Forage yield and nutritive quality of summer-planted annual forages in semi-arid regions after irrigated wheat or in a dryland cropping rotation

Objectives: Two experiments evaluated (1) annual forages planted after wheat harvest with limited irrigation or (2) annual forage mixtures compared with monocultures in a dryland rotation in a semi-arid region. Material and Methods: In Exp. 1, sorghum sudangrass (SS), oats (OAT), and foxtail millet (FM) were planted on 2 dates (D1, D2) following irrigated wheat harvest in a split plot design. In Exp. 2, SS and FM were compared with forage mixtures containing SS or FM and soybeans and forage collards (SC), or cowpeas and forage collards (CC), in a randomized design. Results and Discussion: In Exp. 1, yr 1, SS had greater yield at D1 (P < 0.0001) than the OAT and FM, which did not differ (P > 0.81). The SS, OAT, and FM did not differ at D2 (P > 0.15). In yr 2, yield was greater (P < 0.01) at D1 than D2. The CP was greater for D2 than D1 (P < 0.0001) at fall harvest, before frost. In Exp. 2, yield was decreased when CC were added to SS and FM (P < 0.02). The mixtures had greater CP (P < 0.04) than the respective monocultures. Yield and digestibility were least expensive for SS compared with the mixtures. Implications and Applications: Early-planted annual forages in irrigated wheat stubble have the greatest yield and are acceptable standing winter forage. Annual forage mixtures planted in a dryland crop rotation were not as cost effective as monocultures. Annual forages can be used in semi-arid regions where perennial forage is limited.