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Cover crops offer organic solutions

Dan Gillespie, Hudson, S.D., was one of seven farmers who received South Dakota’s Soil Conservation Award in 2010. One reason he was recognized was for his use of cover crops to help control weeds, improve soil health and produce plant nutrients.

Gillespie’s farm is certified organic. He follows a three-year rotation — corn, followed by oats, followed by soybeans.

He interseeds yellow blossom sweet clover and mammoth red clover with the oats. The oats emerge first in the spring and dominate the field, but when Gillespie harvests the oats, the clovers begin growing through the oat stubble.

Key Points

South Dakota organic farmer finds weed, fertility solutions.

Corn and beans yield 125 and 30 bushels per acre respectively.

Organic buyers pay about twice what the conventional market pays.


The clovers go dormant in the winter, but begin growing vigorously the following spring. In mid to late May, Gillespie plows down the clover, which can be from 1 to 3 feet tall. He then spreads calphos (soft rock phosphate) and pelleted chicken manure on the field. After working in the calphos and pellets, he plants soybeans

“The clover serves as a green manure. In combination with the chicken manure, it greatly improves soil fertility,” Gillespie says.

The cover crops and the late May tillage also help control weeds. He also uses a drag harrow and rotary hoe to kill weeds.

Pelletized power

The pelletized chicken manure comes from Michaels Foods, Wakefield, Neb. The formulation is 4-3-2, 11% Ca. It also contains many other trace minerals, which helps re-mineralize the soil, Gillespie says.

Due to the high heat used in the pelletizing process, the manure has no biological activity. The pellets break down fairly quickly, creating organic acids in the process. The acids interact with the soft rock phosphate and limestone, making both calcium and phosphorus readily available to a crop.

“Since phosphorus is lacking in most soils, I’m trying to use chicken manure to solve that issue on my farm,” Gillespie says. “In researching the benefits of adding phosphorus to soil, I’ve learned it reduces ammonia nitrogen loss in manure. I’m keeping a journal of all my observations about crop and soil quality to help evaluate the effectiveness of what I’m doing.”

Gillespie pays about $25 per acre for organic red clover, sweet clover and alfalfa seed. The chicken manure costs about $115 per ton, or $60 per acre. His corn yields about 125 bushels per acre and soybeans, 30 bushels per acre. He usually receives about twice the conventional prices for his organic grain.

Gillespie is a member of the Northern Plains Sustainable Agriculture Society and eagerly shares what he learns with other farmers.

“I also work with the soil testing lab at South Dakota State University and with my local conservation district and soil consultant to exchange information. I want to be able to document nutrient improvements in my soil and the result on crop yield and quality. I also need to measure my overall profitability,” he says.

Sorensen writes from Yankton, S.D.

This article published in the January, 2012 edition of DAKOTA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.