Last Wednesday, we had an amazing soil workshop led by the lovely Jill Dalton. She works with LifeCycles, has worked on organic farms and went to UBC for agriculture, so she had plenty of knowledge to share with us. Now is the perfect time to learn about soil because it is time to prepare for the coming seasons. There are leaves everywhere to collect!
I have to apologize for not bringing a camera to the workshop. I did find some helpful images to help explain the information on the internet though. I also want to share the credit for this summary with Life Cycles, because I used some of the notes that Jill gave us to write this post.
Jill began by explaining the two ways to approach soil fertility. The chemical route feeds the plant directly with soluble fertilizers. The biological, or organic way, feeds the soil to let the soil organisms provide for the plant. Before you can begin to work with soil, you’ve gotta know what you are working with. There are three categories of soil type and structure:
Sand: fairly large particles that keep the soil open for air and water to pass through; they get warmer and drier earlier in the spring than other soil types.
Silt: medium sized particles, in between the characteristics of sand and clay.
Clay: very fine particles that hold water and provide a rich store of nutrients.
Knowing your soil type is important because it determines drainage and the ability to take up nutrients. If you think about it, the more surface area, the more nutrients and water it can hold. With so many smaller particles, clay has a larger gross surface area. Sand on the other hand, doesn’t hold much water or nutrients and often results in desert like conditions. Soil type is also important in choosing which plants to grow, as some plants grow better in certain soils than others. Dream soil is made up of all three types of soil mixed with a fourth component: organic matter! Ideally, organic matter should not make up more than 10% of soil. Although compost feeds the good micro-organisms that help plants to grow, it also feeds the bad ones that can cause disease.
Preparing for the next growing season is important because it replenishes the nutrients and re-establishes soil structure. One way to do this is through planting cover crops. Bare soil gets compacted and loses nutrients from rain, plus cover crops add organic matter and nutrients when done right. Some of the many fantastic cover crops include clover (a natural mulch and nitrogen fixer) and rye (you can use the stalks as a cheaper alternative to straw).
If you already have a crop, mulching the soil helps to keep moisture in and acts as a cover to avoid compaction and nutrient wash-out. However, there are potential problems to mulching. It can become too wet and the decaying matter can become a breeding ground for slugs and other pests. Weeds can also be imported with mulching materials, especially in straw or grass clippings.
An idea of what lasagna gardening layers looks like. Image from: http://pinterest.com/pin/126452702008193235/
If you do not have good soil to work with, you can create it through lasagna gardening (otherwise known as sheet mulching). It is good not to dig into your soil unless you need to; disturbing the soil causes compaction and nutrient loss when it gets wet. It is called lasagna gardening because it is made up of many layers. The bottom layer, or your existing surface, is covered in cardboard. Make sure that you overlap the pieces of carboard to ensure that the weeds cannot get through. For the next four layers, alternate between a straw/leaves and compost/manure. The greens (nitrogen from your compost) and browns (carbon from the leaves, straw and cardboard) will mix together over time to create a nutrient rich, fluffy soil that is ideal for growing plants. The cardboard takes longer to decompose, keeping the weeds out during the competitive stage of plant growth.
It is also good to know a bit about the chemical make-up of soil, so that you can diagnose problems. The three main nutrients include:
N- Nitrogen facilitates plant growth, especially in the leaves. If there is a nitrogen deficiency, some signs might include stunted growth or yellowing leaves. To fix this, you can add manure, alfalfa pellets or blood meal.
P- Phosphorus helps with plant maturation. If leaves seem more reddish-purple than normal, you can add rock phosphate or bone meal to re-establish the right level of nutrients.
K- Potassium is in charge of cell division, the processing of sugars and root development. Potassium deficiency is difficult to identify, but bronze or brown spots can be a good hint. Add Sulphate of potash or Sulpo-mag to help make the soil healthy again.
The last thing Jill told us about was pH. Unless there is a mystery reason why your garden is dying, it is not necessary to know much about pH. 6.2 to 6.8 is the optimal level for most plants, soil microbial life and bacteria that work with legumes to fix nitrogen, but it is nearly impossible to identify the pH of your garden without a soil test.