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“Aren’t they supposed to be green?”

Corn in the field that is ready for harvest

Fall is an incredibly busy time for farmers. Many will harvest hundreds of acres of soybeans and corn in the fall months. As of today, soybean harvest is well on its way in parts of southern and southwestern Ontario, while the corn is busy soaking in the last of the summer heat. Earlier this month, farmers were busy preparing for harvest: washing and maintaining their combines and tractors and anxiously watching their crops. Like trees and shrubs do in the fall, soybeans and corn both undergo a dramatic physical transformation at this time of year.

Soybean plants change colour in the fall months: their leaves turn from green to yellow before they eventually fall off once the plant reaches full maturity. Full maturity is the last growth stage in soybeans development – the soybean pods have fully developed seeds, and the plant is beginning to dry down. Corn is similar: the kernels will harden, and the rest of the plant will dry out once it is fully grown (usually in mid-October). Corn also turns brown and yellow.

Soybeans and corn need to be dry in order to be harvested. Once they have reached full maturity, the plants begin to dry down and no longer accept nutrients in preparation for winter. Like all other plants (grass, trees, flowers), soybeans and corn begin to prepare themselves for winter once the temperature begins to drop. Farmers want their grains to be dry for harvest, as that means the seeds are fully grown with all the necessary nutrients inside. This is why we wait for grains to turn yellow or brown before we harvest them.