Stirzaker RJ, Stevens JB, Annandale JG, Steyn JM and Backeberg G (2005) Starting a dialogue between irrigators and scientists - lessons learnt from a simple wetting front detector. Presentation at the International Commission for Irrigation and Drainage, Beijing, Sept. 2005 click here to open full article (PDF 228kb)
A minority of irrigation farmers has adopted the proven tools and techniques for improving the productivity of irrigation water. We report on a strategy to draw more irrigators into a dialogue about how to improve irrigation practice. The dialogue is built around a Wetting Front Detector that shows farmers when water has penetrated to a certain depth into the soil after irrigation. We provide examples of how a simple tool has instigated on-farm change.
Stirzaker RJ, Sunassee S and Wilkie J (2004). Monitoring water, nitrate and salt on-farm: a comparison of methods. Irrigation Australia 2004 conference, 11-13 May, Adelaide. click here to open full article in a new window
Different methods of monitoring soil water status and the nitrate concentration and electrical conductivity of soil solution were employed during the growing of a vegetable crop. The aim was to evaluate whether the data collected correlated with yield and to assess how information assisted decision making. From a scientific standpoint more information is better, because each technique gives a different slant on the problem under study. For the farmer however, relatively simple information can improve management decisions. This case study shows that a greater volume of information or greater attention to accuracy increases the cost and complexity of monitoring without necessarily impacting the final management decisions.
Stirzaker RJ and Wilkie J (2002). Four lessons from a wetting front detector. Irrigation Australia 2002 conference, 21-23 May, Sydney.. click here to open full article in a new window
Wetting front detectors were installed on-farm in a drip irrigated pumpkin crop and a sprinkler irrigated garlic crop. The wetting front detector is a funnel-shaped instrument that is buried in the soil. The funnel concentrates the downward movement of water particles so that saturation occurs at the base of the funnel. The free (liquid) water produced from the unsaturated soil activates an electronic or mechanical float, alerting the farmer that water has penetrated to the desired depth. The detectors retain a sample of soil water that is used for nutrient monitoring. Four principles emerged that challenged the farmers' perceptions of how they were irrigating. First, the wetting patterns under drip penetrated deeper into the soil than they had imagined. Second, the wetting fronts from rain or sprinkler irrigation did not penetrate as deeply as they expected. Third, high concentrations of nitrate were measured during the first month after planting from the water samples retained in the detectors. Fourth, it was easy to misjudge the onset of exponential growth and its impact on water use. In each case the farmers found it easy to take remedial action. Irrigation intervals were shortened for drip and the duration of irrigation was lengthened for sprinklers. Extra effort was made to limit water applications in the early stages so that nitrate was not moved below the root zone. Lastly the farmers were alert to the rapidly escalating demand for water at the onset of exponential growth and the importance of avoiding water deficits during the period when yield is most affected. The experience showed that the basics of irrigation scheduling could be captured using a simple tool and simple information in a relatively short period of time.