Yield and Sugar Production by Sugar Beets as Affected by Leaf Area Variations Induced by Stand Density and Nitrogen Fertilization1

Abstract

AbstractSugar beets (Beta vulgaris L.) were grown in combinations of three stand densities with four rates of N application during the season and the leaf area and production of dry weight and sugar measured at weekly intervals to determine the effects of superoptimal N fertilization on beet growth and quality at Huntley, Montana. The highest sugar percentage and yield of extractable sugar were produced without N fertilization with beets 46 cm apart in the row. The highest extractable sugar yields were associated with the lowest leaf area index both at harvest and throughout the season, with the lowest leaf area duration, and with the lowest top:root ratios on a dry‐weight basis. Net assimilation rates per unit of leaf area were negatively correlated with leaf area index and leaf area duration. Optimum leaf area index did not appear to be much above 1.9 at October harvest or above 3 at any time during the season. Although the best beets were produced without N fertilization on this fertile soil, lower rates of N than those used might have been beneficial. High N rates produced more leaf area and higher total use of sunlight, as measured by total dry weight production, but resulted in lower sugar yields and juice purity. The net photosynthesis was calculated to be only about one‐third of the theoretical total photosynthesis for the climatic conditions.