What are the elements your soil is comprised of? What amendments need to be added? How do you 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 soil and the atmosphere. However, much more is needed to grow your veggies or herbs to full-size, good health, and peak productivity. While browsing through this list of other elements, do remember, that these are basically ingredients. And great produce, like a great meal, is the outcome of more than its ingredients. It requires active and positive microbial activity, the right pH balance, aeration, porosity and soil holding capacity, and most importantly, an inspired farmer who is closely tuned in to his crop and to Nature :-). So, here goes:
BASIC ELEMENTS & WHERE TO FIND THEM
- NITROGEN – This promotes overall plant health and ensures good leafy growth. Though nitrogen is easily available in air, it is less readily accessible in soil. Signs of nitrogen deficiency are limp, pallid, and dull foliage. While Manure has high rates of Nitrogen, much of it is lost when applied to soil (mineralization) and leaching into soil (denitrification)*. Thus the best organic amendment to increase nitrogen levels 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 are Compost, Wood Ash (aka Potash) or 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 the plant 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, Bonemeal, Fishmeal, Rock Phosphate (aka Phosphorite), Powdered Limestone (aka Calcium Hydroxide) or 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 Bonemeal, Fishmeal, Bloodmeal, Powdered Cottonseed, Rock Phosphate (aka Phosphorite), Powdered Limestone (aka Calcium Hydroxide), Manure or 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 the soil aeration, texture and holding capacity. All these three factors are critical in assisting beneficial microbial activity, growing strong roots and preventing leaching of water and vital 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. For a finer effect in aeration, especially for germination or micro-green growing, use Vermiculite Dust.
- FOR BETTER POROSITY – Some plants need highly porous soil, as stagnant moisture could cause rotting of its roots. In these circumstances, improve porosity and drainage by amending your Potting Mix with natural and renewable materials like 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 your soil are more 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 use in agriculture again is Bio Char. Made from agri waste using pyrolysis (combustion in the absence of air) this highly recommended carbon-rich amendment acts as a sponge – absorbing and storing water and vital nutrients in the soil for later use by plant roots, thus preventing leaching and the 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 are easily checked using a pH meter. Read more on soil pH levels here…
For growing veggie plants or herbs, the range of pH that will be optimum for growing will depend on particular plant types. You can check against plant types in my Plantopedia. Bear in mind that with rainfall and regular watering, soils tend to leach out elements. So you can imagine, that when this process is extended over time, all soils will tend to move towards acidic states. The issue is most acute in tropical and arid climate soils, those that have not been amended with Bio-char, and is instances of container farming/gardening. Natural amendments to increase soil alkalinity then need to be added. If however, your soil is too alkaline, and you need to increase soil acidity, this situation can also be fixed, naturally. Read on for the effect on pH levels by common soil amendments:
- Neem Cake & other Neem Products will increase acidity levels.
- Wood Ash, Rock Phosphate and Powdered Limestone will increase alkalinity levels.
- Manure of all types – Cow, Pig, Chicken, Horse, Goat & Camel – usually has an alkaline pH value. Fresh manure is strongly alkaline, but dried and composted manure has a moderate alkalinity.
- 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 will buffer your soil, facilitate beneficial microbial activity and enhance the ability of your plant to absorb elements, irrespective of the existing pH level.
- Like compost, Bio-char is similarly neutral and does not affect the soil pH levels significantly.
- Other amendments have negligible impact on soil pH level
All these natural amendments for pH levels, and more, 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, though solution-grade calcium can speed up the process to 1-3 months. So a liquid solution is always better than dusting if you need a quick fix.
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 to asafoetida (heeng) applications. If you find that these work for you, do use them. At this stage, I would think that more research is required to conclusively co-relate elements in each of these amendments, with elements that are deficient in one’s soil. Also, the effect of residual elements of these amendments on one’s soil’s constituent and pH level still needs to be tested.