Deep-ploughing far beyond the common depth of 30 cm was used more than 50 years ago in Northern Germany with the aim to break root-restricting layers and thereby improve access to subsoil water and nutrient resources. We hypothesized that effects of this earlier intervention on soil properties and yields prevailed after 50 years. Hence, we sampled two sandy soils and one silty soil (Cambisols and a Luvisol) of which half of the field had been deep-ploughed 50 years ago (soils then re-classified as Treposols). The adjacent other half was not deep-ploughed and thus served as the control. At all the three sites, both deep-ploughed and control parts were then conventionally managed over the last 50 years. We assessed yields during the dry year 2019 and additionally in 2020, and rooting intensity at the year of sampling (2019), as well as changes in soil structure, carbon and nutrient stocks in that year. We found that deep-ploughing improved yields in the dry spell of 2019 at the sandy sites, which was supported by a more general pattern of higher NDVI indices in deep-ploughed parts for the period from 2016 to 2021 across varying weather conditions. Subsoil stocks of soil organic carbon and total plant-available phosphorus were enhanced by 21%–199% in the different sites. Root biomass in the subsoil was reduced due to deep-ploughing at the silty site and was increased or unaffected at the sandy sites. Overall, the effects of deep-ploughing were site-specific, with reduced bulk density in the buried topsoil stripes in the subsoil of the sandy sites, but with elevated subsoil density in the silty site. Hence, even 50 years after deep-ploughing, changes in soil properties are still detectable, although effect size differed among sites.

中文翻译：

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深耕五十年后：对产量、根系、养分储量和土壤结构的影响

50 多年前，德国北部就采用了远远超过 30 厘米常见深度的深耕技术，目的是打破根部限制层，从而改善地下水和养分资源的获取。我们假设这种早期干预对土壤性质和产量的影响在 50 年后普遍存在。因此，我们对两种沙质土壤和一种粉质土壤（Cambisols 和 Luvisol）进行了采样，其中一半的土地在 50 年前已被深耕（后来这些土壤被重新分类为 Treposols）。相邻的另一半没有深耕，因此作为对照。在过去 50 年里，这三个地点的深耕部分和控制部分均采用常规管理方式。我们评估了 2019 年干旱年份和 2020 年的产量、采样当年（2019 年）的生根强度，以及当年土壤结构、碳和养分储量的变化。我们发现，2019年干旱时期，沙地的深耕提高了产量，这得到了2016年至2021年不同天气条件下深耕地区NDVI指数较高的更普遍模式的支持。不同地点的底土土壤有机碳储量和植物有效磷总量增加了 21%–199%。由于粉质地区的深耕，底土中的根系生物量减少，而沙质地区的根系生物量增加或不受影响。总体而言，深耕的效果是因地制宜的，沙质场地下土的埋藏表土条带的容重降低，但粉质场地下土的密度升高。因此，即使深耕 50 年后，土壤性质的变化仍然可以检测到，尽管影响大小因地点而异。