This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: More water does not necessarily produce more alfalfa seed. A five-year trial near Keith, South Australia, found that strategically delaying irrigation until plants showed early signs of leaf drop generally increased seed yield and consistently delivered the highest gross margin.
The results provide growers with local evidence that controlled moisture stress can improve seed production while reducing irrigation costs. They also show that variety choice remains important, with several varieties performing consistently well across different irrigation strategies and seasons. Established at Warrawee Park near Keith in June 2018, the trial compared 31 proprietary and benchmark alfalfa varieties over five seed harvests, reflecting the productive life of a commercial stand.
Each variety was grown under three flood irrigation strategies. Standard irrigation followed current practice. Under moderate stress, irrigation was delayed until plants began to wilt.
Under high stress, watering was delayed until plants showed early signs of leaf drop. Soil moisture and weather data supported irrigation scheduling. Researchers measured annual seed yield and spring hay production.
A separate herbage trial assessed dry matter production. Gross margins were calculated using seed and hay income, variable costs and irrigation costs. After the establishment year, the high-stress strategy generally produced higher seed yields than standard irrigation.
The exception was 2021–22, when seasonal rainfall disrupted the planned irrigation treatments and differences were not significant. The high-stress treatment produced average yields of approximately 0.6 to 0.7 metric tons per hectare across the trial period. Responses under moderate stress were less consistent, showing that a small delay in irrigation did not reliably improve performance compared with standard practice.
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