SLOW-RELEASE FERTILIZATION REDUCES NITRATE LEACHING IN BAREROOT PRODUCTION OF PINUS STROBUS SEEDLINGS

Abstract

Although nitrate (NO3−) leaching potential from bareroot tree nurseries is considerable, investigations on the effect of slow-release fertilization on NO3−-nitrogen (NO3−-N) leachate concentrations is lacking. The effects of slow-release fertilizer (SRF) on NO3−-N leachate concentrations, seedling morphology, seedling nutrient content, soil N, and cation leachate concentrations were investigated in bareroot production of Pinus strobus (L.) (white pine) seedlings in southwestern Wisconsin. Three fertilizer treatments were used, SRF1 (19-6-12), SRF2 (12-0-42), and a conventional fertilizer (Conv, 15.5-0-0). A total of 180 and 52 kg N ha−1 were applied in the Conv and SRF treatments, respectively. During a 2-year period, soil leachate concentrations were collected weekly (May to December) using porous cup samplers installed at 1 m below the soil surface. Soil samples were collected every 2 weeks and plant tissue at the end of each growing season (late August). There were no treatment differences in seedling morphology (height, diameter, and dry mass) during the first or second growing season. Seedling nutrient concentrations were the same for all treatments at the end of first growing season, but Conv-treated seedlings contained greater N (33 g kg−1 N for Conv compared with 30 g kg−1 for SRF) by the end of the second growing season. Nitrate-N leachate concentrations were greater for the Conv treatment compared with both SRF treatments during the first and second growing seasons. However, treatment did not affect cation leachate concentrations and there was little difference in soil N. Overall, SRF reduced NO3−-N leachate concentrations in bareroot nursery tree production without sacrificing seedling quality.