A major factor to how many ears of corn a stalk will produce per plant is the spacing between plants. Field corn will typically have very tight spacing and only one ear per plant whereas if you plant corn in your garden with plenty of space it may produce 2-4 ears per stalk. Tighter spacing leads to less ears per plant but may lead to an overall larger corn yield.
Varieties of corn used to grow baby corn will grow 6-8 ears. The Guinness World Record for most corn cobs on a single plant is 16 set by a farmers grandson in Iowa. This may have been beaten recently by a man in New Jersey who ended up with a corn plant in his yard that he thinks has 28 cobs on one plant. He did not plant the corn plant it was brought along by the local wildlife and took root in his front yard.
Higher spacing gives a corn plant more sunlight, water, and nutrients that it can turn into multiple ears of corn. Corn on the edges of fields or areas in the field where germination was poor and plants have plenty of space commonly have multiple ears per plant because of the increased sunlight and access to water and nutrients. The primary nutrient the corn plant needs is nitrogen.
About 95% of corn grown in the US is field corn used for livestock feed, ethanol, or processed foods. Sweet corn is most likely not the corn you see in farmers fields.
Farmers today typically use corn varieties that have been bred to do well in tight spaces. The corns goal is to reproduce. It does what it can to produce as many viable seeds as possible. Every kernel is a seed. By putting its limited energy and resources into one or two ears it produces the most viable kernels that it can.
One of the first studies on plant density was done in the 1950’s by a farmer named Forest Troyer. He grew a field of corn with a very high density population. Some of the corn didn’t produce anything but the ones that did had genes that were more tolerant to tight spacing.
Some farmers will grow a field of corn for silage, green fodder like biomass for animal feed. In these fields they will plant the corn very close together because they are not interested in the corn producing ears or kernels. They want green biomass. In these fields the corn plants typically won’t produce an ear at all. The environmental conditions prevent it. Spaced so tight together they simply don’t have enough sunlight, nutrients, and/or water.
For gardeners early maturing varieties of sweet corn will typically have one ear and later maturing varieties that have a longer growing season will produce two usable ears per stalk.
Average Corn Yield Per Acre
A typical corn field has about 32,000 corn plants per acre and yields around 175 bushels per acre. This map of the US shows the average corn yield by bushel per acre in each state.
David Hula, a Virginia farmer, set the record for most bushels per acre and won the 2019 National Corn Yield Contest with just over 616 bushels per acre. It’s the fourth time David Hula has set the world record and the fifth time since 2012 he’s won the 2019 National Corn Yield Contest.
He uses a hybrid variety known as Pioneer P1197 corn, planted at a high rate, for his record corn. On all of his fields together he plants 20 different varieties and suggests other farmers do the same to mitigate risks. For his contest fields he plants between 38,000 and 54,000 seeds per acre. A typical farmers field is around 30,000 corn plants per acre. On contest fields he slows down the planter to 3 to 4 mph and other fields runs it at 5.5-6 mph. Here’s the full article if you want to learn more about his process.
A paper from Purdue Agriculture titled Historical Corn Grain Yields in the US gives the history of corn yields. 1866 was the first year the USDA published average corn yields. From 1866 to the late 1930’s corn yields remained stagnant. In the late 1930’s hybrid corn production was adopted and farmers started to grow corn from seed of two specific varieties. This led to corn yield increases of 0.8 bushels per acre from 1937 to 1955.
In the mid 1950’s increased advances in hybrids and increased adoption of fertilizer, pesticides, and farming equipment led to increased yields of 1.9 bushels per acre. This is still the current rate of yield increases per year. The article linked above goes on to say that GMO may be the next boom of increase but it has not been that yet. Also it states as human population increases a third boom of corn crop yields becomes more important.
Cost Per Acre To Grow Corn
On average it costed $861 per acre to grow corn in Illinois in 2018. In 2019 and 2020 Iowa production costs were estimated at $711 and $689 per acre.
Here’s a breakdown of the costs.
- Variable Costs – Fertilizer, pesticides, seed, drying, repairs, fuel, hiring
- Fixed Non-Land Costs – Labor, buildings, storage, machinery depreciation, non-land interest, overhead
- Land Costs
What Do Farmers Do With Corn Stalks After Harvest?
Corn left in the field after harvest is called corn stover. Left in the field the corn stalks break down and become organic material in the soil, enriching the soil with nutrients. By leaving it in the field and rooted it also prevents soil erosion of quality topsoil.
Grazing cattle on the residue corn stalks is also done. This extends feed for cattle, cuts down the tall stalks, and manure from the cattle fertilizes the field. Some farmers will also harvest the corn stalks and deliver them elsewhere for use as fodder, livestock feed, or bale the stalks and use or sell the bales for livestock bedding.
Some farmers will chop the corn down to 12-18 inches to prevent it being in the machines way next spring and also to speed up its decomposition sending part of the stalks to the ground. Equipment manufacturers have made planters with increased ability to handle heavy corn residue. This has lead to less tillage of the land. Tillage is like plowing or tearing the soil up.
Burning Corn Stalks
Burning stalks is sometimes done by farmers who find it an easier method of dealing with corn field residue and wanting to plant a fall crop. This is not commonly done and farmers doing this are depriving the soil of organic material and the nutrients from it.
Burning the corn stalks will remove almost all nitrogen from the corn residue and about 75% of sulfur. Phosphorous and potash will be lost through smoke and ash. Taking the extra steps to take care of corn residue properly will pay dividends in soil health.
This farmer engineered a crop drying furnace that runs on corn stalks. Now this is a method that makes sense for farmers! They should consider still leaving around 25% of corn in place to provide some organic material and prevent soil erosion.