According to The Agriculture Research Service, narrow spacing has many advantages for sweet corn and other corns, such as increased crop yields, less plant in-row crowding and increased soil shading. Traditionally, rows of corn plants were spaced 16 to 38 inches apart, but with the advancements in technology, fertilizers and better quality hybrids, distance between rows has narrowed down to 15 to 20 inches. However, there are also a few disadvantages associated with narrow spacing.
Reduced Weed Competition
According to The Iowa State University's Agronomy Extension, narrow spacing reduces competition from weeds for nutrients, water and light due to increased light interception per individual plant. The University of Connecticut conducted three studies to compare the effects of two row spacings (15 inches and 30 inches) on weed control. The number of weeds in total were reduced when rows of corn were planted 15 inches apart. Planting corn in narrow spaces reduces the amount of light that reaches the ground, resulting in the presence of fewer competitive weeds. Lesser spacing allows an individual plant's canopy to spread over the ground quicker, reducing the amount of herbicides needed. Studies in Maryland show that narrowing row spacing from the traditional 30 inches to 15 inches reduces the amount of herbicides used by as much as 75 percent.
When spacing between rows is reduced, farmers can grow more corn plants in the particular area, thus increasing plant population that results in increased crop productivity. Agriculture Research Service soil scientists Curtis Reule and Ardell Halvorson (Soil-Plant-Nutrient Laboratory, Colorado) observed an increase in corn production by 20 percent in the first year of providing narrow spacing. Research in Michigan and Minnesota indicate an advantage of 7 to 10 percent for corn plants grown in rows spaced 15 to 20 inches apart, as opposed to those spaced 30 inches from one another. However, some researchers mention the reduction in the quality of the corn with increased plant density and reduced spacing. Iowa State University's Agronomy Extension also mentions that increased crop yield is more likely to occur in northern states due to their shorter growing seasons.
Sharing Planting Equipment
Narrow row spacing also means farmers can share planting equipment between corn and soybean. Soybeans are planted in rows narrower than traditional corn crop. This consolidates equipment, reducing labor, time and effort on part of the farmers that rotate crops yearly to plant corn first, and then soybean. A farmer can use his 22-inch soybean spacing when planting corn.
Increased Equipment Costs
Despite the advantages, the drawbacks to planting corn crops in narrow rows includes increased equipment costs for the farmer. Most farmers need to modify existing farming equipment, such as replacing tires and rims for combines and tractors to allow for the narrow spacing. The minimum row-width for combine heads is 22 inches; combine heads in row widths narrower than 20 inches require a lot of market research.