Reducing nitrate leaching losses from turfgrass fertilization of residential lawns

Fertilizer applications on lawns have raised environmental concerns in many Canadian municipalities. In this greenhouse study, NO₃ -N leaching losses from Kentucky bluegrass (Poa pratensis L.) lawns were evaluated on two soils (a schist loam and a clay loam) and on a sand/peat moss rootzone mix (80% sand, 20% peat moss). Eight different fertilizer N sources (urea, Polyon 8 and 12-wk release, Duration 45 and 90-d release, XCU, corn gluten meal, and UFLEXX) were assessed at five application rates (25-200 kg N ha^-1  yr^-1 ) and two application frequencies over two 8-wk trials. Average NO₃ -N concentration in leachate were measured at levels of 3.5, 7.4, and 1.4 mg L^-1 from turf grown in loam, clay, and sand respectively, but losses from loam and clay were mostly affected by N mineralization from organic matter. Turf fertilized with rates ≥100 kg N ha^-1 generally resulted in acceptable visual quality on both soils, but coated-urea fertilizers were more efficient to reduce leaching. In sand, UFLEXX and urea (150 and 200 kg N ha^-1 ) as well as XCU (200 kg N ha^-1 ) resulted in higher NO₃ -N losses, varying from 8.5 to 23.7 mg L^-1 , and losses from other N sources were consistently below 3 mg L^-1 . Our results show that it is possible to maintain good quality turfgrass while keeping low NO₃ -N leaching losses (i.e., <4 mg L^-1 ) in loam, clay, and sand by selecting the ideal combination of N source, N rate, and application frequency.