Introduction To Strategic Irrigation
When it comes to growing lucerne, also known as alfalfa, for seed production, the common assumption is that more water leads to higher yields. However, a five-year trial conducted near Keith, South Australia, has challenged this notion. The study found that strategically delaying irrigation until plants show early signs of leaf drop can actually increase seed yield and deliver higher gross margins. This approach, known as strategic irrigation stress, has significant implications for growers looking to optimize their lucerne seed production while reducing irrigation costs.
Experimental Methodology
The trial, established in 2018, compared 31 proprietary and benchmark alfalfa varieties over five seed harvests. Each variety was grown under three different flood irrigation strategies: standard irrigation, moderate stress, and high stress. The high-stress strategy involved delaying irrigation until plants showed early signs of leaf drop, while the moderate stress strategy involved delaying irrigation until plants began to wilt. Soil moisture and weather data were used to support irrigation scheduling, and researchers measured annual seed yield, spring hay production, and gross margins.
Key Findings
The results of the trial showed that the high-stress strategy generally produced higher seed yields than standard irrigation, with average yields of approximately 0.6 to 0.7 metric tons per hectare across the trial period. The exception was the 2021-2022 season, when seasonal rainfall disrupted the planned irrigation treatments and differences were not significant. The high-stress strategy also delivered the highest gross margin in each of the four years analyzed, ranging from approximately $3,064 to $4,210 per hectare. This was due to a combination of higher seed yields and lower irrigation costs, with high seed prices further increasing returns in the final year.
Variety Choice And Local Adaptation
The trial also highlighted the importance of variety choice in lucerne seed production. Some varieties, such as SW18NPK91, SARDI 10 Series II, Heritage 10, and SARDI 7 Series II, consistently outperformed others across irrigation treatments and seasons. These varieties maintained comparatively high seed yields under different levels of moisture stress, although seasonal conditions continued to influence results. Growers should consider factors such as local adaptation, dormancy, persistence, disease resistance, hay production, and seed availability when selecting a variety.
Real-World Implications
The findings of this trial have significant implications for lucerne seed producers. By adopting a strategic irrigation stress approach, growers can optimize their seed yields while reducing irrigation costs. This can lead to higher gross margins and increased profitability. Additionally, the importance of variety choice highlights the need for growers to carefully select varieties that are well-suited to their local conditions and irrigation management strategies. As the demand for lucerne seed continues to grow, the adoption of strategic irrigation stress and careful variety selection can help to improve the sustainability and profitability of lucerne seed production.
Sources
This is an original synthesis by Qivorane based on reporting from the outlets below.
