Rainfall key to malt barley
January 2008(w), Mid-Winter Issue, page 10.
December 18, 2007 By Helen McMenamin
Barley usually is not the most difficult of crops to grow well, but growing it to make
malt takes luck as well as skill. “Some things you need for malt are beyond yourcontrol,” says Alberta Agriculture soil fertility researcher, Ross McKenzie at Lethbridge. “All you can do is optimize conditions for malt by seeding early, using the right seeding rate and making an educated estimate on the amount of nitrogen fertilizer. After that, just hope for a good growing season.”
McKenzie and Grant Jackson, agronomy professor at Montana State University, have tested fertility and agronomy programs for malt barley across northern Montana and Alberta. First, they say, choose a field that has not had barley on it for a couple of years to lower disease risk. Avoid fields with low spots if possible, those areas may mature later, so the crop may be cut at higher moisture and add thin kernels into your sample.
There is no stand-out variety, according to McKenzie. “Two row types are better for malt because they have more potential to produce plump kernels,” he says. “But, the differences we found among varieties were very small and inconsistent.
“Seeding date made the biggest difference in our trials. In the south, we saw as much as 25 percent higher yields when we seeded in late April compared to seeding in mid May. The benefits of early seeding were even more obvious when the growing season was dry. The yield increase spreads the plant protein through more material, raising the chances of keeping grain protein below that critical 12.5 or 13 percent.”
McKenzie prefers to see malt barley seeded before canola. Barley can stand frost better than canola because its growing point is below ground level. A minus four degree C frost can mean reseeding canola because its growing point is above the ground.
“Seed size varies even from one lot to another, so take a few minutes to get the rate right,” advises Jackson. “Aim for plant populations of 15 plants per square foot, up to 25 where moisture conditions are excellent. Too high a plant population, or too many tillers, results in more heads than the plants can fill and kernel plumpness suffers.”
Fertility program influences yield and protein
The amount of fertilizer that gives the best chance of meeting malt standards depends on the moisture available and soil nutrient levels. Jackson’s advice is fairly simple: a little more than a pound of N per acre (from soil and fertilizer) for every bushel estimated that can be harvested without the crop lodging. If you have had trouble with too much protein for malt, he suggests cutting N rates by 20 pounds.
Trials of more than 50 site years from northern Montana to central Alberta showed yield potential of the site, mainly due to moisture, is the key to N needs. Where yield potential was over 70 bushels, 1.2 pounds N per bushel gave the best yields within malt standards. At sites yielding less than 70 bushels, N had to be as low as 0.7 pounds per bushel to keep grain protein below 13 percent. At some of these sites, even 50 pounds N per acre produced too few plump kernels to make malt.
Sulphur either depressed or did not affect yields of malt barley, but responses to phosphate (P) and potassium (K) varied. Only four sites showed a response to P and 13 pounds per acre was adequate, McKenzie attributes this to weather that was warmer and drier than normal in July and August. He does not advise skimping on starter P.
Even though soil K levels were above 100 pounds per acre, three sites showed small yield increases in response to K. The chloride in potash likely gave that benefit.
Jackson advises applying some potash, even though soil tests do not show a need for it. “I didn’t believe we needed potash,” says Jackson. “The soil tests don’t show a need and we’d never seen any advantage to it. But, when I grouped all our trial results from many years, the benefit was plain and I had to change my mind. I think most of the benefit comes from the chloride. It seems to help reduce disease impact as well as delaying maturity and increasing straw strength. It can also reduce the amount of physiological leaf spot.”
Jackson says that over the years, he has seen an average increase of five bushels an acre, more in some varieties, less in others. Because soil tests for chloride are not very accurate, he recommends 20 or 30 pounds of potash, slightly more under irrigation. “It’s not a costly product, so we just use it like seed treatment – as cheap insurance,” he explains.
McKenzie suggests choosing any good two row variety, seeding early and targetting N fertilizer to your potential yield is the best strategy for malt barley.
“Whether you’re in an area that is usually dry or generally has good moisture, producing premium malt barley depends on avoiding any moisture stress on the crop,” he says. “Keeping protein low is easier in high moisture areas, but having mainly plump kernels is outside your control. You need good moisture in July and August to fill out the kernels. The only sure way to produce good yields of premium malt barley is under irrigation, where you can ensure adequate moisture throughout the growing season.”