Deep blade loosening and two-dimensional infiltration theory make furrow irrigation predictable, simpler and more efficient

Internationally, furrow irrigation efficiency remains frustratingly less than desired. In Australia, reviews of irrigated cotton farming reveal deep drainage losses are at least 1.0 mL/ha/cropping season, and irrigators are using excessive cultivation which causes rapid consolidation of tilth and slows infiltration. This research sought to: (i) evaluate the ability of deep blade loosening (DBL), shallow cultivation (SC) and no-tillage (NT) soil management practices and 2-dimensional infiltration theory to respectively facilitate and predict lateral water penetration to the centre of wide beds (2 m spacing); and (ii) to develop a simple irrigation practice based on assured wetting of bed centres. Field-scale research was undertaken on self-mulching clay on the Queensland Darling Downs. Bulk density (0-300 mm depth) and soil moisture changes to 1000 mm depth beneath furrows and beds were monitored in a maize crop that was irrigated twice. The duration of water applications, water inflow rates and water advance in furrows were also recorded. The absorption form of 2-dimensional infiltration theory predicted the time for water to reach the centre of beds and the amount of water infiltrated at given times in all treatments. Only the DBL treatment enhanced lateral sorptivity and infiltration. It had a ratio of lateral to vertical water penetration of 3:1. In contrast, the SC and NT treatments had ratios of 1:1, took two to three times longer for bed centres to wet and were much more susceptible to deep drainage losses beneath furrows and bed shoulders. An illustrative example shows how this technology specifies the rate and duration of water applications and improves irrigation efficiency and effectiveness. Conservative estimates of water savings generated by its use lie between 0.25 and 0.80 mL/ha/irrigation (or 20%-30% of water/irrigation).