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Posted: June 25, 2017 5:00 a.m.

Parson: Rain is not always a good thing

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When is more rain too much for the garden? Now would be a good example.

So many people think that rain is good for farmers, always. I know this because I hear comments about the weather like “all this rain must be good for the farm”. But the ideal amount of rain is about one inch per week.  

I talked to a local farmer this week who told me he was trading in his tractor for a boat. It’s been raining so hard that some of his blackberries have been knocked off the vines.

Anyone with a lawn knows how much it’s been raining by how badly their grass needs to be mowed. It turns out that summer grasses love the rain. Which brings me to my first point about the effects of too much rain on the farm: weeds.

Starting at the beginning, a weed is defined as a plant out of place. Similarly, soil is what your plants grow in and dirt is soil out of place. There isn’t much to do with weeds except kill them, and there aren’t many tools for the organic farmer to attack weeds except to cultivate them.

So if the organic farmer’s only remedy for weeds is cultivation, that means our only choice is to disturb the soil, cutting off the tops of some weeds and pulling others out of the ground entirely. Either way, that plant has to dry out and die before it can set root again and live. You can see now why all this rain makes conditions perfect for weeds. One, we can’t cultivate the soil when it is so wet-that’s bad for the soil. Two, if we did cultivate the weeds, they would just replant themselves in the wet soil rather than drying and dying.

Weed growth is obviously not a good thing for the garden. It’s well known that weeds compete with crops for sun, moisture, and nutrients. One thing you might not think about is weeds harboring pests and disease. During summer it is important to maintain air flow between crops. Our climate is humid enough, and crowded plantings don’t help. All that humidity makes the environment perfect for insects and disease.

Some people think that the rain causes disease, but plant pathologists think about it differently. If you learn about plant disease, the first thing you will be introduced to is the ‘disease triangle’. The disease triangle is formed by the three factors that lead to plant disease. The factors are: susceptible crop, presence of the disease, and conditions that are favorable to the disease.

Having a susceptible crop is a given. Pretty much all vegetables are susceptible to some disease and we are growing vegetables. Presence of the disease is a little more complicated. Some diseases are more or less present everywhere all the time, like damping off. Others will arrive in the area seasonally, like powdery mildew. The most common condition good for plant disease is warm and wet.

In addition to disease, plants can die from waterlogged soils. How does that work? Waterlogged soils cause plant death simply by suffocating the roots of the plant. We think of plants making Oxygen, but they also use oxygen. While the plant tops are exposed to air, the roots get their Oxygen from the soil.

Remember that the soil is only half solid-the rest is air, water, nutrients, and organisms. Oxygen diffuses in air 10 times faster than it does in water. When the soil fills with water, it takes much longer for Oxygen levels to be replenished. It does not take long for the plants and soil organisms to take up the available Oxygen and make the soil anoxic. When the plant roots can’t get the air they need, they don’t work very well. Wilting leaves is the first sign that waterlogging is a problem for the crop. By that time there isn’t much you can do but hope the soil dries out in time to bring air to the roots.

If you are hungry for summer crops like tomatoes, beans, peppers, eggplant, and okra, consider signing up for a summer CSA. Ours starts July 13 and can be purchased at our website, oxford.emory.edu/csasignup. We also sell at the Monroe Farmers’ Market in downtown Monroe every Saturday from 8:30am-12:30pm and at the Oxford Farmers’ Market next to the USPS on Thursdays from 3:00-6:00pm. Anyone who raises vegetables, eggs, plants, or meat in Newton or the surrounding counties can get a permit at Oxford City Hall to sell there. Come join us!

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