Ten years of managing water repellent soils research in Western Australia – a review of current progress and future opportunities

Key messages

1. Choice of method for managing soil water repellence is influenced by soil type, climate and associated agronomic considerations.
2. Mitigation strategies (paired-row sowing, near-row sowing, and wetting agents) provide cheap management options, but must be implemented every year and need to be targeted at responsive soils and situations. Paired and near-row sowing typically increased early emergence by 50%, but had smaller and more variable effects on grain yield. Banded soil wetters are most beneficial for dry sown cereals on repellent forest gravels of the south-west with less reliable benefits for break-crops. Benefits of banded wetters are minimal or at best sporadic for dry sown crops on deep sands and there is no benefit with wet sowing for any crop or soil type. Benefits are larger in seasons with low and sporadic germinating rains in autumn.
3. Amelioration of repellent soils with strategic deep tillage (e.g. spading or inversion ploughing) provides long-term and reliable benefits across most repellent soils and locations. For pale deep sands the benefits are present for two-years before declining significantly at many sites. Clay spreading may help sustain benefits for longer on these less fertile soils, but the cost is high and yield potential of these soils is still limited.
4. Repellent soils are often prone to compaction and subsoil acidification and ameliorating these constraints is important for increasing and sustaining yield benefits. For example, deeper ripping following soil inversion can increase average grain yields by a further 10% (340 kg/ha), over inversion on its own.