Tuesday, November 14, 2006 - 3:15 PM

Effect of Residence Time on Nitrogen Uptake Dynamics of Sweet Corn.

Lincoln Zotarelli1, Johannes Scholberg1, Laura Avila2, and Michael Dukes3. (1) Univ of Florida, PO Box 110965, Gainesville, FL 32611-0965, (2) Agronomy Dept, 304 Newell Hall, Gainesville, FL 32611, (3) Agricultural and Biological Engineering, Fraziers Rogers Hall, Gainesville, FL 32611

Improving our understanding of plant N-uptake dynamics is critical for increasing fertilizer-N uptake efficiency (FUE) and is also a prerequisite to minimize the risk of N leaching on vulnerable soils. The objective of our research was to determine the effect of residence time of N-fertilizer on N-uptake and FUE of sweet corn. Plants were grown in large (25 L) PVC Soil-N Uptake Monitoring (SUM) systems during the fall of 2004 and spring of 2006 at Gainesville, FL. Nitrogen application rates were based on standard IFAS recommendation using weekly fertigations with potassium nitrate complemented with a N-depleted complete nutrient solution. Residence times (RT) were 24, 72 and 168 hours prior to weekly removal of residual soil N via application of 3 pore volumes of water combined with a partial (15 cbar) vacuum. Plant N-uptake was calculated by comparing weekly N recovery from planted columns with non-planted (reference) columns. Plant N-uptake and FUE were very low during the first three weeks. Corresponding FUE values at 26 DAP were 3, 11 and 46% compared to 6, 20 and 35% at 61 DAP and  3, 16 and 33 at 89 DAP. Cumulative plant N-uptake was 20, 30 and 56 kg N/ha for the 24, 72 and 168 hours RT treatments, respectively. Corresponding plant dry weight, including ears and roots were 26, 37 and 80 g/plant. Corresponding values for overall FUE were 11, 17, and 33%.  It is concluded that during initial growth crop uptake capacity is limiting and more frequent fertilization may be required to enhance FUE.  Enhancing FUE on sandy soils thus will also require improved synchronization between N application and daily crop N-requirements in addition to increasing RT.