The home that I rent in Upper Fremont has a rundown house, haphazard garden, and up until last year blackberry thicket covered the yard.
Last year two friends cleared the blackberry out and tilled the ground, then created tidy little rows to plant a garden. One day in May they had a planting party and asked me to improvise a plan for seeding. I thought about sun requirements and families, and threw a diagram together. A big group of us planted seeds in the little rows, including herbs, greens, peas, beet, carrot, chard, tomato, pepper and pumpkin. It was essentially a grand experiment with little observation of the land, and no plan! However, it wasn't long before many seeds sprouted - though no peppers, and some more fully than others. With a makeshift irrigation system, and a little tending, we were able to watch the outcome of our best efforts. I ended up spending more time with this garden through the summer and into the fall, when I finally moved in Dec 1.
My (now) boyfriend and I maintain the garden and are slowly learning how the soil influenced last year's yield, so we can improve soil in the upcoming year. We wish to create the conditions for our desired plants to thrive, perhaps discouraging so many weeds, pests and diseases. We are well aware that 'we are what we eat', or, like our food, we are "truly a product of the soil and reflect in [our] bodies - and minds - the wealth or poverty of the land" (Kohnke & Franzmeier 4). We also know our soil is not that dark.
Last year in late summer I sent soil samples to King Conservation District. All King County residents are eligible for one free soil test a year totaling five samples. King Conservation District contracts with A & L Western Agricultural Laboratories in Portland, OR to conduct the analysis. I sent my samples in the mail and received results through email!
Here are snapshots of test results for my two samples:
In addition to lab results we received a Soil Analysis Booklet PDF created by Peaceful Valley Farm Supply - an organization that began in 1976 out of Nevada City, CA, and currently operates the website groworganic.com. Their booklet is specifically directed at chemical analysis (rather than biological or physical).
Instead of providing a thorough analysis of our lab results, I thought I would highlight what appears to be going well, and what needs improvement. Of course this is based on one soil test taken late summer, and likely the results would be different depending on the time of year, and would be different now, reflecting our efforts over the fall/winter:
Organic Matter/humus
We need high organic matter because it binds to clay/minerals to create water-stable aggregates. This type of soil structure facilitates the slow release of nutrition and proper drainage - thereby nourishing "good tilth" (Kohnke & Franzmeier 13). Since organic matter reads above 5% in our soil test, we don't need to worry about adding more (PVFS 3). Formally the soil was covered by invasive grasses and weeds with ongoing root structure being broken down, which possibly explains the organic matter. Also our cool, moist Maritime climate favors humus formation (Kohnke & Franzmeier 54). However organic matter is always being broken down, so in order to maintain current levels, we will need to continue producing biomass through cover crop, or collecting other plant material on site for mulch, as well as using arborist wood chips.
N-P-K
Nitrogen facilitates quick growth response; phosphorus is key for flowering, fruiting, and rooting; and potassium is important for regulating metabolism (PVFS 4-7). Nitrogen, potassium and phosphorus are the elements most needed for crop yield, so we are lucky our reading is Med-High. We won't have to stress about fertilizing - although our test results indicate imbalance. Since we have slightly lower potassium we may want to add a little, which may inadvertently raise pH (PVFS 7). Yet we don't know how much nutrient loss occurred over the fall/winter, and the amount of plant nutrients taken up by crops and removed from the field vary a great deal from year to year (Kohnke & Franzmeier 43). It will be interesting to see what next year's soil test results show. We overwintered nitrogen-fixing cover crop and will grow peas so hopefully we can fertilize via biomass.
Magnesium and Calcium
Calcium, magnesium and sulfur are secondary plant food elements (Kohnke & Franzmeier 37) and unfortunately our readings are Low to Med-Low. Magnesium is important for chlorophyll production and the uptake of phosphorus; calcium is critical for cell wall structure; and sulfur for the fabrication of proteins (PVFS 8-11). Since our pH is low, perhaps influenced by the strong presence of acidic blackberry, it makes sense that our magnesium and calcium levels are low (the higher they are the typically more alkaline the soil). Because the levels are so low we may need to fertilize beyond adding compost to the soil, while trying to raise pH. One concern with adding lime or gypsum, however, is they can contribute to cementation at lower horizon levels, as mineral weathering accumulates to form a pan (Kohnke & Franzmeier 73) thus diminishing drainage over time. Perhaps just a tiny bit of fertilizing will go a long way.
pH
Our low pH could originate from our moderate rainfall climate (PVFS 14), which encourages an environment where blackberry can thrive in disturbed soil, and perpetuate an acidic soil. However this information alone does not mean we necessarily need to add lime (ibid). It really depends on which crops we want to grow and their pH preferences. So we may want to cultivate microclimates based on pH requirements, because we want to grow some acid-loving foods like potatoes, but also some alkaline-loving foods like Brassicas. However since most crops thrive in pH 6.5-6.8 we generally want to work in that direction (Kohnke & Franzmeier 30) . We could experiment with not adding lime and seeing how next year's soil samples read, simply from adding compost and mulch.
Cation Exchange Capacity
CEC represents the soil's ability to retain and release cations for later use, and the higher the number, they greater the capacity. Our reading, which ranges from 10.5-11.7 is considered low, however if we continue to add compost and cover crop, we may steadily build humus to reach a level of 20 (PVFS 14). This little bit of information is particularly important in relation to pH. We have low pH, possibly due to low calcium -- but if we add lime to increase calcium, our low CEC may not be able to retain it (ibid) rendering the effort useless (and possibly just leaching to create a hard pan in the subsoil!) To connect back to our organic matter levels - which are high - because we have low CEC we need to "promote biological activity" to help break organic matter down, in order to release plant nutrient. The more microbes there are, the more fertile the soil (Kohnke & Franzmeier 57). This may be are best angle toward raising CEC: add compost or even microbial inoculations (PVFS 3). Arborist wood chips may be the most affordable option (free) for building microbial activity.
Summary
Our soil test results suggested that we fertilize with lime, nitrogen, potassium and sulfur. Yet as Toby Hemenway aptly put, "In nature, fertility comes from the vegetation and soil life, not from a bag of fertilizer" (Hemenway 31). Indeed we wish to mimic nature in our efforts to build soil. Our goal is to facilitate "good tilth" so we will take the following steps: build biomass, mulch with arborist wood chips, add compost to the soil, plant nitrogen fixers, and cultivate pH microclimates. Ideally these steps will equate to the permaculture approach of "making the least change for the greatest effect" (Hemenway 6).
Works Cited
Kohnke, Helmut and D.P. Franzmeier. Soil Science Simplified. 4th Edition. Long Grove, IL: Waveland Press, 1995. Print.
Peaceful Valley Farm Supply. Understanding Your Soil Analysis Report. 2004, PDF file.
Hemenway, Toby. Gaia's Garden. 2nd Edition. White River Junction, VT: Chelsea Green Publishing, 2009. Print.
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