Abstract
Potato (Solanum tuberosum L.) is an important vegetable crop in Florida and requires nitrogen fertilization for economical yields. Current nitrogen (N) recommendations call for the initial 60 to 90 lb/acre N to be applied at planting. Some commercial potato producers make the initial N application several weeks prior to planting. Early applied N will not be absorbed until the seed tuber sprouts and roots are present in the soil, but this early applied N can be subject to leaching from rain or excess irrigation between the times of application until seed piece sprouting. In the Middle Suwannee River Basin, nitrates have been found in the Suwannee River and associated springs at concentrations greater than 10 ppm nitrate-N. Therefore it is important to determine crop production practices which might reduce the likelihood of N losses to the groundwater. In this study, two early-N timing treatments were evaluated, 60 lb/acre N applied at planting (at planting) and the same amount of N applied at plant emergence (at emergence). Potatoes with both treatments received 15 lb/acre of starter-N banded with the seed pieces at planting. Timing of first N application had no effect on potato tuber yield in any tuber size grade in three years of trials, except for Size A tubers in 2002. In this first year of trials, yield of Size A tubers (but not total marketable yield) was greater with N application at plant emergence than with the planting N application. These results showed that the first large N application can be withheld until plant emergence, increasing the likelihood of fertilizer N being taken up by the young plant and reducing the risk of N leaching losses.
