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Home HortTechnology Reducing Irrigation Pressure Shows Benefits in Tomato Production
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GAINESVILLE, FL—In Florida, where sandy soil is common, researchers are seeking ways to improve water use efficiency and water quality in agricultural production systems. The sandy soil is particularly challenging for growing shallow-rooted vegetable crops; the soil does not retain water sufficiently and fertilizers often leach beyond plants’ roots early in the growth cycle, resulting in lower nutrients and potential pollution of groundwater.

Bee Ling Poh, lead author of the research study published in HortTechnology, explained that previous efforts to reduce the risk of nutrient leaching have not been totally successful. "Limited attention has been paid to reducing flow rate and increasing the irrigation duration as a means to reduce leaching below the root zone," Poh explained. "We theorized that increasing the length of irrigation time by reducing the operating pressure of drip irrigation systems may result in decreased deep percolation and may allow for reduced nitrogen (N) fertilizer application rates, thereby minimizing the environmental impact of tomato production."

The researchers found that higher fresh-market tomato yields were obtained at a reduced irrigation operating pressure (OP) in one year with reduced fertilizer rate and irrigation rates (IRR), without affecting the N and K nutritional quality of the plants. In the second year, where the crop cycle was longer, the higher OP and N rate produced greater yields and the IRR could be reduced.

"Our results suggest that the reduced OP of 6 psi could not replace the standard OP for the whole crop season. Instead, reduced OP could be used for the early part of the season when the plants were small and the OP could be increased as the season progressed," Poh said.

The experiments proved that growing tomatoes at 12 psi OP, 100% of recommended N rate, and 75% of recommended IRR provided the highest marketable yields with least inputs in a drip-irrigated plasticulture system. The scientists said that changing irrigation operating pressure offers growers flexibility to alter flow rates to suit water demands of crops’ growth stages. The approach also allows irrigation to be applied over an extended period of time, which could better meet crops’ water needs throughout the day.

"Our results suggested that smaller amounts of irrigation water and fertilizers (75% and 60% of the recommended IRR and N rate, respectively) could be applied when using a reduced irrigation OP of 6 psi for the early part of the tomato crop season. In the later part of the season, as water demand increased, the standard OP of 12 psi could be used," Poh said. "This irrigation strategy could improve water and nutrient use efficiencies and reduce the risks of nutrient leaching."

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The complete study and abstract are available on the ASHS HortTechnology electronic journal web site:

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at


Original Article:

Use of Reduced Irrigation Operating Pressure in Irrigation Scheduling. I. Effect of Operating Pressure, Irrigation Rate, and Nitrogen Rate on Drip-irrigated Fresh-market Tomato Nutritional Status and Yields: Implications on Irrigation and Fertilization Management
Bee Ling Poh, Aparna Gazula, Eric H. Simonne, Francesco Di Gioia, Robert C. Hochmuth, and Michael R. Alligood
HortTechnology 21:14-21. [Abstract] [Full Text] [PDF]

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