Effect of intercropping forage peas (Pisum sativum L.) with winter wheat (Tritium vulgare L.) or triticale (Triticale hexaploide Lart.) on DM yield, nutritive characteristics when harvested at different stages of growth

An experiment was undertaken over 2 years (2007-09) to determine the effect of intercropping forage peas with either forage winter wheat or triticale for whole-crop silage. Monocultures of triticale (T100), wheat (W100) and forage peas (P100) and plus cereal-pea combinations of 75% triticale : 25% pea (T75), 50% triticale : 50% pea (T50), 25% triticale : 75% pea (T25), 75% wheat : 25% pea (W75), 50% wheat : 50% pea (W50), 25% wheat : 75% pea (W25), with ratios based on sowing rate, were evaluated for DM yield and nutritional characteristics at a range of growth stages. It was hypothesised that an increase in the ratio of peas to cereal would not adversely affect DM yield and would have a positive impact on nutritive characteristics across a range of harvest times based on growth stages of the cereal component of mixes. In Year 1, at the boot stage of growth of cereals, P100 had a lower DM yield than W100 and all triticale-based treatments, while in Year 2 P100 had a lower DM yield than all other treatments. By the soft dough growth stage in Year 1, all triticale treatments except T25 had higher DM yields than P100 and in Year 2 P100 had a lower DM yield than all triticale treatments and W100. The crude protein (CP) concentration of P100 at the boot stage of growth was higher than T100, T75, T50, W100 and W50 in Year 1 and all treatments in Year 2. At soft dough, P100 had a higher CP concentration than all other treatments in both years, while T25 and W25 had higher CP concentrations than their respective monocultures. In Year 1 at soft dough, W100 had a lower estimated ME concentration than other wheat treatments and P100, while in Year 2, T50 and W50 had higher values than T100 and W100, respectively. Bi-cropping forage peas with winter cereal forage crops did not adversely affect DM yields at a range of different harvest times, but did not consistently and significantly improve nutritive characteristics. Despite relatively high sowing rates of forage peas, their total contribution in mixes with cereals to DM yield was low, indicating that their ability to compete with winter cereals under the high fertility conditions of the experiment was low. When grown as a monoculture peas tended to produce lower DM yields but had higher CP concentrations and a higher harvested CP/ha at the soft dough stage of growth. The timing of harvesting will affect DM yields and nutritive characteristics and can be manipulated depending upon the end use of the feed grown and also to allow greater flexibility in the sowing of subsequent forages. Consideration should also be given to the growing of monocultures of winter cereals and forage peas and developing systems to mix during ensiling to capture both DM yield potential and optimum nutritive characteristics.