Fifth generation farmer John Berden, Michigan, uses cover crops for fertilizer in his farm fields and his family vegetable garden. John produces dry beans, soybeans, wheat, oats, and organically certified cover crop seeds on his 500-acre farm without using any commercial fertilizer supplements.
In his home garden, John also depends on cover crops to build soil fertility. He uses a three-year rotation program, planting a cover crop the first year to build fertility, followed by a “light-feeding” vegetable crop, like peas or beans, in the second year and a :heavy-feeding” crop, like corn or tomatoes, in the third year.
“The microbes in the soil thrive on the habitat created by cover crops,” John explains. “When the cover crops are cut and tilled under, the microbes greatly increase in numbers and feed themselves on the plant residues.” In turn, the microbes generate nutrients in forms that plant roots can absorb.
Ingredients and supplies
2 pounds per 100 square feet cover crop seed (soybean, oat, and medium red clover seed)
Rotary tiller or digging fork
1. In the spring, sow 1/3 of your vegetable garden with cover crop seed, spreading the seed lightly by hand and raking it in after planting. John recommends combining 2 or even all 3 kinds of cover crops in the same planting.
2. Water the seeded plot well.
3. When the seed has germinated and the cover crop plants are 10 to 12 inches tall, till the plants into the soil. You can also cut the plants to the ground and dig them in by hand, but be forewarned – digging in a cover crop by hand can be a tough job! You may want to rent or borrow a tiller instead.
4. At the end of August or in September, reseed the plot with more cover crops as before. John says that, for the second seeding, a combination of oats and red clover is best.
5. Allow this crop to remain in place through the fall and winter. The crop will be killed by frost, but leave the dead plants in place to protect the soil from erosion during the winter.
6. The following spring, till the cover crop under. Allow 2 or 3 weeks for the crop residues to break down, and the plot will be ready to plant. You may want to work the soil lightly again just before planting.
7. Sow seeds or plant transplants of light-feeding vegetable crops
8. Tend and harvest the crops.
9. The following spring, sow seeds or plant transplants of heavy-feeding vegetable crops.
10. Tend and harvest the crops. The following spring, it’s time to start again with a year of soil-building cover crops.