Save hay from rain damage - expert tips

By Blake Jackson

Rain poses a significant challenge when timing hay mowing, notes University of Missouri Extension agronomist Hunter Lovewell. “Pop-up showers and storms are a risk this time of the year,” says University of Missouri Extension agronomist Hunter Lovewell. Understanding the impact of rainfall on forage that's drying but not yet baled is essential.

According to Lovewell, not all rains are equal. Brief, sudden showers cause less damage than prolonged, slow rains. Hay exposed to rain tends to be less digestible, with reduced yields and microbial breakdown of plant tissue.

Wet hay requires more mechanical handling to dry, leading to leaf shatter. This decreases digestibility as leaves fall off, leaving tougher stems. Research indicates lower yields and mass when this occurs, prompting livestock owners to consider nutrient supplementation.

Rain affects grasses and legumes differently. Forage legumes like bird’s-foot trefoil and red clover retain more dry matter compared to alfalfa. Studies suggest rainfall minimally impacts crude protein in alfalfa post-mowing.

Leaching and respiration are additional concerns. Leaching involves the loss of soluble plant components such as carbohydrates, lipids, minerals, and nitrogen.

Rain promotes microbial growth like fungi and molds. Respiration, the breakdown of soluble carbohydrates by plant enzymes, occurs regardless of rain, with a small dry matter loss until moisture drops to 30%.

Rain intensity and duration matter. Lower-intensity rain can decrease hay quality and yield more than heavier rain with the same total amount. Research shows higher leaching when hay partially dries before prolonged rain, contrasting with minimal nutrient loss if rain follows cutting.

Lovewell suggests several conditions for better hay quality post-rain:

• Early rainfall after mowing.
• Higher rain intensity (with equal total rainfall).
• Single rewetting event rather than multiple.

To accurately assess hay quality, Lovewell emphasizes submitting samples for lab testing. "A hay test is the only way to truly know the quality of hay,". Lab analysis informs nutrient supplementation strategies based on hay quality.

Photo Credit: gettyimages-pamwalker68