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Pea/cereal intercrop improves forage production

Peas please. While silage and greenfeed production on the Prairies are often based on monocrop cereals like barley, oat or triticale, several research studies are finding that a pea/cereal intercrop can bring added benefits of increased yield, less lodging, higher crude protein and lower neutral detergent fibre.

“I would not say seeding a forage pea intercrop for silage/greenfeed is common practice, but there are certainly producers that have experimented with it and some that will utilize such mixtures regularly,” says Jennifer Heyden, livestock and feed extension specialist with Saskatchewan Agriculture’s regional office in North Battleford, Sask.

One research study was conducted by Bill Biligetu, assistant professor at the Crop Development Centre at the University of Saskatchewan. In the two-year study at Agriculture and Agri-Food Canada’s Melfort, Saskatoon and Swift Current locations in 2016 and 2017, he evaluated forage yield, forage quality, lodging resistance and drying rate of different pea/cereal mixtures in comparison to monocultures of pea, oat or barley. Biological nitrogen fixation of pea crop in pea/cereal mixtures with and without nitrogen (N) fertilizer was also determined.

CDC Maverick forage barley, CDC Haymaker forage oat and forage peas CDC Horizon and 40-10 were grown in mono-cultures and combinations of pea/cereal intercrops.

The seeding rates for monocrop pea CDC Horizon was 110 pounds per acre (123 kg/ha), and was 103 lbs/ac (116 kg/ha) for
40-10. For monocrops, the barley seeding rate was 141 lbs/ac (159 kg/ha) and was 106 lbs/ac (119 kg/ha) for oat. The seeding ratio for pea/cereal mixtures was 100:30 and 50:50, based on their monocrop seeding rate. Row spacing was 12 inches (30 cm) at each site.

A nitrogen fertility treatment of 53 lbs/ac (60 kg N/ha) soil test nitrate-N plus fertilizer was compared to 0 N fertilizer. Soil test nitrate-N values were generally low ranging from 20 lbs/ac (22 kg/ha) at Melfort in 2017 to 33 lbs/ac (37 kg/ha) at Swift Current in 2017.

Improved forage productivity with intercrops
Generally, the forage dry matter yield of a pea/cereal intercrop was statistically similar to a monocrop of oat or barley. The monocrop pea yield was significantly lower by a wide margin compared to the pea/cereal intercrop. There was a trend for the 50:50 seeding ratio to have higher dry matter yield than 100 pea:30 cereal.

For example, monocrop barley at Saskatoon averaged 4.85 tons per acre (10.6 mt/ha) and monocrop oat yielded 3.74 t/ac (8.4 mt/ha). The intercrop of  50:50 CDC Horizon pea/barley yielded 4.45 t/ac (10 mt/ha), and CDC Horizon pea/oat 50:50 intercrop yielded 4.14 t/ac (9.3 mt/ha).  Each were statistically similar.

Average forage dry matter yield was the highest in the Black soil at Melfort at 4.36 t/ac (9.8 mt/ha), falling to 3.87 t/ac (8.7 mt/ha) in the Dark Brown soil at Saskatoon, and the lowest in the Brown soil at Swift Current at 3.2 t/ac (7.2 mt/ha).

Oat and barley made up the greatest proportion of crop biomass ranging from 64.5 to 92.4 per cent of total forage dry matter yield, regardless of seeding rate. The pea component ranged from 11 per cent in the 50:50 ratio to 26 per cent in the 100:30 ratio.

Nitrogen fertilizer increased forage yield of pea/cereal by four to 31 per cent at Melfort. At Saskatoon and Swift Current, N application did not increase dry matter yield, and would have been economically costly.

Application of 53 lbs/ac N fertilizer reduced biological N fixation of pea both in monocrop and intercrop at Melfort and Swift Current, but did not significantly affect N fixation at Saskatoon site. Total amount of biological N fixation was the highest at Saskatoon at 36 lbs/ac (40.7 kg N/ha) followed by Melfort at 32 lbs (35.9 kg) and Swift Current  at 23.6 lbs (26.5 kg). There were few differences in N fixation between the seeding ratios.

Though the total amount of biologically fixed N (BFN) was not high, a significant proportion of BFN was transferred from pea to barley and oat in mixtures. The amount of N transferred was not affected by N fertilizer rate, seeding ratio or site.

The percent of N transferred from pea to barley or oat in the intercrops ranged from 17 per cent to 43 per cent. On average, total amount of N transferred to cereals from pea was 16 lbs/ac (18 kg/ha) at Swift Current, 19 lbs (21 kg) at Saskatoon and 23 lbs (26 kg) at Melfort.

Forage quality improved with intercrops
Based on the animal feeding trial portion of this research, the pea/cereal intercrop increased starch and crude protein of the forage, with increased dry matter intake. Most of the pea/barley and pea/oat mixtures were sufficient to meet minimum CP requirements of beef cows at different gestation periods.

Stage of maturity for pea/cereal intercrop did not affect palatability. Harvesting pea hay at the mid- to late-stage of crop maturity maximized dry matter yield.

Pea/barley intercrop had highest return
An economic analysis was also conducted. Production costs calculated were seed, fertilizer, herbicide, inoculant, machinery cost and specialized labour. Gross returns were calculated based on forage hay prices.

At Melfort, the pea/barley mixtures and barley monoculture had relatively higher economic return than the other mixtures and pea monocultures. For example, the CDC Horizon/barley at 50:50 had an economic return of $611/ac ($1509/ha) while the monocrop barley returned $624/ac ($1541/ha) when no additional N was applied.

At Saskatoon and Swift Current, the highest economic returns were also from pea/barley mixtures and barley monoculture, followed by pea/oat mixtures and oat monoculture.

Similar results in Peace River region
A similar study was conducted by the Peace Country Beef and Forage Association at the Fairview Research Farm in 2018. It compared monocrop barley, triticale and oat to intercrops of these cereals with field peas. Pea/cereal seeding rates were 75 per cent of the pea seeding rate and 50 per cent of the cereal seeding rate.

The CDC Baler oats/CDC Meadow pea and CDC Baler oat monocrop had significantly higher forage dry matter yield than other mixtures and monocrops with yields of more than 4.0 t/ac (8.96 mt/ha). Taza triticale was also in the top three forage yielders. Other than the CDC Baler oat/CDC Meadow peas intercrop, there did not appear to be any yield advantage with intercrops over monocrop cereals.

All intercrops and cereal monocrops had adequate crude protein for dry gestating and lactating beef cows.

Overall, Heyden sees potential benefits to intercropping pea and cereals for forage production. These include the potential to increase crude protein, the ability to decrease N fertilizer application, a potential yield increase, and better standability if peas are mixed with a cereal resulting in an easier harvest. These benefits may reduce the need for grain or protein supplements in winter rations, and can be economically superior to monocrop forage production.