A Bore‐Hole Method for Remediating Compacted Subsoils Increased Maize Yield

ABSTRACT Excessive tillage practices such as deep ploughing and subsoiling have long been employed to address subsoil compaction, a major constraint on crop root development, water infiltration and nutrient uptake. However, these high‐intensity tillage methods often cause soil structure degradation and may contribute to long‐term fertility decline. Therefore, the objective was to evaluate for the precision of the bore‐hole technique for cultivating row crops in soils characterised by a compacted subsoil layer. Two factorial field experiments were carried out, one on sandy soil (Typic Pedzol) with compaction in Odiliapeel, the Netherlands, and the other on sandy loam (Haplic Cambisol) soil in Luancheng, China. The crops studied in these experiments were maize ( Zea mays L.) and sorghum ( Sorghum bicolor L.) as testing crops and grown under bore‐hole treatments comprising C0 (no bore‐hole), C6/60 (bore‐hole to 60 cm depth with 6 cm diameter) and C9/60 (bore‐hole to 60 cm with 9 cm diameter) done by hand driven soil augers had 6 and 9 cm inner diameters with manure (M) and without manure (WM) additions under same loosened soil layers (0–60 cm) to refill the bore‐holes. Each plot (5 m 2 ) contained three bore‐holes with one plant per bore‐hole. Grain and biomass were measured per plant and converted to t ha −1 using the plot area as per standard agronomic scaling. Seeds of maize and sorghum were sown on the bore‐hole area after refilling it, in a single growing season (2018). Results showed that significantly ( p < 0.05), maximum maize grain yield (GY) was recorded in C6/60 (WM) at both experimental sites, followed by C9/60 (WM) when compared with C0. Compared to both sites, the highest mean grain yield was recorded in the Odiliapeel in C6/60 (10 t/ha), followed by C9/60 (7.71 t/ha) and C0 (7 t/ha). A similar but slightly less pronounced trend was observed at the Luanchnge, the highest significant ( p < 0.05) GY was achieved in C6/60 (8.9 t/ha), followed by C9/60 (7.5 t/ha) WM. Maize biomass and sorghum yield did not respond to coring and fertilisation at both sites. The results revealed that C6/60 improved shallow root development (dried root weight at 0–20 cm soil depth) and had averaged (one point within the bore‐hole and at two points in the surrounding bulk soil) lower soil penetration resistance (< 1 MPa) values when compared to C0. On the other hand, C9/60 treatment produced intermediate maize grain yield and biomass yields, better root growth at deeper layers (root weight at 20–60 cm soil depth), and a moderate level of soil compaction compared to C0. The results confirm that localised loosening using 6 cm diameter bore‐holes to 60 cm depth can reduce soil resistance, improve shallow root growth and enhance maize productivity without the need for extensive soil disturbance across varied soil types and climates. This study used hand‐auger bore‐holes; translation to field‐scale practice would require mechanised implementation and further validation.