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William R. Johnston

Bio: William R. Johnston is an academic researcher. The author has contributed to research in topics: Agriculture & Water quality. The author has an hindex of 2, co-authored 2 publications receiving 129 citations.

Papers
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Book
01 Aug 2007
TL;DR: In this paper, the management of agricultural drainage water quality was discussed, where the authors proposed an approach for water quality management in agricultural drainage, using water quality data collected from agricultural drainage.
Abstract: Management of agricultural drainage water quality , Management of agricultural drainage water quality , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

84 citations

Journal ArticleDOI
TL;DR: The need, extent and status of drainage in North America, including water quality issues, drainage water management and disposal problems, were discussed in this article, where the ADMS Coalition was formed to promote research, education and adoption of Drainage water management as a practice that can reduce the delivery of pollutants to streams.
Abstract: The North American continent, comprising Canada and the United States of America, has a wide range of climatic, soils and cropping conditions. Surface and subsurface drainage is required to remove excess soil water in the wetter regions of the continent, as well as to maintain a favorable salt and water balance in the crop root zone in the drier irrigated regions. Drainage and water table management practices are essential for the production of food and fiber. However, these practices may sometimes cause third-party impacts, which are largely of a water quality nature. Drainage practices have therefore evolved from removal of water for increased crop productivity, to a method of environmental control. Consequently, much effort over recent years has been in designing and installing drainage systems, which have multiple objectives. A very recent notable institutional development is the formation of the Agricultural Drainage Management Systems (ADMS) Coalition, comprised of farmers, drainage contractors and the drainage industry, government advisors, and water management and agricultural specialists, to promote research, education and adoption of drainage water management as a practice that can reduce the delivery of pollutants to streams. This paper describes the need, extent and status of drainage in North America, including water quality issues, drainage water management and disposal problems. Copyright # 2007 John Wiley & Sons, Ltd.

51 citations


Cited by
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Book ChapterDOI
01 Jan 2002
TL;DR: In this paper, genetic engineering of crop plants for enhanced salt tolerance will be a very important approach to reach this goal, genetic lines of some crop species have been generated which can grow and develop at fairly high salinity levels in controlled environments.
Abstract: Agricultural losses caused by salinity are difficult to assess but estimated to be substantial and expected to increase with time. Secondary salinization of agricultural lands is particularly widespread in arid and semiarid environments where crop production requires irrigation chemes. At least 20% of all irrigated lands are salt-affected, with some estimates being as high as 50%. Whereas the world’s population continues to rise, the total land area under irrigation appears to have leveled off. The need for increased food production therefore needs to be met by increases in yield per land area. To reach this goal, genetic engineering of crop plants for enhanced salt tolerance will be a very important approach. In dry regions where fresh water becomes a scarce commodity, irrigation of moderately salt tolerant crops with brackish water is feasible. Transgenic lines of some crop species have been generated which can grow and develop at fairly high salinity levels in controlled environments. These transgenics must be tested vigorously for yield potential under field conditions.

550 citations

Journal ArticleDOI
TL;DR: Water short countries can save water by importing most of their food and electric power from other countries with more water, so that in essence they also get the water that was necessary to produce these commodities and is virtually embedded in the commodities.

468 citations

Journal ArticleDOI
TL;DR: The objectives of this paper were to critically review research on P transport in subsurface drainage, to determine factors that control P losses, and to identify gaps in the current scientific understanding of the role of subsurfaced drainage in P transport.
Abstract: Phosphorus (P) loss from agricultural fields and watersheds has been an important water quality issue for decades because of the critical role P plays in eutrophication. Historically, most research has focused on P losses by surface runoff and erosion because subsurface P losses were often deemed to be negligible. Perceptions of subsurface P transport, however, have evolved, and considerable work has been conducted to better understand the magnitude and importance of subsurface P transport and to identify practices and treatments that decrease subsurface P loads to surface waters. The objectives of this paper were (i) to critically review research on P transport in subsurface drainage, (ii) to determine factors that control P losses, and (iii) to identify gaps in the current scientific understanding of the role of subsurface drainage in P transport. Factors that affect subsurface P transport are discussed within the framework of intensively drained agricultural settings. These factors include soil characteristics (e.g., preferential flow, P sorption capacity, and redox conditions), drainage design (e.g., tile spacing, tile depth, and the installation of surface inlets), prevailing conditions and management (e.g., soil-test P levels, tillage, cropping system, and the source, rate, placement, and timing of P application), and hydrologic and climatic variables (e.g., baseflow, event flow, and seasonal differences). Structural, treatment, and management approaches to mitigate subsurface P transport-such as practices that disconnect flow pathways between surface soils and tile drains, drainage water management, in-stream or end-of-tile treatments, and ditch design and management-are also discussed. The review concludes by identifying gaps in the current understanding of P transport in subsurface drains and suggesting areas where future research is needed.

401 citations

Book ChapterDOI
01 Jan 2002
TL;DR: In this article, the authors provide a background on the nature of soil salinity with a particular emphasis on irrigated agriculture, since the chemistry of soil solutions plays a major role in soil saliency, considerable details on this topic are offered.
Abstract: The purpose of this chapter is to provide plant scientists with a background on the nature of soil salinity with a particular emphasis on irrigated agriculture. Since the chemistry of soil solutions plays a major role in soil salinity, considerable details on this topic are offered. Chemical speciation in the soil solution should be of importance to plant scientists. The dynamic nature of soil salinity in the rootzone affects performance of plants. Profile distribution of salts is affected by leaching fraction and changes with changing water content from irrigation and rootwater extraction. Soluble salts in soils are highly mobile and transported by water through mass flow and dispersion. Irrigation water management is one of the keys in maintaining salt balance in the rootzone. Growing regulations on the disposal and management of poor quality drainage waters is now exacerbating the maintenance of salt balance in the rootzone in irrigated lands.

204 citations

Journal ArticleDOI
TL;DR: The primary and fossil salt mobilization has been found to be one of the principalcauses of rivers salinization in irrigated basins in the arid zone as discussed by the authors, highlighting this hitherto insufficiently recognized salinity hazard and discusses related control measures and strategies.
Abstract: Irrigation development in the arid zone almost alwayshas to deal with not only secondarysalinity but also with primary and fossilsalinity. In many cases, irrigationdevelopment brings about large scalechanges in the local geohydrological regimewhich often result in mobilization of saltsstored in the underlying substrata. Thisprimary and fossil salt mobilization hasbeen found to be one of the principalcauses of rivers salinization in irrigatedbasins in the arid zone. The paperhighlights this hitherto insufficientlyrecognized salinity hazard and discussesrelated control measures and strategies.

184 citations