US EPA

2040702 

Journal Article 

Winter Nitrate Leaching under Different Tillage and Winter Cover Crop Management Practices 

Fraser, PM; Curtin, D; Harrison-Kirk, T; Meenken, ED; Beare, MH; Tabley, F; Gillespie, RN; Francis, GS 

2013 

1 

Soil Science Society of America Journal
ISSN: 0361-5995
EISSN: 1435-0661 

SOIL SCI SOC AMER 

MADISON 

77 

4 

1391-1401 

10.2136/sssaj2012.0256 

WOS:000322083200026 

https://www.soils.org/publications/sssaj/abstracts/77/4/1391
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The potential for nitrate (NO3-) to leach is enhanced following cultivation of pastoral land, due to rapid mineralization of labile soil organic matter (SOM). In a 7-yr field trial in New Zealand, we examined the impacts of tillage intensity [intensive (plowing to 20 cm), minimum, or no-tillage] and winter cover crops (forage rape) on NO3- leaching following cultivation of permanent (sheep [Ovis aries]-grazed) pasture to grow arable crops (the rotation included barley [Hordeum vulgare L.], wheat [Triticum aestivum L.], and pea [Pisum sativum L.]). Permanent pasture and permanent fallow (maintained plant-free using herbicides, i.e., not cultivated or fertilized) treatments were included as controls. Losses of NO3--N were calculated from soil solution NO3--N concentrations (measured in ceramic suction cups installed at 600 mm) and drainage volumes. Cumulative NO3--N leached over 7 yr ranged from 20 to 428 kg N ha(-1), with least N lost under pasture. Residual soil mineral N in autumn accounted for similar to 30% of the variability in leaching. Nitrate leaching under arable crops generally increased rapidly as winter rainfall (range 78-352 mm yr(-1)) increased. Winter cover crops were effective in reducing NO3--N leaching losses, particularly in drier winters when about 50% less N leached where cover crops were grown. On average, annual leaching was only 10 to 18 kg N ha(-1) in the presence of cover crops. Tillage had relatively little influence on leaching, though use of minimum tillage for autumn cultivation resulted in significantly (P < 0.001) less NO3--N leaching than either intensive or no tillage. Largest leaching losses were recorded in the unfertilized, permanent fallow where there was no plant sink for NO3-N derived from SOM mineralization. Growing a crop during the winter period, combined with good N management practices to minimize pre-winter soil mineral N, provides the best option to keep NO3- leaching within the acceptable range for arable cropping in New Zealand.