Soil the Foundation of an Organic Farm: Protecting & Building This Living Entity Prepared by: L. Robert Barber, & Ilene Iriarte For: Guam Cooperative Extension Service & Guam Department of Agriculture Funding provided by: United States Department of Agriculture Natural Resources Conservation Service, Western Region Sustainable Agriculture Research and Education, Administration for Native Americans,, & Sanctuary Incorporated

Soil Components Mineral Content: Sand: 0.05 – 2 Millimeters Silt: 0.002 – 0.05 Millimeters Clay: Smaller – 0.002 Millimeters 25% AIR 45% MINERAL 25% WATER 5% ORGANIC MATTER

Why is Organic Matter Important? Provides environment and food for beneficial organisms Better aeration, water penetration Greater water holding capacity Holds soil particles together (forms aggregates) Suitable environment for beneficial organisms Retains & releases nutrients

Soil Structure Good Soil Structure: Poor Soil Structure: Good percentage of sand, silt, and clay Ample pore space: Aeration & Drainage Easy root penetration High in soil organisms activity Poor Soil Structure: Compacted Small amount of pores Shallow soil Low in soil organisms activity

Soil Organisms Majority of microorganisms in soil help crops Some Large Soil Organisms (visible): Earthworms Millipedes Beatles Slugs Some Microorganisms (not visible): Bacteria Fungi (Mycorrhizae)

Soil Organisms Decompose organic matter Help build the soil aggregates Promote aeration & deep rooting Release nutrients into soils Help control pests & diseases

Factors Influencing Soil Fertility Soil depth Water Availability Water holding capacity Drainage Water Logging Aeration Root growth & microbial activity pH Acidic & Alkaline

Factors Influencing Soil Fertility Mineral Composition Soil structure Organic Matter Soil life Soil Organisms Activity Nutrient availability Water retention Decomposition of organic matter

Improving & Maintaining Soil Fertility Conservation Methods Maintain soil ground cover Contour practices & tillage Nutrient Management Nitrogen Fixing Trees (or other plants) Rotations

How to Increase Organic Matter Incorporate crop remains into the field Compost Mulch Animal manures Green manures & Cover crops Crop Rotation Reduce Tillage Agroforestry Systems

Soil Sampling Why do you need to take soil samples? Nutrients content Nutrient are limited or excess When should you take soil samples? Beginning of each growing season Tools needed for sampling. Hand trowel or shovel Zip lock bag

Soil Sampling Identifying differences in your field. Sampling pattern. Not all fields have uniform soils Split the fields and take separate samples Color, texture, drainage, and yield differ Sampling pattern. Take several samples Walk through your field in a “W” pattern If the samples are uniform mix them together

Soil Sampling Sampling and Submission Procedures Dig a V-shaped hole about 6-8 inches deep Place the soils in a zip lock bag Write your name and field location Fill out a soil sample information sheet at the University of Guam Cooperative Extension Service Drop off your samples at the Cooperative Extension Service