Preparing your garden beds for spring
Guest Contributor: Cassey Anderson, CSU Horticulture Agent
It’s March, and the beginning of the growing season is just around the corner. Depending where you are you may be thinking about starting seeds, planning what to do with the far-too-many seeds you purchased, but if you’re itching to get in the garden you'll want to start with your soil.
Existing garden beds, growing well
If your vegetable beds are well established and growing productively each year, you’re probably good with how you’ve been managing things. A soil test after amending new material is always a good idea of give you an idea of your baseline, but if it’s not broken, no need to fix right?
It may be necessary to amend with compost every few years to keep your organic material (OM) in the ideal 4-5% range, and it’s always a good idea to test your soil to see what your new baseline is after amendment events.
Existing garden beds, not doing so well
I know I raise this alarm frequently, but if your garden beds aren’t growing so well it is time for a soil test. Take samples 6-8” deep throughout all of the beds that you manage in the same way. Soil tests generally run from $20-40 depending on how much information you want. You can contact your local Extension office for a recommended list of soil testing facilities.
Soil tests will typically provide you some baseline information. It’s always a good idea to learn your soil texture, % organic material, and to get at least a snapshot idea of the nutrient levels in your soil.
Nitrogen is one of the most limiting nutrients as it can move through the soil with water. There are two ways to get more nitrogen in your soil. The first is to incorporate compost into the top 8-12” of your garden soil, to the point of having 4-5% organic material. The second option, particularly if your other nutrients such as phosphorous and potassium are high, or your OM levels are too high, is to amend with organic or synthetic nitrogen. Keep in mind, your plants don’t have a preference where they get their nitrogen from, so it’s up to you.
Phosphorous and potassium are less likely to be limited and are found abundantly in soils that are amended with compost, but it’s a good idea to track that your numbers aren’t going above or below recommended values.
You may also see results such as EC (electrical conductivity) which tells you how salty your soil is, or CEC – the cation exchange capacity which measures the ability of the soil to hold nutrients, in particular molecules of a particular charge (positive such as Calcium, Magnesium, and Potassium). This gives you a baseline idea of your soil properties, i.e. is it sandy or clay.
For further soil test interpretation reach out to your local Extension office, there can be a lot to unpack!
Getting into an in-ground or raised bed for the first time? Expanding? Ideally, it’s best to do the above-mentioned soil test first and then begin your garden preparation. I won’t get into the nitty gritty of site planning or establishing good sun for your future vegetables, but ensure you have a site with good access to water and sun.
To prepare a new area you can loosen the soil by double digging, this is a task often best performed by a young family member who has a strong back and needs some pocket money. Double digging is when you dig 8-12” out of the ground, then dig an additional 8-12” deep. If your garden beds are in-ground and not raised it is important at this point to establish good pathways, so you don’t get tempted to walk on your newly dug growing space. This can cause compaction which can reduce water movement and plant growth.
If you’re building raised beds you may not need to double dig, but it can be beneficial to mix your native soil with soil you bring in to fill your beds. This prevents issues of water movement between the two layers. It is not recommended to put barriers in between your raised beds and the garden soil unless you have particular circumstances such as contaminated soil, particular pest issues, or mobility issues that mean you’re raising your garden bed at least 18”.
Amend your new garden beds with 1-2” of compost, dug at least 8-12” down. Organic material can improve the nutrient holding capacity of sandy soils, and improve the drainage of clay soils (amongst many other things). Over time a garden soil that has 4-5% organic material in it can release enough nitrogen to allow a vegetable garden to grow healthily.
The gold standard for vegetable garden bed amendments is compost and there are generally two types: Plant based and animal-based. Provided you follow certain precautions, it can be perfectly fine to use either plant-based or animal-based compost in your vegetable gardens. Do be aware, that you cannot use as much animal-based compost due to higher salt content. Salts are not just sodium chloride, or table salt, but other nutrients, in high quantities as well such as magnesium, calcium chloride etc. Too many salts in a soil can cause toxicity to plants. Follow the amendment guide in this CSU Extension Colorado Master Gardener Garden Note for specifics: https://cmg.extension.colostate.edu/Gardennotes/241.pdf see page 3.
Amending can be done by hand with a garden fork or shovel, you can use a broadfork, or you can use a rototiller. The rototiller is least recommended because it can destroy soil tilth that you have developed. For first time gardens rototilling is fine, it’s just not recommended to rototill frequently.
If you’re a container gardener, it’s recommended to use new potting soil for your vegetable plants each year. You can use last year’s soil for ornamental containers or incorporate into other beds/use as a mulch in your garden if you have one (or find a gardener who wants a donation of material!). Using new media (potting soil) ensures that you eliminate any disease remnants that may have persisted in your containers from the previous season.
As always, reach out to your local Extension office with additional questions and for further resources. Happy Gardening!
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