Programs

The first step when amending soil is to understand what type of soil you have, its advantages and what common issues are associated with that soil type. All soils are a combination of different particle sizes, but the proportion of those different sized particles can drastically alter the properties of your soil. This is referred to as the soil texture and is categorized by the proportion of sand, silt, and clay.
• The terms sand, silt, and clay refer to the particle size of the soil – sand particles are the largest of the three and round, whereas clay is the smallest and is thinner and flatter. The differences between these particles will determine the characteristics of your soil.
Sand particles are large and round – creating large pores or cavities. These cavities fill with air, offering the plants an abundant supply of oxygen and carbon dioxide. However, since the cavities are so large, water cannot be retained in them, making sandy soil fast draining and predisposing plants to drought.
• Clay particles are very small and flat, which allows them to pack together tightly. This means water is unable to travel very quickly and is retained in the soil – a clay soil will not need to be watered as frequently as other types. However, since the particles pack tightly together, clay soil may be compacted – the soil particles are so tightly clumped together that there are not many cavities. This can not only suffocate the plant as not enough air is reaching the roots, but can also hinder root growth and earthworm movement through the soil, which may have other devastating effects on the plants. Most soils are a mixture of sand, silt and clay, and the overall properties will be dependent on which particle size makes up the majority of the bulk.

An easy way to determine the texture of your soil is to feel it with your hands. Take a small handful of soil and drop water on it until it is wet enough to form a ball. If the soil is sandy, when you rub it between your fingers it will feel gritty. Conversely, silty soil will feel floury when dry, but greasy when wet. Also, if your soil has a majority of silt particles, the soil will form a ball when wet, but if you try to roll it into a thinner cylinder, it will crack. Finally, clay soil feels greasy even when dry, will form a ball when wet and does not break when you roll it out into a long ribbon.

While the soil texture cannot be altered, the soil structure can be amended. The structure of the soil refers to the arrangement of the sand, silt, and clay particles and can overcome some of the downfalls of the different soil textures. Good soil structure reflects a variety of pore spaces in a variety of sizes. Ideally, over half the soil volume would be empty spaces between soil particles, filled with air and water.

Desirable soil structure is granular or crumb-like soil with large aggregates. These soils will appear loose and fluffy when manipulated.
• Soil aggregates are clumps of soil, held together by root hairs, bacteria exudate and fungi. Aggregates, and in particular, water-stable aggregates are important for soil health as they allow the soil to resist severe weather conditions – for example, they keep the soil from compacting during heavy rains or cracking during drought.
Poor quality soil cracks and dries out during hot summer months, and standing water may be seen on the surface after a heavy rain. Additionally, digging holes in your soil should be easy when soil is both wet and dry; a poor soil will be compacted, making it difficult to dig.

Organic inputs and biostimulants may improve soil structure. Additionally, reducing tillage may allow aggregates to form and be maintained, as repeated tillage can break down the aggregates and reduce soil tilth – the suitability of the soil for growing crops.
The addition of organic matter to soil can improve the water-holding capacity, enhance nutrient supply, and supports soil microorganisms. Organic matter encompasses a large variety of substances that may be added to soil, and includes plant and animal matter and microorganisms. These may be added in order to alter the physical properties of the soil to benefit plant growth. The most common sources of organic material are, biostimulants, and organic input material.
• Soils rich in organic matter are dark in colour and have a rich, earthy smell. Also soil should have no standing water – the water should be absorbed into the pore spaces between the soil particles.
Finally, if you rub the soil between your fingers, it should appear to contain crumbs, or aggregates. If your soil ever smells sour, it may be a sign of poor air circulation or compaction and is a signal that your soil needs additional organic matter.
It is a misconception that adding sand to clay soil will enhance its water carrying capacity. Even though it is true that increasing the proportion of sand would offer enhanced soil texture, mixing sand directly into clay can be very detrimental. The clay can stick to the sand particles creating a cement-like substance. Instead, a sandy loam soil can be used in place of a portion of the existing clay.

There are three main nutrients that all plants require – nitrogen (N), phosphorus (P) and potassium (K). These are known collectively as plant macronutrients. Many fertilizers are labeled with a number that represents the proportion of the N, P and K contained in the product – this number is generally in the form of 0-0-0 with the first number representing the nitrogen, the second phosphorus, and the third potassium (N-P-K).

Nitrogen
 
Without adequate amounts of nitrogen, fruit and flower size and yield may be drastically reduced. As crops are harvested, soil nitrogen is depleted, risking the starvation of future progeny. It is important that plants are supplemented with proper amounts of nitrogen to enhance growth and production and improve survival. It is especially important to supplement with nitrogen if the soil is acidic or woody materials have been mixed in, as these cause nitrogen deficiencies in the soil.
In nitrogen deficiency, plants appear starved. They are thin and pale and growth is stunted. Chlorophyll development also requires adequate nitrogen, so leaves may appear yellow or pale green and they tend to remain small and drop prematurely.

Phosphorus
 
Phosphorus is required for the proper growth and development of all plants, but especially seedlings. It is often recommended as a starter fertilizer to enhance the early growth of plants. That being said, it is also important to have adequate phosphorus throughout the entire lifecycle as it is required for plants to use energy and continue growing, developing and most importantly, producing fruits and flowers.
Phosphorus deficiency is the most common soil deficiency seen in North America. Root and shoot growths are both stunted, with shoots appearing spindly and leaves appearing abnormally dark in colour. In severe cases, leaves may develop a reddish purple colour. Phosphorus deficiency manifests with little to no flowers or fruit produced, delayed maturity, and winter hardiness is diminished.

Potassium
 
Potassium, the third essential macronutrient, is responsible for proper movement of water, carbohydrates and nutrients through plant tissue. It also plays a vital role in the energy status of the plant, which affects photosynthesis. Adequate potassium enhances stress resistance and rigidity of crops, which increases survival and protects against harsh weather conditions.
Crops deficient in potassium are more susceptible to injury and disease due to its tolerance boosting effects. Also, since potassium plays a critical role in water movement, stunted growth, yield reduction, wilting, and premature defoliation are common during a potassium deficiency. Shelf life of harvested fruits may also be reduced during low potassium, and lower leaves often develop white, yellow or brown spots.

Micronutrients encompasses a large variety of different elements that may be used to enhance the growth or quality of plants.
 

 
Boron
 
Boron is an essential micronutrient required for proper reproductive and vegetative growth – it is responsible for root and shoot growth, pollen development, fruit and flower production, as well as proper development of roots and shoots. Boron deficiency first appears as yellowing of new leaves and can progress to the formation of thick, brittle branches and short stubby roots.
 

Copper
 
Copper is an essential metal required for proper photosynthesis. When used as a nutrient, only very small amounts are required, as copper may persist in the soil for many years. Copper deficiency affects young leaves and reproductive organs and worsens as soil pH increases. Soil without adequate copper content may cause light green or yellow leaves, reduced flowering, as well as malformed and/or necrotic leaves.
 

 
Iron
 
Iron is an essential micronutrient that plays a critical role in respiration and photosynthesis and is required for the proper growth of all plants. Additionally, adequate iron enhances the nutritional quality of crops. Acidic soils and waterlogged soils tend to have the highest natural iron content. Iron deficiencies are quite common and may lead to yellowing leaves and poor root formation. A certain level of iron is required for all plants in order to properly grow, however too much iron may be toxic.
 

 
Manganese

Manganese is an important element that is present in small amounts in most soils. It enhances the efficiency of photosynthesis, which boosts growth, yield and quality. Manganese works synergistically with other fertilizers by optimizing the plant’s usage of the three primary macronutrients. Manganese deficiency affects the chloroplast of the plant’s cells and results in severely diminished yield and quality.
 

 
Zinc
 
Zinc is crucial for the production of many plant growth regulators. It enhances yields, improves resistance to injury, and improves production of pollen, fruits and flowers. In zinc deficiency, growth may cease and plants become more susceptible to injury. Small, malformed leaves with necrotic spots and stunted roots are the characteristic signs of a zinc deficiency.

Secondary nutrients are those that do not fall into either the micro- or macro-nutrient category. There are two main compounds that are used as secondary nutrients – calcium and magnesium, and they are often used in combination.
 

 
Calcium
 

Calcium is an essential second messenger that is associated with virtually all aspects of plant growth and development. It signals the growth of plant roots and shoots and is crucial for the incorporation of cell wall components. A calcium deficiency may present as leaf curling, fruit cracking, or inferior root growth.
 

 
Magnesium
 

Magnesium is the other secondary nutrient. Often calcium and magnesium are used in combination and referred to as “Cal-Mag” in commercial products. Magnesium application to deficient soil can enhance root formation, chlorophyll synthesis and pigmentation, and regulates cell turgor.

Auxins

Auxins are a group of naturally occurring plant growth promoting hormones containing the compounds IBA (indole-3-butyric acid) and NAA (napthaleneacetic acid). Together these compounds stimulate root formation, and in particular, promote the development of adventitious roots. This can be used to enhance the roots of crops or even reduce transplant shock.

Cytokinins

Kinetin is a common cytokinin that is native to many plants and stimulates growth rate. It works by inhibiting root growth and using all the plants energy resources for the rapid growth of shoots and leaves. This is a helpful property to reduce transplant shock as well as increase the number and size of fruits and flowers.

Gibberellins

 
Gibberellic Acid (GA3) is a very potent plant hormone that functions to control plant development. GA promotes plant and flower growth as well as increases fruit set. It aids in frost protection, overcoming dormancy, and inhibits root formation in cuttings.

Newer plant growth regulators offer unique plant growth regulating properties. Some of the most common of these compounds are as follows:
 
 
Brassinolides
 
Brassinolide (BR) is a brassinosteroid that, when released, encourages plants to grow taller, while also offering some protection against heat, cold, water, drought and salt stress. Additionally, brassinolide optimizes the efficiency of other fertilizers and pesticides, allowing the plant to use them more efficiently.
 
 
Salicylic Acid
 
Salicylic acid (SA) is a naturally occurring plant hormone that can improve a plant’s resistance to drought and other environmental stresses like salinity, heavy metal toxicity and extreme heat. SA also enhances hardiness, flowering and fruit yield, and aids in systemic acquired resistance (SAR).
 
 
Triacontanol
 
Triacontanol (TR) is naturally found in the leaves of most plants. It acts on many growth pathways to boost yield, uptake of water and nutrients, fruit and flower number, size and quality, and essential oil production.
 
 
Jasmonic Acid
 
Jasmonic Acid (JA) and its derivatives are naturally occurring plant hormones that promote plant growth as well as protection against environmental and biological stress. Airborne jasmonates are also used as communication signals between neighbouring plants – so the surrounding crops can preemptively protect themselves