Catch crops promote soil physical recovery after forage crop grazing

Abstract

Soil compaction-induced physical degradation is a threat to sustainable crop production and environmental performance. While measures have been evaluated to alleviate compaction, the impact of catch crops establishment on soil physical recovery following winter grazing remains underexplored. Six New Zealand trials over different years investigated: (1) the effects of soil compaction induced by winter forage crop grazing on soil health, and (2) the effectiveness of catch crops establishment in facilitating soil recovery. Our findings revealed that winter grazing resulted in significant soil physical degradation in the top 10 cm, evidenced by significant reduction in total porosity, macroporosity, available water content, saturated hydraulic conductivity (Ks), and soil quality S index. The degree of soil degradation was higher under increased grazing intensity (fodder beet grazing compared with kale grazing) and wetter conditions. For example, in Te Pirita-2019 with kale, changes in Ks were not significant. However, in Te Pirita-2019 with fodder beet, Ks decreased significantly from 1548 mm day^-¹ to 88 mm day^-¹, representing a 94.3 % reduction. Compared with fallow after grazing, growing catch crops promoted soil restoration. Conventional moldboard ploughing and the recently introduced single-pass ‘spader-drill’ outperformed direct drill for soil recovery. This study highlighted the importance of catch crop establishment using conventional tillage and spade drill to mitigate soil degradation resulting from winter forage crop grazing. The spader-drill, where soil conditions allow, is preferred because it allows earlier sowing of catch crops, leading to broader benefits such as increased crop biomass and reduced nitrogen leaching.