Comparison of Foliar and Preplant Applied Nitrogen Fertilizer for Sugar Beet
- J. A. Lamb and
- J. T. Moraghan
Leaf canopies of sugar beet (Beta vulgaris L.) grown in the Red River Valley of Minnesota and North Dakota sometimes display midseason (July) symptoms of N deficiency. The influence of in-season foliar N applications on sugar beet grown under non-irrigated conditions on a Wheatville loam (coarse silty over clayey, frigid Aeric Calciaquoll) with low and medium levels of soil N fertility was studied for 3 yr. A combination of eight soil and foliar treatments were investigated. The soil treatments were (i) soil NO−3 −N in the 0- to 60- cm depth of soil in the previous autumn (45 kg ha−1 in the 1986 and 1987 experiments, and 78 kg ha−1 in the 1988 experiment), and (ii) the above soil NO−3 −N levels plus sufficient fall-applied urea-N to give the equivalent of 157 kg N ha−1. In-season foliar-N treatments, using an urea-NH4NO3 solution (28-0.0), were applied in 22 kg N−1 increments on 1 July, 15 July, and 1 August to give total foliar-N treatments of 0, 22, 44, and 66 kg N ha−1 at both levels of soil-N fertility. Overall, the use of foliar N application did not effect root yield and extractable sugar per hectare in 2 of the 3 yr. In one year, 1986, it did increase root yield by 5.2 Mg ha−1 and extractable sugar by 0.9 Mg ha-t under N deficient conditions with no differences occurring under adequate N nutritional levels. There was a significant increase in both root yield and extractable sugar per hectare in 1986 and 1987 as a result of fall applied fertilizer N but not in 1988. If soil moisture conditions are favorable for plant growth such as in 1986, the use of a mid season foliar N application may be beneficial in N deficient situations.
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