What are the elements your soil is comprised of? What can you add to amend soil for different growing needs? How do you not only add nutrition but also improve aeration, porosity, holding capacity and alter soil pH levels? Read on for more info….
SOIL ELEMENTS – AND ELEMENTARY AMENDMENTS
Structurally, plants are comprised of Carbon, Hydrogen and Oxygen. These are absorbed from the environment naturally. These elements are available in the atmosphere and in soil. However, much more is needed to grow veggies or herbs to good health, and peak productivity. It’s simple, we need to invest in our soil if we seek to enjoy its harvest. And the investment is not just soil elements to ensure nutrition, aeration, porosity, holding capacity and pH balance, but a pro-active guardianship of soil viz. an inspired farmer who is tuned in to his/her soil and to Nature 🙂
BASIC ELEMENTS & WHERE TO FIND THEM
- NITROGEN – This promotes overall plant health and ensures lush leafy growth. Though nitrogen is easily available in air, it is not readily accessible in soil. Signs of nitrogen deficiency are limp, pallid, and dull foliage. Manure has high rates of Nitrogen, but tends to lose it when applied to soil because of mineralization and leaching (denitrification)*. The best organic amendment to increase nitrogen levels in soil is Compost.
- POTASSIUM – This synthesizes protein, helping your plant grow faster, stronger and disease-resistant. Signs of potassium deficiency are yellow and brown spots or veins, in plant leaves. The best organic amendments to increase potassium levels in soil are Wood Ash (aka Potash), Neem Cake & other Neem Products.
- PHOSPHORUS – This gives your plant energy, helping it grow quickly from seed to plant, and then enhance its flowering and fruiting. It is most easily accessed by plants when soil pH is close to 6.5. Signs of phosphorus deficiency are stunted growth, small and acidic-tasting fruit, and older leaves with bluish or purplish tinges. The best organic amendments to increase phosphorus levels are Manure, Rock Phosphate (aka Phosphorite), Powdered Limestone (aka Calcium Hydroxide), Bonemeal, Fishmeal, Bloodmeal, Neem Cake & other Neem Products.
SECONDARY ELEMENTS & WHERE TO FIND THEM
- CALCIUM – This helps your plant build stronger cell walls, enhance its metabolism, fight heat stress, develop greater resistance, and grow better quality fruit. It is most easily accessed when soil pH is neutral or alkaline. Signs of calcium deficiency are discoloration and spotting of leaves, curling up of young leaves and shoots, burnt tips of buds and leaves, and blossom end rot in tomatoes. The best organic amendments to increase calcium levels are Powdered Cottonseed, Rock Phosphate (aka Phosphorite), Powdered Limestone (aka Calcium Hydroxide), Manure, Bonemeal, Fishmeal, Bloodmeal, Neem Cake & other Neem Products.
- MAGNESIUM – This increases seed germination rate, overall plant vitality and growth, and enhances production of flowers and chlorophyll. It is most easily accessed when soil pH is neutral or alkaline. Signs of magnesium deficiency are yellowing between leaf veins, marbling of leaf tissue, and premature aging of your plant. The best organic amendment to increase magnesium levels is Epsom Salts.
- SULPHUR – This improves plant growth and nutrition, while also improving the efficiency of other elements in your soil. Signs of sulphur deficiency are discoloration and/or purplish coloration of leaf and stem. The best organic amendment to increase sulphur levels in your soil is Epsom Salts.
- ZINC – This enhances plant metabolic activity. It is most easily accessed when soil pH is acidic. Signs of zinc deficiency are small, thin leaves, stunted growth and yellow discoloration of plant tissue between leaf veins. The best organic amendment to increase zinc levels in your soil is a Foliar Spray of Zinc Sulphate, Zinc Oxide, Zinc Silicate or Zinc Carbonate, to be used only when the plant is not flowering or fruiting.
- IRON – This helps your plant produce chlorophyll. It is most easily accessed when soil pH is acidic. Signs of iron deficiency are paleness or yellowing of leaf tissue. The best organic amendment to increase iron levels in your soil is Manure.
- BORON – This helps your plant develop new cells. It could be toxic to plants when administered at high doses. Signs of boron deficiency are dying of plant tips and buds. The best organic amendment to increase boron levels in your soil is Borax.
- MOLYBDENUM – This supports protein production in your plant. It is vital for nitrogen fixating plants like beans. High soil acidity decreases access of this element to the plant. Signs of molybdenum deficiency are irregular leaf blade formation and mottling or discoloration of leaf tissue. The best organic amendment to increase molybdenum levels in your soil is to add an alkaline amendment like Wood Ash to decrease soil acidity, or Compost, to buffer existing soil pH levels.
- COPPER– This helps your plant’s metabolic activity and growth. Copper deficiencies usually occur in sandy, nutrient-poor soils that are often alkaline. It is most easily accessed by the plant when soil pH is acidic. Signs of copper deficiency are stunted growth, dying back of stems and pale green, weak leaves. The best organic amendment to increase copper levels in your soil is Compost, to buffer existing soil pH levels.
- CHLORIDES – This helps photosynthesis in your plant. It is rarely deficient in soil. Signs of chloride deficiency are wilting or restricted root structures. The best organic amendment to increase chloride levels in your soil is to add Compost, thus giving your soil access to a variety of fresh nutrients to enhance its composition.
- MANGANESE – This promotes healthy growth of your plant. It tends to occur when soil pH is acidic. Signs of manganese deficiency are browning and yellowing of leaf tissue. It is best not to attempt to administer organic amendments to increase manganese levels in your soil, as excess dosages can be highly toxic in your soil and produce.
Looking to buy any of these amendments? Do check out my Shop….
SOIL AERATION, POROSITY & HOLDING CAPACITY & HOW TO DO IT
Besides the nutritional needs of your plant, you may also want to consider soil aeration, porosity and holding capacity. All these three factors are critical for enhancing beneficial microbial activity, growing strong roots and preventing leaching of water and nutrients. These three factors, with their optimum amendments are:
- FOR BETTER AERATION – Well-granulated, light and loamy soil will allow air into your potting mix, making it easy for tender roots to reach out, while also improving microbial activity. Increase aeration in Clay or Silty Soils by amending your Potting Mix with natural minerals like Vermiculite Granules, Pumice Stone, Clay Balls & Perlite. For a finer effect in aeration, especially for germination or micro-greens, use Vermiculite Dust.
- FOR BETTER POROSITY – Some plants need porous soil where moisture can be accessed by roots without them sitting and rotting in water. This is especially important for germination. The best amendment to improve porosity and water retention is Coco Peat.
- FOR BETTER HOLDING CAPACITY – Leaching of nutrients is a common issue in many soils found in tropical and arid climates. All of the vital nutrients you add to soil are likely to be lost if your soil pH value, microbial activity and CEC ratios (cation exchange capacity) is at odds with the soil environment. One material that has been used since ancient times, and is now rightfully finding its place in agriculture again is Bio Char. Made from agri waste using pyrolysis (combustion of materials in the absence of air) this highly recommended carbon-rich amendment acts as a sponge – absorbing and storing water and vital nutrients in soil for later use by plant roots, thus preventing leaching and the costly loss of soil amendments.
If you prefer to use pre-assembled organic Potting Mixes, find them at my Shop….
SOIL pH LEVELS AND HOW TO ALTER THEM
Soils vary in their pH levels from strongly acidic (pH value 5) to neutral (pH value 7) to strongly alkaline (pH value 9). Levels can be checked using a pH meter/litmus test. Read more on soil pH levels here…
For growing veggie plants or herbs, the recommended pH level will depend on plant type. This can be referenced in my Plantopedia. However it is important to know that once you prepare your potting mix with the right elements and the right pH balance, it will not stay the same permanently. With rainfall and regular watering, soils will be prone to leaching of elements, and over time, will tend to move towards more acidic states. Thus the more base elements will either be lost or become less bio-available because of the acidic environment. This phenomenon is most acute in tropical and arid climate soils and in all instances of container farming. The best long term option is to use Bio-char so that at least the holding capacity of soil increases and vital and expensive nutrients are not lost. If this is not done, one can still alter pH levels using natural soil amendments as follows:
- To Increase Soil Acidity: Use Neem Cake & other Neem Products
- To Increase Alkalinity: Use Wood Ash, Rock Phosphate, Powdered Limestone and Manure (Generally, manure of all types – Cow, Pig, Chicken, Horse, Goat & Camel will move soil towards alkalinity. Fresh manure is strongly alkaline, but dried and composted manure is moderately alkaline).
What about Compost? Compost, during its various stages of decomposition, moves from highly acidic to neutral states. Once thoroughly decomposed and integrated in your soil, it will not change pH levels but acts as a humus-rich buffer, facilitating good microbial activity and enhancing the ability of roots to absorb elements, irrespective of the existing pH level.
What about Bio-char? Like compost, Bio-char is neutral and does not affect soil pH levels significantly.
What about other Soil Amendments? Other amendments have negligible to no impact on soil pH level
All these natural amendments for pH levels, PLUS plants, at my Shop….
What quantities of soil amendments are needed?
Using organic soil as your base ingredient, you can add these amendments as described –
- Vermiculite and Coco Peat should be 50% max for Germination and 25% max for General Purpose Growing. These amendments lack nutrition so balance them with good quality earth or other amendments.
- Compost should be 25% max. This amendment generates heat – the less biodegraded the hotter it is and vice versa – so balance it with good quality earth which should cool down your mix.
- Manure, Bone Meal, Fish Meal, Blood Meal, Powdered Cottonseed and Wood Ash should not exceed 20% all put together. These are very strong amendments and need to be thoroughly mixed with base earth and watered down after mixing. Manure, especially, is extremely heat-generating and can burn seeds and young plants. All manure should be well aged and dried thoroughly before use to reduce alkalinity levels and eliminate pathogens.
- Neem Cake & other Neem Products should be 5% max of your Potting Mix. This amendment is extremely beneficial in terms of nutrients, helps increase soil acidity, and is potent as a fungicide. However, if used in excess, it can inhibit plant growth.
- Rock Phosphate and Wood Ash should not exceed one handful per plant. They can be sprinkled on soil but work much better if they are mixed into the soil. Wood Ash can also be sprinkled on foliage when used as a natural insecticide against leaf-eaters etc. Bear in mind that Rock Phosphate is a slow release fertilizer and so its positive effects will only show up next season.
- Powdered Limestone and Epsom Salts should not exceed one teaspoonful per plant, finely sprinkled on your soil surface, or diluted and watered into your soil (not foliage). Once again, these are strong amendments and need to be used sparingly.
- Zinc-based Foliar Sprays and Borax should be used strictly per manufacturer’s instructions.
Dosage instructions for each amendment are on product labels for items at my Shop….
How are soil amendments added?
Most soil amendments need to be thoroughly mixed so they get integrated into your Potting Mix (as a basal dressing) giving your plant roots access to its elements. The finer the grain of the amendment, the sooner it will breakdown and the easier it will be for plant roots to access nutrients. Grinding down chunky pieces and sieving is, therefore, a good idea. Also remember, that amendments that tend to generate heat like Manure, Blood Meal, Cotton Seed & Compost should always be watered down after mixing and use in soil. With Manure, special precautions should be taken to bury the manured content within the soil (deep disking) and prevent exposure of foliage and crop to it. Direct contact of “truck-garden” crops like lettuce and tomatoes with infected manure has been linked to e-coli outbreaks.
Powdered Limestone and Epsom Salts can be sprinkled on, or watered into the soil (as a top dressing) to dissolve gradually into your Potting Mix. Do not place them in proximity to root, stem or foliage as they can burn/irritate the plant when at full-strength.
Calcium can take up to 3 years to be integrated into your soil if it is sprinkled on the top layer (yes, and this is true even for egg-shells!) though liquid based calcium can speed up the process to 1-3 months.
Foliar sprays of Zinc & Boron are to be sprayed on leaves and stems only, by dissolving the amendment in recommended quantities of water/oil.
Usage instructions for each amendment are on product labels for items at my Shop….
What about other home-made soil amendments?
There is a plethora of home-made soil amendments recommended by organic farmers – from panchagavya to diluted buttermilk, asafoetida (heeng) applications to papaya leaf/other leaf juice. These may well work but there is little research done that can link these amendments with elements deficient in soil. If you find in your experience that these work for you, do use them. However, whatever you choose to use, needs to be in moderation as soil balance is critical. Healthy soil is a living phenomenon, replete with myriad elements and an active, if often unnoticed, microbial population. Any element in excess, be it chemical or organic, can disrupt the processes at work. So in soil, as in life, moderation is critical 🙂