量平均为31.98mg/ L。五大植烟区比较 ,全盐含量顺序为 :豫东 >豫中 >豫西 >豫南 >豫西南 ;氯含量顺序为 :豫东 >豫中 >豫南 >豫西南 >豫西。全省约有 80 %烟田灌溉水氯含量比较适宜。     

干旱区农业水资源供需水预测分析及对策研究

针对西北干旱区农业水资源短缺的问题,以新疆洛浦县为例,从作物种植结构调整和灌溉面积变化、灌溉水利用系数提高及灌溉方式改变等方面进行节水分析,并对预测水平年农业供需水平衡进行了预测计算,预测结果表明：现有的灌排工程不能满足农业可持续发展要求;提高灌溉水利用系数势在必行;采用滴灌技术极大地减少了农业用水量,是解决农业供需水矛盾的有效措施。最后,根据预测结果,提出了解决农业水资源短缺、可持续发展的对策,为其他区域水资源的合理开发利用提供有益的参考。     

Could deficit irrigation be a sustainable practice for quinoa (Chenopodium quinoa Willd.) in the Southern Bolivian Altiplano?

The application of deficit irrigation (DI) to stabilize yield and to increase water productivity of quinoa (Chenopodium quinoa Willd.) raises questions in the arid Southern Altiplano of Bolivia where water resources are limited and often saline. Rainfed quinoa and quinoa with irrigation restricted to the flowering and early grain filling were studied during the growing seasons of 2005–2006 and 2006–2007 in a location with (Irpani) and without (Mejillones) water contribution from a shallow water table. It was found that the effect of additional irrigation was only significant above a basic fulfillment of crop water requirements of around 55%. Below this threshold, yields, total water use efficiency (TWUE) and marginal irrigation water use efficiency (MIWUE) of quinoa with DI were low. Capillary rise (CR) from groundwater was assessed using the one-dimensional UPFLOW model. The contribution of water from capillary rise in the region of Irpani ranges from 8 to 25% of seasonal crop evapotranspiration (ET_c) of quinoa, depending mostly on the depth of the groundwater table and the amount of rainfall during the rainy season. DI with poor quality water and cultivation of crops in fields with a shallow saline groundwater table pose a serious threat for sustainable quinoa farming. To assess the impact of saline water resources, soil salinity and required leaching were simulated by combining the soil water and salt balance model BUDGET with UPFLOW. The results indicate that irrigation of quinoa with saline water and/or CR from a saline shallow water table might, already after 1 year, result in significant salt accumulation in the root zone in the arid Southern Altiplano. A farming system with only 1 year fallow is often insufficient to leach sufficient salts out of the root zone. In case the number of fallow years cannot be increased, leaching by means of an important irrigation application before sowing is an alternative. Although potentially beneficial, DI of quinoa in arid regions such as the Southern Bolivian Altiplano should be considered with precaution.     

大型水稻灌区高产节水灌溉优化配水模型研究

根据江苏省北部地区水资源供需矛盾突出的现状,以大型水稻灌区为研究对象,研究水资源的优化分配问题,从水稻水分生产函数和作物需水模型入手,建立了外引河湖水、内提回归水两种水源供水条件下的水稻全生育期适时调度优化配水数学模型。以灌区典型年供水资料,对优化配水模型进行了复核验证。所建立的模型,与灌区实际用水条件基本相符,为水稻灌区用水管理提供了一条新路。     

Beyond irrigation efficiency

Parameters for accounting for water balance on irrigation projects have evolved over the past century. Development of the classic term irrigation efficiency is summarized along with recent modifications such as effective irrigation efficiency. The need for terms that describe measurable water balance components of irrigated agriculture is very important, as demands and competition for available renewable water supplies continue to increase with increasing populations. Examples of irrigation efficiency studies conducted during the past few decades are summarized along with related irrigation terminology. Traditional irrigation efficiency terminology has served a valid purpose for nearly a century in assisting engineers to design better irrigation systems and assisting specialists to develop improved irrigation management practices. It still has utility for engineers designing components of irrigation systems. However, newer irrigation-related terminology better describes the performance and productivity of irrigated agriculture. On a river-basin level, improved terminology is needed to adequately describe how well water resources are used within the basin. Brief suggestions for improving irrigation water management are presented.     

四川盆地丘陵区条田规划与工程设计研究

针对丘陵山区条田规划和工程设计研究不足的问题,借助ArcGIS对条田建设的工程数据及图件进行处理和分析,建立重庆市合川区大石镇高川等4个村以及重庆市开县厚坝镇大坝等4个村田面平整、灌排畅通及道路完善的高标准条田.研究结果表明:条田建设是以道路和沟渠分割的格田为基础,根据地形条件、耕作方式、农业种植习惯及社会经济状况等确定田块规模;地形坡度较大的地区,适宜局部平整,而地形坡度相对平缓的地区,适合大规模的耕作区划分;地形起伏较大,条田规划应首要满足灌溉和机耕的要求,田间灌渠采用横向布置形式;当地势平坦时,应更多考虑排水问题,田间灌渠采用纵向布置形式.因此,通过条田规划与工程设计实现了四川盆地丘陵区高标准农田的基本建设,达到了土地资源的高效利用.     

Simple microirrigation techniques for improving irrigation efficiency on vegetable gardens

Microirrigation techniques can be used to improve irrigation efficiency on vegetable gardens by reducing soil evaporation and drainage losses and by creating and maintaining soil moisture conditions that are favourable to crop growth. Water balance experiments in Zimbabwe showed that over 50% of the water applied as surface irrigation on traditional irrigated gardens can be lost as soil evaporation. This result gives an indication of the potential improvement in irrigation efficiency that can be achieved by adopting irrigation methods that reduce soil evaporation at the same time as minimising losses due to drainage and canopy interception. During the period 1985 to 1995, irrigation trials and experiments were carried out in south-east Zimbabwe and northern Sri Lanka with the main aim of comparing and quantifying the benefits of using simple microirrigation techniques on traditional vegetable gardens. This paper reviews the results of these trials and experiments. Microirrigation techniques that were evaluated included low-head drip irrigation, pitcher irrigation and subsurface irrigation using clay pipes. Of these methods, subsurface irrigation using clay pipes was found to be particularly effective in improving yields, crop quality and water use efficiency as well as being cheap, simple and easy to use. The comparative advantages of subsurface irrigation were maintained for a range of crops grown under different climatic conditions. Good results were also obtained with subsurface irrigation when irrigation was carried out using with poor quality irrigation water.     

考虑地下水人工回灌的灌区水资源管理研究

主要探讨人工回灌情况下的灌区水资源管理问题。将研究区域的整个地下含水层视为单一单元 ,分别介绍了该单一单元的各个输入变量和输出变量 ,基于地下水的水均衡方程 ,得到了可用于对灌区的水资源进行有效管理的数学模型。文中举一示例介绍该模型的应用 ,结果表明该模型可用来确定需要抽取的地下水量以及地下含水层的蓄水量 ,为灌区的水资源规划管理提供有益的指导。     

Deficit irrigation of sunflower (Helianthus annuus L.) in a sub-humid climate

The response of sunflower (Helianthus annuus L.) to 14 irrigation treatments in a sub-humid environment (Bursa, Turkey) was studied in the field for two seasons. A rainfed (non-irrigated) treatment as the control and 13 irrigation treatments with full and 12 different deficit irrigations were applied to the hybrid Sanbro (Novartis Seed Company) planted on clay soil, at three critical development stages: heading (H), flowering (F) and milk ripening (M). The yield increased with irrigation water amount, and the highest seed yield (3.95 t ha⁻¹) and oil yield (1.78 t ha⁻¹) were obtained from the HFM treatment (full irrigation at three stages); 82.9 and 85.4% increases, respectively, compared to the control. Evapotranspiration (ET) increased with increased amounts of irrigation water supplied. The highest seasonal ET (average of 652 mm) was estimated at the HFM treatment. Additionally, yield response factor (k _y) was separately calculated for each, two and total growth stages, and k _y was found to be 0.8382, 0.9159 (the highest value) and 0.7708 (the lowest value) for the total growing season, heading, and flowering-milk ripening combination stages, respectively. It is concluded that HFM irrigation is the best choice for maximum yield under the local conditions, but these irrigation schemes must be re-considered in areas where water resources are more limited. In the case of more restricted irrigation, the limitation of irrigation water at the flowering period should be avoided; as the highest water use efficiency (WUE) (7.80 kg ha⁻¹ mm⁻¹) and irrigation water use efficiency (IWUE) (10.19 kg ha⁻¹ mm⁻¹) were obtained from the F treatment.     

A model for regional optimal allocation of irrigation water resources under deficit irrigation and its applications

It is important to promote efficient use of water through better management of water resources, for social and economical sustainability in arid and semi-arid areas, under the conditions of severe water shortage. Based on the developments in deficit irrigation research, a recurrence control model for regional optimal allocation of irrigation water resources, aiming at overall maximum efficiency, is presented, with decomposition-harmonization principles of large systems. The model consists of three levels (layers). The first level involves dynamic programming (DP) for optimization of crop irrigation scheduling. The second level deals with optimal allocation of water resources among various crops. The last level concerns optimal allocation of water resources among different sub-regions. As a test, this model was applied to the combined optimal allocation of multiple water resources (surface, ground and in-take from the Weihe river) of Yangling, a semi-arid region on the Loess Plateau, China. Exemplary computation showed that not only are the results rational, but the method can also effectively overcome possible “dimensional obstacles” in dynamic programming of multiple dimensions. Furthermore, each sub-model is relatively independent by using various optimization methods. The model represents a new approach for improving irrigation efficiency, implementing water-saving irrigation, and solving the problem of water shortage in the region studied. The model can be extended in arid and semi-arid areas for better water management.     

Modeling the potential for closing quinoa yield gaps under varying water availability in the Bolivian Altiplano

In the Bolivian Altiplano, the yields of rainfed quinoa are relatively low and highly unstable. We use a validated crop water productivity model to examine the potential of closing quinoa yield gaps in this region. We simulate the expectable yields under rainfed cultivation and under different deficit irrigation (DI) strategies using the AquaCrop model for the Northern, Central and Southern Bolivian Altiplano. Simulated DI scenarios include a reference strategy avoiding stomatal closure during all sensitive growth stages and allowing drought stress during the tolerant growth stages (DI₀) and various restrictive deficit irrigation strategies (DI_i) representing cases when water resources are limited. We obtain a logistic crop water production function for quinoa by plotting the seasonal actual evapotranspiration versus total grain yield. Due to the large scatter, this function only indicatively provides expectable yields. From the scenario analysis, we derive yield probability curves for the 3 agro-climatic regions. DI, without restriction in irrigation water during the drought sensitive growth stages, is able to close the yield gaps in the Northern, Central and Southern Bolivian Altiplano, and would guarantee a high and stable level of water productivity (WP). The yields of quinoa under rainfed cultivation during dry years are only 1.1, 0.5 and 0.2 Mg ha⁻¹ in the Northern, Central and Southern Bolivian Altiplano, whereas under DI₀ they are 2.2, 1.6 and 1.5 Mg ha⁻¹, respectively. Under limited water availability for irrigation, these stable yield levels decrease, most drastically in the Southern Bolivian Altiplano. Below a minimum water availability of 600 m³ per ha and 700 m³ per ha in the Central and Southern Bolivian Altiplano, respectively, the application of DI for quinoa is not significantly effective and should be avoided to save valuable resources. The yield probability curves we derive can serve as input for stochastic economic analysis of DI of quinoa in the Bolivian Altiplano.     

基于熵权的模糊物元模型优选夏玉米沟灌方式

为了探究沟灌方式下不同灌水处理对夏玉米主要性状及水资源利用效率的影响,采用基于熵权法的模糊物元模型,以大田夏玉米为试验材料,进行了常规沟灌(conventional furrow irrigation,CFI)和宽垄沟灌(wide-ridge furrow irrigation,WFI)种植下3种灌水水平(土壤水分控制下限分别设置为田间持水量的60%,70%和80%)对夏玉米形态指标(株高、叶面积)、产量性状(穗长、穗粗、百粒质量、产量)以及水资源利用效率(灌溉利用效率、水分生产效率)的影响分析.结果表明:同一水分处理下,夏玉米WFI灌溉组合方案优于CFI灌溉组合方案;对于水资源相对丰富地区建议采用WFI-70%θ灌溉方案,对于水资源相对匮乏地区建议采用WFI-60%θ灌溉方案;基于熵权法的模糊物元模型较CRITIC法的模糊物元模型评价效果更好,基于熵权法的模糊物元模型对沟灌夏玉米主要性状和水资源利用效率方面具有一定的应用价值.该研究为沟灌夏玉米合理灌溉提供了科学依据.     

山东省引黄项目区农业灌溉水平衡分析研究

山东省利用世界银行贷款加强灌溉农业(二期)引黄项目区,插花分布在10个县,水资源时空变化大,灌溉水源除当地水外还引用黄河水补充灌溉,引黄水和当地水丰枯遭遇不同,因此进行项目区水资源供需平衡分析对项目立项和建成后可持续发展具有重要作用。采用典型年净平衡和水平衡模拟模型2种方法,对引黄项目区农业灌溉水资源水平衡进行了分析计算,使农业灌溉水资源评价结果更加科学和符合实际。     

节水压采区农业种植结构多目标优化研究——以衡水市为例

针对节水压采区水资源紧缺、种植结构不合理、灌溉定额较大等问题,提出了基于作物水分生产函数的多目标种植结构优化模型。以衡水市为例,以种植结构和灌水量为优化变量,以经济效益最大和总灌溉水量最小为优化目标,建立了多目标优化模型,通过改进的NSGA-II算法进行优化计算,得出了不同灌溉水价水平下对应的种植结构和灌水量调整方案。结果表明,小麦种植面积比现状种植面积有所减少,玉米、花生等耗水量小的作物面积有所增加。通过优化,合理提高灌溉水价可促进高耗水作物种植面积的减少,扩大低耗水作物种植面积。     

山丘区高效节水灌溉工程设计要点

该文根据山丘区地形地貌、气候特征和水资源条件等情况,对山丘高效节水灌溉设计中应该注意的问题进行汇总,主要从水源工程设计、灌溉制度拟定、灌水方式选择、管材选择和管网布置等方面进行分析,提出了山丘区高效节水灌溉工程的设计要点,可供相关的工程设计进行参考。      

不同节水灌溉方式及栽培模式下粳稻生长特性研究

【目的】缓解农业水资源供需矛盾,保障粳稻种植可持续发展,开展不同灌溉栽培模式下粳稻生长特性、耗水规律研究,为粳稻节水栽培技术提供支撑。【方法】利用称重式蒸渗仪,设置了湿润灌溉(SR)、控制灌溉(KZ)、浅湿灌溉(QS)3种节水灌溉方式,水直播(SZB)、旱直播(HZB)2种栽培模式,分析了不同节水灌溉方式和栽培模式下粳稻生长特性、耗水规律、产量及其构成因素。【结果】相同栽培模式不同节水灌溉方式下,KZ处理在有效分蘖数、耗水量、产量方面均最优,水分生产率与SR处理相当,是最优的节水高产灌溉制度;QS处理耗水量比KZ处理高19.90%,产量比KZ处理低4.22%,水分生产率比KZ处理低20.11%,产生无效分蘖多,株高高于KZ处理;SR处理水分控制严格,粳稻有效分蘖不足,耗水量低、水分生产率高,但产量远低于KZ处理和QS处理。相同节水灌溉方式不同栽培模式下,直播种植模式在生长期上较移栽种植滞后,但分蘖中后期直播种植分蘖和耗水表现出补偿效应,SZB处理分蘖数与KZ处理基本持平,HZB处理补偿效应后劲不足;直播种植在同种节水灌溉方式下产量低于移栽种植,HZB处理尤为明显,与移栽条件下不同节水灌...