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Alfalfa (Medicago sativa L.) is among the top four field crops in United States (U.S.) in terms of acreage harvested and economic value. Several studies have documented that alfalfa requires high amount of water compared to other major field crops. However, more than 65% alfalfa in the U.S. is grown under rainfed condition where severe to moderate drought condition has been pronounced during alfalfa growing season. The magnitude of yield loss due to water-limited conditions is still unknown. In this context, the objective of our study is to evaluate the forage dry matter yield and forage nutritive value of field-grown alfalfa cultivars exposed to a range of water-deficit stress conditions under different stages of maturity. A three-year experiment (2020-2022) has been set up in the open field and inside rainout shelters at Kansas State University Agronomy Research Farm with 3 water treatments (drought imposed, irrigated and rainfed), 5 commercial varieties (HybriForce3400, 54HVX42, HighGest AFX460, 455TQRR and HarvMegatron) and 4 replications. Watermark sensors were installed at 0.15 m, 0.46 m and 0.91 m depth in each plot to monitor the soil moisture. Nine hundred samples were collected in the first production year (2021) from 3 growth stages (late bud, early flowering, and 7 days after early flowering) and forage dry matter yield and forage nutritive value parameters were evaluated. The highest dry matter yield (DMY) was observed in the variety HybriForce 3400 followed by HighGest AFX460 grown under irrigation and harvested 7 days after early flowering. As expected, irrigated plots had the highest DMY (19.4 Mg ha-1) followed by rainfed (16.3 Mg ha-1) and drought imposed (15.0 Mg ha-1) when harvested at late bud stage. Forage quality was affected by water treatments and stages of maturity in alfalfa.

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Irrigation Effects on Forage Dry Matter Yield and Nutritive Value of Alfalfa

Alfalfa (Medicago sativa L.) is among the top four field crops in United States (U.S.) in terms of acreage harvested and economic value. Several studies have documented that alfalfa requires high amount of water compared to other major field crops. However, more than 65% alfalfa in the U.S. is grown under rainfed condition where severe to moderate drought condition has been pronounced during alfalfa growing season. The magnitude of yield loss due to water-limited conditions is still unknown. In this context, the objective of our study is to evaluate the forage dry matter yield and forage nutritive value of field-grown alfalfa cultivars exposed to a range of water-deficit stress conditions under different stages of maturity. A three-year experiment (2020-2022) has been set up in the open field and inside rainout shelters at Kansas State University Agronomy Research Farm with 3 water treatments (drought imposed, irrigated and rainfed), 5 commercial varieties (HybriForce3400, 54HVX42, HighGest AFX460, 455TQRR and HarvMegatron) and 4 replications. Watermark sensors were installed at 0.15 m, 0.46 m and 0.91 m depth in each plot to monitor the soil moisture. Nine hundred samples were collected in the first production year (2021) from 3 growth stages (late bud, early flowering, and 7 days after early flowering) and forage dry matter yield and forage nutritive value parameters were evaluated. The highest dry matter yield (DMY) was observed in the variety HybriForce 3400 followed by HighGest AFX460 grown under irrigation and harvested 7 days after early flowering. As expected, irrigated plots had the highest DMY (19.4 Mg ha-1) followed by rainfed (16.3 Mg ha-1) and drought imposed (15.0 Mg ha-1) when harvested at late bud stage. Forage quality was affected by water treatments and stages of maturity in alfalfa.