Do Corn Cobs Compost Well?

Nothing screams of summer louder than fresh sweet corn right off the stalk. Seeing trucks on the side of the road selling watermelon and corn brings up pleasant childhood memories. Not only is my head filled with recollections of the taste and excitement of eating corn, but also the fun ways we used the cobs and husks after our feast.

The entire corn plant can be safely composted and will break down just fine if all of the correct conditions are met. If corn cobs and other hard plant materials are going to break down small pieces of plant material, correct moisture levels, green leaves, and grass clippings will be needed to start the decomposition process. With all these steps necessary for the decomposition of corn husks and cobs, is it really worth it to throw this food waste into the compost pile?

Can You Compost Corn Cobs and Husks?

It is easy and recommended to add corn husks and cobs to your compost pile. The unique structure of corn pieces creates air pockets and retains moisture. Both are important for a compost’s decomposition process. The added moisture can help in garden soil and in compost piles making corn stalks, cobs, and husks great to compost. 

Composting corn cobs is not as easy as other kitchen and yard waste. The size and texture of the cobs can affect how quickly it breaks down in the compost heap. Raw cobs with corn kernels will take a long time to break down as the microbes have a hard time gripping the outside of each kernel. Increasing the moisture content can help soften the kitchen waste and speed up the composting process.

Too much moisture and an incorrect carbon-to-nitrogen ratio can cause serious problems when composting something difficult, like corn stalks and fresh corn husks. The space where corn cobs absorb water can develop a foul odor if heat or oxygen isn’t available. Turn the compost heap frequently and reduce the size of the corn cobs to make better garden soil faster. 

Getting finished compost that contains corn cobs, fresh corn husks, and corn stalks can take longer if other organic materials are unavailable. To make a rich organic fertilizer for your garden, green materials and nitrogen-based compost ingredients such as coffee grounds should be added to the compost heap.

Without the correct nitrogen levels and biodegradable materials, a batch of corn cobs would take more than one harvest season to be reduced to beyond recognizable pieces in a compost heap.  

How Long Until Corn Cob Breaks Down?

It can take anywhere from 1 to 3 months to over a year for corn stalks and cobs to decompose in a compost pile. Corn crops are high in carbon content and brown materials and can help round out a compost pile’s ratio. But without green husks and other nitrogen-rich materials, the average carbon content of corn is so high it would take over a year to break down where it lands in the field.

If we want to compost corn husks and make a complete compost for productive plants, the brown materials in corn cob compost must be cut into small pieces. The smaller the pieces, the faster they will decompose. Cutting raw corn cobs is difficult, so use a very sharp knife and extreme caution. 

Cooked corn cobs will break down during an average batch of compost without needing to be cut up. They add moisture to carbon-rich compost piles and can be mixed with fresh corn husks and other kitchen scraps. Adding other brown materials like wood chips and making the compost wet enough to activate microbes can break cooked cobs down faster.

Raw corn cobs should not be dried out but can instead be soaked to add more moisture and speed up decomposition. If your corn cob compost only has brown compost materials and no green compost ingredients, then you can use the wet raw corn cobs as mulch and add natural fertilizer to garden plants.

Active compost techniques like hot composting and constantly turning composting heaps can reduce the decomposition time of corn cobs to just a couple of months. 

Can Corn Cobs Help Gardens?

Corn Cobs

Corn cob mulch can offer gardening solutions where few other mulching methods would help much at all. The thick cobs can trap heat in the soil and promote early germination and retain moisture longer into the summer. In a cold compost pile, corn cobs and stalks might persist for several seasons inoculating all current compost material with hungry microbes year after year. 

Closed compost bins work best at breaking down cobs and composting corn plants without depleting moisture. To keep the compost healthy, make sure the compost pile rotation is regular and that the green compost ratio is reduced. Too much nitrogen in a closed compost bin can build up an unpleasant odor and stall microbe activity. 

Corn cobs can be used to add nutrients to the soil and build up the carbon needed for healthy soil structure. Corn parts that are not completely decomposed can help improve garden soil and increase the average compost yield. Corn kernels can also be used to keep birds and pests away from your garden and at the edge of your property instead.

Common Issues With Corn Cobs in Compost

The nature of corn stalks, cobs, and husks in the compost to decay slowly and sporadically can lead to soil issues. These issues range from mild odors to a build-up of harmful bacteria that could harm plant roots and good soil microbes. If the common problems with corn cobs in compost can be anticipated and avoided, then the resulting compost will be of a much higher quality and be ready sooner. 

Corn Cob IssuesSigns of ProblemsHow to Fix
Mold Build-UpFurry white growth on decaying corn cobsMix compost to increase aeration and increase the temperature to kill off fungus spores
Slow DecayLittle or no physical change of corn cobs in the compostIncrease moisture levels, nitrogen-rich organic materials, and temperature to increase microbe activities and speed up decomposition
Low in NutrientsOnly corn materials and brown waste in a cold compost pileIncrease the temperature and green materials available to fuel the decomposition process and release better nutrients to plants in the garden
Denser Compost IngredientLarge sections of the compost heap are stuck together with corn cobs and plant materials that won’t break downAdd small amounts of brown material like corn husks into the compost at a time. Add plenty of moisture and turn the compost every 2 days
Inconsistent BreakdownSome corn materials are gone, and others are still intact even though they were composted at the same timeSift compost piles and sort materials by similar stages of decay. After a few attempts, compost conditions should be balanced and even throughout future heaps

Mold Build-Up

Too much moisture, nitrogen-rich materials, and not enough airflow can lead to fungus in a compost pile. While certain types of mycelium are helpful for gardens, the white mold common to corn cobs is not desirable. While not entirely harmful, it is a good indicator that the compost conditions are out of whack, and other issues could occur shortly. 

One of the main problems with mold build-up is that the fungus feeds off of the nitrogen that plants will need. The more mold that grows on your compost pile, the fewer nutrients will be available to your garden’s plants. Since the entire point of compost is to enrich our garden soil, losing nutrients to mold is not ideal. 

Adding more brown materials can help to balance the compost and absorb the excess moisture. Rotating or turning the compost can increase airflow and reduce the humidity fungus needs to thrive. Repeat these steps until all the mold has dried up and disappeared. 

Slow Decay

Corn Cobs Decaying

Sometimes it appears as if the corn cob is not breaking down at all. This slow decay can leave you puzzled and a bit frustrated. It is important to build a proper compost pile in order to break down woody and thick materials like corn cobs. Adding more fresh corn husks and other green materials can speed up the decomposition of large corn pieces. 

Increasing the moisture content and using a closed compost bin to raise the temperatures can jump-start microbial activity. Once the bacteria in the soil have multiplied enough to break down the corn cob, start turning the pile to prevent stagnation. Keep adding water and turning the compost until all the material has broken down. 

Low In Nutrients

Since corn plants are predominantly carbon-rich, there will be little to no nitrogen available for plants to use. Without adding other kitchen and yard waste, a corn cob compost would not have what a growing plant needs. Coffee grounds and other high-nitrogen food items are great additions to corn compost. 

Denser Compost Ingredients

The denser compost ingredients can hold a lot of moisture and become hard to mix in and move through the compost pile. As the dense materials build pockets around them, they can either break down quickly or rot and stink. Surrounding dense compost ingredients like corn cobs with the correct organic materials can help reduce issues from denser materials. 

Grass clippings are an excellent source of nitrogen and break down quickly. The rapid fuel source of freshly cut grass adds to bacteria growth and can help stubborn cobs get eaten faster. The more activity and heat around dense ingredients the more microbe will come to chow down on them. 

Inconsistent Breakdown

New compost piles that are processing corn stalks, cobs, and husks for the first time can have trouble breaking down all the materials evenly. A well-made compost pile will take all the materials through all the stages of decay and leave a gardener with rich humus-dominant compost. All of the materials that were put into the compost pile originally will have broken down simultaneously, and the uniform compost can be added anywhere it is needed in the lawn or garden. 

The first time you build a compost pile, the microbes may not be at the number needed to break down corn cobs as fast as the other organic materials. If there are still large chunks of cob left after the composting season, place those in the new season’s compost materials. Over time everything will break down uniformly as the microbe population explodes and your experience with composting with these ingredients grows.