If you follow along closely with me, you are probably aware that I am currently taking the course, Soils for Horticulture through University of Saskatchewan as I begin working towards my Prairie Horticultural Certificate. One of my assignments during this course was to write about my own garden soil with suggestions on improving soil quality.
I have had so much fun learning more about soil and especially loved getting to take a closer look at my own soil! I ordered the SF3 soil test from soil analysis lab Down to Earth Labs in Lethbridge Alberta so that I would have a better idea of what I needed to work on. This soil analysis showed that my nitrogen was extremally deficient and my sodium levels high. Along with my high soil pH, these are things I definitely want to address.
Here I share with you my assignment report of what I plan to do to improve my soil. You can read more about testing and amending your soil here. If you would like to have me write up suggestions for your personal soil, I would love to work with you! Please reach out and we can make a plan! You can email me at email@example.com.
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Managing Alkaline, Grey Wooded, Luvisolic Soil for the Home Vegetable Gardener
Most vegetables grow best in slightly acidic soil with good soil structure. Maintaining adequate levels of nutrients is important for vegetable growth and for fruit production for plants like tomatoes, cucumbers and squash. The soil I am working with is alkaline grey wooded luvisolic soil in raised garden beds that has been amended with compost. Soil test from Down to Earth Labs shows N-deficient; P-excess; K-excess; Ca and Mg optimum; Zn, B, Cu, Fe, Mn, Cl, and Nh4N deficient and Na-excess. Salinity levels have been found to be high – likely due to irrigation with well water high in dissolved sodium (230mg/L).
Below are suggestions of ways to improve poor soil structure, decrease soil pH, increase soil nutrients and decrease soil salinity.
Improving Soil Structure
Hand texturing of the discussed soil shows silty clay soil, with soil forming a strong ribbon 5 cm or longer before breaking. Soil structure needs to be improved to decrease compaction and improve root growth and drainage.
Suggestions for soil structure improvement include:
Adding organic matter such as high quality compost, peat moss, mulched leaves.
Planting a cover crop. Plant legume plants such as vetch, clover or alfalfa in late August or early September. Till young plants into soil in April or May. A cover crop will not only improve soil structure but will also help to increase missing micronutrients and slightly lower pH.
Avoid equipment or standing in garden beds when soil is wet to decrease chances of compaction.
Do not over till. Reduce tilling and till at a slower speed.
Take measures to reduce sodium content in soil (specifics addressed further on) as sodiac soils tend to be dense and impervious to root growth.
Decreasing Soil Alkalinity
Alkaline soil – how high is too high when it comes to pH; options for adjusting pH; where to by pH soil amendments/cost
The high pH (8.1) of this soil is less than ideal for vegetable and fruit growth. Aim to bring soil pH between 6 and 7 – a drop of at least 1.1 to 1.6. Be aware, buffering capacity may be high in this soil as I expect the C.E.C. is high due to high clay content and high calcium levels. This may make the pH value more difficult to change.
Here are a few different considerations and treatment suggestions for decreasing soil pH:
Consider an alternate water source – as irrigation water has a pH of 8.8. Make use of the water in the dugout for as long as it is available. Consider using a gas powered sump pump to get water onto the garden. This will also help improve soil salinity issues.
Using Table 2-5, I have calculated the discussed 540 square feet (0.012 acres) of garden beds will need 24 lbs of elemental sulfur to lower reduce clay soil pH from 8.1 to 6.6. These bags of elemental sulphur from Amazon are $45 for 5 lbs. The cost of lowering pH will using elemental sulphur will be approximately $225 to purchase 25 lbs. These are pelleted sulphur pellets. Expect the changes in soil pH to happen over the two year post application.
Iron sulphate would also be an excellent source of sulphur in place of elemental sulphur for the discussed soil, as it tested completely deficient in Iron. If iron sulphate is used, 144 lbs would be needed (6 x the elemental sulphur amount).
As discussed for improving soil structure, consider adding peat moss which has many benefits to soil and is also acidifying, and/or compost to soil on a yearly or by year basis.
Addressing the Nitrogen Deficiency
This soil tested ++deficient in Nitrogen. Nitrogen is essential for healthy plant leaf growth. Many vegetables, such as corn, squash and brassicas are heavy feeders and do best in a soil high in nitrogen.
My top suggestion for addressing nitrogen issues in the discussed soil would be to use a cover crop. Using a cover crop has dule benefits as it will also help improve soil structure. Other benefits of using a cover crop to increase soil nitrogen levels in this garden is that cover crops tend to be inexpensive and are completely organic, they are easily accessible to the home gardener, and they can add micronutrients to the soil and they protect the soil from erosion.
My option for a cover crop is going to be crimson clover seed from William Dam Seeds, as that is something I have on hand right now. The seed packet states to sow 20 lbs/acre. For the discussed garden beds totalling 540 square feet use 0.24 lbs (or 109 grams) of seed. Unfortunately I do not know if the required Rhizobia bacteria are present for this to fixate nitrogen properly.
Other options for increase soil nitrogen levels include:
This Urea Fertilizer from Amazon is another great option for increasing N in the discussed garden. It is easily accessible to anyone, has excellent handling properties and is easy to apply. A 2 lb bag costs just $22.95. According to the suggested application amount on the bag, only 1.08 lbs is needed for the 540 square feet of garden beds in this project.
Animal manures can be used to increase N levels. Well-decomposed manure is preferred as there is lower risk of e coli contamination, it has less odour and has fewer weed seeds. Applied at a rate of 20 tonnes per hectare, this project requires 0.1 tonnes, or 224 lbs of barnyard manure to cover the 540 square feet of garden. Manure will not only increase nitrogen but will improve soil structure as well.
How to Decrease Soil Salinity
Unfortunately the soil test from this project shows very elevated sodium levels, measured at 1456mg/kg. This is likely due to high sodium levels in well water used for irrigation over the past few years of drought. Well water test shows dissolved sodium levels at 230mg/mL.
High saline soil makes it difficult for plants to take up water because the salts in the soil pull the water towards themselves. Seeds and seedlings are most sensitive to soil salinity. It is difficult to change soil salinity.
Suggestions for dealing with the high salinity of this garden soil include:
Use water from the dugout nearby for irrigation for as long as possible each growing season.
Consider enlarging the dugout as a rain water holding pond for irrigation.
Keep irrigation with well water to a minimum.
Start vegetables that transplant well in a potting medium prior to planting them out in the garden.
Grow more of the vegetables that most sensitive to saline soil (beans, broad beans, carrots, celery, onions, peas, potatoes, pumpkins, radishes, corn and sweet potatoes).
Again, if you are interested in having me write up suggestions for your personal garden soil, you can email me at firstname.lastname@example.org. I would love to use what I have learned to help others!
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