Organic Corn – Soybean – Wheat/cover crop: This system is managed according to the USDA’s National Organic Program Standards. Fertility is derived from biologically fixed N, composted poultry manure, and potassium sulfate. Weed control is achieved via mechanical means as well as by using cover crops. High yielding organically certified corn hybrids and organically certified soybean and wheat varieties are planted. Following wheat harvest, a berseem clover and oats cover crop is planted to help preserve soil and nutrients.