Nutrient Management Research Database
General Information
Research Title
Link to File
Research Specifications
Authors
Summary/Abstract from Original Source
Potato (Solanum tuberosum L.) requires steady, but not excessive nitrogen (N) supply for maximum tuber yield, size, and solids, as well as minimal internal and external defects. Although more costly and labor intensive than dry broadcast applications,growers typically apply a majority of N via fertigation. A controlled release N fertilizer,polymer coated urea (PCU), is a possible alternative to this growers’ standard practice.A newly formulated PCU may meet plant demand in a timely and efficient manner through temperature-controlled release of N into the soil solution, thereby possibly increasing yield and tuber quality, reducing N loss via leaching and denitrification, and reducing application costs. The objectives of this study were to determine the effects of PCU on the yield and quality of Russet Burbank potatoes grown in Southeast Idaho during 2006-2007. Nitrogen was applied at four rates (33, 67, 100, or 133% of recommended) at three locations with four methods of application, namely: 1) urea at emergence, 2) urea split applied, 3) PCU at emergence, and 4) PCU pre-plant (only the67% rate) and compared to an untreated control. Results showed significant increases in US No. 1, marketable, and total yield, as well as increases in crop value for PCU treatments over the other treatments. Post harvest soil analyses showed that nitratelevels in and below the rooting zone were reduced for PCU as compared to uncoated urea. The optimum rate of 67% PCU applied at emergence consistently yielded higher than the other treatments and was significantly greater (4.2 Mg ha-1or 1.9 ton ac-1) in marketable tubers than the grower’s standard practice. The optimum PCU rate resulted in 6 mg kg-1(ppm) less residual soil nitrate than the grower standard practice.
Research Highlights
Design and Methods
This study investigated the effectiveness of a commercial controlled release urea fertilizer (Environmentally Smart Nitrogen) in increasing N use efficiency, tuber yield, tuber quality, and N losses via nitrate leaching and nitrous oxide.
The fertilizer was applied at 0, 33, 67, 100, or 133% of the Idaho state recommendations (the recommended rate varied between 2200 and 280 lbs N/acre).
Fertilizer was applied in one of four ways:
- Regular urea at emergence
- Regular urea split applied
- Controlled release urea at emergence
- Controlled release urea at pre-plant (only at 67% rate)
Harvested potatoes were graded for size, shape, solids, and defects after 4-6 weeks of storage.
Results
Total, U.S. No. 1, and marketable yields were consistently higher at the 67% rate applied at emergence and higher than the grower's standard practice (100% rate split application).
These findings suggest that the optimum N application rate with this polymer coated urea product is around 40 lbs N/ac lower than conventional fertilizer. In this trial, this resulted in a 6 ppm decrease in post-season residual nitrate. This reduction lowers the risks of nitrate leaching and nitrous oxide emissions.
Applying this polymer coated urea product at emergence appears to be the best timing of application.
Other Considerations
Care should be taken in applying these findings in California's warmer climate.