Let's Talk Soil Health

S O I L 
Soil is a powerful resource; it's the home, the temple, of all you grow.  Having a fundamental understanding about soil, what makes its healthy and how to care for it directly impacts the soils ability to grow foods and herbs as well as protect the environments natural resources.  Here's  a general overview of healthy soil outlined below.  

Soil Organic Matter (SOM) - SOM is made up of living organisms both fresh (no more than 3 years; still provides food for soil organisms) and decomposed (between 5-1000 years old; mainly carbon and no longer food for soil organisms).  

• What living organisms? earth worms, bacteria, fungi, insects, plant roots and small animals like moles.  

• Examples of beneficial living organisms:
  • Ladybugs (predator to “pests”)
  • Bees (pollinators)
  • Worms (example shared below)
  • Nematodes (microscopic worms that eat larvae)
  • Birds “pollinate” by spreading seeds 

• What is the relationship between the living organisms and soil?  full circle; the living organisms feed off of the debris of other living organisms, plant residues and compost then release back into the soil food for the plants (mineralization).  Living organisms also help with reducing disease and aerating the soil via soil aggregation.  
  • For example - earthworms do the following:
    •  Breakdown large matter into smaller pieces that are more digestible for smaller organisms
    • The channels earthworms pave as they burrow deeply into the soil supports the breathability of the soil; roots need air to grow.
    • Mucigel - a secretion that comes from earthworms aids in the soil’s ability to bind together
• Maintaining OM in the soil is important and can be supported by:
  • practicing cover cropping adds OM to soil
  • planting cover crop adds OM to soil
  • manure adds OM to soil
  • no/low till (tilling reducing OM and can lead to soil erosion and loss of soil nutrients)
• Note: Adding OM to soil adds nutrients to the soil which is great AND can be overdone.  Adding OM must be done mindfully; there is such a thing as too much nutrients, water and tilling.  ​

Soil Tilth: tilth is referring to the physical condition of the soil; preferably porous, breathable, penetrable by root systems and easily able to receive water.  

• Soil porosity is derived from:
  • soil aggregates - glued together soil particles that impact the structure of the soil and its ability to breath and receive water while minimizing erosion and run off.  
    
• Why is soil porosity important? 
  • roots need oxygen and ample air flow for growth potential
  • enables roots to explore and receive nutrients
  • can aid plants in resisting stressors like harsh weather and compaction​

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• What is soil compaction? Soil that is heavily pressed together with low to no porosity
• Why is soil compaction problematic? It reduces porosity which inhibits plant root systems from breathing, growing and receiving nutrients; this can result in nutrient build up and soil imbalance.  Compacted soil has poor drainage and gets waterlogged which impacts the health of the soil and can lead to soil erosion.

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• ​How to improve compacted soil?
  • Tilling - while tilling can reduce the OM in soil it can also aerate the compacted soil to aid in building porosity.  Try to till the soil once a year at the beginning of the planting season. 
  • Adding amendments like gypsum and vermiculite
  • Adding organic materials like peat moss and compost
  • Adding earthworms

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Erosion

• What is soil erosion?
  • When valuable topsoil is lost (and with it valuable nutrients).  
• High amounts of organic matter in the soil and good soil structure will help minimize erosion because it naturally enables the soil to withstand rains and harsh weather as well as take in water easily. ​

Soil pH - a neutral soil pH is 7.  Acidic soils are below pH7 and alkaline soils are above pH 7. pH impacts the availability of nutrients in the soil. Most crops prefer a pH of 6-6.8​

When doing research on plant pH it is commonly centered around the need to maintain and monitor the soil's N (nitrogen), P (phosphorus) and K (potassium) levels so let's begin there.

Nitrogen promotes healthy foliage (too much can result is rapid growth but poor flowering, too little stunts the growth) Signs: short plants, small leaves and yellowing

Phosphorus promotes strong roots, flowering and larger seeds (excess leads to poor growth and bleaching because it impacts symbiotic bacteria and fungus that aid root systems in taking in water and nutrients / too little causes leaf death) Signs: excess weed growth, stunted plant growth and bleaching leaves, older leaves turning “fall” colors early and falling off.

Potassium supports overall plant health (excess can block Nitrogen and Phosphorus uptake / too little can lead to disease and poor health) Signs: brown scorching and curling of leaf tips, yellowing between leaf veins, stunted growth and purple spots on the bottom of leaves

When you procure fertilizers there are always 3 numbers on the product.  Those 3 numbers correspond to the products levels of N (nitrogen), P (phosphorus) and K (potassium).  For example a fertilizer with a 10-10-10 is equal percentage (10% to be exact) of N P K. 

How do you determine the correct fertilizer?  You can learn the fertilizer needs of individual plants as well as test the soil to determine its pH and what it will need to return to homeostasis.  You can procure a testing kit online or at most gardening stores.  For folks that are local to me in VT I also recommend sending a sample of your soil off to the University of Vermont (UVM) for testing at the beginning and end of each grow season.   https://pss.uvm.edu/ag_testing/?Page=soils.html 

Maintaining soil N P K can be challenging and requires frequent soil testing (monthly and at the different stages of plant growth), observation of the behavior and physical attributes of the plants and soil and using that information to continue to feed the plant(s) throughout the grow season.   

Soil fertility is the ability of soil to provide a holistic environment for growing healthy plants. To do this is needs a balance of nutrients. It's important to note that soil fertility extends beyond understanding soil pH and monitering N P K alone.  

Biodiversity both above and below the soil is important to soil health, fertility and mitigating plant disease  and minimizes pest infestation.  So as much as you tend to the health of the soil directly it’s equally important to tend to the soil indirectly by planting a variety of plants (heirloom, organic), feeding the wild birds, growing a pollinator garden and allowing the growth of wild plants that serve as both habitat and food for beneficial organisms.

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