Exploring the impact of soil water variability and varietal diversity on alfalfa yield, nutritional quality, and farm profitability

Background

Despite high nutritional and economic value, alfalfa yield has not been improved in the United States. Soil moisture critically influences alfalfa's yield and quality, affecting its physiological processes, nutrient uptake, and stand growth. Additionally, the maturity stage at harvest can significantly impact both hay yield and quality. Thus, this study aimed to assess the effect of different soil moisture levels and harvesting times on forage yield, nutritive value, and the overall profitability of commercially cultivated alfalfa.

Methods

Two conventional and three lower-lignin alfalfa varieties were planted in a randomized complete block with split plot design under drought, rainfed, and irrigation conditions in 2020 in Manhattan, Kansas, USA. The dry matter yield (DMY) and forage nutritive value were evaluated at late bud, early flowering, and 7 days after early flowering stages, respectively.

Results

DMY varied with production year, soil water availability, and growth stages, with drought conditions causing a decline in DMY of 5% to 38% in the second production year. Water conditions and maturity stages influenced crude protein (CP) and in vitro dry matter digestibility (IVDMD). Higher soil moisture and advancing maturity stages negatively impacted CP, IVDMD, and relative forage quality. The study revealed net profit margins of 62%, 64%, and 52% for drought-prone, rainfed, and irrigated production, respectively.

Conclusions

Harvest timing and irrigation practices were found to have substantial implications for forage yield and nutritive value of alfalfa. The yield-quality trade-off differed under drought and irrigation, with early harvesting leading to lower yields but higher protein content and digestibility. The study findings provide potential guidance for improving alfalfa hay yield, quality, and profitability.