Sept/Nov 2002 Tips

Fall-Sown Green Manure Mulches Potatoes in Spring

Dr. Ron Morse of Virginia Tech has developed a system for growing no-till organic potatoes. In September, he makes raised beds, adds lime, phosphorus and potassium as needed, and sows winter rye. In late April, he uses a subsurface tiller-transplanter to work the soil about 8 inches deep, apply organic starter fertilizer (5-5-3) 6 to 7 inches deep, set potatoes 4 to 5 inches deep in a 3- to 4-inch-wide slot in the top of the bed, and lay drip irrigation. In mid-May, when the potatoes begin to emerge, he flail-mows the rye, leaving a heavy mulch of 5 tons dry matter per acre, which suppresses most weeds until eight weeks after planting and eliminates the need for hilling. Yields in this system have averaged 17% higher than in conventional tillage. The raised beds are necessary to avoid excessive moisture at ground level. [Ed. note: I have planted potatoes in the home garden in a similar way, by digging a furrow with a spade in May through late-summer-sown hairy vetch; planting seed potatoes in the furrow; letting the remaining vetch grow until the potatoes are ready for their first hilling, then pulling the vetch by hand, hilling the potatoes, and using the vetch as mulch.]

Morse notes, incidentally, that Yukon Gold potatoes should be planted 7 to 9 inches apart within rows to avoid hollow heart, a brown cavity in the center of the potato. Also, for any variety, whole, small seed potatoes give better stands than cut pieces, which tend to decay. Also, adding gypsum (calcium sulfate) can add calcium to the soil when needed without raising the pH of the soil.

Source: "Appalachian Harvest Organic Production Workshop--Growers Making the Transition to Organic," The Virginia Biological Farmer, Second Quarter, 2001.