Variable Rate Fertilizer/Manure Saves Money and Environment

Kurt LawtonConservation, Fertilizer, sustainability, Variable rate

Auburn University biosystems engineer Jonathan Hall recently highlighted the value of prescription maps and VR (variable-rate) application to reduce runoff and save up to 30 percent in annual costs.

With the spring growing season finally underway, many Alabama farmers are fertilizing their fields to enhance crop yields. Most people are familiar with farm-grade fertilizers such as 8-8-8 and 10-10-10. Granular fertilizers are meant to be worked into the ground or sprinkled around plants. It is recommended that they be worked into the ground prior to planting. Granular fertilizers take longer than liquid fertilizers to dissolve into the soil. They can last anywhere from 1 to 9 months, depending on the type. The nutrients need time to break down with some watering, and it usually takes a few days to see results.

Variable-rate technology (VRT) is recommended when applying granular fertilizers. By using VRT, farmers can apply fertilizer and nutrients on a site-specific basis. However, organic fertilizers, such as manure and poultry litter, are commonly used in Alabama. Poultry litter is used extensively in the northern half of the state due to the state’s growing poultry industry. In Alabama, about 2 million tons of poultry litter is generated annually with 90% of it land applied as a fertilizer or soil amendment. Over the years, continuous application of litter has generated environmental concerns due to excessively high phosphorous levels. Therefore, the use of guidance systems, VRT, and other precision agriculture technologies can be used in an attempt to reduce over-application and application in undesired areas.

By forming prescription maps and using VRT during the application process, runoff is reduced and the field is provided with site-specific nutrients. It is also economical! Research has shown that up to 30% of annual costs can be saved. This includes the cost of fuel, labor, and the fertilizer itself. While money is being saved, crop yields are also improved by providing the plants with nutrients as needed throughout the field. By incorporating VRT into the application of granular fertilizers, Alabama farmers can be economical while being good stewards of the land at the same time.

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