Reducing nitrate leaching losses from turfgrass fertilization of residential lawns

Abstract

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.