Nutritional improvement of maize silage for dairying: mixed-crop silages from sole and intercropped legumes and a long-season variety of maize. 1. Biomass yield and nutritive value

Fifteen legumes were evaluated for their potential to provide high yields of good quality material for inclusion with maize biomass to improve the nutritional value of maize silage. Optimum time of harvest and planting date relative to the maize crop were determined. In addition to growing the legumes as sole crops, their performance as in-row intercrops with a long-season maize cultivar was investigated, to determine whether the nutritive value of the maize biomass could be increased with little compromising of yield, and with a view to decreasing harvesting and mixing procedures and machinery requirements. High yields of biomass of high digestibility and crude protein content were produced by sole crops of soyabean, forage soya and lablab. Maximum digestible dry matter (DDM) yields of grain and forage soyabean were 4840 and 6140 kg/ha (at mid and late green pod), respectively, whilst the highest DDM yield measured for lablab of 5243 kg/ha at early green pod indicated that this legume had not reached its peak. Though sunnhemp was very productive as a sole crop, its stemminess and poor quality restricted its use to being harvested at very early flowering. To ensure synchronization of harvesting between these legumes and maize cut for silage at 16–17 weeks after planting, based on quality and yield of biomass, grain soya should be planted 1–2 weeks later than, and forage soya and lablab at approximately the same time as, the maize. The legumes showing potential for intercropping with maize were the soyabeans, lablab and velvet bean and possibly sunnhemp and cowpea. In-row intercropping with long-season maize did not prove to be a viable system: the proportion of legume in the biomass was only 15% or less, except with velvet bean which comprised nearly 30% of the biomass but depressed maize yield unacceptably.