Farmers have long understood weather. As they have grown and raised fruits, vegetables, flowers and animals over millennia, they’ve had to cope with unusual weather events, too much rain or too little, overly hot or overly cold.

Now, they must learn to understand and handle the changing climate, Glen Koehler told a crowded lecture hall at the Agricultural Trades Show in Augusta earlier this month. Koehler, a fruit-tree specialist with the University of Maine Cooperative Extension who also studies climate, spoke on “Farmer Adaptation to Changing Weather.” The first half of the talk, he used charts, maps and statistics to prove that, yes, the climate is changing.

Here is how:

The average temperature had stayed about the same – changing less than 1 degree centigrade – since the last Ice Age, about 12,000 years ago. That is, until the last 30 years, when it has risen 1 degree centigrade. Climate scientists expect it to go up another degree by 2047.

The rise in average temperature does not mean cold spells will disappear. Case in point: temperatures in Maine in late December and early January. As the polar ice cap melts, the jet stream is increasingly wavy, rather than straight, and those waves bring the cold air southward, Koehler explained.

For the Maine audience attending the talk, the Maine statistics probably hit home harder.

The average temperature in Maine has risen 3 degrees Fahrenheit since 1895, more than most of the rest of the country. A different study, covering just the years between 1980 and 2010, corroborates that the average temperature has risen – it has gone up about 3 degrees in winter but almost nothing in the summer. The average rise in temperature is mostly attributable to the rise in daily lows, not daily highs.

Perhaps more striking is the change in the growing season, which is measured from the average last frost in spring to the first frost in fall. That period has increased by 11 days since 1895 and is expected to rise another 10 to 17 days by 2045 – not bad news for the vegetable garden, at least in some respects. You’ll have more time to grow vegetables, which is nice. Unfortunately, many pests will thrive on a warming globe.

In addition to being warmer in Maine, it has also been wetter, and the weather has been more extreme. The average annual rainfall has risen 6 inches since 1895, and the number of rainfalls of 2 inches or more has risen 71 percent from 1958 to 2011. Yet despite higher than average rainfall, every Maine gardener and farmer knows that the state has suffered periods of drought over the past two summers; in other words, sometimes we get a lot of rain all at once, and then we get no rain at all.

To adapt, both farmers and home gardeners will have to more faithfully follow what are already recognized as good farming practices. First and foremost, both groups should add more organic matter to the soil. “Organic matter holds onto moisture,” Koehler explained.

Irrigation will be important, too. Koehler told the farmers that improving their irrigation systems, as well as improving their farm ponds, would likely be money well spent. Home gardeners may need to accumulate rain barrels and install drip irrigation rather than just hauling out hoses. In addition, they should monitor their soil so they can irrigate when it is necessary, not simply according to a prearranged schedule.

With the increase in severe rainstorms, farmers will have to develop plans to prevent the topsoil from running off. “Use more no-till methods,” Koehler suggested. “Plant cover crops and companion plants.” In addition, berms can slow down the water in the garden and ditches at the side of the fields can direct water to flow away without taking the soil with it.

Because heavy rains will wash away fertilizer as well as soil, people should lightly side-dress their crops throughout the season rather than heavily fertilizing once in the spring, Koehler said.

WHICH BRINGS US TO DISEASE

Climate isn’t the only problem facing Maine growers. In another talk I attended at the Ag Show, Alicyn Smart, a plant pathologist hired last summer for the University of Maine Cooperative Extension in Orono, listed the most common diseases sent to her lab last year.

Here are some of her tips to prevent disease in your backyard or farm field:

Always plant the most disease-resistant varieties of any crop. “It’s the easiest thing you can do,” she said.

Sterilize any pots and trays you use with 10 percent bleach solution, and not just any bleach. “It has been scientifically proven that Clorox kills pathogens better than any knock-off brand,” she said.

Also, get a soil test and don’t over-fertilize. If plant roots grow too fast, they don’t have a chance to create a protective layer and are more susceptible to diseases.

Smart urged farmers and home gardeners to send her samples of any diseased plants. Not only can she provide solutions, it will help her keep track of the plant diseases hitting the state.

Eric Sideman, organic crop specialist of the Maine Organic Farmers and Gardeners Association, was in the audience. He piped up to advise people to sign up for the pest report he sends out during the summer.

With all that advice, I’m ready for the gardening season – even though it’s still deep winter.

TOM ATWELL is a freelance writer gardening in Cape Elizabeth. He can be contacted at 767-2297 or at: tomatwell@me.com.