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

Abstract

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 ∼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.

Soil nitrogen retention is increased by ditch-buried straw return in a rice-wheat rotation system

“…However, the tillage pan may reduce root growth, reducing the effective soil volume (Nie, 2013). Although deep-ploughing is capable of overcoming these drawbacks, a potential risk is increased N leaching (Fraser et al, 2013). Our DBSR method successfully achieves deep-ploughing but may minimize N leaching .…”

A critical review of the impacts of cover crops on nitrogen leaching, net greenhouse gas balance and crop productivity

“…Tribouillois et al (2018) and Wortman et al (2012) reported that the large quantity of soil water used by the cover crops, at the cost of the subsequent primary crop and immobilization of soil N due to incorporation of low quality cover crop residues into the soil, is also a major concern. Fraser et al (2013) found that tillage had some effects on N leaching, though the use of minimum tillage for autumn cultivation resulted in significantly less N leaching than either intensive or no-till. Fraser et al (2013) found that tillage had some effects on N leaching, though the use of minimum tillage for autumn cultivation resulted in significantly less N leaching than either intensive or no-till.…”

“…Fraser et al (2013) and Hooker et al (2008) found that inter-annual weather variability and soil types explain the variability of cover crop effectiveness in the temperate regions. Fraser et al (2013) and Hooker et al (2008) found that inter-annual weather variability and soil types explain the variability of cover crop effectiveness in the temperate regions.…”

Effects of nitrogen fertilization on yield components in a corn-palisadegrass intercropping system

“…With this technique, it is possible to achieve greater production of vegetal biomass to cover the soil Ceccon et al, 2013;Crusciol et al, 2013), and it also allows the establishment of pastures for livestock Fisher et al, 2012;Borghi et al, 2013). This technique can provide many benefits for the soil-plant system, such as reducing soil loss by erosion (Montenegro et al, 2013;Lima et al, 2014), a reduction in the occurrence of weeds (Amossé et al, 2013;Scopel et al, 2013) and the maintenance of a vegetated area, allowing for greater nutrient cycling and the reduction of nutrient loss in the off-season (Fraser et al, 2013;Hashemi et al, 2013).…”