A graphical method to evaluate irrigation water application uniformity

Abstract

Drought reduces pasture production. Irrigation can be an effective response in such situations, but if we apply too little water, production will be less than in the well-watered potential. If we apply too much, nutrients can be leached, reducing soil fertility and causing environmental concern. To evaluate uniformity of water application, we developed a graphical method to analyse measurements along linear transects. By plotting the data, variable results were readily identified as well as potentially systematic patterns. The plot was divided into quadrants and the observations in each quadrant counted. For a random spatial distribution, one-quarter were expected in each quadrant. The observed and expected counts were compared using a Chi square statistical test. To illustrate, we analysed measurements from eleven irrigated farms and data representing contrasting hypothetical situations. The results were informative and appropriately responsive. Using a picture to classify and count the data can be an intuitive, practical method to evaluate an irrigator’s performance.