Nitrogen Partioning and Budget Assessment for Potato Cultivation: Environmental Implications.

Recent increases in nitrate-N concentrations in the Suwannee River springs in northern Florida have raised concern over the river’s water quality. Row-crop and dairy farms have been identified as potential non point sources of excess nitrogen in the springs. Best management practices are being encouraged for agricultural fertilization in this watershed.  However, many farms are diversified with animal and crop enterprises involving several nitrogen sources and fates on the farms that are not well understood or quantified. There is a need for assessment of nutrient inputs and outputs for these farms that will increase our understanding of nutrient movement onto, within, and away from the farms. Assessment will help in identifying challenges in nutrient management and quantifying the risk of nutrient loss to the environment. The objective of this study is to quantify the nutrient balance associated with potato cultivation for a diversified farm in northern Florida using sandy soil and center-pivot irrigation. The partial nutrient balance (Doberman, 2007) was determined for the growing seasons of 2010 and 2011. Of the total nitrogen available (280 kg/ha) to the crop, 69 % was found in the plant and tubers and 2% in the soil.  N accumulation in potato was dominated by the tubers compared to other plant parts beginning 55 days from planting. Harvested tubers represented 48.6% of the N budget which was sold off the farm, whereas 20.3% of crop N remained on the farm in the crop residue. Twenty-nine percent of N could not be accounted-for and possibly could be associated with leaching or volatilization.