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An ecological approach to forage research

Top AAFC research scientist shares his thoughts on growing forages

Dr. Shabtai Bittman, one of Canada’s top sustainable cropping systems research scientists at the Agriculture and Agri-Food Canada Research Centre in Agassiz, B.C., says growing forages for hay and pasture is very different than growing grain crops.

“With forages, we are dealing with perennial crops that are subject to encroachment from other grasses and from weeds, even shrubby weeds, and with the interaction of grazing animals and the complexity of harvesting plants when they are actively growing. There are usually fewer inputs of fertilizers and pesticides for forage production. Therefore forage stands can be seen as closer to natural ecological systems than annual crops.

“I started my research career with Agriculture and Agri-Food Canada at Nappan, Nova Scotia and later moved to Melfort, Sask., and finally to Agassiz, B.C. During my research across Canada I have always looked at the ecology of forage-based systems from a regional viewpoint. In each part of the country there is a different climate, different soils and different types of farms.

“When I worked in Nova Scotia, the traditional forage mixture seeded was a mix of timothy, white clover and red clover, called triple mix. In contrast, farmers in the black and gray wooded soils of Saskatchewan, where it is much drier and colder than Nova Scotia, have been seeding smooth bromegrass (more recently meadow bromegrass) with Rambler alfalfa. In coastal B.C., where there is an abundance of manure, farmers seed pure stands or mixtures of orchardgrass and tall fescue for their dairy cows, and very little clover or alfalfa is grown. It is the natural ecology and the nature of the industry that determines what is seeded.

“In Nova Scotia, we surveyed pastures on many farms and found that two or three years after forages were established the plant communities became more complex. For example, Kentucky bluegrass encroached on upland soils and red top in the dike-land soils. Both grasses can be quite productive, so yield would remain high, but when brown top invaded, it was a sign that production was declining and renovation might soon be needed. As the names suggest, brown top and red top are related species, but agronomically they have evolved towards different ecological niches. The volunteer grasses can help indicate productivity and aspects about the habitat in a field.

“We saw similar types of plant community changes happening in provincial community pastures on the northern prairies of Saskatchewan. The pastures in this region, which covers thousands of square kilometers, had been cleared of aspen trees and seeded with smooth bromegrass, creeping red fescue and smooth bromegrass and some 20 other forage species. The bromegrass and alfalfa had gradually declined and it seemed that the short fine grass, creeping red fescue, was expanding. But when we started to have a closer look we found a more nuanced story. In the pastures toward the northeast of this range, the creeping red fescue had been largely replaced by Kentucky bluegrass, which at a distance on dry soils has some resemblance to creeping red fescue. But on pastures in the more arid southwest portion of the region, it was still mainly fescue. We thought that the balance between bluegrass and fescue, which are both grazing tolerant, was a good indicator of the moisture gradient from the dry southwest to the moister northeast. Our still untested hypothesis is that bluegrass is indicative of good bromegrass land and fescue is indicative of land better suited to crested wheatgrass.

“Unlike the Maritimes, on the Prairies the Kentucky bluegrass stands were low yielding.

“It is interesting that Kentucky bluegrass invades in pastures as far apart and different as Saskatchewan and Nova Scotia, and we even find bluegrass on the west coast right into Alaska. And, of course, Kentucky bluegrass is found in lawns and golf courses all over North America. The wide adaptation and different appearance of bluegrass ecotypes is linked to its strange reproduction system (called apomixes). It produces seeds, which are clones of the mother plants. This means there is very little genetic mixing that would occur with cross pollination, so there can be a lot of genetic variety in close proximity.

“We initially attributed the decline in alfalfa in pastures to grazing stress, but this was not exactly right. We found that very winter-hardy strains would survive in both pure stands and in grass mixtures but less winter-hardy strains that could survive in pure stands might not in mixtures, and grazing had little effect on this. So grazing tolerant mixes must include a very hardy alfalfa variety like Rambler or an even hardier yellow-flowered variety (called falcata) like Yellowhead.

“How did we uncover the story of persistence? At Melfort, we had long-term studies to evaluate how different alfalfa varieties would perform in pure pasture stands compared to seeding with bromegrass. We mob-grazed different plots right down to the ground several times during the summer while other plots were grazed more leniently for comparison. We found that the alfalfa varieties performed differently when seeded with bromegrass than when seeded in pure stands, regardless of grazing intensity. Varieties with the least winter hardiness could not compete with the encroaching bromegrass and bluegrasses and gradually died out. However, the winter-hardy varieties didn’t die out and remained in the stand for many, many, years. That’s how we found AC Yellowhead alfalfa which we were finally able to register and put into commercial production.

“Besides winter hardiness, the persistence of species was influenced by the balance of nutrients in the soil. In multi-year experiments carried out on five different paddocks on community pastures in northeast Saskatchewan, we found that applying nitrogen without phosphorus favoured grasses over alfalfa, but adding phosphorus protected the alfalfa. We had expected these results but unexpectedly nitrogen without sulphur favoured bluegrass over bromegrass and alfalfa on pastures that were sulphur deficient. Low-sulphur soils could only support bluegrass.

“When the herbage is harvested or animals go off pasture, nutrients are removed from fields and for many cow-calf operations very little fertilizer is added back. For these farms how are the nutrients returned? We recently completed a study of cattle farms across Canada and we discovered to our surprise that in Western Canada most of the new nitrogen over a large land base comes from nitrogen fixation thanks largely to the presence of even small amounts of alfalfa. In southern Ontario and Quebec much of the nitrogen is deposited from the atmospheric, a combination of nitrogen emitted from farms and from cars and industry, some of it coming from the U.S. On the pastures themselves the nutrients tend to migrate from the overall grazing paddocks and concentrate in the areas where the cattle gather or camp such as near shade and water sources. The concentrated nutrients can be pollutants if not managed properly.

“Now, in southern British Columbia you have an entirely different situation. Here we are looking at very intensive animal agriculture in high-rainfall area and very expensive land worth almost $100,000 per acre. Forages are used mainly for dairy and managed very intensively; corn and grass are the main forage crops. Special eco-strategies are required to manage nutrient cycling in these intensive forage systems. The 50:50 split of corn and grass produces a very good ration for cows. In southern B.C., sometimes the grass is a foot high by early February. You certainly can’t do that in Saskatchewan. Most farmers get five cuts of grass a year and the protein content is very high (over 16 per cent), partly because of the high rates of manure and fertilizer used. Orchardgrass is the main grass followed closely by tall fescue.

“Tall fescue is interesting because it often associates with a fungus called endophyte, which improves its adaptation but harms its nutritional value. B.C. farmers were reluctant to grow tall fescue until we demonstrated that as long as clean seed is used, tall fescue in B.C. is free of endophyte. In fact, tall fescue is related to very high-quality perennial ryegrass and can be crossed with perennial ryegrass to produce intermediates forms called ‘festuloliums.’ These varieties may combine the good properties from the two parents. The fescues contribute high dry matter yield, resistance to cold, drought tolerance and persistence while the ryegrass provides rapid regrowth, good digestibility and soft palatable leaves.

“It is widely assumed that grass is very beneficial for the environment, whereas corn is a relatively harmful crop because it requires cultivation, pesticides and is prone to nutrient leaching. However, if we take into account the animal’s needs, feeding mainly grass will give lower milk yield and excess nitrogen in urine because of unbalanced feed nutrients. Thus, grass alone is environmentally problematic with our limited land base in B.C. But, by including corn into the farming system, we improve on the overall environmental footprint of the farm since corn has lots of energy and is low in protein while grass is relatively low in energy and high in protein. Together they provide a good balance of feed so farmers buy less feed and animals excrete less nitrogen in the manure.

“Still, the corn crops leach nutrients in the soil. To address this problem, farmers can use winter cover crops. To get the most overall yield and least leaching, my colleague Derek Hunt and I developed a local system of planting Italian ryegrass between the rows at the six-leaf stage of the corn. Biennial tetraploid ryegrasses work best. After the corn is harvested the Italian ryegrass is ready to grow very quickly. We have found that this ‘relay’ or ‘intercrop’ is the best way to capture nutrients that could be lost through leaching during our wet fall and winter periods and to maximize production of the cover crop so it can be harvested in April. Our cover crop was about 30 cm tall in the first week of February this year.

“The point of all this narrative is to emphasize how we need to apply ecological concepts to understand how the climate, soil and forage systems all fit together regardless of what part of Canada we are talking about. While the agricultural regions are so very different these ecological concepts are similar no matter where you are.”

Bittman has co-authored a new book called COOL FORAGES: Advanced Management of Temperate Forages, available from www.farmwest.com.

About the author

Contributor

Duane McCartney is a retired forage-beef systems research scientist at Lacombe, Alta.

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