Yield and Forage Quality of the New Forage Perennial Legume Bituminaria bituminosa var. albomarginata cv. Lanza in Response to Rainfall Reduction and Competition

Bituminaria bituminosa is a promising drought-tolerant perennial legume which could reduce the vulnerability of Mediterranean livestock systems to drought. A 3-year field split-plot experiment was carried out in southern Spain to test the response of Bituminaria bituminosa cv. Lanza (tedera) to a 24% annual rainfall reduction and competition in terms of yield and forage quality. The experiment included a whole-plot factor, Rainfall, with two treatments, 24% annual rainfall reduction and no rainfall reduction, and two subplot factors: Species (tedera and alfalfa) and Stand (pure and mixed). In the sowing year, tedera in pure stands was as productive as alfalfa in rainfed conditions (2740 kg ha⁻¹). In the second year, a suitable distribution of rainfall until April and a mild winter allowed production of tedera of 9526 kg ha⁻¹ compared to 1811 kg ha⁻¹ of alfalfa. In the third year, both species had a similar yield of 1843 kg ha⁻¹. Rainfall reduction marginally affected (p < 0.1) the species production. The 24% rainfall reduction had less impact on tedera than management and the contrasting weather over years. In the second year, rainfall reduction caused a decline in the yield of, on average, 36% in alfalfa and 17% in tedera. Contrary to the previous year, in the third year, both species showed a similar increase in yield under reduced rainfall due to a possible protective effect of the rainout shelters in winter. Tedera suffered from frost damage indicating the cold tolerance of cv. Lanza may not be enough to persist in some Mediterranean areas of the Iberian Peninsula. Competition strongly affected both species, leading to failure, especially in tedera, whose establishment may be severely limited by fast-growing grasses. Tedera showed suitable forage quality, especially in the leaf fraction (CP = 16%). However, uncut tedera developed lignified stems that caused a great decline in forage quality. Rainfall reduction had little or no impact on forage quality.