Organic Matter What is organic matter Nature of

Organic Matter What is organic matter

Nature of O. M. • 1. Is the portion of the soil which includes animal and plant remains at stages of decay – Forest= leaves, dead trees, – Prairies=grass roots and tops – Farmland= crop residue

Chemical Makeup of O. M. • 1. Consists of complex carboncontaining compounds • 2. Long chains are formed and other elements use these to make more organic compounds

Chemical Makeup of O. M • 3. The most important compounds are – A. Carbohydrates: simple sugars, starches, and cellulose – B. Lignins: is 10 -30% of plant tissue, makes plants rigid, resists decay

Chemical Makeup of O. M –C. Protein • Amino acid chains • Supplies N when broken down

Decomposition • 1. Micro-organisms digest organic matter • 2. Releases CO 2 and H 2 O • 3. Carbohydrates are first to be consumed • 4. Lignin-becomes humus and slowly broke down

Decomposition • 5. Decay Organisms need O 2 and microorganisms use O 2 to oxidize the different compounds • 6. 1 st breakdown is quick and requires weeks or months • 7. Well drained soils will lose 13% of humus a year to oxidation

Factors affecting O. M. • 1. Vegetation – 2 times as much o. m. on grassland to woodland –O. M. is deeper in prairie soil and is in soil

Factors affecting O. M. • 2. Climate –Arid conditions soil has less O. M. –High temperatures decay O. M. more rapidly

Factors affecting O. M. • 3. Texture –Fine textured soils hold more organic material because clay protects hums from decay

Factors affecting O. M • 4. Tillage –Prairie will return more than cropping

Functions of O. M. • A. Nutrient and water storage – 1. O. M. stores many of the nutrients used by plants and does it in 2 different ways • Colloids hold water and nutrients • O. M. stores nutrients as part of its own makeup

Functions of O. M. – 2. Both humus and O. M. absorb water like a sponge, humus can store 6 times its own weight

Functions of O. M. • B. Nutrient Availability –Makes several nutrients more available for plant use

Functions of O. M • C. Soil Aggregation – 1. Heavy clay responds best. Breaks down particles, aerates, and makes easier to work with

Functions of O. M • D. Prevents Erosion – 1. Soils kept supplied with O. M. have improved structure that improves water infiltration – 2. Stops excessive water runoff – 3. Increasing O. M. from 1 -3% will reduce erosion 1/5 -1/3

Functions of O. M. • Undesirable Effects – 1. Nitrogen is immobilized or tied up during the decay process and is unavailable to plants – 2. Certain plant residues are toxic to other plants

Maintaining Soil O. M. • A. It is impractical and not economical to raise O. M. levels significantly but should be a goal to maintain at highest levels

Maintaining Soil O. M. • B. Adding fresh organic matter will improve soil the best

Maintaining Soil O. M. • C. Crop Residues –Leave all crop materials possible. Don’t burn residues, harvest some –Use good fertilizer, healthy plants make more residue

Maintaining Soil O. M. • D. Green Manure – 1. Turn over alfalfa, clover, sudan grass, will increase N levels – 2. Increases O. M. levels and fixes more nutrients

Maintaining Soil O. M. • E. Crop Rotation – 1. A rotation between row crops, small grains, and legumes is better for keeping high O. M.

Maintaining Soil O. M. • F. Organic Matter Additions – 1. Animal Manures, sludge, organic wastes – 2. Industries may provide organic wastes, by products, meat scraps, etc.

Maintaining Soil O. M. • G. Mulches – 1. Not economical in large acres – 2. Reduce tillage leaves some mulch – 3. Limits water evaporation, keeps soil temperature cooler on hot days, and warmer at night

Maintaining Soil O. M. – 4. Horticulture crops are mulched

Maintaining Soil O. M. • H. Conservation Tillage – 1. Conserves topsoil which is high in O. M. – 2. Crop residue decays slower when left on top – 3. No till soils are high in O. M. in the top layer

Nitrogen Tie-up and Composting • A. Soil Microorganisms need both Carbon and N in their diet to grow and multiply – 1. Fresh organic matter will increase number of organisms because higher food supply

Nitrogen Tie-up and Composting – 2. They compete with plants for N and can cause slow plant growth

Nitrogen Tie-up and Composting • B. Carbon-Nitrogen Ratio (C: N ratio) – 1. The measure of carbon amounts compared to N amounts – 2. Plants with high c: n ratio’s are of greatest concern

Nitrogen Tie-up and Composting – 3. Matter with a low c: n ratio N rich • A high c: n ratio is N poor

Nitrogen Tie-up and Composting • Soil Humus 10 12 • Young Alf 12 20 • Rotted manure 20 residue 23 • Corn stalks 60 Garden Soil compost 15 Clover Straw 60