Effects of Various Preplant and In‐Season Nitrogen Management Practices for Potatoes on Plant and Soil Nitrogen Status

Abstract

Adequate availability of nitrogen (N) to satisfy potato crop N requirement is critical for production of optimal tuber yields with high processing qualities, which will contribute to maximum net returns. The agroclimatic conditions in the Columbia Basin region in the Pacific Northwest (PNW) supports high potato tuber yields with high processing qualities. Best management of N fertilization is important to increase N uptake efficiency and to minimize N losses. Monitoring soil and petiole N provides a basis to evaluate available N in the soil and N status in the plants. This study was conducted on a Quincy fine sand (mixed, mesic Xeric Torripsamments; >95% sand) using ‘Ranger Russet’ potato cultivar. Potato followed by 2 years of sweet corn rotation was adapted in this study. Treatments included the following preplant (PP) + in‐season (IS) N rates in kg ha−1: (i) 56 + 280, (ii) 112 + 224, or (iii) 112 + 336 in 2004 or 112 + 112 in 2005. The IS N was applied in five equally divided doses at 2‐week intervals, 3 weeks after seedling emergence. An additional treatment was included with treatment (ii) N rates, except that IS N was delivered in 10 weekly applications. Total tuber yield ranged from 54 to 64 and 78 to 90 Mg ha−1, respectively, in 2004 and 2005. In 2004, during the first 65 days after emergence (DAE), petiole nitrate (NO3) concentration was lower in the treatment (i) than that in the other treatments. This difference was not evident in 2005. The petiole NO3 concentrations were lower in 2005 than that in 2004, particularly during latter part of the growing period. Soil available N [nitrate NO3‐N + ammonium (NH4) N in the top 30 cm] concentrations were also greater in 2004 than those in 2005. Soil N appeared to increase toward the end of the growing season in 2004, which has negative effects on tuber yield and quality. Across all treatments, total tuber yield and that of >340‐g grade tubers were greater in 2005 than that in 2004.