Nitrogen use efficiency in irrigated potato: Effects of polyolefin-coated urea and genotypic variation

Use of high fertilizer nitrogen (N) rates on irrigated potatoes grown on coarse-textured soils can increase the risk of nitrate leaching. Controlled-release fertilizers (CRF) and N efficient potato genotypes may play an important role in reducing nitrate leaching and improving N use efficiency. This research evaluated, through a series of studies, the efficacy of polyolefin-coated urea (POCU) and potato genotypic variation in improving N use efficiency and minimizing nitrate leaching.; In one study, a single application of 50-day (POCU-50) plus 70-day (POCU-70) POCU resulted in higher total and marketable yields than split urea at rates of 110 to 290 kg N ha−1. Net return, however, was lower for the more expensive CRF.; In a related study, POCU-70 applied at 280 kg N ha−1 reduced leaching by 34 to 49% compared to three applications of urea. Nitrogen uptake efficiency (NLTE) at that rate averaged 56% for POCU and 44% for urea, and marketable yield was 13% higher with POCU than urea.; A study to evaluate N use efficiency of three Texas clonal selections of Russet Norkotah potato at N rates of 28 to 336 kg ha−1 resulted in similar fresh tuber yields and NUE for the selections versus the standard clone. The selections accumulated 46.9 g total biomass per g N absorbed compared with 25.9 g g−1 for the standard clone.; In a similar study, fresh tuber yield was maximized at a lower N rate for transgenic (NewLeaf) Superior than standard Superior. Total tuber yields were higher for NewLeaf than the standard clone at lower N rates. At higher N rates, however, yields were higher for the standard clone due to a larger decrease in harvest index of the transgenic clone as N rate increased. Nitrogen uptake efficiency was 18% higher for NewLeaf than standard Superior at the low N rate (112 kg ha−1).; Results from this research indicate that POCU fertilizers can increase NUE and reduce NO₃−-N leaching in potatoes grown under high leaching conditions. Genetic transformation and clonal selection of standard potato cultivars, even for traits unrelated to plant nutrition, may result in more N efficient genotypes.