Dry matter yield and nutritive value of pea/wheat bi-crops differing in maturity at harvest, pea to wheat ratio and pea variety

Studies were conducted over 3 years to evaluate the effect of maturity at h arvest (Year 1 and 2), pea content (Year 2) and pea variety (Magnus versus Setchey, Year 3) on the nutritional quality of inter-cropped, spring-sown, pea/wheat bi-crop forages. Herbage samples were taken at different stages o f growth for separation of component crops (peas and wheat) and estimation of dry matter (DM) content, DM yield, chemical composition and in vitro dig estible organic matter in DM (DOMD). The DM yields generally increased with maturity and the average bi-crop IDM yields was highest in Year 3. Peas ha d higher crude protein (CP) and DOMD but lower neutral detergent fibre (NDF ) and acid detergent fibre (ADF) than wheat. For both peas and wheat, the D M, CP, starch, NDF and DOMD at harvest were higher in the second cut (15 we eks after planting) than in the first cut (13 weeks after planting). The DM yield, CP, starch, WSC, NDF, ADF content of the bi-crops and their DOMD yi elds were all influenced by the stage of maturity and the proportion of pea s to wheat in the bi-crops. The results show that inter-cropped spring sown pea/wheat bi-crops can be harvested between 13 and 16 weeks after planting . However, relative to other stages of maturity measured, harvesting when t he wheat was at early to soft dough stage and the peas at yellow wrinkle po d stage appeared optimal. In comparison with the pea variety Magnus, the lo wer NDF and ADF, and higher CP, WSC, starch and DOMD in the pea variety Set chey suggests that the latter is nutritionally better. In deciding when to harvest, the chemical composition and stages of growth of both peas and whe at are important. However, because there is little decline in the quality o f peas with maturity, it may be possible, in certain conditions (e.g. absen ce of lodging, infections or senescence in peas), to use the stage of matur ity of wheat only as the index of the ideal time to harvest pea/wheat bi-cr op for conservation as forage for ruminants. (C) 2001 Elsevier Science B.V. All rights reserved.