Are compost and fertilizer the same?

Compost and fertilizer are not the same. But compost does have fertilizer value.

Wikipedia describes fertilizer as any material of natural or synthetic origin that is applied to soil or to plant tissues to supply one or more plant nutrients essential to the growth of plants.”

Compost’s nitrogen, phosphorus, and/or potassium (a.k.a. NPK) values are low compared to a synthetic fertilizer.  Some may add ingredients like urea to hike these macronutrient numbers.

That said, compost’s NPK value does have dollar value. The nutrients delivered by a compost product should be a factor in any input decisions involving synthetic fertilizer purchases.  Compost also adds a slew of micronutrients not typically found in common synthetics and improves nutrient uptake.

Compost feeds the soil. In turn, the soil takes care of the plants, offering a smorgasbord of nutrients, pest and disease resistance, and more.   But those nutrients are slow-release, feeding plants over time.  The benefits of a single compost application can stretch over multiple seasons.

Fertilizer’s sole purpose is feeding plants.  The primary function of most synthetic fertilizers is adding N, P, and/or K.  Application gives an immediate burst of nutrition.

Do you need fertilizer if you use compost?

For the home gardener, probably not, especially if that gardener is a long time compost user.

But for a commercial grower?  Maybe.  If the crop likes a punch of nitrogen (for example) at a certain point in the growth cycle, the addition of a synthetic fertilizer may be warranted.

However, the smart grower will carefully weigh the cost of any input against the expected return on investment. Sometimes, a lower yield will still net higher profits if input costs for synthetic fertilizers and pest control products are reduced or eliminated as a crop management expense.

Also, keep in mind that compost-amended soil reduces rainwater and irrigation runoff, which means more nutrients are retained in the soil.   This will impact synthetic fertilizer input requirement, as well.

Jared Burch, Burch Farms

Jared Burch, 4th generation farmer

Burch Farms in Sampson County has been using McGill AG compost for many years.  I met fourth-generation grower, Jared Burch, in one of their fields late last summer as he prepared to plow sweet potatoes.

A graduate of North Carolina State University, 25-year-old Jared farms about 6,000 acres with his father, uncles and cousins. He is well aware of the need to keep the soil enriched to produce crops and spoke of the importance of returning organic matter back into the sandy soil where they farm.

The Burch family incorporates about 15 cubic yards of compost per acre prior to planting. Burch Farms is known for their sweet potatoes, peppers, greens and other produce. Over the years, Ted Burch, Jared’s uncle, has seen money savings from purchasing less fertilizer and better moisture-holding capacity in irrigated fields during the hot summer months.

CONTRIBUTOR:  Ruth King, McGill-Delway compost sales

“Excellent crop response,”  says Britt Riddle of Riddle Farms in St. Pauls, NC.  “The compost seems to last longer with less leaching than commercial-grade fertilizer.”

A conventional grower, Britt tested fertilizer and compost side-by-side on corn.   His May 2010 test plot pix (right) shows commercial fertilizer left of the ditch and McGillAG compost on the right.

Excellent crop response with reduced input

Britt’s “excellent crop response” is not restricted to corn.  Farmers growing everything from greens to melons have reported good results when using compost alone or in conjunction with reduced commercial fertilizers.  Other input, like pesticides and even irrigation, can be reduced, as well.

For more information about compost’s impact on crop performance, visit our compost sales website at

NOTE:  Some content has been updated since the original post.