Organic Farming

Main Goals of Managing for Soil Health

1. One of the key concepts of Lecture 1 was that soil fertility is a feature of soil health as applied

to agroecosystems. It is the capacity of a soil to provide nutrients that plants require for

growth.

2. Key indicators of soil health include

a) The ability of the soil ecosystem to mineralize nutrients and make them available to

plants

b) A moderate pH, which promotes nutrient retention and makes nutrients available to

plants

c) Good structure, or tilth, that resists degradation and provides adequate air and water to

roots

d) Good biotic habitat, particularly for beneficial organisms

3. One of the main ways to support these goals is by increasing the carbon content of the soil

in the form of soil organic matter (SOM)

a) SOM has three main constituents. As summarized by Cornell University Cooperative

Extension, these are:

i. Plant debris and living microbial biomass

ii. Detritus (active soil organic matter, made of partially decomposed plant, animal, and

microbial tissues)

iii. Humus (stable soil organic matter)

b) The microbes help decompose the plant debris and the detritus, while humus (a black,

sticky substance) is the final product of decomposition

c) SOM has many benefits for the soil, supporting the key indicators of soil health listed

above. Some of these functions include those below (and see the Cornell University

Cooperative Extension Fact Sheet 41 [franklin.cce.cornell.edu/resources/soil-organicmatter-fact-sheet] for more functions and details):

i. It provides the source of substances for mineralization

ii. SOM, especially the humus fraction, helps maintain soil pH biochemically

iii. It helps soils resist crusting and decreases erosiveness

iv. Plant debris and detritus fractions of SOM provide food for the microbial biomass

4. All these benefits of SOM make it “money in the bank” for the agroecosystem. Maintaining

and increasing SOM are the basis of the soil health practices described in this lecture.

B. Soil Cultivation in Sustainable Agriculture (see also Unit 1.2, Garden and Field Tillage and Cultivation)

1. Cultivation is physically working the soil for seedbed preparation or weed control, using

hand tools or mechanical implements. It is synonymous with tillage.

2. Services provided by tillage

a) Prepares soil for seeds or transplants by improving soil aeration and breaking up soil

clods

b) Incorporates crop or cover crop residue, helping make carbon and macronutrients,

especially nitrogen, available to soil microbes

Managing Soil Health

Part 1 – 14 | Unit 1.1

Lecture 2: Soil Fertility Management—Sustainable Agriculture Practices

c) Enables the incorporation of amendments such as compost and lime

d) Allows soil to dry more rapidly

e) Allows soil to warm up more rapidly

f) Increases microbial activity and mineralization rates in the short-term

g) Deep tillage can break through compacted layers that are a barrier to root growth and

water movement

h) Controls weeds by burial or exposure of seeds or seedlings (see Unit 1.10, Managing

Weeds)

i) Controls overwintering insects by exposure to the surface

3. Disadvantages of tillage

a) May accelerate the rate and extent of long-term declines in soil organic matter

b) May increase sub-soil compaction problems and impede drainage and root growth

c) Has high energy and labor costs

d) Loss of soil organic matter (SOM) from excessive tillage can lead to crusting of bare soils,

impeding seedling emergence and water infiltration

4. Advantages of conservation tillage systems

a) Residue cover on the soil surface protects the soil from wind and water erosion

b) Increases moisture retention

c) Increases SOM over time (years), reaching a higher “steady state” than tilled systems in

5. Limitations of conservation tillage systems

a) Residue cover lowers soil temperature, which delays seed germination and slows

seedling growth and may place grower at an economic disadvantage

b) Weed control is very difficult without use of herbicides