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Forage Growth and Quality Changes as Plants Mature

Plants grow and develop a viable seed head to improve the longevity of the forage stand. With cool and dry conditions this spring, plant growth was slow. Plants stems did not elongate as normal, resulting in shorter plants. Heading occurred early in the growing season. This completed a majority of the plant life cycle for the year. Filling of the seed heads to make it viable is the final step. Nutrients developed by the plant are used to keep the plant alive, extend the root system to enhance future nutrient uptake.

Surplus nutrients are translocated into the root system and used to develop vegetative buds which are needed to generate next year’s plant growth. Winter survival is compromised if the root system does not have adequate food reserves. This is a common problem when alfalfa is cut within forty five days of a killing frost.

Forage quality decreases as plants mature. In the vegetative stage, quality is high. After heading out the, protein and energy content decreases. Acid Detergent Fibre (ADF) and Neutral Detergent Fibre (NDF) increase over time. As fibre levels increase, energy decreases. Research done at the Northern Alberta Crop Research Centre; thirteen different grass species were cut on a weekly basis from the five-leaf stage to full maturity (Suleiman, Journal of Range Management 52: 75-82 January 1999). They found that protein content decreased by 2 to 2.5% per week after heading. Acid Detergent Fibre (ADF) increased by 3% per week resulting in a reduction of energy or Total Digestible Nutrients (TDN) content by approximately 1% to 1.5% per week.

This year, plants are shorter but have developed a seed head. The plants will not elongate and thus waiting for more yield per acre is not likely. Waiting two or three weeks will only reduce the quality of the harvested forage. If the plants are cut now without having develop a fertilized seed head, the plant will re-grow to accomplish this task in the second growth. In many areas, the substantial rains last week could stimulate regrowth. It is possible that the yield from the second cut will be higher than from the first cut.

When the weather patterns look promising, take the first cut as soon as possible to save quality and increase the potential for a good second cut.

For more information on when to cut hay, contact Barry at 403-741-6032 or


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