High value crops in coarse-textured soil and nitrate leaching - How risky is it?

To identify practices that minimize the risk of NO3-N leaching to groundwater from high-value crops produced on coarse-textured soil, NO3-N movement was determined from varied water (overhead vs. drip irrigation) and nutrient (pre-plant broadcast vs. fertigation) management in cucumber (Cucumis sativus L.) over three growing seasons, and municipal compost rate and mulch type in ginseng (Panax quinquefolius L.) over 5 yr. Under cucumber, seasonal NO3-N leaching ranged from 4 to 28 kg ha-1, and was reduced by 10 kg NO3-N ha-1 yr-1 in 2 of 3 yr using drip delivery of water and nutrients as compared with pre-plant broadcast fertilizer with overhead irrigation. Under ginseng, 452, 321 and 173 kg NO3-N ha-1 leached from C260 compost (170 Mg ha-1 incorporated compost under 90 Mg ha-1 compost mulch re-applied annually), C200 bark (200 Mg ha-1 incorporated compost under pine bark mulch) and C0 straw (no compost, straw mulch), respectively, during the initial fall plus subsequent 4 yr. Following fall application of compost, subsoil solution NO3-N concentrations increased to > 100 mg NO3-N L-1 by early December. Even with no compost applied, NO3-N concentrations in water draining from the ginseng soil profile usually exceeded the drinking water standard.