Effects of Alfalfa and Alfalfa-Grass Mixtures with Nitrogen Fertilization on Dry Matter Yield and Forage Nutritive Value
Received: Oct 07, 2020; Revised: Dec 12, 2020; Accepted: Dec 21, 2020
Published Online: Jan 04, 2021
Alfalfa <italic>(Medicago sativa </italic>L<italic>.) </italic>is an important forage legume grown in Kansas, USA and its productivity with cool-season grasses however is unknown. The objective of this study was to determine the dry matter yield (DMY) and forage nutritive value of alfalfa-grass mixtures compared to those of alfalfa and grasses grown in monoculture with and without nitrogen fertilization. Three different alfalfa varieties were planted (reduced-lignin alfalfa, Roundup Ready, and conventional alfalfa) and two kinds of cool-season grasses (smooth brome, <italic>Bromus inermis</italic> Leyss, and tall fescue, <italic>Festuca arundinacea</italic> Schreb) were planted as a monoculture or in alfalfa-grass mixtures. Nitrogen fertilizer (urea) was applied at a rate of 56 kg ha<sup>-1</sup> and 56 kg ha<sup>-1</sup> in 2016 and 2017, respectively and control treatments received no nitrogen. DMY was significantly higher in monoculture alfalfa and alfalfa-grass mixtures than in grass monocultures. Between alfalfa monoculture and alfalfa-grass mixtures, no significant differences in DMY were found. For all treatments, nitrogen application significantly increased DMY compared to the control. In 2016 and 2017, the low-lignin alfalfa monoculture had the lowest acid detergent fiber (ADF) and the grass monocultures had the highest ADF. In 2016 and 2017, neutral detergent fiber (NDF) in smooth bromegrass and tall fescue was higher than in other species treatments. A low-lignin alfalfa monoculture had significantly lower NDF concentration compared to alfalfa-grass mixtures. When averaged over 2016 and 2017, relative feed value (RFV) was highest in low-lignin alfalfa and lowest in the grass monocultures. In both years, nitrogen fertilizer application did not affect nutritive values.