Modelling the fate of water and nitrogen in the mixed vegetable farming systems of northern Tasmania, Australia

A combination of high input management systems, high annual rainfall and deep, permeable soils in northern Tasmania create conditions that are conducive to high drainage and nitrogen losses below the root zone. An understanding of the extent and mechanism of such losses will enable farm managers and their consultants to identify and implement more sustainable management practices that minimise potential adverse financial and environmental consequences. Analysing the fate of water and nutrients in farming systems is complex and influenced by a wide range of factors including management, soil characteristics, seasonal climate variability and management history of the paddock/farm in question. This paper describes a novel farm system modelling approach based on the model APSIM, for analysing the fate of nitrogen and water in mixed vegetable-based farming enterprises. The study was based on seven case farms across the Panatana catchment in northern Tasmania. Substantial simulated drainage losses (>100 mm average seasonal loss) were apparent for all crop and rotation elements across all farms in response to the surplus between crop water supply and crop water use. Crop nitrogen demand was found to be close to crop nitrogen supply for all crop and pasture rotation elements with the exception of potato, which had an average surplus nitrogen supply of 89 kg N/ha. This resulted in potato having much higher nitrate nitrogen leaching losses (32 kg N/ha) compared to other crops (<10 kg N/ha). Simulations suggest that practicable management options such as deficit-based irrigation and reduced N fertiliser rates will maintain current levels of productivity while reducing potential offsite N loss and generating significant financial savings via reduced input costs.     

A methodology for up-scaling irrigation losses

This paper presents a methodology for up-scaling field irrigation losses and quantifying relative losses at the irrigation area level for potential water savings. Two levels of analysis were considered: First, the field level where irrigation is applied. Second, the irrigation area level, where the field level losses are aggregated, or up-scaled, using average loss functions. In this up-scaling approach, detailed crop-soil-water modelling can capture the variability of physical parameters (such as soils, crops, water table depth, and management practices) at the field level which are then used to derive loss functions for aggregating losses at higher scales (irrigation area level). This allows potential field-level adaptations and water management changes made by individual farmers to be assessed for impact at the larger irrigation area level. The APSIM farming systems model was used for simulation of crops (wheat, rice, and soybean) and their interaction with the wider system processes at the field level. Given the climate, soil, and management information (sowing, fertilisation, irrigation, and residue management), the model simulates infiltration, the soil moisture profile, plant water uptake, soil evaporation, and deep drainage on a daily basis. Then, by placing the field level analysis in the context of the wider irrigation system or catchment, it is possible to correlate field level interventions (e.g. water savings measures) with water requirements at these higher levels. Application of this method in the Coleambally Irrigation Area in NSW, Australia, demonstrated that an exponential function can describe the relationship between deep drainage losses and the water table depth for different soil, crop, and water table depth combinations. The rate of loss increase (slope of the curve) with the water table depth is higher on lighter (higher intake rates) soils than on heavy soils and is more pronounced in areas under rice cultivation. We also demonstrate that this analysis technique can assist in identifying spatial distribution of losses in irrigation areas, considering water table depth as an additional factor, leading to targeted areas for water-saving measures.     

云南省农田水利建设多元化投入机制研究

农田水利在减少洪涝灾害损失、增加粮食产量、提高农民收入和促进县域经济发展方面有重要作用,而投入是加强农田水利建设的关键因素。云南省的农田水利投入存在着主体不明、财政投入不足、融资渠道狭窄等问题。文章分析了云南省农田水利建设投入不足的原因,论证了建立多元化投入机制的可行性,从明确政府投资的主导作用、加大公共财政投入、完善金融支持、鼓励社会投资等方面构建云南省农田水利建设多元化投入机制,促进云南省农田水利建设的可持续发展。     

膜下调亏滴灌对制种玉米耗水规律及产量的影响

通过大田膜下调亏滴灌试验,测定了制种玉米叶面积指数、耗水量和产量等指标。结果表明,拔节—抽穗期缺水抑制了叶面积的生长,对产量负面影响极为显著,水分利用效率显著降低;灌浆—成熟期缺水对叶面积指数和产量影响甚微,而水分生产效率却显著提高,通过建立产量与叶面积指数以及叶面积指数与日耗水强度模型,提出了在抽穗期充分供水,苗期和成熟期减小供水、保持适度的水分亏缺的制种玉米节水高产水分调控模式。     

提高毛水生产率研究

分析了减损性节水和增效性节水与水分生产率的概念,论述了农业技术在优种、培肥土壤、精耕细作、覆膜与化肥及水利技术在适时适量灌溉、输水系统减损、灌水技术、雨养农业农田基本建设等方面对提高水分生产率的作用。重点指出当前亟须加大育种投入,使流失的有机肥归田,抓好城市肥源归田、灌区输水系统管道化、山区农田基本建设3类试点,要农业与水利相结合,发挥各自优势,提高水分生产率,提高单产。     

黄河下游引黄灌区冬小麦节水灌溉与增产效益分析

应用麦田水分动态平衡模型和干旱预报模型计算小麦的适宜灌溉期和灌溉水量。依据实测资料，对小麦的节水灌溉与增产效益进行了分析。结果表明，应用这种节水灌溉技术，可充分利用土壤储水和自然降水，减少灌水次数，降低麦田水分的无效消耗，提高土壤水利用率，达到节水增产的目的。同其它方法相比，此方法的优点除投资省外，主要是能对旱情进行早期预报，从而能在大面积的农田上进行适时适量的灌水，这对促进农业节水增产具有十分重要的意义。     

我国农业应对干旱灾害的技术研究现状及展望

干旱灾害对农业生产的威胁最大,造成农业经济损失较严重。分析了我国农业干旱具有发生频率高、持续时间长、受灾范围广、经济损失大、突发性和季节性较强的特点,从农艺技术、化学调控措施、节水灌溉技术与应急抗旱装备等方面,探讨了目前我国农业应对旱灾的技术研究现状,分析了我国农业生产过程中应对干旱存在的问题,提出今后我国农业应对干旱灾害的研究重点,主要是加强对农作物干旱发生发展规律的研究,大力推广农业节水技术提高作物水分利用效率,加强研发适合区域农业生产特点的应急性抗旱装备,大力开展抗旱预警技术研究与防控预案制定等方面。     

辽宁省实施农业节水灌溉的效果分析及建议

农业节水灌溉是缓解当前农业用水供需矛盾、提高水资源利用效率效益、落实水资源管理制度要求、推进节水型社会建设的重要举措.本文通过对辽宁省农业节水灌溉现状及实施农业节水灌溉的效果进行分析,对实施农业节水灌溉提出了几点建议.     

北京市节水型园林绿地建设现状

从应用乡土植物、耐旱植物;灌溉方式;再生水应用;雨水收集和利用几方面对北京市园林绿地节水情况进行调查.结果表明,很多绿地中应用耐旱植物,应用喷灌、滴灌等节水灌溉方式;应用雨水收集系统、下凹绿地、透水材料铺装等收集雨水和增加入渗量;有务件的绿地应用再生水等各种措施减少对自来水的消耗.但节水型园林绿地建设存在一些问题,设计中仍未采用节水灌溉方式,未考虑雨水收集利用;地面铺装过大并采用不透水砖,造成雨水的浪费等;使用再生水等的绿地所占比例少;养护工人在养护浇水过程中存在水资源浪费现象.针对存在的问题,提出建议,以利于加快节水型园林绿地的建设.     

节水农业综合示范工程研究——以河北省涿鹿县辉耀节水灌溉示范工程为例

介绍了张家口地区涿鹿县辉耀节水灌溉示范工程的概况,水资源现状和农业用水状况,通过需水量预测及供需平衡分析,计算出涿鹿县辉耀节水灌溉示范工程所取得的经济效益,示范工程的研究对建设节水灌溉工程、推广节水灌溉技术起到一定的借鉴作用。     

Options for alternative irrigation water supplies in the Murray–Darling Basin,Australia: a case study of the Shepparton Irrigation Region

Irrigated agriculture in the Murray–Darling Basin (MDB) currently faces serious challenges due to water scarcity, degradation of water quality, waterlogging and salinity resulting from inappropriate water and land use practices. In particular, there is now increasing risk of water quality degradation due to nutrient rich drainage water in the river system. Therefore, the future of irrigation will depend on the strategies that protect water quality and make best use of water available in the Basin. In this paper, we examine various options that irrigators have to augment water supplies on their farms using the Shepparton Irrigation Region (SIR), Victoria, as a case study. Here, we also discuss the suitability of the ‘Drainage Water Storage Scheme’ (DWSS) in providing additional water supplies to irrigators and in reducing the risk of water quality degradation due to flow of nutrient rich runoff into Basin’s river systems.     

农业节水措施对地下水涵养的作用及其敏感性分析

以北京市大兴区为研究区,利用经校验的水平衡模型,通过调整灌溉满足率和灌溉水利用系数,探讨了不同农业节水措施对增加地下水补给量和减少地下水开采量的作用及其敏感性。结果表明,不同水文年型下,降低灌溉满足率及提高灌溉水利用系数都能减少地下水开采量,且降低灌溉满足率对减少地下净开采量的作用更为显著,有利于区域地下水涵养。在参数取值范围内,地下水净开采量对灌溉满足率的敏感性较大,而地下水补给量对灌溉水利用系数的敏感性较高。与提高灌溉水利用系数相比,对资源性缺水区域,采用先进节水技术,适度降低区域灌溉满足率,对促进水资源持续有效利用及加大地下水涵养具有更显著的效果。     

干旱胁迫下茶园节水灌溉技术研究进展

随着全球气候变化和水资源短缺，干旱胁迫对茶叶生产的制约作用日益凸显。从干旱胁迫对茶园影响的内在机理和外在表现着手，结合我国茶区节水灌溉技术应用现状，从工程措施、农艺措施、抑蒸集水措施和管理节水等方面总结茶区节水灌溉技术，探讨茶园节水抗旱发展趋势，为茶区规划和茶业持续发展提供技术支持和理论依据。      

USBR canal lining experience

The US Bureau of Reclamation has been constructing irrigation water distribution systems since the early 1900s in the 17 Western United States. The advent of this construction soon necessitated a means for preventing excessive seepage from some canals or portions thereof. Numerous types of linings have been installed including concrete, asphalt, masonry, buried plastic membrane, exposed membrane, compacted earth, etc., with varying degrees of success. The three most commonly used at the present are concrete, buried plastic membrane, and compacted earth. Although not a type of lining, buried pipelines are also used extensively and among other advantages they reduce seepage losses very significantly.     

Assessing the groundwater dynamics and impacts of water saving in the Hetao Irrigation District, Yellow River basin

Water resources allocated to the agricultural sector in the Yellow River basin are being reduced due to severe water scarcity and increased demand by the non-agricultural sectors. In large-scale irrigation districts, the application of water-saving practices, e.g., improving the canal system, using water-saving irrigation technology and adjusting cropping patterns, is required for the sustainable agricultural development and the river basin environmental equilibrium. Adopting water-saving practices leads to lowering the groundwater table and to controlling salinity impacts related to excessive irrigation. However, assessing the effects of water-saving practices on the groundwater system requires further investigation. The Jiefangzha Irrigation Scheme of the Hetao Irrigation District is used as a case study for analyzing the temporal and spatial dynamics of the groundwater table. A lumped parameter groundwater balance model has been developed with this purpose and to assess impacts of various water-saving practices. The model was calibrated with monthly datasets relative to the non-frozen periods of 1997-1999 and validated with datasets from 2000 to 2002. Results indicate that canal seepage and deep percolation account for respectively 48% and 44% of the annual groundwater recharge. Groundwater discharge by direct evaporation and plant roots uptake represents 82% of the total annual groundwater discharge. After validation, the model was applied to assess the impacts of various canal and farm irrigation water-saving practices. It was observed that improvements in the canal system (e.g., canal lining, upgrading the hydraulic regulation and control structures, improving delivery schedules) might lower the groundwater table by 0.28-0.48 m, depending upon the level of implementation of these measures. Higher declines of the groundwater table are predicted when water-saving technologies are applied at both the canal and the farm systems. That decline of the water table favours salinity control and reduces capillary rise, thus reducing the groundwater evaporation and uptake by plant roots; that reduction may attain 128 mm. However, predictions may change depending on the way how water-saving measures are applied, which may be different of assumptions made; therefore, there is the need to perform a follow-up of the interventions in order to update predictions. Results indicate the need for appropriate research leading to improved irrigation management when the decline of the groundwater level will reduce groundwater contribution to vegetation growth.     

漳河灌区节水灌溉影响分析

为了解决越来越严重的水资源危机，发展节水灌溉已经成为灌区越来越重要的任务。自改革开放以来，漳河灌区灌溉用水量有了大幅度下降，而农业生产总产量却有所上升。灌区通过节水灌溉，使得灌溉水分生产率不断提高，在保证农业生产总产量稳步提高的前提下节约灌溉用水。与此同时，将所节约的农业灌溉用水转移到如发电、城镇供水、工业用水等非农业用水部门，从而大大提高了单方水利用效益。这是我国开展节水灌溉较为成功的典范。通过研究漳河灌区节水灌溉的影响，寻求大型灌区真实节水的途径，使得有限的水资源得到更加充分、合理的利用。     

Improving agricultural water use efficiency in arid and semiarid areas of China

Water shortage in China, particularly in the north and northwest of China, is very serious. The region accounts for half of the total area of China, but has less than 20% of total national available water resources. While the water shortage in this region is severe, irrigation water use efficiency is only about 40%, with a typical agricultural water use efficiency of about 0.46 kg m⁻³. Excessive irrigation in Ningxia and Inner Mongolia has had a significant influence on downstream water users along the Yellow River. It is widely believed that an increase in the agricultural water use efficiency is the key to mitigating water shortage and reducing environmental problems. This paper reviews water-saving agricultural systems and approaches to improve agricultural water use efficiency in the arid and semiarid areas of China. The paper will cover biological mechanisms of water-saving agriculture and water-saving irrigation technologies, including low pressure irrigation, furrow irrigation, plastic mulches, drip irrigation under plastic, rainfall harvesting and terracing. In addition, the paper addresses the compensatory effect of limited irrigation and fertilizer supplementation on water use efficiency and highlights the need to breed new varieties for high water use efficiency. Considerable potential for further improvement in agricultural water use efficiency in the region depends on effective conservation of moisture and efficient use of the limited water.     

内蒙古河套灌区节水改造工程综合节水技术研究

河套灌区属季节性冻土地区,针对渠道冻胀破坏与渗漏严重、灌溉用水量大、灌区管理粗放等问题,开展了6个方面的专题研究,简要总结了不同级别渠道适宜的衬砌结构型式,聚苯乙烯保温与风积沙换填防冻措施,土壤固化剂新材料应用,渠道防渗效果监测,田间节水改造技术和节水改造工程实施后对灌区环境的影响等诸多方面,并对大型灌区节水改造工程建...     

皖东江淮丘陵区不同水文年水稻优化灌溉制度的研究

依据安徽省天长市气象局1961-2008年多年气象资料和安徽省天长二峰灌溉试验重点站多年水稻灌溉试验成果,从不同水文年的水稻需水量、渗漏量、降雨量入手,利用建立的水分生产函数模型和水量平衡原理分析了皖东江淮丘陵区不同水文年水稻在不同供水条件下的优化灌溉制度。为准确客观评估皖东江淮丘陵区的水稻干旱损失,制定抗旱减灾工作预案,水资源的优化调度,合理的调整产业结构等提供科学依据。