I can't begin to tell you the number of times I've heard gardeners make statements like "I don't need fertilizer because I use manure," or "add lime to your garden each spring it will 'sweeten' the soil." Statements like those are falsehoods and can actually cause more problems, than any good the gardener thinks they are doing.
I think all of you who have been reading my articles know I am a huge advocate of soil testing so I'm not going to elaborate on that again. What I am going to do is explain the difference between soil amendments and fertilizers and explain a little bit about soil structure and how to improve it.
What is soil? Tiny particles of rock and minerals make up 90% of most soils; the size of these particles is what determines your soil structure. The types of soil structure are
- Sand: Large particles, drains very quickly, usually very low in nutrients.
- Silt: Medium particles, has a good balance of moisture holding particles and air spaces. (Did you know that plants roots need oxygen in order to survive?)
- Clay: very small particles, drains very slowly, few if any air spaces.
- The other 10% of the soil is made up of organic materials. This is the part that we can adjust to create healthy soil. Understand this is a time consuming task and doesn't happen overnight.
Smell your soil. A handful of a healthy should smell "earthy" and a sour or fishy smell indicates that your soil has poor drainage.
How do I improve my soil structure? By adding soil amendments. My number one choice is compost or other organic material such as shredded leaves, straw or grass clippings. You can never get too much organic material in your soil.
As I said earlier, it takes time but constant addition of organic materials will improve your gardens soil structure each and every season.
Here's how I handle it in my gardens: each fall I add 5 to 6 inches of shredded leaves to my garden and till them in. In my area we have mostly maple trees so the majority of my leaves are maple. If you don't have a chipper/shredder lay the leaves out on the lawn and run over them a couple of times with the lawnmower. I bag up as much of the excess leaves as I have room for and store them over the winter. I get many of my leaves from neighbors.
In the spring as soon as the soil can be worked I spread another 1-2 onches of leaves on the garden and till them in.
Any excess leaves go into the compost bin. When planting bedding plants, tomatoes, peppers, etc. I add a couple of handfuls of compost into the planting hole. Throughout the growing season I mulch my vegetables with straw and topdress my tomatoes and peppers with compost about once a month.
When I moved into my home some 40 years ago my soil was all clay, poor drainage, and poor fertility. Over the years I have changed it into a very fertile garden.
A healthy soil benefits your plants by ensuring nutrients are readily available and makes it easy for your plants to absorb them.
A word on manures. Many gardeners swear by them but if not applied correctly, they can burn plants. Especially chicken and sheep manures which contain high amounts of nitrogen. Horse and cow manure often contain high numbers of weed seeds. Manures offer very little in nutrients to the garden other than a small amount of nitrogen.
I recommend composting manures before appling them to the garden. The heat in a compost pile will kill any weed seeds and break down the nitrogen than tends to burn plants.
A word on municipal provided compost. Many cities and towns are making compost available to residents. I do not recommend using this compost on vegetable gardens. It often contains grass clippings, and weeds where herbicides have been used. Oftentimes residues of these products may be present and can be taken up by your vegetable plants.
The final word:
- Soil amendments improve soil structure to improve drainage and make nutrients more available to plants.
- Fertilizers provide nutrients to plants to ensure health, and enhance growth.