Efficiency of Controlled‐Release Urea for a Potato Production System in Quebec, Canada

Abstract

Proper N management is essential to prevent N losses and ensure high potato (Solanum tuberosum L.) yield and quality. Controlled‐release urea (CRU) could increase nitrogen use efficiency (NUE) by matching the release of N with potato N uptake. This 3‐yr study conducted in Quebec, Canada, compared four treatments, namely an unfertilized control (0 N), calcium ammonium nitrate (CAN) application at rates of 150 kg N ha−1 (150CAN) and 200 kg N ha−1 (200CAN), and CRU application at a rate of 150 kg N ha−1 (150CRU). The effects of treatments were assessed on potato yield, specific gravity, NUE, and chlorophyll meter readings (CMR) for two cultivars (Goldrush and Chieftain) along with soil nitrate adsorbed on anion exchange membranes (NO3AEMs). Marketable yield and the yield of jumbo and medium size classes significantly increased with N fertilization up to 150 kg N ha−1, and yields were higher with 150CRU than with 150CAN or 200CAN. Nitrogen fertilization increased CMR, but had no effect on specific gravity. The CRU continually released more nitrate during the growing season as indicated by higher NO3AEMs values, and had higher NUE compared with other treatments. Relative yield (RY) was significantly related by linear‐plateau functions to CMR and NO3AEMs measured 40 to 50 d after planting, hence providing the critical values of 41.9 for CMR and 15 μg cm−2 d−1 for NO3AEMs, above which the probability of a yield response to additional N is low. Controlled‐release urea is a promising N source for increasing the yield and NUE of potatoes produced in eastern Canada.