Carver developed techniques to improve soils depleted by repeated plantings of cotton. Together with other agricultural experts, he urged farmers to restore nitrogen to their soils by practicing systematic crop rotation: alternating cotton crops with plantings of sweet potatoes or legumes (such as peanuts, soybeans and cowpeas). These crops both restored nitrogen to the soil and were good for human consumption. Following the crop rotation practice resulted in improved cotton yields and gave farmers alternative cash crops. To train farmers to successfully rotate and cultivate the new crops, Carver developed an agricultural extension program for Alabama that was similar to the one at Iowa State. To encourage better nutrition in the South, he widely distributed recipes using the alternative crops.