US: Plant size and light found most important in predicting daily water use

Water, a worldwide necessity, is becoming increasingly scarce. Across the globe, water supplies are insufficient to meet growing urban, industrial, and agricultural demands. In the ornamental plant industry, where growers often apply excess water to plants to minimize damage from drought, researchers are looking for ways to predict water consumption and recommend efficient irrigation practices. Scientists recently introduced a model that can help commercial growers improve their watering accuracy and greenhouse irrigation schedules, thus conserving valuable water resources.

Excessive watering not only wastes water but also increases plants' vulnerability to disease and causes economic loss from leaching fertilizers. This is particularly true in container plant production. According to scientist Jongyun Kim, scheduling irrigation in greenhouses is challenging because there has been little quantitative information about ornamental plant water requirements and how water use changes when plants are grown in varying greenhouse environmental conditions. Kim and colleagues from the University of Georgia and the University of Maine set out to develop a model that would quantify how environmental conditions affect daily water use of plants so that growers can save water and increase profits. Their results were published in HortScience.

Using two petunia cultivars--'Single Dreams Pink' and 'Prostrate Easy Wave Pink'--the team transplanted seedlings into three different-sized pots to determine the effect of container size on water use. The plants were grown in a greenhouse and were watered with a sensor-controlled irrigation system. Sensors measured and recorded water use, soil moisture, and weather. The data collected was used to calculate the daily water usage of the plants in relation to "days after planting", daily light integral, vapor pressure deficit, temperature, and container size.

Results showed that days after planting and container size were the most important factors affecting daily water use and were indicative of plant size. Among the environmental factors, daily light integral affected water use of the plants the most.

The researchers developed a model based on the daily water use as a function of the days after planting and environmental conditions. "This model can provide greenhouse growers quantitative estimates of the water requirements of their crop and may help to irrigate more efficiently," the study said. The new set of guidelines gives the ornamental plant industry another tool to help growers be better stewards of water resources while increasing economic gains.

The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/content/46/9/1287.abstract