FRUIT CROPS

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Irrigation and fertigation

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INSERTING TUBE

VIEW OF ROOTS

Irrigating fruit orchards pays off with larger fruit and larger yields
Because South Carolina fruit growers have experienced several years of drought, Clemson researchers investigated the effects of irrigation and “fertigation” (fertilizer applied through the irrigation system) on peach orchards.

A trial orchard planted at the university’s Musser Tree Fruit Research Farm monitored soil moisture content throughout the growing season. In addition, rainfall, evaporation rates and other environmental data were collected each day from the weather station. This information is being used to develop an irrigation scheduling protocol.

The study found that new trees that were irrigated grew 50% more than non-irrigated trees in the first two years. This early tree growth helps establish tree structure and fruit-bearing surface so the trees can produce and support more fruit in later years.

In the first year of the study, irrigated trees produced 100% higher yields than non-irrigated ones. In the second year, the yield was 50% higher for the irrigated trees. In addition, the fruit on irrigated trees was marketable size (2-1/2 inches or larger) while the fruit on non-irrigated trees was more likely to be lost because it was smaller than marketable size due to the drought.

An underground camera system is recording root development in the irrigation study. In the first season, the scientists observed that irrigated trees developed many more feeder roots than the control trees. This means the irrigated trees have more capacity to receive water and nutrients. The scientists plan to use this data to develop recommendations for optimum times to apply fertilizer in irrigated orchards.

Deliver fertilizer through the irrigation system
The study also investigated the use of liquid fertilizer applied through the micro-sprinkler irrigation system, known as “fertigation.” A highly soluble formula applied in small doses four to six times in the spring. This approach uses smaller doses of fertilizer, allowing the trees to fully absorb the nutrients and put them to use.

Traditional granular fertilizers are applied only once or twice during the season. When a major rain occurs, some of the fertilizer goes to the tree in one big dose, while the rest may be washed away. By comparison, fertigation is very efficient, requires 50% less fertilizer, delivers a more constant level of nutrients, and reduces the environmental impact of agricultural chemicals.

As a result of this study, the scientists expect that the cost to install irrigation equipment can be offset by stronger trees, larger yields, more marketable fruit, and reduced fertilizer costs.