Growing spring cereals in a white clover (Trifolium repens) crop

SUMMARYSpring barley and spring oats were strip-seeded into crops of the white clover cultivar Alice at Hereford in 1987 and cultivar S184 at Aberystwyth in 1988. Drilling was done with or without a band-spray of glyphosate, a moderate or low (1988 only) dose of paraquat or into plots where the clover had been killed by herbicide 2 months previously.In the first experiment, initial cereal emergence was sparse; growth was suppressed in the unchecked (unsprayed) clover base but was vigorous in the clover-free plots; the cereals also became dominant in the swards sprayed with herbicide. Whole-crop yields in mid-August were 13, 3–4 and 8–10 t DM/ha in the plots in which clover was killed, unchecked or checked with herbicide. Clover contributed 4–12% of the harvested herbage in the latter treatment. This treatment also yieldedc. 70 % as much N, carbohydrate and fibre as that without clover. Grain yields exceeded 7 t/ha without clover but were only 0·3 t/ha for barley and 1·1 t/ha for oats with unchecked clover; in the checked clover plots, barley yielded 60% and oats 78% as much as on the clover-free plots. Four and 5 weeks after whole-crop harvest, residual clover growth was 27 and 39% of that on unchecked plots for oats and barley, respectively.In the second experiment, the cereals emerged thickly but were later dominated by the clover, and an equitable balance was achieved only with the larger dose of paraquat. However, the oat cultivar Emrys was suppressed less than the tall barley cultivar Dandy; the short barley cultivar Digger was the most suppressed. Mean whole-crop yields were 11 t/ha in the treatment without clover, about half this in the unchecked bases andc. 9 t/ha with the larger dose of paraquat. Differences in chemical composition reflected much larger clover contents in 1988 than in 1987. Yields of N and water-soluble carbohydrate were at least as large or larger with moderate paraquat than for the clover-free plots. Grain yields ranged from 5·6 to 6·9 t/ha for the three cereal cultivars without clover but were negligible to very small in the unchecked and band-sprayed treatments, and were 3·4 and 2·0 t/ha for oats and barley, respectively, with the larger dose of paraquat. Residual stolon weights, 70–80 days after whole-crop harvest, greatly exceeded initial values in all treatments. They were smallest following the larger dose of paraquat, and larger in Digger than in Dandy, which in turn was larger than in Emrys.It is concluded that the concept of growing cereals in a clover base shows potential as a low input–moderate output system of cereal production. However, further longer term work is needed on regulation of the cereal–clover balance, on the release and uptake of N and the environmental effects of the technique.