Seed production generally requires the plants to be longer in the field, typically until the end of their lifecycle. Therefore, the soil amendment strategy must be designed with that specificity in mind, maintaining good soil structure and fertility by slowly feeding the plants with adequate nutrients during the entirety of their life.
Often readily available, inexpensive or free, as well as easy and fast to implement, local inputs are usually favored to build a rich and resilient soil. The amount of inputs necessary will gradually be reduced over time, with a soil that will eventually require less maintenance. To this end, the soil is here built and nourished organically using a synergy of several types of amendment, which can be used individually or combined based on the context and the needs of your soil at a given time.
Surface Composting
Surface composting is the simplest and oldest form of composting used by our ancestors. As they harvested crops, farmers cut off the edible parts, then dropped and spread the residues onto the ground. Those would then decompose and slowly feed the soil and the crops for the following year. Being akin to the natural process observed in nature (i.e., a forest floor) and involving no turning, this in situ composting technique therefore requires less work, offers more flexibility, and is a great way to reconnect with the ancestral practices of past farmers.
Two types of material are used: nitrogen-rich greens such as kitchen scraps and grass clippings; and carbon-rich browns such as dry leaves and straw, as well as wood chips/ramial chipped wood. Kitchen scraps can be further chopped up to accelerate the decomposition process. Already-made rich compost with a good microbial/fungal balance can also be added in reasonable quantities when planting, as it will help to jump-start the composting process. As the materials break down, the pH will stabilize to become more neutral over time, which is best for most plants.
In surface composting, weeds are often avoided, as perennial weed roots or weeds with seeds might sprout and become “opportunistic” (invasive). The process involved in hot composting usually resolved this, as high temperatures will mostly kill any weed seeds present in the pile. Do not add any dairy product or meat, as they might attract rats and other animals. Avoid adding diseased plants as well as seed heads, which might self-sow.
Once the mixed compost material is spread (not too thickly) on the surface of the garden beds, it will then be exposed to the elements and will be further broken down by insects, earthworms, and microorganisms. Alternatively, small trenches (along the garden beds) or pits can be dug up, filled with organic waste, then covered with a layer of grass clippings, leaves, or straw as mulch, creating nutrient-rich material that will feed and improve the soil. Pits are particularly suited for demanding plants such as brassicas, squashes, and tomatoes.
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Mulching
Because of its benefits, mulching is often paired with other types of composting. It decomposes similarly and enrich the soil over time. Mulch has the extra advantage of further protecting the soil by limiting erosion and nutrient loss, retaining moisture (and thus reducing the watering needs of your plants), reducing weed growth, and providing habitat for insects and other small animals. Organic material such as straw, leaves, grass clippings, or wood chips can be used as mulch, which is then spread over a layer of surface compost and replenished as needed through chop-and-drop. As a low-maintenance alternative, light feeder (which does not compete for nutrients) and versatile ground cover crops such as white clover (Trifolium repens), perennial peanut (Arachis glabrata), or gotu kola (Centella asiatica) can be planted, which will then act as a living much while, in some instances, fixing nitrogen.
Biochar
Biochar is a form of charcoal rich in carbon that is produced through a pyrolysis process of biomass in the absence of oxygen. Pre-Columbian Amazonians produced directly (in pits or trenches) or indirectly (byproduct of fire management practices) biochar in combination with organic waste to improve soil fertility. Having the capacity to sequester carbon in the soil for hundreds of thousands of years, biochar is a promising tool to mitigate climate change. With its high specific surface area and porous structure, it has the ability to retain both water and water-soluble nutrients, as well as reducing fertilizer requirements, resulting in an even more gradual and sustained release of nutrients in the soil when mixed with compost. It has proven to be useful in increasing soil fertility in acidic soils, agricultural productivity, and in providing protection against some foliar and soil-borne diseases. Biochar can be “charged” or inoculated with nutrients and EMs (effective microorganisms) before its application in the garden to help prime the soil for improved fertility. This can be done by adding biochar to a compost heap or by soaking it in a liquid compost.
The two most common small-scale methods used to make biochar in a garden are the barrel method and the pit technique (or open earth kiln) – the former usually being easier and producing a more homogeneous result, while the latter being inexpensive if not free as it requires fewer tools. The pit method is a low-tech option consisting in digging a conical hole in the ground, ideally measuring at least 1 m deep and 1.5 m wide for more efficiency, and sheltered from the wind. Most kinds of dry wood can be used and broken up into manageable sizes. Pieces of wood are disposed inside the pit in a tower-shape fashion about three quarters of the pit height, lighted from the top, and left to burn down to coals. When this newly surface layer begins to be covered with white ash, the first fresh layer of biomass can be added. The zone of glowing coals should be covered evenly but not too thickly. Once this new layer also becomes coated with white ash (sign that it has reached pyrolysis temperature), the next layer of biomass can be added. This process is repeated for all subsequent layers, using only small branches for the last two or three layers (as larger pieces added at the final stages will likely remain incompletely charred). Note that timing when adding new layers of biomass to the pit is important. If one waits too long, the char starts to oxidize, which reduces yield and increases the ash content of the biochar. Finally, the pit is thoroughly quenched (watered down) or covered with dirt/sand to stop the burning process and cool down the newly created biochar.
Making biochar can easily take several hours, depending on the burning material used and the size of the pit. The pit can be reused multiple times and its durability as well as efficiency further improved by lining it with compacted earth or bricks. Production can also be optimized through the use of several pits operated simultaneously by a group of people.
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