NPK is one of the primary markers you’ll notice on fertilizer bags—it stands for “nitrogen, phosphorus, and potassium,” the three macronutrients that compose complete fertilizers. We call them macronutrients because they are directly related to plants growth. Nitrogen is considered to be the most important, and plants absorb more nitrogen than any other element. It is essential in the formation of protein, and protein makes up much of the tissues of most living things, including plants. Phosphorus is linked to plant’s ability to use and store energy, including the process of photosynthesis. It’s also needed to help plants grow and develop normally. Phosphorus in commercial fertilizers comes from phosphate rock. Potassium is the third key nutrient of commercial fertilizers. It helps strengthen plants’ abilities to resist disease and plays an important role in increasing crop yields and overall quality. Potassium also protects the plant when the weather is cold or dry, strengthening its root system and preventing wilt. These NPK numbers correspond, respectively, to the nitrogen content, phosphorus content, and potassium content of that fertilizer and they directly represent the percentage of that nutrient in the fertilizer mix. The remaining percent of the bag’s weight is comprised of other minor nutrients or fillers. To sum it up: the higher nitrogen levels are responsible for fast, green growth. Phosphorus aids with root and flower development, while potassium provides for the plant’s overall health.

The only difference is the size of particles but that fact affects how and where these materials can be used in a garden. 

Sawdust is very fine and has much more exposed surface area than wood chips or wood shavings do, so incorporating fresh sawdust into soil is never a good idea because of excessive nitrogen tie-up. Best way to use sawdust is as a brown material in your kitchen scraps composting. It will not only provide the necessary carbon for the proper decomposition; it will also absorb the excess moisture released by kitchen scraps and it will also absorb any unpleasant odors that might otherwise escape from the compost bin. Sawdust also makes a spectacular mulch for perennial crops. As long as you scatter a bit of organic fertilizer, poultry manure, or other nitrogen source over the surface each time you throw on a fresh layer, sawdust makes unsurpassed mulch for acid soil loving plants like blueberries, strawberries, and raspberries, and it can work well with asparagus, too. Garden paths can also be layered thicky with newspaper or a layer of cardboard and then covered with sawdust. After it has rotted, sawdust contributes mightily to soil’s texture, because the spongy tidbits persist in the soil for a long time. 

Wood shavings and wood chips can be tilled into the top layer of soil to add organic matter once they decompose. They are also excellent mulch for perennial plants. I thick layer of either woody material will with time tremendously increase the quality of the soil not only by adding organic matter but also by feeding the soil’s biota and by increasing soil’s ability to hold nutrients and moisture. Wood shavings and wood chips are also excellent cover for paths. They are also aesthetic to see once neatly arranged around your raised beds to create dirt free paths. 

In general, it is best to use woody materials around established plants only and avoid the vegetable bed except to create paths. Keep chips away from stems and trunks and the siding on the house to not invite termites to close to your home. Use 10 to 15 cm of wood mulch, best if applied over a nicely broken organic layer such as leaf litter or compost. 

Field studies suggest that a high-fiber diet of woody materials is exactly what many soils need. Rotted bits of wood persist as organic matter for a long time, enhancing the soil’s ability to retain nutrients and moisture, which results in bigger, better crops. But there is an important point to consider: woody materials are high in carbon and cellulose, so they need nitrogen and time in order to decompose. If you ignore these facts by mixing fresh sawdust or wood chips directly into your soil, the materials will bind up much of the soil’s nitrogen and render the spot useless for gardening for a season or two. The outcome changes, however, if you add nitrogen or time. For example, when researchers planted a new organic apple orchard in northern Maine in 2005, fresh wood chips combined with blood meal (a very high-nitrogen organic material with a typical analysis of 12-0-0) and tilled into the top layer of the soil — plus a surface mulch of wood chips — proved better than three other treatments at promoting rapid tree growth. And, in less than two years, the organic matter content in the chip-amended plots went from near zero to 2 to 3 percent. We do advise however against mixing sawdust into the soil. It has much greater surface than wood chips or saw shavings and would therefore greatly If you don’t plant to add any nitrogen while adding woody materials, we suggest you use it only as the mulch and give it time to break down unhurriedly. The decomposition will take longer and still take some nitrogen out of the top few cm of the soil, but that will happen at a very slow rate and decomposed wood material will eventually add a much important organic matter to your soil. 

The concern that woody amendments acidify soil is sort of true but only short term. In the early stages of decomposition there is a fast release of acids, when cellulose fibers begin to degrade. Long-term studies of the effects of wood chips and sawdust in soil actually show a slight rise in soil pH, which is good news for most crops in most gardens. (The lower the pH, the more acidic the soil. Most plants are thriving around neutral ph7 or slightly alkaline soil where pH is a bit above 7)

EM or Effective Microorganisms are mixtures of bacteria that result from naturally regulated fermentation processes, without any genetic or chemical modification. EM is safe to use, 100% organic and consists of phototrophic bacteria, lactic acid bacteria (found in dairy matter), yeast (found in bread), actinomycetes and fermentation fungi. These microorganisms are physiologically compatible with each other and coexist in fluid culture. There are different preparations of EM: EM1, EM2, EM3, EM4. The differences are the content of microorganisms in them. EM4 contains 90% lactobacillus spp. and microorganisms that produce more lactic acid. EM4 is The most widely used type in Asia for agricultural and fisheries development. It is mainly used as additive to compost pile to accelerate the decomposition of organic matter and as a foliar spray or as a watering dilution to support the health of the plant and soil microbiota. 

Leacheate is a liquid that seeps from the bottom of the worm composting been. In fact, every compost pile releases some leacheate but worm compost more so. Leacheate can be used directly to water the plants or can be diluted up to 10x before used for watering. It is advised to avoid wetting the leaves since leacheate in raw material and we want to avoid consuming some unwanted microbes. Compost tea is on the contrary a fermented liquid, brewed with water and the addition of small amount of molasses to increase the numbers of microbes. It can be applied to the plants and soil by watering or used as a foliar spray. It is advised to not use it as a foliar spray at least a week prior to consumption.