Soils & Compost

Understanding soils and compost is fundamental to successful gardening. Healthy soil provides the essential nutrients, water, and support plants need to thrive, while compost enriches the soil and enhances its structure. 

Understanding Soil Basics

1. Soil Composition
   • Minerals (45%): Soil is composed of mineral particles, which come from weathered rock. These particles are classified by size into sand, silt, and clay.
   • Organic Matter (5%): This includes decomposed plant and animal material, which provides nutrients and improves soil structure.
   • Water (25%): Water is held in the spaces between soil particles, supplying moisture to plants.
   • Air (25%): Good soil has pores that allow air to reach plant roots, which is essential for respiration and root health.
2. Soil Texture
   • Sand: Large particles with a gritty feel. Sandy soil drains well but doesn't hold nutrients or water effectively.
   • Silt: Medium-sized particles with a silky feel. Silt holds moisture better than sand but can become compacted.
   • Clay: Small particles with a sticky feel. Clay soil holds water and nutrients well but can be heavy and poorly draining.
   • Loam: A balanced mix of sand, silt, and clay, loam is considered ideal for most plants because it retains moisture and nutrients while providing good drainage.
3. Soil Structure
   • Definition: Soil structure refers to the way soil particles clump together into aggregates. Good structure creates spaces for air and water to move freely.
   • Improvement: Adding organic matter, such as compost, can improve soil structure, making it easier for roots to grow.
4. Soil pH
   • Definition: Soil pH measures the acidity or alkalinity of the soil. It ranges from 0 (very acidic) to 14 (very alkaline), with 7 being neutral.
   • Ideal Range: Most garden plants prefer a pH between 6.0 and 7.0. Soil pH affects nutrient availability, so it's important to adjust it if necessary.
   • Adjustment: Lime can be added to raise pH (make it more alkaline), while sulfur can lower pH (make it more acidic).

Testing Your Soil

1. Soil Testing Kits

   https://hles.unl.edu/news/nebraska-soil-water-testing-labs/ 

   • Availability: Soil testing kits are available at garden centers or online. These kits test for pH, nutrient levels (nitrogen, phosphorus, potassium), and sometimes organic matter content.
   • Use: Follow the instructions to collect soil samples from different parts of your garden and mix them together for an accurate reading.
2. Professional Soil Testing
   • Where to Get It Done: Local agricultural extension services or commercial labs can perform more detailed soil tests.
   • Benefits: Professional testing provides a comprehensive analysis of your soil, including recommendations for amendments.
3. Visual and Physical Inspection
   • Texture: Feel the soil to determine its texture. Does it feel gritty, silky, or sticky?
   • Drainage: Test drainage by digging a hole, filling it with water, and timing how long it takes to drain. Ideally, it should drain within a few hours.
   • Compaction: Stick a shovel into the soil. If it's difficult to dig, the soil may be compacted and need loosening.

Improving Soil with Compost

1. What is Compost?
   • Definition: Compost is decomposed organic material that enriches the soil. It adds nutrients, improves soil structure, and enhances moisture retention.
   • Ingredients: Compost is made from a mix of green (nitrogen-rich) materials, such as grass clippings and vegetable scraps, and brown (carbon-rich) materials, such as leaves and straw.
2. Benefits of Composting
   • Nutrient Supply: Compost adds essential nutrients like nitrogen, phosphorus, and potassium to the soil.
   • Soil Structure: It improves soil structure by increasing the number of aggregates, which helps with aeration and water retention.
   • Microbial Activity: Compost encourages beneficial microbial activity, which helps break down organic matter and makes nutrients more available to plants.
   • Sustainability: Composting recycles garden and kitchen waste, reducing the need for chemical fertilizers and minimizing landfill waste.

Composting at Home

1. Compost Bins and Piles
   • Bins: Compost bins help contain the composting materials, reduce odors, and keep pests out. They come in various sizes and designs, including tumblers, stationary bins, and DIY options.
   • Piles: A simple compost pile can be started in a corner of your yard. It requires regular turning to aerate the compost and speed up decomposition.
2. What to Compost
   • Greens (Nitrogen-Rich): Fruit and vegetable scraps, coffee grounds, tea bags, fresh grass clippings, and plant trimmings.
   • Browns (Carbon-Rich): Dry leaves, straw, paper, cardboard, wood chips, and sawdust.
   • Avoid: Meat, dairy, oils, diseased plants, and weeds with seeds, as these can attract pests or spread diseases.
3. Layering
   • Start with Browns: Begin with a layer of coarse browns like straw or wood chips for aeration.
   • Alternate Layers: Add alternating layers of greens and browns. A good ratio is 2-3 parts browns to 1 part greens.
   • Water: Keep the compost moist, like a wrung-out sponge, but not soggy.
4. Turning the Compost
   • Aeration: Turning the compost every few weeks introduces oxygen, which speeds up decomposition and prevents odors.
   • When to Turn: If the compost smells sour or isn't heating up, it may need more aeration.
5. Composting Time
   • Fast Composting: With regular turning and a balanced mix of materials, compost can be ready in as little as 2-3 months.
   • Slow Composting: If left alone, composting can take up to a year or more.
6. Using Finished Compost
   • Application: Spread a 2-4 inch layer of compost on garden beds in the spring or fall. It can also be mixed into potting soil or used as mulch.
   • Incorporation: Work compost into the top few inches of soil or use it as a top dressing around plants.

Soil Amendments Beyond Compost

1. Organic Matter
   • Mulch: Organic mulches like wood chips, straw, or leaves decompose over time, adding nutrients and improving soil structure.
   • Manure: Aged manure from cows, horses, or chickens is rich in nutrients and organic matter. It should be composted before use to prevent burning plants.
2. Mineral Amendments
   • Lime: Used to raise soil pH if the soil is too acidic.
   • Sulfur: Lowers soil pH if the soil is too alkaline.
   • Gypsum: Helps break up clay soils and improves drainage without altering pH.
3. Fertilizers
   • Organic Fertilizers: Include bone meal, blood meal, fish emulsion, and seaweed. These release nutrients slowly and improve soil health.
   • Inorganic Fertilizers: Provide quick nutrient boosts but don't improve soil structure or long-term fertility.

Building Healthy Soil Over Time

1. Cover Crops
   • What Are They: Plants like clover, rye, or vetch grown specifically to cover the soil during the off-season.
   • Benefits: They prevent erosion, add organic matter, and fix nitrogen in the soil.
2. Crop Rotation
   • Principle: Avoid planting the same crops in the same spot year after year.
   • Benefits: Reduces the buildup of pests and diseases and improves soil health by varying nutrient demands.
3. No-Till Gardening
   • Method: Instead of tilling, add compost or mulch to the surface and let the soil organisms do the work of mixing it in.
   • Benefits: Preserves soil structure, reduces erosion, and promotes healthy microbial activity.