Growing Potatoes with Slow-release Nitrogen Fertilizer

Nitrogen management practices have an effect on crop yields but they can also have a negative impact on the environment. Practices such as banding fertilizer and/or split-applying total nitrogen needs per acre offer a more efficient use of nitrogen by significantly reducing nitrate leaching potential. Heavy rains occurring when plants are small and nitrogen demands are low can also increase nitrate contamination of ground and surface waters. For instance, split-applying nitrogen minimizes the amount of nitrogen in the soil profile early, when plant N demands are low and there is a greater potential for leaching from rain events. Recently, fertilizer companies have added another tool growers can use to increase plant nitrogen use efficiency and decrease nitrate leaching potential. Slow-release, or controlled-release, nitrogen fertilizers have been commercially available for many years in the Floriculture industry with products such as Osmocote but recent advances have made this technology economically feasible and available for use in row-crop production. Controlled-release nitrogen fertilizers that we evaluated are made up of a urea (44-0-0) core which is surrounded by a polymer coating. The polymer coating allows water to enter, liquefying the urea core. Then, through temperature controlled diffusion, the liquid urea is metered out of the polymer coating over the course of 90 days or so into the soil profile. Coating thickness can be adjusted to increase or decrease days to 90% nitrogen release. As temperatures increase, so does nitrogen release rate and plant nitrogen demands thus increasing nitrogen use efficiency. Controlled-release nitrogen fertilizers were evaluated against conventional nitrogen fertilizer sources over the past several years as a means of increasing nitrogen use efficiency and decreasing environmental impacts of nitrogen in potato production systems. This year, leachate samples were collected to quantify nitrate leaching from the different fertilizer programs. The trials were established in a Haven loam soil in Riverhead, NY. The controlled release nitrogen fertilizer source used was ESN ® (44-0-0), a polymer coated urea from Agrium Advanced Technologies which was then blended with conventional nitrogen fertilizer sources to achieve two controlled release nitrogen fertilizer blends: ESN ® 60:40 and ESN ® 80:20. The 60:40 blend contained 60% of the total N in the form of controlled release N or ESN ® and the remaining 40% of the total N as conventional N from monoammonium phosphate (MAP) (11-52-0) and ammonium sulfate (AS) (21-0-0). The 80:20 nitrogen blend contained 80% of the total N as …