ABSTRACT
The blending of seed mixtures has come a long way since hayloft sweepings were used for sowing out land. The use of hayloft sweepings was followed by the sowing of different strains (ecotypes) of grasses and legumes, collected, multiplied and usually combined in complex mixtures. These mixtures mirrored field observations of the botanical make-up of existing natural and semi-natural swards. However, as plant breeding and selection increased and a wide range of cultivars developed, these replaced most of the ecotypes. Fairly complex mixtures were still formulated on the premise that at least some constituents would be resilient and persistent enough to survive the vagaries of soil, climatic and management factors (Lazenby, 1981). As grassland use intensified in the 1960s to the 1980s, with increased N fertilizer and stocking rates, and as plant breeding expanded further, the make-up of seed mixtures on intensively-managed farms became increasingly simplified and adapted to special-purpose management regimes, e.g. special mixtures for grazing. This trend used the rationale that modern certified cultivars were bred with specific growth, production and forage quality characteristics that matched them to specific management regimes. Thus, to exploit their potential fully, simple mixtures were formulated using highly compatible constituent cultivars, rather than diluting the required characteristics by combining too many constituents, each with differing traits. Nevertheless, many farmers in general tended to prefer a certain degree of seed mixture complexity, equating it with ability to tolerate flexible management if required. Therefore, general-purpose seed mixtures with several grass and legume species were still available, though sometimes simplified by mixing fewer species, but perhaps also including a few compatible cultivars of the same species.
