Sustainability is the name of the game in the citrus industry in the HLB era; everyone is working to keep citrus production sustainable until a workaround to citrus greening is found. UF/IFAS associate professor Davie Kadyampakeni led a citrus seminar at the recent Citrus & Specialty Crop Expo where he presented the “5Rs of sustainable citrus production.” These are five strategies that are needed to keep HLB-infected trees productive, and nutrients play a huge role.
The Details of the 5Rs of Sustainable Citrus Production
Kadyampakeni patterned the strategies found in the 5Rs of sustainable citrus production on the 4Rs of nutrient stewardship—the Right Source, Right Rate, Right Time, and Right Place—that aim to improve the economic, social, and environmental outcomes in agriculture where nutrient applications are concerned. Kadyampakeni shared the recommendations for each of the 5R strategies for the citrus industry. They are:
- Right Water Management. Kadyampakeni advised citrus growers to use soil moisture sensors to know the water status of the soil and to guide irrigation. He advised daily, frequent irrigation for optimal tree performance. However, he shared that a rainfall of ½ inch or greater means that irrigation can be skipped for two days.
- Right Nutrient Rate. The goal is to apply the exact rate of nutrients needed, and no more. Kadyampakeni urged growers to follow the current recommendations of UF/IFAS for nitrogen and phosphorus, such as 180 to 200 pounds per acre of nitrogen, until revised recommended rates are released. He added that growers can apply other nutrients at elevated levels for fruit-bearing citrus, giving examples like “3 pounds per acre boron, 15 pounds per acre zinc and manganese, and 10 pounds per acre iron.”
- Right Fertilizer Placement. Kadyampakeni advised that granular slow-release fertilizer should be placed on the ground in the irrigated zone or at the location of the microjet wetting pattern, advising growers to choose those with polymer-coated micros because they are more effective on HLB trees.
Furthermore, micronutrients and some macronutrients like potassium and calcium for soils with high pH (>7) can be applied as a foliar fertilizer in combination with ground fertilizers.
- Right Fertilizer Source. Kadyampakeni shared that enhanced fertilizer blends led to improved root growth efficiency and higher fruit yields. He recommended a “blend of 9-1-14, 11 calcium, 7.6 sulfur, 2 magnesium, .08 zinc, .04 manganese and .025 boron, applied with 180 pounds nitrogen per acre annually.” He maintained this formulation doubled root density when compared to a 16-2-16 fertilizer blend and other nutrients applied by themselves.
- Right Timing. Kadyampakeni gave recommendations for the timing of different fertilizer applications; when using fertigation, applications should be applied weekly, biweekly, or monthly; slow-release or controlled-release fertilizer should be applied two to three times per year, such as applying in February, in May, and again in September; conventional granular fertilizer should be applied in four splits per year in February, in April, in May, and in September; foliar fertilizer should be applied three to four times a year in February/March, April/May and August/September.