Knee High by the Fourth of July

There are several types of corn: sweet, pop, flour, silage, or grain. Each have been historically bred, selected, and adapted for different uses. In Pennsylvania, most of the corn fields you see are silage or grain corn used to feed livestock. Over the course of this past week, you may have heard the phrase “knee high by the fourth of July” in conversation, but what does it mean and why wouldn’t corn reach knee height?

“Knee high by the fourth of July” is an old adage that has served as a benchmark for a good yield of corn at harvest time. With new varieties allowing farmers to plant earlier, most corn crops surpass knee height by Independence Day, but there are cases when the corn doesn’t reach the desired height. Here are a few reasons why: 

Low pH: Corn growth can be stunted when the soil pH is too low, since soil pH plays a critical role in the availability of nutrients. Aluminum and Manganese particularly become more available at low pH levels, and can reach toxic concentrations that could suppress growth or kill the plants. Low soil pH also decreases the available of key nutrients the plants need like nitrogen and phosphorus. To adjust the pH, farmers would need to apply lime in the fall, in hopes of a better harvest for next year. The ideal soil pH for corn is between 6 and 7.

Shallow planting depth: Corn should be planted about 1.5 inches deep. Corn planted at a depth one inch or less, could have poor root development. Once and if the plants germinate, the shallow roots, being so close to the soil surface, are likely to dry out faster during hot, dry weather; whereas, kernels planted at the proper depth will have roots that can access deeper soil moisture.

Weather: This spring brought heavy rain and cool conditions. Heavy rain can ruin soil structure, by compacting the soil, eliminating pore space for water infiltration, and creating a soil surface that is sealed and crusted. The crusted, compacted soil prevents water from soaking through to the plants roots, creating a difficult environment for plants to survive. Increasing organic matter, crop rotations, manure applications, and reduced tillage could help improve soil structure for future plantings.

Sources: http://extension.psu.edu/plants/crops/grains/corn

Support Your Farmer:

LEHIGH VALLEY: Newhard Farms is a 5th generation grain and vegetable farm located in North Whitehall Township, Lehigh County. Don Newhard and his son Joel are currently farming over 2500 acres of crops, which include corn, wheat, soybeans and sweet corn. In the summer, their primary focus is growing and selling their premium quality sweet corn. Most of the sweet corn they grow is sold at The Corn Shed, which is located on their farm in Ruchsville.

BERKS: Fisher’s Farm Fresh Produce is located in Oley. The Fisher family has been farming in the Oley Valley for over 200 years and a sizeable portion of the family's 150+ acre farm is now devoted to growing sweet corn. Fisher's Farm Fresh Produce also offers an array of fresh vegetables for sale.

BUCKS: Eastburn Farm is a family operated farm located in Pineville. They sell delicious white sweet corn starting in mid-July through September, as well as tomatoes through the summer season. They also sell pumpkins, ornamental squash, and gourds in the fall.