In Thursday’s Garden Journal we wrote about using amendments to improve soil structure. Today’s post is about adding amendments to improve fertility. As always we are recommending only organic amendments, which for our purposes are those that are derived from living organisms or that are naturally occurring.
Let’s start with one very important concept that should help you understand what we are trying to accomplish. We aren’t feeding the plants directly (like when you use synthetic fertilizers such as Miracle-Gro); we are building soil fertility and supporting naturally occurring organisms which convert organic components into nutrients which feed the plants.
This conversion happens relatively slowly providing your plants with a consistent, long-lasting source of nutrients which is much better for plant health and disease resistance. Synthetic fertilizers tend to stress plants, leach into groundwater, and kill beneficial organisms. This sets up a downward spiral of fewer nutrients, fewer microbes producing nutrients, and stressed plants. But once you commit to feeding the soil, you’ll build fertility instead of destroying it.
There is some crossover in amendments in that those that improve soil structure also improve fertility and vice versa, but we’ve tried to make things a little simpler by listing them by their primary function. For instance, kelp and seaweed are highly nutritious and in their natural form their bulk opens up soil and improves structure so they are on Thursday’s list. On the other hand, if we were to use the liquid form, its function would be primarily a fertilizer.
There are many, many organic amendments that can be added to your soil to improve fertility. Here is a list of our favorites.
- Aged horse manure — be sure to get manure that has been well-aged, at least 3 months. Otherwise you may get weeds from seeds that have passed through undigested.
- Aged chicken manure — should be aged at least 3 months.
- Alfalfa meal — use no more than a couple of times a year. More can have negative effects.
- Commercial mixes such as Yum Yum Mix, which Mary Beth loves. (Still haven’t found it in OC.)
- Composted kitchen and garden waste
- Cottonseed meal – a slow release, slightly acid fertilizer. Good for azaleas and camellias.
- Cow manure — can be used fresh, but wait 2 weeks to plant. Otherwise it should be aged 2 – 3 months.
- Fish meal and fish bone meal
- Green manure/cover crops such as alfalfa, clovers, crown vetch which can be grown and turned into the soil to decompose.
- Leaf mold — this is appropriate for acid-loving plants such as azaleas and camelias.
- Llama poo — can be used fresh without fear of burning. (Available in the Durango area. Have not heard of a source in Orange County.)
- Rabbit manure — don’t need to age this. Safe to use straight on the ground.
There are a few rules to follow when applying these amendments and those that we discussed last Thursday. Depending on your existing soil structure and fertility and the amendments you choose, you could use an amendment or two from Thursday’s list and one or two from this list, but be careful not to overdo it.
If you dig in a nutrient rich compost, that might be all that you need. But if you are amending a new bed and add a lot of straw or sawdust, you’ll need to add a high-nitrogen amendment from this list such as a manure. When creating new beds work the soil when it is neither too wet, nor too dry. Dump the amendments on top of the soil and dig in to a depth of 12″ to 18″.
If you are amending/fertilizing an existing bed you should rake back the 2″ – 3″ layer of mulch, distribute the amendment(s) around the plants (but not too close to the trunk/stalks/stems). You may want to lightly scratch it in, but some plants have surface roots that can be damaged, so watering it in is a better choice. Rake back the layer of mulch and you’re done.
You can fertilize once or twice a year depending on the needs of your plants (some plants need more than others) and the existing fertility level of the soil. Always follow the directions on the package — more is NOT better. It can burn or kill your plants. If you are unsure of which of these to use, check with your county Cooperative Extension or local nursery for expert advice that is appropriate for your area.
Keep in mind that under the surface of your existing beds lies a complex web of garden helpers often referred to as the soil food web. It includes worms, bugs, nematodes, fungi, bacteria, and protozoa. The soil is laced with these creatures and webbed with threads of fungi. You want to maintain this as much as possible, which means that after your initial new bed amendment you’ll dig into the soil only as much as you need to for planting. The less you disturb it the better. As a matter of fact, you’ll want to walk on your soil as little as possible too to avoid compacting it. So set some stones, create narrow walkways, or lay down boards to keep compaction at a minimum.
One last caution: pets and other creatures can be attracted to organic fertilizers. I have many times turned my back for just a second only to find my dog’s face buried in the mulch licking up the apparently very tasty stuff. So far she hasn’t suffered any ill effects, but it’s a good idea to keep your pets out of a freshly amended area until the attractive smell wears off. This is especially true if you’re using fresh manure which can cause a very upset tummy.
Improving your soil structure and fertility will go a very long way to making you a spectacularly successful gardener. Soil is where it all starts, so make sure yours is the best it can be.