Nitrogen should be applied early to sugarbeets
Spring nitrogen applications to sugarbeets should be applied no later than the six leaf stage.
Nitrogen availability in early season is important to promote growth and leaf canopy. Light interception of leaves is directly related to sucrose production. It is desirable to have canopy closure by June 20, the longest day of the year. Nitrogen applications should be applied so that the majority, if not all the nitrogen, is available early to the plant. If some nitrogen is to be applied by sidedress, it is recommended that it not be applied any later than the six leaf stage.
Research conducted in the last several years by Michigan State University Sugarbeet Advancement and Michigan Sugar Company agronomist has shown benefits to early season nitrogen. There are different options that growers can use to get nitrogen on early. The first option is to put all the nitrogen up front by pre-plant incorporated. This option can work for those growers who are not stale seedbed planting. If urea is being applied, rates approaching 100 lbs/acre or more can occasionally have some effect on emergence. Growers that are applying starter fertilizer 2 inches to the side and 2 inches below the seed should consider including about 40 lbs. of nitrogen per acre and the additional needed nitrogen could be applied before planting or after planting by sidedress.
The importance of early season nitrogen has been very pronounced when beets are planted into a high residue previous crop such as corn or wheat. The growth of young sugarbeet plants is greatly hampered due to nitrogen tie-up by the previous crop’s residue. In these fields, we highly encourage 40 lbs. of nitrogen in the starter. In high residue situations, a total of 125 to 150 lbs. of total nitrogen is generally adequate for optimum yield and quality.
Be aware, if the nitrogen has been appropriately applied, by August sugarbeets will have taken up most of the required nitrogen. A total of 80 to 90 percent will be in the shoot. This nitrogen can be remobilized from the tops to the roots for supplying plant needs. The effect of excess late nitrogen can be detrimental to quality for several reasons. The crop will continue to take up N, resulting in less mobilizing from the older leaves. These old leaves will be retained longer along with producing new large late formed leaves. These factors combined will give huge tops at harvest. This energy to produce and retain leaves has been diverted from sucrose production and storage.
Optimizing tonnage and quality of sugarbeets can be achieved if nitrogen is applied early in the sugarbeet growing season and not over applied.