ASK Jeff: The Rodale Institute’s farm manager, Jeff Moyer, answers your hardcore farming questions

Some questions on managing clay soils.

Posted July 13, 2006

What Jeff brings to the table

Jeff Moyer, who’s been the farm manager here at the 333-acre Rodale Institute research farm for more than a quarter of a century, receives lots of mail from farmers just like you asking for advice. Jeff’s hands-in-the-dirt experience over the past 26 years has run the gamut from refining the farm's cover cropping and crop rotation systems (including managing 270 acres in a rotation of corn, small grains, hay, and edible soy beans for a Japanese market) to overseeing The Rodale Institue Farming Systems Trial®, the world’s longest running side-by-side comparison of organic and conventional agriculture. We thought it would be fun and informative to share some of these farmer-to-farmer exchanges, and Jeff’s practical wisdom, with our readers … and we’ll be doing it on a regular basis.

Got a question of your own? Click here to send it to Jeff.

Dear Jeff,

I wanted to pick your brain on a matter related to management of heavy clay soil. We got an inch of rain the other night but from mid-May to mid-June there was zero moisture in our part of Ontario, Canada. Our clay soil showed signs of extreme drought stress, while loamier ground hung in there pretty well despite the lack of rain. I'm convinced the problem with the heavier clay is inadequate organic matter. We've taken good crops from this same ground when rainfall was adequate. One year with ample spring rains, I took the heaviest hay crop I've ever harvested in my life from this clay ground. A mixture of red clover/brome/perennial ryegrass produced just over 4 tons per acre from a single cut. The swath from the back of the windrower was actually thigh-high!

My point is that the soil is not compacted, and fertility is adequate. The only reason I can see for poor performance under drought conditions would be inadequate organic matter levels. I've been spreading composted sheep manure on this ground, but it obviously needs more. This year's grain crop (oat/barley mix) should come off early/mid-August. What are your thoughts for a cover crop that might help build organic matter? I'm thinking about either oilseed radish or buckwheat. I would welcome your thoughts regarding cover crop selection, and any other ideas for building organic matter levels.

Ian Campbell

Dear Ian,

Thanks for the email and the question on cover crop selection and organic matter. I believe you're on the right track with your analysis of the situation. It sounds like your fertility is high and the only thing holding you back is the soil’s ability to manage water. Compost is a great way to introduce organic matter and you're already adding that. You're left with cover crops to do the rest of the work, as you've already identified. Oilseed radish, buckwheat, hairy vetch, small grains (wheat, rye, oats) and any of the clovers (red, white, sweet, etc.) will all add organic matter to the soil and loosen it up. As the organic matter content of the soil improves both in quantity and quality, the soil will hold water and release it to the plants. Although you should see gradual improvement, building soil and improving soil quality can be a long-term process. Your clay soils may never be as rich or productive as your loamy soils, but over time they'll improve.

Look for various places within your crop rotation to add cover crops. Many times between the time you harvest one crop and get ready to plant another cash crop, there is room for a cover crop. You can get buckwheat in and out in about six weeks for example. Then look for places to build in legumes to fix nitrogen. And, finally, plant winter cover crops of any type, even small grains to protect the soil, store nutrients, and in the spring build organic matter.

Sometimes it's just helpful to know you're on the right track…you are.