How to Increase Organic Matter in Soil

Soil organic matter is a dynamic soil property and continuous work is required to maintain or increase its value. The ultimate source of almost all organic matter in soil is plant material.

Plants create energy through photosynthesis. The energy can then be used by the life forms in the soil. Historically, more attention is given to the soil organisms that harm our crops and the purpose was to control them. Now we have come to the realization that the vast majority of life in soil performs an important role that helps soil maintain or improve its productivity.

The question becomes how to feed the various forms of soil life. Following are some principles and practices that can help sustain soil life and increase organic matter content.

Plant Cover Crops

Cover crops provide continuous living vegetation in the field. Plant roots have their own particular effects on soil quality. Fibrous, fine root systems stimulate soil aggregation. Taproots help subsequent crop's roots explore subsoil and stimulate water infiltration and aeration of subsoil. Living plants in the soil at all times protect leachable nutrients against loss to the groundwater. In addition, many soil microbes live in the 'twilight zone' between root and soil (the rhizosphere) where they 'graze' on the root surface. They eat root exudates, secretions and decomposing root cells.

There is now research to suggest that the root systems of plants contribute twice as much organic material to the soil during the growing season as what remains in the root system at the end of the growing season. All this organic matter feeds life in the soil.

Eliminate Tillage

It is now firmly established that no-till can work on all soils in Pennsylvania, considering there are farmers who are successful with the practice in all regions of our state. Tillage is like stoking the fire; it burns up organic matter. Eliminating it is important if we want to increase organic matter content.

Unfortunately, one year of tillage can erase soil improvement achieved through many years of no- tillage. Therefore, it is important to practice no-till continuously. In long term no-till soils, microbial activity is higher than in tilled soils. Fungi are also more prevalent in no-till soils than in tilled soils; their hyphae (hairlike structures) are an important component of the improved soil tilth found in no-till soils. Maintaining crop residues at the surface of no-till soil fields is essential for biological activity including earthworm habitat and feedstock.

Add Organic Matter Inputs

The primary sources of organic residues in crop production are manure and compost. Bedded ma- nure contains more organic material and will lead to greater gains in organic matter content than liquid manure. All liquid manure is not equal either. Swine manure contains fewer solids than dairy manure, and can be expected to contribute to small gains in organic matter.

Adapted from an article in Field Crop News by Sjoerd W. Duiker, Soil Management Specialist.

Contact Information

John Rowehl
  • Educator
Phone: 717-840-7408