By Ashley Robinson
Appropriated timing of fertilizer application during crop development ensures soil nutrient availability thorough the onion growing season. Typically, fertilizer is applied five times for Vidalia onion production in Georgia. However, researchers have found that control release fertilizer applications can significantly reduce the number of fertilizer applications while maintaining crop yield.
During the 2018-19 Vidalia onion growing season, researchers at the University of Georgia (UGA) conducted a field experiment to evaluate different fertilizer strategies, including control release fertilizer for Vidalia onion production.
According to Andre da Silva, UGA Cooperative Extension vegetable specialist, the field experiment compared grower standard practices with five control release fertilizer strategies. After harvest, statistical analyses were performed comparing total yield and bulb size distribution of the onions among treatments.
“Based on our findings, all of the control release fertilizer strategies increased yields compared to the standard practice used by growers,” da Silva says.
On average, control released fertilizer treatments proved to increase total yields by 25% compared to the grower standard practice. While all of the control release fertilizer strategies showed yield increases, applying the fertilizer once or twice throughout the season allowed for less fertilizer applications and nutrient requirements.
“When applying the fertilizer once or twice during the season, we applied only 96 pounds of nitrogen per acre versus 126 pounds,” da Silva says. He also mentioned that these strategies allowed for additional savings due to a reduction in tractor use and labor.
In addition to higher yields, the study also proved that control release fertilizer programs had an impact on bulb size, producing more colossal and jumbo bulbs compared to medium bulbs.
According to da Silva, control release fertilizer applications will be especially helpful to growers during the rainy seasons to ensure nutrient availability during the year and provide high crop yields.