Although cover crops (CC) are a promising option for reducing N losses, CC impacts on N availability and subsequent yields are highly inconsistent. Therefore, in a medium-term CC experiment in Ontario, Canada, the effect of using annual CC six times over 8 years on N cycling and processing tomato yield and quality during CC and tomato growing seasons was assessed. The five treatments included no cover crop control (no-CC), oat, oilseed radish, winter cereal rye, and mixture (radish + rye). Cover crop biomass was sampled in fall (2014 and 2015) and spring (2015 and 2016). Cover crops did not decrease fall soil mineral N content but accumulated an avg. of 93.5 kg N ha⁻¹ in above-ground tissues. In both fall seasons, greater (avg. 38%) above-ground N content from radish than the other tested CC suggests the enhanced ability of radish to scavenge N and mitigate N losses. Except radish C:N (32.3) in spring 2015, spring above-ground C:N (< 30) was favourable for mineralization. Despite greater C:N in spring 2015, soil mineral N content was greatest from radish (avg. 255 kg N ha⁻¹) at June in both years. Although CC increased tomato marketable yield up to 22%, tomato above-ground N content did not increase with CC. In contrast to crop yield, tomato fruit quality was not impacted by CC treatments. Our results of greater or equal tomato yield with CC than no-CC suggests that integrating CC in cropping systems is an effective approach to maintain and potentially enhance agroecosystem resiliency in the long-term.

尽管覆盖作物（CC）是减少氮素流失的一种有前途的选择，但CC对氮素有效性和后续单产的影响高度不一致。因此，在加拿大安大略省的一项中期CC试验中，评估了在8年内每年使用6次CC对氮素循环以及CC和番茄生长季节中番茄产量和品质的影响。这五种处理方法包括不进行遮盖作物控制（no-CC），燕麦，油菜萝卜，冬季谷物黑麦和混合物（萝卜+黑麦）。在秋季（2014年和2015年）和春季（2015年和2016年）对表层作物生物量进行了采样。覆盖作物并没有减少秋季土壤矿质N的含量，但积累了平均值。93.5千克N ha ^-1在地上的组织中。在两个秋季，萝卜中高于地面的氮含量（平均38％）均高于其他试验CC，这表明萝卜清除N和减轻N损失的能力增强。除2015年春季的萝卜C：N（32.3）外，春季地上C：N（<30）有利于矿化。尽管2015年春季C：N有所增加，但萝卜中的土壤矿物质N含量最高（平均255 kg N ha ^-1）。尽管CC将番茄的可销售产量提高了22％，但番茄的地上氮含量并未随CC的增加而增加。与农作物产量相反，番茄果实品质不受CC处理的影响。我们的研究结果表明，使用CC的番茄产量要比不使用CC的番茄产量更高或相等，这表明将CC纳入作物系统是长期保持并潜在增强农业生态系统适应力的有效方法。