Yield and leaf nitrate concentration of starch potato on sandy humic soils supplied with varying amounts of starter and supplemental nitrogen fertilizer

Abstract

From 1979 to 1989 trials with varying nitrogen fertilizer rates, either applied prior to planting or split in starter and supplemental applications, were carried out with starch potato crops on reclaimed peat soils in the North-East of the Netherlands. They were aimed at optimizing the N-fertilization of starch potatoes and investigating whether or not leaf nitrate concentration could be corrected during the growth of the crop. Increased pre-planting rates from 75 to 300 kg ha−1 N did not always lead to increased tuber yields, showing that in these field trials nitrogen seemed not to be the main factor limiting yields. Higher starter applications led to increased leaf nitrate-N concentrations, especially early in the season, but the increase varied strongly with site and year. High yields were not associated with high leaf nitrate concentration early in the season. Nitrogen top dressings led to higher leaf nitrate-N concentrations but were not consistently associated with increased yields. Leaf nitrate concentrations reflected the combined effects of the age of the crop and the nitrogen rates applied to the soil, but they were not indicative of possible benefits of supplemental nitrogen applications on soil with a high organic matter concentration.