This Herbage Update summarises three seasons of irrigation experiments investigating yield penalties from early versus late-season drought and identifying mechanisms to guide irrigation strategies for improved water-use efficiency.
Key Points:
- Around 220-320mm of irrigation water increased seed yield of 'Grasslands Samson' by 520-1300 kg/ha across three seasons.
- In a single season trial, the later-flowering cultivar 'One50' needed about 97mm more irrigation than 'Grasslands Samson' to achieve the same seed yield.
- Yield losses only occurred when the soil moisture deficit exceeded about 75mm no matter when the dry period (drought) happened.
- Applying 50-66% of evapotranspiration (ET) each week used less irrigation but still kept soil moisture above the critical deficit level in all seasons by making better use of the rainfall.
- In fully irrigated treatments, rainfall was commonly lost as drainage.
- Greater yields came from more seeds per square metre heavier seed, compared with droughted (non-irrigated) plots.