Seeding next to previous year's crop row (near-row sowing) can increase grain yields on water repellent soils

Context. The combination of no-till and stubble retention has been shown to preserve old crop roots, which behave as pathways for water infiltration into water repellent soil, by-passing repellent surface soil layers. Aim. To evaluate the benefits to soil properties and crop performance of seeding close to the previous season's crop rows (near-row sowing) compared with inter-row sowing on water repellent soils. Methods. At four field sites, near Moora, Pingrup and Calingiri in Western Australia and Wanilla in South Australia, measurements were made of: (1) crop performance of near- and inter-row sown crops (Moora and Wanilla); and (2) differences in soil properties between the crop row and inter-row at Wanilla, Calingiri and Pingrup. Key results. Biomass accumulation (Moora) and grain yields (Moora and Wanilla) were significantly improved by near-row sowing compared with inter-row sowing, particularly under no-till and stubble retention, but these differences were reduced after cultivation, which either buried repellent surface soils or disrupted root pathways. At Calingiri and Pingrup, where near-row sowing had been practised for [greater than or equal to] 4 years, and at Wanilla, soil water contents were higher in the crop row than the inter-row by up to 4% v/v, and this was associated with significantly reduced repellency (Calingiri and Pingrup) and larger communities of wax-degrading bacteria (Pingrup). Conclusions. Near-row sowing may enhance crop production directly through improved water infiltration down root pathways, and indirectly by reduced soil water repellency in the row. Implications. Near-row sowing is potentially a low-cost management for enhanced crop production on water repellent soils. Keywords: crop establishment, crop row placement, non-wetting soils, on-row sowing, preferential water infiltration, siliceous sand, soil water repellency, soil water repellence, strategic tillage, wax-degrading bacteria.
Introduction Soil water repellency associated with the surface layers of coarse sandy soils restricts crop and pasture production on 10 million ha of agricultural land in south-west Western Australia (WA) [...]