Effect of Fall and Spring Applied Nitrogen Fertilizer on Growth and Yield of Sugarbeets *

Received for Publication July 27, 1984 INTRODUCTION The time and amount of nitrogen (N) uptake affects both root and extractable sucrose yield of sugarbeets (Beta Vulgaris L.). Either excessive or late N fertilizer applications and subsequent plant N uptake from applied•or residual N sources cause an increasing proportion of the photosynthate to be used for top growth at the expense of both root dry matter and sucrose accumulation (6, 7). Adequate but not excessive amounts of soil and fertilizer N available early in the growing season are needed for adequate top and root growth, while maintaining sufficiently high sucrose percentage and purity for profitable sucrose extraction and yield. For maximum N efficiency and economy, N fertilizer should be applied either near the time of planting or sidedressed early in the season. This reduces the time between N application and N uptake which allows less opportunity for N to be leached out of the root zone, denitrified, or incorporated into soil microorganisms and their by-products. Fall bedding and fertilization of fields to be used for sugarbeets is a common practice throughout the intermountain area of the western United States. Although this practice increases the time between N application and N uptake, it has the following advantages: 1) possible earlier planting, 2) improved moisture level in the seedbed at planting, 3) less irrigation water is required