Randy Toman, a farmer near Guernsey, Sask., began growing alfalfa for seed production over a decade ago. With lighter land well suited to forage and legume production, alfalfa was a good fit for his operation. Adding alfalfa also served to extend Toman’s crop rotation.

With fewer farmers in the area producing seed than forage, Toman faced less competition and had the added benefit of income from the leafcutter bees he added to pollinate the alfalfa.

Similar reasons drew the Mennies into the business in the 1970s. “Farming was a bit of a struggle back then,” says Bob Mennie, production manager of Mennie Bee Farms Inc., near Parkside, Sask., “so we gave this a shot.”

Toman says, “Getting contracts to produce (alfalfa) seed is fairly easy now,” as alfalfa seed acreage has declined. Of the three prairie provinces, Saskatchewan sees the highest alfalfa seed acreage. In 2010, about 100,000 acres of alfalfa seed was produced in Saskatchewan, nearly 75 per cent of total Canadian alfalfa seed acreage.

• More from the Grainews website: Leafcutter bee production

Growing alfalfa seed

Choosing the right field is important. Alfalfa favours lighter, sandier soil, and flatter fields will see a more even maturity, as with other crops. More rolling land has the benefit of seeing a decent crop more consistently, as the hollows may produce more in drier years and the hilltops in wetter years while uniform fields are more inclined to yield well or yield poorly overall, depending on the weather conditions of each particular year.

Because of the limited chemical products registered for use on alfalfa, weed control is vital. “There are a few chemicals registered for alfalfa that do a pretty good job on most weeds,” Mennie says, but it can be difficult to rotate chemical groups to avoid developing resistance.

A good, clean field prior to seeding is key. “If you start with a clean piece of land, it’s much easier to maintain it rather than try to clean it up when it’s in alfalfa,” says Toman. Problematic weeds include sweet and red clovers, cleavers, wild oats, various grasses, kochia, night-flowering catchfly and Canada thistle.

Crop rotation is key. Keeping a field out of alfalfa production for two to four years is typically enough time to clean up weed problems.

The most common insect pests in alfalfa are lygus bugs, alfalfa plant bugs and aphids, with alfalfa weevil increasing in prevalence. It can be more difficult to control insects when the field in question is near to a field seeded to alfalfa for haying.

Leafcutter bees are released once the alfalfa begins to bloom. Spraying fields before this point is often enough to control the insects. “Once the bees have been released,” Toman says, “it is usually cost prohibitive to put on any kind of insecticide because you risk damaging a significant number of bees.” However, sometimes a late hatching or infestation of insects can necessitate a second or even third application once the bees are out in the field. According to Mennie, “when the right chemical is sprayed at night, there is minimal bee loss.”

Fungicides can usually control plant disease with relative success. However, in wetter years, alfalfa can grow very lush and forms a thick, dense canopy, meaning it can be difficult to control disease. “Burning the crop residue in the spring can make a huge difference for disease (control),” says Mennie, as does “light cultivation to break up the residue.” The worst diseases include black stem rot, sclerotinia and botrytis.

As a legume, alfalfa can fix nitrogen. But alfalfa is also perennital — the number of production years varies, but it typically between three and five. It is important to keep up an adequate fertility program to ensure that the soil has enough nutrients to sustain the crop for as many years as it is kept in rotation.

The number of production years varies but is typically between three and five years.

Alfalfa needs to be inoculated with a species-appropriate inoculant to induce nodulation on the root system of the plant and increase its ability to fix nitrogen. “The bacteria may already be in the soil, especially if alfalfa has been there before,” says Mennie, “but (inoculant) is very inexpensive,” so it is best to apply it to ensure that the bacteria are present in high enough numbers to induce good nodulation. Even when seed from seed is purchased coated with an inoculant, it can be good to apply additional inoculant.

Alfalfa can be seeded with or without a companion crop during its establishment year. The companion crop may be seeded at the same time as the alfalfa, as is done on the Toman farm. Their particular setup involves seeding alfalfa with canola, using a triple shoot on the seed drill to seed two rows of canola between every row of alfalfa. Alfalfa has a small seed like canola, and therefore seeding depth is shallow, about one-half to one-quarter inch deep. Alfalfa is seeded in 36 inch rows.

Alternatively, the companion crop can be seeded at a different time, at right angles to the alfalfa.

Seeding alfalfa with a companion crop limits weed control options with registered chemicals. The cover crop competes with the alfalfa for water and nutrients and, in some cases, can increase disease pressure. For these reasons, the Mennies tend not to use companion crops and seed alfalfa on a 12- to 24-inch spacing at a rate of 0.74 lbs./acre. If they do use companion crops, they choose less competitive crops like flax and peas

The Tomans still see a return their first year from companion cover crop.

Harvesting alfalfa

Alfalfa seed is considered dry at about 10.5 to 12 per cent; moisture levels greater than 13 per cent means the seed must be dried before storage. Harvest usually falls towards the end of the season, after most of the other crops have been harvested. Yields typically range anywhere from 200 to 400 lbs./acre.

Most farmers straight cut their crops after desiccating and let it dry down in the absence of a killing frost. Swathing alfalfa is rare. “Alfalfa can be very bushy in the swath, and because it has to be swathed fairly close to the ground, it has a high risk of blowing in the wind,” Toman says.

The crop threshes hard, requiring a fast rotor speed and tight concave opening. The seed is quite small. It can be difficult to initially find the right balance between wind speed and keeping the sieve settings as tight as possible without plugging the return system or blowing the seed out the back of the combine.

Alfalfa seed is a high value crop and should be treated as such, with diligent checking to ensure there is no spoilage. While alfalfa doesn’t require any special storage, the volume is small. “Keeping varieties separate can seem to waste space,” Mennie says. “Some small hopper bins are ideal for storing alfalfa.”

Benefits of alfalfa

There are several benefits to growing alfalfa:

1. Alfalfa only needs to be seeded in its establishment year, so there is less pressure on farmers during seeding in subsequent years.

2. Alfalfa spreads out the harvesting period.

3. In drier years, established alfalfa will thrive because its extensive root system enables it to scavenge for water unreachable to traditional crops. “We see the alfalfa seed as a bit of a safety net against drought,” Mennie says, noting that in wetter years, “it will hold its own as far as return.”

4. The diversified income for those who raise and sell their own leafcutter bees is also beneficial. Both the alfalfa seed and leafcutter bee markets are doing well at present.

Alfalfa seed production does have fairly high management requirements, particularly if the seed grown is certified seed, but the hard work can reap rewards.

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Managing the bees

Bees are put out into the field when the alfalfa has five to 10 per cent bloom, to ensure that the bees have food. This usually happens around July 1. Bees released too early will stray from their shelters to search for food.

The bees moved to the field are about 75 to 90 per cent hatched. They will live out their life cycle, then the farmer will retrieve the next generation of bees at the end of the season. In general, there will be one and a half to two times as many new bees, in the larval form.

Bees in the field are fairly self-sufficient. Checking the shelters weekly for wildlife or wind problems is a good management practice. Toward the end of the season, Mennie says, “Getting the nesting block out of the field and into the safety of the processing building as soon as the bees have finished working is a good idea.”

Crop insurance requires 20,000 bees per acre; this is the benchmark for good alfalfa pollination. Flying fewer bees per acre tends to increase bee production, but more bees per acre means more cross-pollination and therefore better seed production.

The number of bee shelters per field varies depending on each farmer’s individual setup. Smaller plastic shelters may be placed at rates of about one shelter per 2.5 acres, as on the farm of alfalfa seed producer Randy Toman of Guernsey, Sask. The Mennies use large shelters of their own design — one shelter can cover 15 to 25 acres. Fewer shelters means the Mennies have a lower cost per acre for shelters as well as increased efficiency.

The number of nesting blocks per shelter depends on the size of the shelter.

The plastic shelters are lightweight and can be stacked inside each other as one would stack chairs. Metal and wood shelters are more expensive, but may last longer than the plastic ones. Setting up shelters is fairly straightforward, requiring a couple of people and either a trailer or a tractor with a front end loader to move the shelters to the field.

“Efficiency is the name of the game in the bee business,” Mennie says. Labour is expensive and difficult to find.

• From the Country Guide website: Keeping bees

The two popular types of nesting material available are wood or polystyrene blocks. Polystyrene blocks are cheaper, lighter, reasonably simple to treat for disease or sample for sale, and are easier to work with, making them the current industry standard. However, they are more prone to damage than wood blocks.

Of the bees put out in the field, about 35 per cent are females. In a typical polystyrene nesting block, there are 3,540 tunnels. On the Mennie farm, there are approximately five nesting blocks per acre, and each female has about two to 2.5 tunnels to fill over the season. At the end of the season, these tunnels are filled with the cocoons built from the alfalfa leaf material the bees collect.

Pest and disease control

Two species of small, parasitic wasps target leafcutter bees. While there are insecticides that can be used in the incubators to control these pests before the bees hatch, Randy Toman, a farmer from Guernsey, Sask., says there is no chemical control for parasites in the incubator after hatching. The best defence against parasites in the field is good management: proper assembly and installation of nesting blocks and replacing damaged blocks. “There’s a backing that goes on the back of the nests that prevents parasites from getting in,” Toman says. “It’s very important to have your nests put together properly before you take them out to the field. That’s a major control.”

Disease-wise, moisture means mould. The alfalfa leaf material collected by the bees contains millions of naturally-occurring mould spores, so the faster the cocoons are dried, the less mould there will be. Mould affects bees’ overall health and virility.

Sterilization is the simplest way to control mould. The fungal chalkbrood disease can be even more devastating than mould to bee populations. The simplest way to control this disease is to avoid purchasing bees of poorer quality or from areas known to have disease, and to thoroughly clean any used equipment purchased so the chalkbrood spores are not brought onto the farm.

The sterilizing agent paraformaldehyde is a gas that kills mould spores. It can be used on the collected cocoons at the start of the season as well as on the used nesting material and equipment, including harvest equipment and the incubators used to hatch the bees. A bleach solution can also be used. Wood nesting blocks can be heat treated.

Once the nests are brought in from the field, they should be dehumidified by blowing fans over the nests in preparation for harvest of the bees. At this point, they are kept at about 18 to 21 C to ensure that the larvae have had enough time to spin their cocoons inside the leaf cocoons. The Mennies allow at least two weeks for this to occur, after which they harvest the bee larvae and store them in cardboard boxes at about 4 C and as low a humidity as possible. “[The larvae] can’t get too cold or they’ll freeze, and if they get too warm they’ll start to incubate,” says Toman.

Come spring, the larvae are incubated for 22 to 24 days. Incubation typically starts in the first week of June. In the incubators, the humidity is kept relatively high as the bees develop and the temperature is kept around 30 C. At the end of this period, all of the males and about 80 per cent of the females have hatched, and the incubation trays are taken to the field and put into the shelters. When the lids are taken off, the hatched bees fly out.

Selling excess bees

Farmers who maintain their own bee populations keep enough bees for pollination in the coming year and sell the excess. While most bees are sold into the U.S., other markets include the hybrid canola market and Eastern Canada’s blueberry industry. “There is some red tape exporting [bees] to the United States,” says Mennie.

Bees are sold by the gallon — about 10,000 bees. While price per gallon varies, last year’s top price was about $100/gallon.

Farmers interested in growing alfalfa for seed but not interested in getting into leafcutter bee production can look into custom pollination. Information is available through the Alfalfa Seed Commission (Alberta), the Manitoba Forage Seed Association, or the Saskatchewan Leafcutters Association.

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Dr. John O’Donovan, Agriculture and Agri-Food Canada (AAFC) research scientist, notes that “only about 20 to 25 per cent of the barley in Western Canada is accepted for malting every year.”

Farmers can increase their likelihood of getting malting quality barley by focussing on a few key things.

1. Variety choice

According to Dr. Aaron Beattie, assistant professor and barley and oat breeder at the University of Saskatchewan, two row malting barley acres account for roughly 50 per cent of the total barley acres grown in Western Canada.

AC Metcalfe is the most commonly grown malting barley variety, having about 50 to 60 per cent of the two row malting barley acres. The second most popular, CDC Copeland, has about 20 to 25 per cent of the acres, and a few other varieties occupy the remaining five to eight per cent.

2. Seed lot

The barley seed itself should come from a pure lot, typically certified seed. Some preliminary studies conducted in Alberta by Dr. T. Kelly Turkington, AAFC research scientist, in conjunction with Rahr Malting Canada, Ltd., in Alberta suggest that, when examining the productivity and malting quality of the seed, there are “very little if any differences between certified seed and seed that is one year — and I emphasize that, one year—away from certified” where the non-certified seed in question has been accepted as malting quality and was obtained from Rahr Malting barley growers.

If seed is more than one year away from certified seed, there can be dramatic differences in the seed that can lead to significant problems, including lower germination rates, lower quality characteristics, and a potential mixture of varieties or crop types.

3. Seeding timing

Because barley tends to mature earlier than canola or wheat, most farmers seed it later. However, O’Donovan observed that earlier seeded barley tended to produce better yield and quality characteristics. “The protein was always higher when we delayed seeding,” he says about his trials, and in all but the Peace River region, yield was higher with earlier seeding.

Early seeding also means that the crop may have matured early enough to avoid frost damage or other weather-related harvest difficulties that can occur.

Furthermore, desiccant use is not allowed on malting barley, so farmers with later crops must wait for the barley to dry down or, if possible, finish drying it in storage, which would come at an added cost.

4. Seeding rates

The ideal plant density is about 200 to 240 barley plants per square metre. O’Donovan achieved this by planting 300 seeds per square metre.

Assuming that only about 70 per cent of the seed put in the ground germinates, this means farmers must seed approximately 100 to 120 pounds per acre to achieve a similar density, depending on factors like row spacing, drill type, and variety.

Too high a seeding rate can see a reduction in yield and a reduction of net return; too low a seeding rate means barley yield and quality will not be optimized and farmers’ net return will again be reduced. Crop and kernel uniformity and disease levels are quality characteristics impacted by plant density.

5. Field choice

Field choice can also impact uniformity — level land typically means more even maturity.

The previous crop grown on the field has a major impact on disease. Barley grown on barley stubble poses the greatest disease problems, and productivity and kernel characteristics decline significantly compared to barley grown on canola or field pea stubble.

Malting barley is not often grown after a pulse crop in rotation because of concerns of higher nitrogen levels in the soil leading to a higher protein content in barley grain at harvest time. However, Turkington observed in his trials that “the protein content [in barley grain] after field peas was not significantly higher than after canola,” although he admits there was an indication of an upwards trend, and that the barley grown on field pea stubble yielded higher than barley grown on canola stubble. If farmers are careful and fine tune their nitrogen program, they could capitalize on the rotational benefit of planting malting barley after peas.

Crop rotation is greatly beneficial when it comes to management of disease and weeds. “A single year between cereal crops is simply not enough to see a huge benefit for crop rotation,” says Turkington. There is simply not enough time for crop residue to decompose. However, even with multiple years between cereal crops, farmers cannot assume that they have managed their disease problem. Some crop residue will remain in the field, acting as an important source of disease, and there is always the possibility of seed borne infections.

6. Fungicide

While spraying fungicide at along with herbicide to reduce a pass over the field is convenient, “it has very little direct impact in terms of protecting upper canopy leaves,” notes Turkington.

This is because leaves that emerge after the application are not protected, and the fungicide degrades over time. Spraying at the flag leaf stage will provide the most effective control of disease in the upper plant canopy at a time when the plant is trying to fill the head, which in turn leads to the plump, uniform kernels desired by maltsters.

7. Nitrogen

Nitrogen is “great for increasing yield,” says O’Donovan, “but it can have a negative impact on malting barley quality” because protein tends to increase as nitrogen increases.

In addition, nitrogen is linked to other malting quality traits like friability, beta-glucan content, and amount of malt extract, always having an unwanted effect. O’Donovan recommends that barley growers apply nitrogen at about 70 per cent of the soil test recommendation. Applying at higher rates becomes uneconomical and tends to drive down net returns.

8. Harvesting

Come harvest time, farmers must make the decision to either swath or straight cut their crop, a decision often influenced by the weather and how well the harvest is going in a particular year.

“It comes down to… how mature the crop is,” says Beattie. Straight cutting is generally preferred if farmers can get away with it, but without the use of desiccants, many farmers are forced to dry down their crop by swathing.

Turkington points out that, under wet conditions, there is a greater chance of microorganisms to grow on the dead plant tissue of a swathed crop because of the close proximity of the plants and the reduction in air movement through those plants. The presence of certain microorganisms impacts the malting and brewing quality of barley, sometimes leading to it being unacceptable for malting.

9. Storage

Malting barley, according to the Grain Grading Guide, is considered dry at a moisture content of 13-1/2 per cent or less. However, a moisture content of 14.8 per cent or less is considered dry and safe for the storage of feed barley. If the barley is stored under good conditions, there is little difference.

Ideal storage conditions include dry, clean bins where measures have been taken to prevent infestation and to make it rodent proof. These conditions can be maintained by both natural aeration or frequently turning the grain in the bin. †

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“It used to be the exclusive malting barley type,” says Dr. Aaron Beattie, assistant professor and barley and oat breeder at the University of Saskatchewan.

In addition to tradition, reasons for this include that some brewers felt it imparted a certain flavour on the beer and that breeders were not focussing on breeding two row barley to the same extent as six row, meaning that two row barley varieties were less desirable for malt.

The largest initial difference between the two barley types was the amount of enzyme activity present to break down the starch in the kernels. However, over the years, breeders have improved the malting quality characteristics, called the malting profile, of two row varieties and therefore these varieties are now the most common.

The biology of the plant in terms of the head shape of two row versus six row barley differs. The kernels of two row barley tend to be more uniform than that of six row barley. Uniformity of kernels is important in the malting process, so two row varieties have a greater advantage.

According to Beattie, “six row barley is a barley type that is unique to North America,” and it currently has no use outside of North America. Within North America, only one major brewing company is still looking to use six row malting varieties; consequently, six row barley acres in Canada have dropped below 10 per cent of the total barley acres grown.

Even so, six row varieties still have a good agronomic fit in a lot of areas of the Prairies. Traditionally, they have been shorter and stronger plants, meaning that there was less chance of lodging. In the black soil zone or in areas that are a bit wetter, “six rows tend to perform a little bit better,” says Beattie. Farmers might want to grow six row varieties for this reason, but “these days it would be very hard to sell a six row malting barley for malting purposes.” †

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With certain contracts, storage payments will be provided if they don’t take the barley immediately, though the amount of time the farmer holds the grain is negotiable. It is rare that farmers would have their barley rejected as malting quality after storage, the most prominent reason for this being improper storage leading to poor germination rates.

Farmers selling barley are most likely to get malt quality if their grain meets the standards set by the Brewing and Malting Barley Research Institute (BMBRI) as available on its website (bmbri.ca):

•  pure seed lot;
•  at least 95 per cent germination;
•  no of pre-harvest sprouting;
•  moisture content up to, but preferably less than, 13.5 per cent;
•  protein content of 11 to 12-1/2 per cent on a dry basis;
•  uniform, plump kernels;
•  fully mature;
•  not weathered or stained;
•  less than five per cent peeled or broken kernels; and,
•  free of disease, toxins, chemical residues, frost or heat damage, insects, treated seed, admixtures, and odour.

The malting process

As Dr. Richard Joy, vice president of operations and technical director for Rahr Malting Canada, Ltd., says, “Malting is probably the only process that [needs] to have 100 per cent live seeds, therefore… it’s extremely important that [the barley] has as close to 100 per cent germination as possible.”

The malting process has four general steps: cleaning, steeping, germination and kilning. Steeping involves soaking the barley kernels to increase the moisture content to a uniform level. This step, which takes approximately two days, involves wet periods where the barley is under water, but with continuous aeration, and dry periods called air rests (where the barley is not immersed under water), but with aeration to maintain oxygen levels in the grain environment.

The kernels, now referred to as green malt, are then transferred to a germination vessel and germinated for four days. Growth is stopped with the final step, kilning, where the green malt is gently dried down. After analysis, cleaning, binning, and blending, it is sent to the brewer.

Some of the characteristics desired in barley, such as kernel plumpness, relate directly to the controlled germination process. Plumpness and uniformity of the kernels means that they will take up water at roughly the same rate. Grain with high water sensitivity is undesirable as it has reduced germination rates in excessive moisture conditions.

Other characteristics, such as protein content, relate to the amount of finished malt that is delivered to the brewer and the quality of the malt extract, or wort, created from it; too much protein could potentially lead to cloudy beer. Characteristics like moisture content, however, relate just as much to economics as they do to ease of malting or quality of the end product.

Dry grain means that the processor, who is purchasing the grain by weight, is not paying for water. At the same time, less moisture means better storability and a uniform moisture level in the barley.

Maltsters, according to Joy, are looking for “good quality malting barley that has good agronomy, good disease resistance, and thirdly good malt quality.” However, Joy says that “new varieties are of interest because we want to keep the producers interested in growing barley.” †

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Provincial guidelines

The provincial guidelines for recommended fertilizer rates are based on local research completed within each province.

In some cases, such as with field peas, the phosphorus recommendations are markedly different. In Alberta, Saskatchewan, and Manitoba, the safe amount of seed-placed phosphate is set at 30 lbs./ac., 15 lb./ac., and 20 lb./ac., respectively.

The trials which led to these recommendations likely focused on a narrow seedbed utilization, which is found by dividing the width of the spread of the seed and fertilizer by the row spacing, to mimic the practices of many farmers today; a seedbed utilization of around 10 per cent, for instance, would see seed applied with a one inch spread in nine inch row spacing. A lower seedbed utilization means a greater concentration of seed and fertilizer, leading to lowered recommendations for the amount of fertilizer that can be safely placed with the seed.

According to Dr. Rigas Karamanos, manager of Agronomics Solutions with Viterra, the research generated in each province probably reflects different ecological conditions. “Some of the research done in Saskatchewan,” Karamanos points out, “was done in areas on the drier side.” However, research trials in Alberta, some of which Karamanos was involved in, saw no problem with placing up to 30 lb./ac. of phosphate with the seed. “If you put 30 pounds [down] in Saskatchewan,” Karamanos says, “you’re most likely going to kill the crop.”

Under wet conditions, it is possible to place slightly more phosphate with the seed due to reduced availability and mobility of phosphorus. Even so, the outcome of the provincial research is based on both the experimental and the agro-ecological conditions. There is always an element of conservatism when setting guidelines, so the lowest rate deemed ‘safe’ of all the provincial trials is going to be the official recommendation.

Dr. Jeff Schoenau, a professor in the Department of Soil Science at the University of Saskatchewan and Saskatchewan Ministry of Agriculture Chair in Soil Nutrient Management, notes that many factors influence a phosphorus recommendation. Both the plant itself and the soil in which it is grown play important roles. A crop’s phosphorus demand, for instance, “is a function of its physiology,” according to Schoenau. High phosphorus users include high yielding cultivars of cereals and oilseeds, particularly canola, as well as forage legumes and C4 plants (like corn) with a high metabolism and growth rate.

Soil and phosphorus rates

On the soil side, factors to consider include everything from soil microbiology to the pH of the soil solution. For phosphorus, “solubility and availability are pretty much synonymous,” says Karamanos, and when looking at phosphorus solubility, “pH is the primary factor.” At a low or acidic pH, phosphorus reacts with aluminum or iron and precipitates out of the soil solution; at a high or alkaline pH, it reacts with calcium or magnesium.

Once phosphorus has precipitated out of solution, it is no longer in the plant available form of orthophosphate. Therefore, phosphorus availability is said to be maximized at a neutral pH, with an optimum range of pH 6.5 to pH 7.5.

While acidic soils are uncommon on the Canadian Prairies, alkaline or calcareous soils (basic soils with a high lime content) are not. Some crops such as legumes can be beneficial in improving phosphorus availability in these soils because they can acidify the rhizosphere, the area of the soil near the plant root.

Phosphorus, being a relatively immobile nutrient in the soil and moving anywhere from a few millimetres to a few centimetres in the growing season, needs to be near a plant’s roots to be effective. Soil texture influences the mobility of phosphorus, with orthosphosphate moving more readily in light textured or sandy soils. Consequently, additional starter phosphorus can be important in heavy textured soils, namely clays, as well as in cold or wet soils.

Phosphorus and microorganisms

The activity of soil microorganisms is reduced in cold soils, which can slow the cycling of organic phosphorus from these organisms into the soil. Soils rich in organic matter see more soil microorganisms, but their presence, particularly that of arbuscular mycorrhiza (AM) fungi, can be encouraged through particular farming practices.

According to Schoenau, “the formation of beneficial relationships like AM fungi on crop roots is beneficial in phosphorus availability.” This relationship can be encouraged through good crop rotations as well as through the reduction or elimination of tillage to preserve the AM fungal network in the soil.

Long-term land management, therefore, influences phosphorus availability. Anything that maintains soil moisture, from high cut stubble to catch snow in the winter to leaving the crop residue on the land (as opposed to bailing or burning), will help because moisture is important for phosphorus to move by diffusion and ensure available phosphorus. It is also possible to build up phosphorus in the soil. Soil conservation practices like zero till build organic matter over time and therefore build the phosphorus supplying power of that soil.

Nutrient timing

A soil which has seen repeated applications of phosphorus fertilizer in the past can, in a year where the price is high, have a reduced requirement of phosphorus fertilizer necessary to maximize yield. Such nutrient mining, Karamanos cautions, cannot be maintained indefinitely.

“People who have been fertilizing with phosphorus probably have a very good labile pool,” which consists of phosphorous adsorbed onto minerals and soil particles and the available phosphorus maintained in the soil solution which is replenished throughout the year by phosphorus in the solid phase, “and can afford for three or four or five years to discount it.”

However, even when fertilizer is put down with the crop, a phosphorus deficit can be incurred because higher yielding crops require more phosphorus than is typically seed placed or side-banded.

Phosphorus deficiency

Signs of a phosphorus deficiency are not as clear in plants as with other nutrients like nitrogen. “We call [it] a hidden hunger,” Schoenau says, noting that a lack of phosphorus leads to overall reduced crop growth, reduced head size, and reduced number of seeds. In some cases, there will be purpling or a bluish-green colour developing along the leaf margins; because phosphorus is mobile in the plant and can be reallocated to younger leaves, these symptoms would be found on the bottom parts of the plant, among the older leaves. However, the discolouration “is not something you’ll always see in a field, even with yield reductions.”

It is unlikely that any farmer is over-applying phosphorus when only using commercial fertilizer. With repeated applications of animal manures, however, it could be a different story. Manure has a low nitrogen to phosphorus ratio, meaning the relative amounts of each nutrient are about the same, which can be problematic as plants require more nitrogen than phosphorus.

“When we apply manure solely to satisfy the nitrogen requirement,” Schoenau points out, “[we] end up applying more phosphorus than what we can use over time.” While Prairie soils have a good ability to adsorb phosphorus, repeated applications can lead to saturated adsorption sites and the phosphorus will stay in the soil solution.

During the spring melt period or heavy rains, this phosphorus can be moved off the field and into nearby water bodies, causing problems with water quality.

While each field has a different management history and soil makeup and each crop a different phosphorus requirement, the general guidelines given by the various provinces are good rules of thumb. When Karamanos was asked if he agreed with the provincial recommendations, he noted that it is important to look at the research and cited an incident where a farmer exceeded the provincial recommendations, saying, “it didn’t work very well.” †

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There are two major causes for this deficiency, says Flaten. “One is that most of our soils are naturally fairly low in phosphorus and what phosphorus they have is often tied up with chemical and biological processes that don’t let the phosphorus be easily taken up by crops.”

The other factor lies in the large amount of crop production on the Prairies. Farmers don’t always match removed phosphorus with supplementary application. Regular soil testing will give farmers an idea of how much phosphorus should be applied.

Besides crop removal, here are six factors that influence the availability of phosphorus in your soil.

1. Form

Phosphorus availability is greatly determined by its solubility — its ability to dissolve. Solubility relates to the form of the phosphorus (dissolved or particulate).

Dr. Jeff Schoenau, a professor in the Department of Soil Science at the University of Saskatchewan and the Saskatchewan Agriculture chair in soil nutrient management, says phosphorus in the soil is most commonly found as “orthophosphate that is adsorbed onto soil particles or part of minerals or part of organic matter; that is to say in the solid phase, as opposed to in the soil water.”

Because most soil phosphorus is in the solid phase, it is less susceptible to leaching loss than other elements like nitrogen, and can be considered relatively immobile.

2. Soil pH

The plant-available form of phosphorus is orthophosphate. There are two forms of this: primary and secondary.

You’ll find primary orthophosphate in acidic soils. In alkaline soils, secondary orthophosphate dominates. In soil with a neutral pH, you’ll find both in approximately equal amounts.

Soil pH is a primary factor in determining phosphorus availability. In low pH soil, orthophosphate will react with aluminum and iron and form a solid. In this form, the orthophosphate is no longer available for plant uptake.

In high pH soil, orthophosphate reacts with calcium and magnesium to form a solid, again leaving less orthophosphate available for plants.

Soils with a neutral pH have more phosphorus in the soil solution.

3. Microorganisms

Phosphorus available in the soil is determined by soil biology, particularly the actions of microorganisms in the soil around the roots.

4. Minerals

Over the long term, weathering of minerals such as apatite will release phosphorus into the soil.

5. Erosion

Most phosphorus is found in the top six inches of the soil, so whenever topsoil is lost, so is phosphorus.

On most fields, tillage has little effect on phosphorus erosion — more phosphorus is lost in the dissolved form than the particulate form. However, erosion is an important factor on slopes.

6. Water

Dr. Rigas Karamanos, manager of agronomics solutions with Viterra, says, “If you can control the movement of water, you can control the movement of phosphorus.”

Typically, there are three main ways to lose phosphorus from a field to a nearby water body: leaching, erosion, and runoff.

Flaten says leaching rarely results in significant phosphorus loss on the Canadian Prairies.

Runoff is the major form of phosphorus loss in Prairie watersheds. In most soils, the amount of phosphorus lost in soil water would be very small, even considering runoff in manured soils.

Schoenau says, “environmentally, the amount of phosphate that would be moved is significant enough to be of concern, but in terms of pounds per acre, it’s typically less than one.”

Phosphorus that finds its way to water bodies can seriously deteriorate water quality, interfering with the nutrient balance in the water and encouraging the growth of algae.

Applying phosphorus

Farmers may not always see a response to applied phosphorus. Phosphorus is a very reactive compound — crop growth and phosphorus supply are very sensitive to environmental conditions. Crop response to phosphorus can vary greatly in the same field in a given year.

There is a finite supply of phosphorus available for farm use. There is a debate about how much easily accessible phosphorus can be mined. Lobbyists are working to stop corporations from expanding existing mines and starting new ones

More research is needed into finding new ways to use insoluble phosphorus in our soils, and breeding new crops that can more effectively scavenge nutrients in the soil.

Schoenau says farmers “always need to be looking at ways to maintain phosphorus.” There is a finite supply in the soil. Once phosphorus is washed out into oceans, it’s no longer available to farmers. †

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There are five main types of commercial phosphorus fertilizers: monoammonium phosphate (MAP), diammonium phosphate (DAP), triple super phosphate, orthophosphate and polyphosphate.

Of these, MAP, orthophosphate, and polyphosphate are used in Western Canada, with the most widespread fertilizer type being MAP, a granular fertilizer which includes blends such as 11-52-0.

DAP tends to be slightly more toxic to seedlings than MAP, and triple super phosphate, though popular in Europe and Asia, is too expensive to distribute in the Prairie provinces when most of it is produced overseas.

Relatively immobile

According to Dr. Jeff Schoenau, a professor in the Department of Soil Science at the University of Saskatchewan and Saskatchewan Agriculture chair in soil nutrient management, “The main thing to keep in mind with phosphorus, regardless of form, is that it’s relatively immobile in the soil; it won’t move very far from where it’s placed to another location in the soil.”

The key, then, is to place the phosphorus close to the plant roots so that it will be available to the plants early in the growth cycle and to do so without exceeding the recommended rates of phosphorus. Crops sensitive to high fertilizer rates, such as flax or pulses like peas, cannot tolerate the high salt content as well as cereals, so placement of the fertilizer is important.

Because of its limited mobility in the soil, broadcast phosphorus is not very effective unless incorporated and is considered inferior to other placement methods at lower rates (typically 10 to 30 lbs. of phosphate per acre). If broadcasting, the rate should be increased to at least 50 to 60 lbs. phosphate/acre.

Most often, phosphorus is seed placed or side-banded (often one inch below and one inch to the side) or both, with the distance from the seed in side-banding meaning that more phosphorus can be put down at once than with seed placed phosphorus. Other placement methods — below the seed (typically about one inch) and deep banding (four to 12 inches) — are uncommon in Canada. Dr. Rigas Karamanos, manager of agronomics solutions with Viterra, believes that “the most efficient way is to apply [phosphorus] in a band.”

Residual effect

A large application of phosphorus, typically broadcasting between 100 to 150 lbs. phosphate/acre, has been used in the past to take advantage of the residual phosphorus effect and to build up the phosphorus reserves in the soil.

In the 1970s and ’80s, some research showed that such applications could improve yields substantially. Today, however, as pointed out by Dr. Don Flaten, a professor in the Department of Soil Science at the University of Manitoba, the land tenure situation is different, since many farmers are working on rented land, and “the economics are a lot less favourable than years ago.”

Furthermore, when a large amount of phosphorus is put down in the soil, the mycorrhizae are killed. Because these soil microorganisms will beneficially infect plant roots and increase their ability to take up certain nutrients, such as the micronutrient zinc, new deficiencies can be caused. Therefore, if a farmer seeks to improve the soil fertility on his land, perhaps even just on eroded knolls, it’s better to look for manure or a similar low cost, useful amendment which will increase organic matter as well as phosphorus.

Ultimately, the type of phosphorus fertilizer applied does not matter, as it will convert to the plant available form of orthophosphate by the time the seed has germinated and the plant can take up nutrients. Karamanos has found that after four to eight days, “by the time the plant starts utilizing [phosphorus], [the products] are all the same.” This phosphorus will not all remain available, with some of it adsorbing to soil particles, but it is likely retained in the soil as residual phosphorus for the coming years.

According to Schoenau, some say that phosphorus fertilizer “is inefficient because in the year of application, [we] might only get 20 per cent of it recovered by the crop,” but “in the longer term, phosphorus fertilizer and recovery can be quite efficient because it’s not readily lost from the system.”

Consequently, there are few differences between liquid and granular or non-aqueous fertilizers.

Granular versus liquid

While the forms of phosphorus differ initially, with granular fertilizers often being orthophosphate and the liquid fertilizers ammonium polyphosphate, the polyphosphate will rapidly convert to orthophosphate.

Liquid fertilizers may be easier to handle, and separation of fertilizer from seed can be readily achieved to avoid damage. Like granular fertilizers, however, spacing remains an issue.

Karamanos says, “People think that when you apply liquid, it’s a constant stream, and yet, it’s not.” Rather than a steady stream of liquid, the fertilizer hits the ground in individual droplets, so the supply would depend on the rate of application, the kind of dribble system used to apply the fertilizer, and the specific equipment figuration therein. The higher the rates applied, the smaller the spaces between the droplets. At lower rates, such as 15 lbs./acre, studies have found that the distance between the fertilizer droplets is greater than the distance between granular fertilizer particles.

For some farmers, it makes sense to apply manure to meet the necessary phosphorus requirements and to use fertilizer to meet the plant’s remaining nutrient requirements. However, it can be difficult to evenly distribute the manure, particularly since it must be applied in tonnes per acre to meet a crop’s phosphorus requirements.

Schoenau says, “Solid manure still might only be a half to one per cent phosphorus by weight, so it still means that you have to have a lot of it in terms of volume of manure.” As such, manure is usually applied in excess of what crops require, which can lead to increased phosphorus loss and has prompted some places, like the province of Manitoba, to instigate soil-based guidelines for the application of phosphorus.

There are no major differences between solid or liquid manure, so the product of choice would depend on the equipment and supply available. For example, solid manure requires the use of a manure spreader and liquid manure that of an injection system. In both cases, “it’s good to get [the manure] into the ground, [to] get it close to the roots where the roots can take the nutrient up,” says Schoenau. However, since some of the phosphorus in manure is in the organic form and must be broken down and mineralized by microorganisms, not all manure phosphorus is available in the year of application. Compared to a commercial fertilizer source, there is only about 50 per cent phosphorus availability.

If possible, it is best to do a soil test and apply phosphorus based on those recommendations, especially if the land management history is not known.

“Recognizing… what your cropping system is taking out of the system, out of the soil, over the long term is something useful to keep in mind,” Schoenau says. “Economics are important to consider.”

With crops usually removing more phosphorus from the soil than is being applied, a soil test can help farmers determine the probability of a yield response to additional phosphorus fertilizer and whether or not they are currently applying at rates that will deplete, maintain, or build up soil phosphorus.

“Once a soil has an established history of phosphorus application, the method [becomes] a bit more irrelevant,” observes Karamanos. “What determines the method to a great extent is the amount of phosphate you can place safely with the seed.” †

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