Liquid manures are typically applied via surface broadcasting; however, subsurface injection is an alternative characterized by greater nutrient retention and a spatially distinct application pattern, altering management strategies and nutrient cycling dynamics. Thus, a field study was conducted from spring of 2016 through fall of 2018 on seven sites to assess pre-sidedress nitrate test (PSNT) methodology, seasonal soil nitrate nitrogen (NO3−-N) trends, corn (Zea mays L.) silage and grain yield, estimated milk production via MILK 2006, and biological soil health among surface broadcast and subsurface injection applications of dairy slurry. A weighted sampling method had a coefficient of variation of 37%, ~8% higher relative to random (28%) and equispaced (30%) sampling methods. Soil NO3−-N was greater in 7 out of 25 measurements under subsurface injection and 30% higher under injection on average during the corn PSNT. There were no significant differences in crop yield or milk production between surface and injected slurry applications, but means were always higher for injection. Biological soil health tests were highly variable, and analyzing carbon mineralization (C-min) took considerably more time than other tests. There were no significant differences in C-min between manure application methods; although, mineralization values increased with soil organic matter. Estimated microbial biomass was on average 46% lower under subsurface injection relative to surface broadcast in 2017, but results were inconsistent in 2016 and 2018. Overall, the biological indicators of soil health were not productive in showing differences between application methods. Nevertheless, it is apparent that injection can decrease chemical sidedress N applications, and either the standard method of PSNT soil sampling or an equispaced method can be used in injected fields.

中文翻译：

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牛粪施用方法对土壤健康和硝酸盐的影响评价

液体肥料通常通过表面撒播施用；然而，地下注入是另一种选择，其特点是养分保留更大，空间不同的应用模式，改变管理策略和养分循环动态。因此，从 2016 年春季到 2018 年秋季在七个地点进行了一项实地研究，以评估侧裙前硝酸盐测试 (PSNT) 方法、季节性土壤硝酸盐氮 (NO3--N) 趋势、玉米（Zea mays L.）青贮饲料和谷物产量，通过 MILK 2006 估算的牛奶产量，以及在地面撒播和地下注入乳浆应用中的生物土壤健康。加权抽样方法的变异系数为 37%，比随机 (28%) 和等距 (30%) 抽样方法高约 8%。在地下注入下的 25 次测量中，有 7 次土壤 NO3--N 更高，在玉米 PSNT 期间平均高出 30%。地表和注入浆液应用之间的作物产量或牛奶产量没有显着差异，但注入的平均值总是更高。生物土壤健康测试变化很大，分析碳矿化 (C-min) 比其他测试花费的时间要长得多。不同施肥方法之间的 C-min 没有显着差异；尽管如此，矿化值随着土壤有机质的增加而增加。相对于 2017 年地表撒播，估计地下注入下的微生物生物量平均低 46%，但 2016 年和 2018 年的结果不一致。总体而言，土壤健康的生物学指标不能有效地显示应用方法之间的差异。然而，很明显，注入可以减少化学辅助氮的应用，PSNT 土壤采样的标准方法或等距方法均可用于注入领域。