The Modern Victory Garden

There are many of us who have limited space availability for food production gardening and yet still manage to produce a tremendous amount of our own food supply.   This post is the final segment of a blog series devoted to exploring the many techniques available to optimize food production gardening.   There are quite a few topics that relate to this pursuit - including (among others):

• Crop Selection
• Intensive Planting Practices
• Season Extension
• Soil Management & Fertility

Focusing on Crop Selection kicked off the blog series, which was then followed by a four-part exploration of Intensive Planting Practices - including the topics of Raised Beds, Closely Spaced Planting, Intercropping & Succession Planting, and Vertical Growing.   The next segment was devoted to a discussion of Season Extension and now this week we will wrap the series up by talking about the topic of Soil Management and Fertility.   You can see all of these blog series posts by selecting "Blog Series" from the Categories in the side bar menu on the right side of the screen.                    

Soil Management and Fertility -                                                   

Soil is so much more than just an anchor for our plants to grow from.     It’s a living breathing environment that if carefully tended will continue to provide garden production for future years, despite intense planting practices.   Soil that is regularly replenished with organic matter and depleted nutrients will ensure that the food we harvest is truly nutrient dense.   On the other hand, poor soil management generally results in more plant diseases, declining production levels, poor water percolation and moisture retention, crops that do not contain maximum nutrient potential, and plants that generally fail to thrive.                     

There are three main points I personally focus on as it relates to soil management and fertility.

1. It is incredibly important to replenish organic matter in the soil.
2. The structure of the soil and it’s layers should be maintained – or at least as much as is possible within the artificial environment of the garden.
3. Vegetables and fruit plants deplete the soil of nutrients, which must be replenished to maintain fertility of the garden beds.

The Importance of Replenishing Organic Matter

Decaying and decomposing organic matter in the soil provides several important benefits.   First, it releases nutrients as the decomposition process occurs – both major nutrients (nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur) as well as others generally referred to as trace minerals.   Second, the organic matter itself acts like a sponge to hold water (needed by our plants) and prevents soil particles from densely compacting down (particularly clay or silt soils) which then pushes out air (also needed by our plants).   As gardeners we want the organic matter to decompose to provide the nutrient benefits, but that same decomposition process means that the organic matter must be periodically replenished or we face reduced soil fertility and declining soil structure.   If we do nothing else for our gardens, regularly adding organic matter is probably the most effective action we can take.   As a general rule, we need to strive to keep organic matter at 4% to 5% levels in our soil.   This translates into an annual addition of approximately a ¼ inch of compost (or equivalent organic matter) to replenish what is lost through normal decomposition processes.   A new or depleted bed that needs rejuvenating will benefit from greater amounts being added.   Hot and/or wet climates will also benefit from greater additions of organic matter than the general rule, because heat and moisture speed up decomposition.                                   

Adding organic matter must be done thoughtfully because high carbon organic matter that is added directly to the soil will initially utilize all available nitrogen to break down and if plants are in that bed too, they will be robbed of needed nitrogen until the carbonaceous material has largely decomposed.   One method to deal with that is to compost materials in piles and then add the finished compost to the garden.   However, some of the nutrients from the decomposition process in compost piles is lost in the form of leaching and off gassing - particularly cold compost piles that are just heaped and allowed to naturally decompose over a fairly long period of time.   Hot composting (which requires frequent turning and careful balancing of the nitrogen to carbon ratios) is more effective in that it reduces the amount of lost nutrients but requires considerably more attention and work.   Green manure crops can also provide needed organic matter replenishment.   Turning a green manure crop over into the soil several weeks prior to the bed being used for crops – allows the vegetation to decompose sufficiently before the plants are introduced into the bed.   The warmer the soil, the shorter the time needed to finish that first major decomposition process.   When I turn my winter cover crops over in the very early spring, I try to do it six weeks prior to the planned planting date for the bed because the soil is so cold that the decomposition process is achingly slow.   One can also compost directly in the garden bed (known as sheet composting) but again, it must be done in advance of planting to ensure that nitrogen is available for decomposition but not at the expense of a crop planted in the bed.               

(bucket of finished compost)                

Maintaining Soil Structure

Soil is actually a delicate living substance.   It’s ability to hold sufficient water (without getting water logged), and provide nutrients through organic matter decomposition and from living organisms feeding and excreting “stuff” - is very much a function of it being maintained properly.   Microbial activity in soil is what makes all this magic happen and sufficient organic matter to fuel it is the primary input.   The other major soil management task (after sufficiently replenishing organic matter) is to protect the soil structure from excessive compaction and excessive tillage.   The living web in soil is extremely important in that it works in symbiosis with roots to improve uptake of water, air, and nutrients.   Heavy duty tilling on a regular (annual) basis and walking on garden bed soils both have the affect of damaging the soil structure and disrupting the microbial activity in the soil.   Once a raised bed has been prepared initially, it really should not need more than an annual aeration with a broadfork and a cultivation of the top few inches with a three-tined cultivator to mix in compost, fertilizers, and to create a fine textured bed for direct seeding.   Compaction will naturally occur just from gravity, rain, snow, etc but the annual aeration process with a broadfork helps to counter those forces.                                                    

(broadfork)                       

If soil is composed of heavy clay (which is inclined to compact readily), or has suffered from other compacting activity, then it may require another double dig process to rejuvenate it.   Luckily, digging a bed subsequent to the first bed-establishing dig is much easier and faster than an initial double dig process.   Walking on the soil or using a rototiller is obviously not the end of the universe, but avoiding both has been proven to increase soil fertility and soil health.            

Replenishing Nutrients

While regular additions or organic matter to the garden provides nutrients for plants (both macro and micro), the depletion of nutrients by heavy feeding plants (such as corn) can outpace the slow and low level release of nutrients provided by decomposing organic matter.   In addition, not all compost or organic matter is created equally.   The inputs to the compost pile, the care by which it was tended, and the amount of heat and rain it was subjected to – all determine it’s relative value as a provider of nutrient replenishment.   In general, most of us do not have the skills or inputs available to ensure our compost contains a uniformly consistent and properly balanced level of nutrients.    Many of our common vegetable garden crops are classified as medium to heavy “feeders” and can place a significant demand on the available nutrients in our garden beds.   I have found a three-pronged approach to nutrient replenishment works best for me.   First, I add lots of organic matter through either compost or green manure crops.   Second, I add rock minerals to the soil when initially establishing a bed and then periodically re-mineralize the beds about every three years or so thereafter.   I add rock phosphate powder (phosphorous), and green sand (potassium and many trace minerals) at the rate of about 10 pounds per 100 square feet for the initial application – generally less in later additions.   I also use dolomitic lime when the soil ph needs raising - which adds calcium and magnesium while affecting the soil ph as needed.   If the soil ph needs lowering I use garden sulfur (which as the name implies adds sulfur!).            

(rock powders)             

Rock powders are long-term resources that provide needed nutrients slowly over time.   Because these rock powders break down so slowly, it is difficult to put too much into your garden - so if you get heavy handed you will only be wasting some money rather than potentially harming your soil and plants, which can happen with a heavy handed application of organic or chemical fertilizers.   Finally, I use organic fertilizers and fish or kelp emulsion drenches to provide a more fast acting nutrient replenishment or to specifically add more nitrogen or phosphorus for plants that require more of those nutrients.   I generally use a general-purpose balanced organic fertilizer when I first plant up a bed in the spring or when transplanting out seedlings – adding more nitrogen (generally leafy greens) or phosphorous sources (fruiting or root crops) if the crop needs one or the other in larger amounts.   Good nitrogen sources are alfalfa pellets (50lb bags from the feed store are fairly inexpensive), blood meal, or fishmeal.   A good phosphorous sources is bone meal.   I use fish emulsion or kelp emulsion drenches to give a mid season fertility boost if a crop indicates it needs something more – otherwise, I generally no longer use a mid season side dressing of fertilizer.   I have found it to be generally unnecessary once soil has been sufficiently amended and improved – particularly if rock powders are used and organic matter is kept high.                               

There are certainly many more aspects to soil management and fertility than this brief discussion has touched upon, but these three elements are from my perspective the most important to pay attention to.   What are some of the methods and practices you use to manage soil health and provide nutrient replenishment?