Opportunities for improving irrigation efficiency with quantitative models, soil water sensors and wireless technology

Increasingly serious shortages of water make it imperative to improve the efficiency of irrigation in agriculture, horticulture and in the maintenance of urban landscapes. The main aim of the current review is to identify ways of meeting this objective. After reviewing current irrigation practices, discussion is centred on the sensitivity of crops to water deficit, the finding that growth of many crops is unaffected by considerable lowering of soil water content and, on this basis, the creation of improved means of irrigation scheduling. Subsequently, attention is focused on irrigation problems associated with spatial variability in soil water and the often slow infiltration of water into soil, especially the subsoil. As monitoring of soil water is important for estimating irrigation requirements, the attributes of the two main types of soil water sensors and their most appropriate uses are described. Attention is also drawn to the contribution of wireless technology to the transmission of sensor outputs. Rapid progress is being made in transmitting sensor data, obtained from different depths down the soil profile across irrigated areas, to a PC that processes the data and on this basis automatically commands irrigation equipment to deliver amounts of water, according to need, across the field. To help interpret sensor outputs, and for many other reasons, principles of water processes in the soil–plant system are incorporated into simulation models that are calibrated and tested in field experiments. Finally, it is emphasized that the relative importance of the factors discussed in this review to any particular situation varies enormously

USCID 14th technical conference

Presented at Contemporary challenges for irrigation and drainage: proceedings from the USCID 14th technical conference on irrigation, drainage and flood control held on June 3-6, 1998 in Phoenix, Arizona.Includes bibliographical references.The use of drainwater for irrigation is a viable technology both for improving overall irrigation efficiency and for protecting water quality by reducing the mass output of salts and trace elements from irrigated areas. This was demonstrated in a field study at NewIands Agricultural Research Center in Fallon, NY by growing spring wheat (Triticum aestivum) under four irrigation water treatments. The four treatments were: 1) the exclusive use of canal water applied during the day; 2) the exclusive use of drainwater applied during the day; 3) the exclusive use of drainwater applied during the night; and 4) the conjunctive use of drainwater and canal water beginning with a day-time application of drainwater and finishing with canal water. The drainwater came from a shallow aquifer which had elevated levels of salinity and boron. The effects on crop yield of boron and salts applied with drainwater treatments were of primary interest. The field was divided into four blocks representing different soil conditions. Each block was divided into four plots and each plot was randomly assigned one of the four treatments. The growth response to these water qualities was evaluated by weighing plant samples harvested four times during the growing season. The hypothesis that daytime irrigation with drainwater would significantly reduce growth of spring wheat was rejected. The use of drainwater for irrigation appears technically feasible and offers opportunities for improving irrigation efficiency and for reducing the mass output of salts and trace elements from the Newlands Project

Cokriging for evaluating agricultural pollution

Agricultural irrigation is a major non-point source polluter. Evaluating the extent of this type of non-point source pollution requires sampling and analysis of drainage waters. To reduce costs, sampling efficiency is important. Cokriging can be used as a tool for interpolating between sampling times or locations. In this experiment, subsurface drainage data from irrigated lands near Twin Falls, Idaho were used. Total Dissolved Solids and NO3-N were selected as variables. The objective was to determine if 50 and 65 percent of the measured data could be removed (creating two new data sets) and accurately estimated via cokriging using a variogram model based on the remaining data. Cokriging models were developed using statistical information obtained from variograms of the remaining data. Once accurate models were developed for both the 50 and 65 percent removal cases, estimations were made for the missing data values. One-way analysis of variance and t-tests were used to test whether the means and variances of the estimated values were significantly different from those of the measured values. At the 65 percent removal level, there were significant differences in the means and variances of the estimated and measured values for NO3-N. One way analysis of variance and similarity of variance tests were used to test whether differences between the error values of the modeled and removed data were significant. By using the unedited full set of measured data for variogram modeling none of the tests produced rejections

Architectuur en veiligheid

ARTIKELEN: W. Vanstiphout - De architect heeft het gedaan! De rol van stedenbouw, architectuur en stadsbestuur in de rellen in de Franse voorsteden van 2005 M. Oudenampsen - Amsterdam Noord: van sociale naar ruimtelijke maakbaarheid S. Graham - Het nieuwe militaire urbanisme P. van Calster, M.B. Schuilenburg en R. Guitjens - Bedrijfsverbetergebieden; een verkennend onderzoek naar de veiligheidszorg in winkelcentrum Alexandrium N. Boonstra en M. Ham - Overlast op het plein; over de architectuur van de openbare ruimte L. Bijlsma, M. Galle en J. Tennekes - De herbergzame ruimte van de stadswijk A. Oosterman - Tbs-kliniek Almere: stedelijk complex achter een glazen gevel Internetsites. SAMENVATTING: De vraag naar de relatie tussen mens en omgeving lijkt sterk aan belang te hebben ingeboet. Het huidige wetenschappelijke debat lijkt vooral in de ban van de vraag: 'Wie is de mens?' Dit is terug te zien in onderzoeken naar biologische factoren voor deviant gedrag en verklaringen die zich beroepen op onze genetica en DNA. Om die eenzijdige kijk op de mens en het vraagstuk van veiligheid enig tegenwicht te bieden, wordt in dit themanummer een ander probleem aan de orde gesteld. In plaats van 'Wie is de mens?' gaat het over de vraag 'Waar is de mens?