Where Is My Nitrogen: A Florida Case Study On Nitrogen Budgeting and Assessment for Potato Cultivation?.

Potato is considered to have high nitrogen requirement among vegetable crops. More than 500,000 hectares of land is planted to potato annually in the United States. Nitrogen losses related to high fertilizer application and coarse textured soils have been associated with environmental concerns for N leaching.  Increases in nitrate-N concentrations in Suwannee River springs in northern Florida are examples of these concerns (SRWMD, 2007). Best management practices are being encouraged for agricultural fertilization in this watershed; however there is critical need for quantifying the sources and sinks of nitrogen for agricultural operations. Quantification of inputs and outputs will give a better insight on the probable pathways leading to loss of N to the environment. Once the sources are quantified, the current best management practices can be fine tuned to prevent the direct losses such as leaching loss to groundwater. The objective of this study was to quantify the sources and sinks of N associated with potato cultivation on a diversified farm located in Northern Florida using sandy soils and centre-pivot irrigation system for a period of three years. For the growing season 2010, a partial nitrogen balance for potato crop indicated a total nitrogen recovery of 67% within the plant (total N available was 288 kg ha^-1) with an estimated unaccounted N loss of 88 kg ha^-1. In 2011, the average N recovery in the plant was 45% (total N available was 304 kg ha^-1) with an average estimated unaccounted N of 157 kg ha^-1. The two major pathways associated with unaccounted N were hypothesized to be the leaching and volatilization losses.