Where sulphur and magnesium fit
Last issue, we began our look at secondary nutrients by discussing calcium, including what it does in the plant and in the soil, and what you should think about if your fertilizer dealer recommends you invest in a calcium program.Now, let's look at magnesium and sulphur, two other secondary nutrients about which there seems to be as much misinformation as fact.
MAGNESIUM
Chemically, magnesium is a first cousin to calcium. Both are 'alkaline earth' elements that carry two positive charges, and both are found in carbonate minerals.Their functions in the plant are quite different, however. Magnesium is the heart of the chlorophyll molecule which converts sunlight into sugars. Magnesium is also involved in activating a number of enzyme reactions.
Because of its role in chlorophyll, the first symptoms of magnesium deficiency show up as yellowing, usually between the veins of the older leaves. This indicates that magnesium is somewhat mobile within the plant and will move to the younger tissue.
In severe deficiencies, the entire leaf will turn yellow or red and then brown, with symptoms progressing up the plant.
Like calcium, magnesium supply is related to pH, with deficiencies showing up most commonly on sandy, acid soils. It is also related to the parent materials of the soil, with magnesium deficiency more common east of the Niagara Escarpment than to the west where the glaciers deposited a healthy dose of ground-up dolomitic rock.
Magnesium is routinely measured in soil tests, and a reading below 20 is considered to be deficient. In most cases, if the soil requires magnesium, it also requires lime to correct soil acidity. In such cases, the most economical source of magnesium is dolomitic limestone.
If the magnesium soil test is below 100 and lime is required, dolomitic lime should be the source to protect against any future magnesium shortages. Above this level, either calcitic or dolomitic lime may be used.
In the rare situation where magnesium is low but the pH is acceptable, magnesium can be applied as Epsom salts (magnesium sulphate), or as sulphate of potash magnesia (Sul-Po-Mag or K-Mag), but both of these sources are much more expensive than dolomitic lime.
For most field crops, about 30 kg per hectare of magnesium is all that is required to correct a deficiency. It does not make sense to apply all of the potash requirements for a corn crop as sulphate of potash magnesia, simply because of the cost.
Instead, use enough of the more expensive fertilizer to meet the magnesium requirements of the crop, then blend in muriate of potash to meet the balance of the K requirement.
It is possible to induce a magnesium deficiency if the soil magnesium is borderline low by applying too much potash. These nutrients "look" similar to plant roots, and will actually compete for crop uptake. This is occasionally a problem in crop production, but it shows up much more commonly as mineral imbalances in forages fed to livestock, especially dry cows. Use a soil test to determine your potash requirements, and feed supplemental magnesium to the cows.
SULPHUR
The third secondary nutrient is not at all like the other two, and in fact behaves more like nitrogen.Sulphur is absorbed by plants as the negatively-charged sulphate ion, and much of the soil supply of sulphur is bound in the soil organic matter. In the plant, sulphur is a component of two amino acids which are necessary for protein synthesis. It is also involved in several enzyme reactions, and is a part of the compounds which give onions, garlic or mustard their distinctive smell.
Deficiency symptoms are uncommon, but where they occur, they tend to mimic the symptoms of nitrogen deficiency with a pale green to yellow colour along with stunted growth.
Most of the sulphur supplied to plants comes from sulphate contained in rainwater or from the breakdown of organic matter. There has been some concern that, with the pollution control legislation, and with the reduction in industrial activity during the last recession, we wouldn't receive enough sulphur from the air to meet the needs of high-yielding crops.
While there is some variation in the annual deposition of sulphur, mostly with the amount of rain we receive, the latest surveys by Environment Canada show that we are still receiving adequate sulphur from the air.
This is backed up by the fertility trials on hard red winter wheat, which showed no difference in yield or protein content between crops fertilized with ammonium sulphate or urea.
The exception to this general pattern is Northwestern Ontario, which is upwind of most of the industrial sources of airborne sulphur. Even here, responses to sulphate fertilizers has been inconsistent.
None of the soil laboratories routinely test for sulphate in the soil, but a test can be performed as a special request if you are in an area where sulphur deficiency is suspected.
There are no parts of Ontario where it appears that routine applications of sulphur are required.
In summary, secondary nutrients are important for plant growth, but there are only a few situations where they will be a major part of a fertilizer program. Keep them in mind, but also keep them in perspective.
Keith Reid is soil fertility specialist for the provincial agriculture ministry at Walkerton. E-mail: kreid@wcl.on.ca
back to Contents Seedbed
Hard red wheat a hard sell
By TOM BUTTON
It's do or die time for Fundulea wheat. This fall, Ontario's 20-year campaign to grow hard red winter wheat faces the prospect of a withering collapse.And if Fundulea sinks, so could the province's hopes of cracking Eastern Canada's 1.1-million-tonne-per-year hard red milling market, industry watchers believe.
"There's a danger this would send a signal to the bakers not to rely too much on Ontario," says Andy Rankine, food industry specialist for the provincial agriculture ministry.
Peter Johnson, crops specialist for the ministry at London agrees. "Don't ignore hard red," Johnson is telling growers.
Whatever happens, it's clear that processors want to buy Ontario-grown Fundulea.
Over the last three years, Fundulea has carved out a steady 120,000-tonne- per-year domestic market for crops coming out of the field at about 11.5- per-cent protein. The wheat board says it could sell another 100,000 tonnes of Fundulea over 12 per cent.
The Ontario Red Wheat Committee, with members from the provincial marketing board, bakers, millers, elevators, and the seed industry, has held at least two emergency sessions in the last few weeks to find a way to rescue Fundulea.
The only hope, says J.D. Cameron of C & M Seeds, the Ontario distributor for Fundulea seed, is if processors offer planting incentives, probably in the form of a $10 to $15-per-tonne bonus above the board when the 1998 harvest is delivered.
By early September, seed orders for the soft red Freedom were outpacing orders for Fundulea by three to one, Cameron says. "If we're going to save Fundulea, something has to happen fast."
Yet millers say they can't absorb the cost of a premium, says Derek Jameson, president of the Ontario Flour Millers Association. "We hope Ontario continues to grow Fundulea," Jameson told Farm & Country. "Any incentives would have to come from specific end users. To date, we haven't seen any such offers."
Ontario's biggest Fundulea user is Griffiths Laboratories in Scarborough, which blends Fundulea in its dough for breadings. Other bakers, including Canada Bread and Robin Hood, are buying smaller amounts, but are steady customers.
Under long-standing board agreements, Ontario millers buy Fundulea at the same price as soft white wheat, explains Jim Whitelaw, board marketing manager.
This year, Fundulea is expected to pay about $150 per tonne ($4.10 per bushel), exactly the same as soft white wheat, even though it costs an extra $30 an acre to grow Fundulea due to higher nitrogen expenses.
As well, only about 20 per cent of this year's 110,000-bushel Fundulea crop had enough protein to earn the board's $15-per-tonne (41-cent-per-bushel) premium for 12-per-cent protein.
Planting Tips
Peter Johnson, provincial government crops adviser who specializes in wheat, offers these six planting tips for wheat.Plant on time. Every day that planting is delayed after the optimum date for each area can be expected to cut yields next summer by a bushel per acre;
Plant by seed number, not by the pound. Aim for 1.4 to 1.6 million seeds per acre, Johnson advises. Seed is too expensive to plant by weight. "Fifty dollars an acre for wheat seed is too much," he says. "Wheat isn't corn. This isn't a crop with a 150-bushel yield potential";
Apply phosphorus through the planter. Phosphorus starter helps the crop develop strong seedlings that survive the winter. Placement is crucial, Johnson says. It's almost impossible to get the same effect through broadcasting.
Plant no-till. With soybeans coming off so late, there's no time to waste on unnecessary tillage, Johnson says. Instead, follow the combine as closely as possible with the drill.
Plant red or white based on price outlook. Typically, red wheats out-yield whites by four bushels per acre. Reds also sprout less. "In my books, I have to get paid $10 a tonne more for soft white or I'm better off planting soft red." Johnson says growers should take a hard look at Fundulea as well.
Plant wheat. Some growers had fusarium in 1996 and dwarf bunt in 1997, and are simply turned off wheat. That's a mistake, Johnson says. He points to a farmer-run trial showing that when wheat is left in the rotation, corn yields are 21 bushels an acre higher, and soybean yields jump 5.5 bushels. With average prices, that's $120 per acre of pure profit.
Borers beat it in first year of Bt corn
By TOM BUTTON
Where have the corn borers gone? And when will they come back?Corn growers who paid an extra $5 per acre last spring to buy corn seed with the Bt gene are now thinking that Murphy's law applies to corn borers: the year you can finally hit back at corn borers is the year they disappear.
Throughout most of the province, borer populations are at a mere fraction of their levels over the past two years. Experts such as Zeneca agronomist Kent Schubert are seeing almost no difference between their test strips of Bt and conventional corn.
For a recent Middlesex county crop tour, Schubert headed into the field to find a plant that would show the growers what corn borer damage looks like. He came back empty handed. "I looked and looked and looked for a riddled plant," Schubert said. "You just can't find them.
"It isn't a very good year for companies trying to make their bread and butter from corn-borer tolerance."
While populations across the province are down, there are lots of hot spots, warns Cathy Soanes, product development specialist for Novartis Seeds. "We're suggesting growers look at their crops on a field-by-field basis," Soanes says. "Some of the fields I've been in are getting smoked."
Multi-year research suggests that a population of just one borer per plant can reduce yield by four to seven per cent, Soanes points out.
"This year could be even worse," she says. Borers weaken the stalks and ear shanks by tunnelling into the plant and exposing it to more stalk rots. With most growers facing the prospect of a late harvest, a single borer could result in a dropped ear, "zero yield from that plant".
Soanes recommends keeping an eye out for leaves that turn red because of the sugar changes brought on by the interruption of normal circulation inside the plant. Growers may also see broken off tassels and stalk damage.
Closer inspection will reveal the build-up of frass - borer excrement, to put it politely - in leaf axils.
This year's low pressures can be blamed on the backward spring, says Tracey Baute, researcher for the Corn Borer Action Coalition, a group of private and public scientists testing Bt technology across Ontario.
When the moths started to fly in June, corn crops were so small that they were still protected by dimboa, an insecticide manufactured by all corn seedlings. As a result, the moths laid their eggs on other hosts, including pepper crops.
The coalition's counts of moths caught in its pheromone traps shows a big drop from 1996. See Table One. And where the research team has gone into fields and cut open sample plants to measure the length of tunnels, the scientists are also finding the damage from each borer has been relatively small.
As well, through late August, probably because of the onset of cooler, wetter weather, researchers were finding few second-generation moths. Drought may also have curbed the number of moths.
Late August, fields where researchers would expect to catch 100 to 150 moths per week were only producing 30 to 60.
"We expected the population to be down this year," Baute says. "The reasons vary from one year to the next, but there always seems to be this cycle of heavy pressure one year and light pressure the next."
Fewer moths and fewer borers this year should mean there will be fewer larvae to overwinter and turn into egg-laying moths next year, reports Paul Hagerman, crops specialist for the provincial agriculture ministry in Middlesex.
Hagerman, however, warns against betting that the borers will be a non- issue in 1998. "The biggest factor, year after year, is whether the moths have good weather during the egg-laying period," he says. "If the nights are clear and calm, it doesn't take much of an overwintering population to produce a field full of borers."
Hagerman says growers must decide whether to pay the Bt premiums based on the results of long-term yield trials, as well as on their own long-term experience with the pest.
"You can't predict corn borer populations," Hagerman says. "It's as simple and frustrating as that."