Quantifying and modelling nitrate leaching from a lettuce field in Annapolis valley Nova Scotia

Abstract

Nitrate leaching (NO3-) from vegetable fields has become significant environmental issue in North America. The objective of this study was to evaluate the effect of timing and rate of nitrogen (N) fertilizer on lettuce yield and NO3- leaching. LEACHN model also was used to simulate NO3- leaching. Nitrogen fertilization treatments include preplant application; 90 kg N ha-1 a week prior to planting and 30 kg N ha-1 two weeks after planting and split application; 60 kg N ha-1 both before and two weeks after planting with four levels of sidedress N fertilizers (0, 15, 30, 45 kg N ha-1) for split and two levels of 0 and 30 kg N ha-1 for preplant treatments. Extra irrigation (8 cm) was applied to preplant treatments late in the season. Results showed no significant yield differences but 11% greater residual mineral N in top 30 cm of soil for preplant treatments which indicates increased risk of NO3- leaching in the following fall and winter. The LEACHN predicted average of 101 and 61 kg N ha-1 leaching from 1 June 2012 to 31 March 2013 in preplant and split treatments respectively. This showed major leaching during non-growing season so the management practices should focus on methods preserving N in the soil after harvest.