Posts Tagged ‘Soil Amendments’

Mary Beth and I decided to have our soil tested a few weeks ago. We were curious to know if all the work we’ve been putting into improving the soil over the past few years would show up in the test results. The bottom line is: of course the addition of all those organic amendments, mulches and fertilizers made a difference. We could have guessed that because our plants are happy, healthy and provide an abundance of flowers and crops, but we also wanted to know if there might be any problems cropping up or if we’re about to overdo it with fertilizer.

Mary Beth has been improving her soil for more than 12 years. All of her new beds get a generous addition of organic matter, she mulches often, and fertilizes every spring and fall with her favorite product, Yum Yum Mix. I, on the other hand, got a later start and have only been at it for a little over two years. I also dig organic matter into all my new beds and side dress plants with my own organic compost at least once a year, but I haven’t been so great about mulching.

We had our soil tested at two different labs just to see what the differences might be. Mary Beth sent her sample to the Colorado State University Soil, Water and Plant Testing Lab. She used the Horticultural Applications for Gardeners test which costs $28. I used the University of Massachusetts Soil and Plant Testing Lab. They charge $15 for a Standard Soil Test w/Organic Matter.

Here are the two reports: MB Soil Test and BW Soil Test. They both have their plusses and minuses. The CSU report is well-organized and presented in an easy-to-read chart. The U Mass report is visually a little bit of a mess — clearly this is a report that is based on a format used for scientists not home gardeners, but if you give it a good look it contains a more detailed analysis. It also reports the lead levels in the soil, so this is a test we would recommend for urban and suburban gardens if you plan on growing food crops.

We both live in the West in areas where the soil pH tends to be alkaline. Most plants do best when the pH is slightly acidic to neutral, somewhere between 5.5 and 7.5, though acid loving plants like azaleas and camellias like a soil pH of  5.0. Both of our soil samples tested in the acceptable range for all but acid-loving plants. The U Mass report suggests that I use an acid mulch like pine needles for those plants.

The levels of organic matter in our samples reflected our efforts. Mary Beth’s report indicates that her OM is high and they recommend that she maintain it using organic mulch. My soil OM level is “lower than desired for most herbaceous perennials” and the report recommends that I use plants that are adapted to such conditions or improve the humus content with finished (aged) compost. It goes on to make suggestions for both new bed prep: “in early spring incorporate 1 part peat moss into 2 parts soil along with 3 parts of dried blood per cubic yard of soil;” and established beds: “in early spring and early June sidedress with 1.5 cups dried blood per 100 square feet taking care not to damage foliage and water afterwards.” We really liked that the U Mass report provided a remedy that was so specific.

Both reports give the levels of individual nutrients in our soil and U Mass also included two documents that will be very helpful. One is Soil Test Interpretation and the other is Fertilizer Products and Their Properties. Note that this second one provides info for both organic and synthetic fertilizers. I’ve marked the synthetic fertilizers with X’s to indicated that we do not recommend your using them in your garden. There’s also a handy guide showing the capacity of some common household containers. CSU also provides lots of useful information on their site.

Getting your soil tested is a good idea. It’s a very inexpensive way to find out what your garden needs and it will take the guess-work out of deciding what kinds of amendments to use. It will also help you figure out how much fertilizer you need. Mary Beth found out that her nitrogen is very high. This means that she can skip the Yum Yum mix for a while. Too much nitrogen can result in an overgrowth of foliage at the expense of fruiting and more than that can actually harm plants and the environment. My nitrogen is very low, so I’ll be fertilizing with liquid fish emulsion fertilizer (contains nitrogen that is immediately available to plants) and with another longer lasting organic fertilizer on a regular basis until future tests show a better level.


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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.

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Tuesday we talked about when you can start working your soil. (Click here for more on that topic.) Today we’re going to talk about the different types of soils and the kinds of amendments you can use to improve soil structure. In our next post we’ll finish up the topic by telling you what amendments to use to improve fertility.

First, why should you use amendments and how do you know if your soil needs them? Amendments help soil retain the right amount of moisture and provide a good flow of nutrients and air to the plant’s roots. If your plants don’t thrive, or the soil is always wet, or always seems dry, you should think about adding amendments.

Next you’ll need to identify the type of soil you have. The Sunset Western Garden Book suggests thoroughly wetting a patch of soil, then letting it dry out for a day. Then grab a handful and squeeze it. If it feels gritty and falls apart, it’s sandy soil. If the soil has formed a tight ball and feels a bit slippery, it is mostly clay. If it kind of holds together, yet is crumbly, it’s probably loam.

While sandy soil has good drainage, it won’t hold water or nutrients long enough for plants to take them up. This type of soil needs lots of organic matter.

Clay soil is the most difficult to work with. It bakes hard in the heat and holds too much moisture when it’s wet. The one virtue of clay, or heavy soils, is that they are very mineral rich. These soils need lots of organic matter to open them up. One thing to note is that there are times when it’s just too hard to fix this type of soil. In this situation the best you can do is to build some raised beds, fill them with nice loamy soil and take it from there.

Loamy soil is the best type of soil for growing healthy plants and it’s the soil structure we’re aiming for when we add amendments. It has a good balance of sand, silt and clay — the three main elements of soil. Loamy soil doesn’t need much in the way of amendments for improving structure, but might need amendments for fertility.

Here’s a list of organic amendments for improving soil structure:

  • Compost
  • Composted wood shavings
  • Commercial amendments
  • Kelp and seaweed
  • Lawn clippings
  • Peat moss (some controversy as to whether or not this is a renewable resource)
  • Sawdust (you’ll need to add a high nitrogen fertilizer such as aged horse manure)
  • Straw (don’t use hay, it will give you lots of weeds)
  • Leaves

You can use any one of these or a combination. Some people recommend amending with sand, but we don’t think it’s such a good idea, especially with heavy, clay soils where you could end up with something resembling cement.

When amending poor soil for the first time, you can use as much as 30% by volume of any of the above. Soil should be neither too wet, nor too dry when working it. Dump the amendments on top of the soil and dig in to a depth of 12″ to 18″.

Some final notes:

  • Be sure to ask for organic amendments.
  • Don’t use sewage sludge-based or “biosolids” amendments. They claim to use “natural, organic” ingredients and they’ll say “natural organic fertilizer” on the package, but they are NOT what any organic gardener would consider to be truly organic. Worst of all they contain heavy metals which are toxic even in very small amounts. Absolutely NEVER use them in a vegetable garden.
  • If you use horse manure make sure it’s well-aged, at least three months. Otherwise it can be too “hot” and burn your plants, plus it might contain live seeds if it’s not aged properly.

If you are still unsure of what kind of soil you have, call your local Cooperative Extension or go to your local nursery — you might even bring a small baggie of your soil with you. The folks there will know about the soil in your area and will be able to recommend the appropriate amendments.

There are lots of other amendments out there; things like rice hulls, bean straw, coir, apple and grape pomace, and they are all good but less readily available. If the local experts recommend something that works in your area and it’s easy to get ahold of, use it.

Good soil texture, or structure, is just half of the equation. You’ll also want to add amendments to improve fertility and we’ll talk about that next week.

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Most of us are SO over winter at this point and all we want to do is get our hands and feet in the dirt again. But hang on a minute! Even though we’re ready to get going, our gardens may not be. Working the soil now could actually harm it and create a difficult growing environment for plants.

Whether you’re thinking about planting flowers or vegetables, the soil in your beds must be completely thawed and not saturated before you start. If your soil is very wet from melted snow or winter rains, don’t do anything! Even walking on it will compact it and make it more difficult to work later. (As a matter of fact, once you get the soil in your beds in good shape, you should try to walk on it as little as possible. A few well-placed rocks, boards or paths will help.)

Here’s a little test to help you decide when soil is ready to be worked. Dig into the ground where you want to work (note that different parts of the garden may have different levels of moisture) and bring up a trowel full of soil. Take a handful and squeeze it. Now open your hand. Does it stay in a tight ball? If it does, it’s too wet to work and you’re going to have to wait until it dries out a bit. If your handful starts to break apart when you open your fingers, poke at it. Does it crumble into small pieces, kind of like chocolate cake? Very good! It’s ready to go.

Once your soil is workable, you’ll want to start thinking about amending it and here is where things get slightly more complicated. When we talk about amending soil, we are really talking about two separate but related things — soil structure and soil fertility, or good tilth as it is sometimes referred to. These are two critical elements that will make or break you as a gardener and in Thursday’s Garden Journal we’ll help you figure out what you need to do to create the best possible soil in your garden.





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Note: This week’s tips are aimed at our home communities of central Orange County, CA and Durango, CO, though if you are in another location you might glean some ideas about where to look in your own area.

The UCCE Orange County Master Gardeners have a great hotline (714-708-1646 or hotline@uccemg.com) that’s available to OC residents to ask any kind of gardening, horticulture or pest-related questions. Once the question is phoned or emailed in, our Master Gardeners consult with each other, research the literature, and make sure that any answers they give are based on University of California research, so it’s all very correct and scientific — as opposed to that great tip that your grandma gave you that may or may not be good for your garden.

This past week a question came in about where to find soil, amendments, etc. in Orange County. In Southern California it’s time to think about beefing up the soil so we’ll have a successful growing season and the rest of the county isn’t that far behind. So here are some ideas about where you’ll find what you need to get your garden ready for planting.

This first set of suggestions was complied by OC Master Gardener and workshop presenter extraordinaire, Kay Havens. Kay is a terrific presenter and she’ll be speaking at the one of the spring workshops at the Great Park Food and Farm Lab on March 19th. Don’t miss it!. (The complete schedule is over to the right.)

During talks Kay encourages gardeners to…

Ask pros at “better nurseries” in their area which products will produce the end result you desire. A potted tomato needs an entirely different product than a reseeded lawn. A list of “better nurseries” in Orange County would begin with; Green Thumb, Plant Depot, Rogers Gardens, Armstrong Garden Centers, and Village Nurseries.These “one stop” shops stock plants, bagged soil materials, and tools. For many gardeners knowledgeable assistance and a variety of healthy plant materials is worth paying a little more for. Big boxes such as Lowe’s and Home Depot are economical alternatives.

There are some specialty businesses. Orange County Farm Supply is the most quixotic — geared towards the more advanced gardener who knows what they need. If you need something special, like Citrus Leaf Miner pheromone traps, it is often a good idea to call before going to be sure it is in stock. Their stock is geared towards gardeners and small orchards. They have specialty tools and a very wide range of bagged goods, including bagged pumice. They do stock plants, but the inventory is ever-changing. If you want a 40# bag of Cottonseed meal, an avocado picker, or Texas tomato cage this is the place for you. They give everyone a discount — not just MG’s. Orchard Supply Hardware (OSH) will stock some of the same things.

“Bulk” amendments are most cost effective with a pickup truck load costing less than $30 at some locations. Most bulk distributors such as Tierra Verde Industries (TVI) and Aguinaga sell a range of soil amendments. The problem is you do need a pick up truck and some way to cover and secure the load for the drive home. You’ll also need wheelbarrows and shovels to move the materials when you get there, and a big clean up after. Materials are priced and loaded by the tractor scoop ONLY, and that is how it is. No, they don’t have a smaller pricing structure. They don’t want homeowners taking up space in their yard shoveling into buckets.

Most homeowners will find it easier to use bagged goods… so it is worth knowing that some of the local “Big Box” Scotts products use local TVI goods. Serrano Creek Amendments is another place to know about. It sells only composted horse manure, which is available bagged.

For those of you in Durango Mary Beth says:

Native Roots Garden Center and Durango Nursery and Supplies are the two nurseries I visit the most in Durango. Between the two you will find everything you need to get you started off on the right foot this season. They both have friendly knowledgeable staff who can answer all your gardening questions and they have a huge selection of perennials, trees and shrubs that will survive in this tough climate.

Native Roots has some great gardening hand tools (Cape Cod weeders!) and seeds. They both carry several different kinds of mulch; shredded cedar, pine bark, spruce bark, chipped aspen, and recycled pallets (oak) in both bags and bulk. They have samples for you to look at at the checkout desks. Both nurseries carry the Soil Menders line. Yum Yum Mix and Back To Earth are two products I use every year in my gardens to improve the soil.

In Bayfield, I love to visit Bayfield Gardens. It has a wonderful lush indoor nursery that has a large selection of perennials, annuals, vegetables, and beautiful hanging baskets and containers packed with great color combinations. They also carry bagged soil amendments and fertilizers.

The “Big Box” stores and hardware stores in town and in Bayfield carry bagged soil, mulch  and a variety of plants. Home Depot has a large variety of tools, hoses and pond kits.

If you’re looking for soil to be delivered to your gardens, Soiled Rotten Topsoil (love the name!) will deliver. I hear they have custom mixes to suit your gardening and landscaping needs.

If it’s beautiful colorful pots of all shapes and sizes you want, go to Dietz Market. It’s always a fun place to visit. In the spring it’s overflowing with colorful, unique home and garden accessories that will pick you up out of the winter doldrums.

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