Rye-vetch mixtures – their potential as multifunctional crops

Reducing the environmental impact of farming systems whilst maintaining or
improving production and profitability is central to the concept of sustainable
intensification. Mixture of rye and vetch have a the potential to achieve this due to their multifunctional end uses; they can be grown as an overwinter cover crop, taken to a silage wholecrop or allowed to ripen, for use as anaerobic digestion feedstock or for novel protein extraction technology. This inherent flexibility gives farmers much more potential to grow rye/vetch mixtures profitably than cover crops that can only be ploughed in spring. Here we explore the effect of growing rye vetch mixtures on the yield and the quality of silage.
Trials of pure stands of winter rye (Secale cereale var. SU Performer), winter vetch (Vicia sativa, var. Early English) and two mixtures of these were sown in late September at a site in Aberdeenshire in the 2018/19 and 2019/20 growing seasons. Sole crops of vetch and rye were planted as well as mixtures containing either 80% rye + 20% vetch or 60% rye + 40% vetch. Background P & K applications of 70 kg ha-1 were made around sowing time, but no N was applied. The crops were overwintered and grown through the following season until the rye had reached the dough stage (Zadoks 83–85). After manual chopping, samples were quadruple wrapped in black polythene sheeting to achieve an airtight seal with a sugar additive to produce silage.
In terms of the total yield of the sole crops, rye yield was approaching double that of vetch. However, the greatest yields were from the mixtures with Rye 60 yielding significantly more than sole rye, but not different from Rye 80. The protein content of vetch silage was about four times greater than that of rye silage, while silage from the mixtures had intermediate levels. However, when protein yield was calculated many of these differences disappeared. The silage protein yields of vetch and the two mixtures were not significantly different, whereas that of rye silage was significantly lower and only about one third of that of the highest protein yield in Rye 60. Metabolisable energy (ME) yield followed a similar pattern to total yield in that vetch had a significantly lower ME yield than the other treatments. The greatest yields were seen in the two mixtures and that in Rye 60 was significantly greater than that in pure rye. These differences in silage parameters are probably due at least in part to the significantly lower fibre levels in the vetch compared with rye (data not shown). Thus rye-vetch mixtures give greater silage yields and also the greatest protein and energy yields, although if protein production alone was a priority then sole cropped vetch would also be a reasonable option.