Thursday, November 16, 2006 - 9:45 AM
325-7
Can Control Release Fertilizer Reduce Nitrogen Loss from Forest Nursery Systems?.
Excessive nitrogen (N) in agro-ecosystem is considered a significant source of the ground water contamination. Relative to conventional fertilizers (CVF), it has been suggested that controlled-release fertilizers (CRF) reduce excessive N leaching without a loss in biomass production. However, finding the most efficient rate of CRF application is still a big challenge, especially in bare-root nurseries where the N application rate commonly exceeds the typical rate in agricultural systems. We hypothesize that 1) CRF management will achieve higher seedling growth relative to CVF by synchronizing N input and N uptake by the seedlings, and 2) CRF management will result in reduced N leaching relative to CVF due to higher fertilizer-use efficiency. To test these hypotheses, we conducted a field experiment with northern red oak (Quercus Rubra, L.) at two sandy bare-root nurseries in Boscobel and Hayward , WI . We applied a total of 192 kgN·ha-1 of CVF (21-0-0 ammonium sulfate, divided eight times into 24 kgN·ha-1 applications) and two rates of CRFs (36-0-0-24S, 188 kgN·ha-1 and 112 kgN·ha-1) during the first growing season (2005). We estimated excessive N leaching using a mass-balance approach and used these data to quantify allocation of biomass and N, as well as variation in fertilizer-use efficiency. About 85% of applied N was released from CRF during the growing season. We observed a trend of difference in total seedling biomass as CRF (160 kg-released N·ha-1) = CVF (192 kgN·ha-1) > CRF (95 kg-released N·ha-1). Moreover, the N leached from CVF was significantly larger than the N from CRF. These results coupled with others to be presented support the use of CRF as a nutrient management program that is environmentally sensitive without a loss in seedling productivity relative to traditional CVF practices in bare-root forest nurseries.
Recorded presentation