Growing peas and barley together for silage produced the highest dry matter yield in a two-year study in central Alberta.
In the study, which was conducted in 2004 and 2005, barley, faba beans, lupins and peas were grown alone and the results were compared to intercropping barley with each of those crops. No commercial fertilizer was added.
Researchers from the University of Alberta, Alberta Agriculture and Agriculture Canada discovered that the pea-barley silage mix produced 5.5 tonnes per acre of dry matter, which was 0.77 tonnes per acre greater than any of the crops grown on their own.
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Growing annual pulses with annual cereal crops is not a common practice in Alberta. Most silage crops are cereals grown on their own and require a significant amount of commercial nitrogen.
However, previous research suggested that pulse crops can break disease cycles, reduce grassy weed pressure, increase protein production and improve forage quality in silage. The researchers wondered if using a pulse crop rather than a commercial fertilizer could still provide a cost effective silage crop.
The study investigated whether pulse-cereal combinations would compare favourably with cereal silage crops and tested which pulse species and seeding rates would work the best.
Faba beans, lupins and field peas were grown at four planting densities: 50, 100, 150 and 200 percent of the recommended planting densities for a regular crop. The same pulse seeding rates were used when they were intercropped with barley, which was seeded at 25 percent of the normal rate.
The study found that the pulse-barley silage yields were not strongly influenced by pulse seeding rates. Silage yields increased from five tonnes per acre to 5.1 tonnes per acre when changing from a 0.5X to 2X pulse seeding rate, but that 0.1 tonne per acre increase carried a substantial increase in seed costs.
The ability to achieve similar pulse-barley silage yields with lower pulse seeding rates can reduce input costs and makes intercropping more attractive to producers. However, low seeding rates will work only if there is enough pulse crop dry matter in the silage to gain the feed quality benefits.
The researchers had wondered if pulse crops, with their typically poor competitive ability, might allow the barley to put too much competitive pressure on the plants. Lower pulse growth would reduce biological nitrogen fixation, non-nitrogen benefits and silage feed quality.
However, in the faba bean-barley mixes, faba beans comprised 55.7 percent of the total silage yield and in the pea-barley mixes, peas made up 67.8 percent of total silage yield. Only lupins were a concern, with just 31.2 percent of the lupin-barley silage yield. The researchers felt this low proportion means lupins may be unsuitable for mixed species silage.
Increasing the pulse seeding rate beyond 1X provided small gains in pulse content of the silage. With the pulse seeding rate at 1X, the intercrop yield contained about half pulse and half barley.
Previous research also suggests that increasing the number of species in the silage crop allows the cropping system to be more resilient under fluctuating environmental conditions. The mixed species silage crops may have increased yields, greater yield stability, increased quality, improved nutrient cycling, increased subsequent crop yields and higher land use efficiency.
The study concluded that adequate pulse-barley ratios were achieved with a 1X pulse seeding rate and 0.25X barley seeding rate. The use of pulse species in annual silage crops appears feasible and a sustainable means of reducing nitrogen fertilizer costs.
