Nitrogen Application Timing Influences Performance of Early and Medium Maturity Russet Potatoes.

Nitrogen (N) is the most important nutrient needed in any successful potato production system. For efficient N utilization, N fertilizer application has to synchronize with times of higher N demand by the potato crop, and this is especially important for potato varieties with different growth patterns (early versus medium maturity potatoes). Studies were conducted at Colorado State University, San Luis Valley Research Center, to evaluate the performance of early and medium maturity Russet potatoes as influenced by timing of N fertilizer application. Treatments included (i) pre-plant application of all required N, (ii) pre-plant application of 33% required N, (iii) pre-plant application of 50% required N, and (iv) pre-plant application of 66% required N. The remaining N fertilizer needed to be applied for each treatment was applied in split applications during the growing season. For early cultivar Mercury Russet, leaf senescence was delayed, and green leaf area duration was longer when 66% or all required N fertilizer was applied pre-plant. However, total and marketable tuber yields were highest when 66% and 50% of the seasonal N requirement were applied, respectively, at pre-plant. For medium maturity cultivar Crestone Russet, green leaves persisted longer when 33% or 50% of the seasonal N requirement was applied pre-plant. Total and marketable tuber yields were higher when 33% of seasonal required N was applied pre-plant. Data from these studies indicate that optimum N application timing differs for early and medium maturity potato cultivars. Pre-plant application of 66% and 33% of seasonal required N for early and medium maturity Russets, respectively, can improve the performance of these potatoes. These responses show that for early maturity varieties, higher amounts of nitrogen need to be applied pre-plant, while for medium maturity potatoes, it is more efficient to apply larger percentages of the total applied nitrogen during the growing season.