The gardener’s greatest asset is healthy soil. No matter where you are or what you are trying to grow, taking care of your soil will help your crops.
Learning soil science can be overwhelming. It involves lots of chemistry, and you can easily get lost in technical details.
We are here to help, with this beginner’s guide to soil care. To have a successful garden you don’t need a Ph.D. in soil agronomy, you just need basic understanding of nutrients and pH.
土壤为什么重要?
Soil health is the foundational ingredient in all plant growth! Soil is more than just something that holds plants up—it provides almost all the essential elements that make up plant cells, as well as holding and delivering water. Organisms in the soil perform essential tasks of decomposition and nutrient recycling. Soil quality directly affects what you can grow and how well.
By the way, it’ssoil, not dirt. Soil refers to the complex combination of organisms, minerals and organic material, unique from place to place, that makes up the land. Dirt is what gets on your feet and is tracked into the house—it is displaced and no longer has any of the complexity of soil.
There are two major things to check to find out how healthy your soil is: nutrient levels and pH.
Nutrients
Plants, like humans, needlarge quantities of some nutrients and very small quantities of others. We get our nutrients mostly from what we eat, and so do plants; regular fertilizing is essential to a thriving garden.
Fertilizers can be synthetic or organic, like compost, manure, and blood or bone meal. Nutrient levels in the soil change throughout the year, depending on what is being grown, and on other factors like rainfall and leaching. For best results, you should fertilize your garden every time you plant a crop.
The“big three” nutrientsfor plants are nitrogen, phosphorus and potassium, or NPK, known as the primary nutrients. Secondary nutrients include calcium, sulphur and magnesium.
A complete organic fertilizer like manure will have roughly balanced proportions of these macronutrients. Synthetic fertilizers will have their nutrient information printed on the label.
Look for something that includes all six of the main nutrients, since some fertilizers only include NPK, or only include nitrogen. These supplements can be helpful to give your plants a boost during the growing season, but a balanced nutrient mix is important to start each crop.
The Importance Of Nitrogen
Nitrogen is the number one nutrient to keep track of, since it is critical to plant health but doesn’t occur in the soil without bacterial activity. Nitrogen is also water-soluble so it leaches quickly out of the soil, into groundwater, and is lost.
Most of the nitrogen on earth is gaseous nitrogen, in our atmosphere. To be available to plants, it needs to be “fixed,” orconverted from elemental nitrogeninto compounds of nitrogen and oxygen, called nitrates.
硝酸盐是水溶性的，以植物可以吸收的形式存在。植物也可以从氨中获得氮，氨是氮与氢结合的产物，自然存在于动物和人类的尿液中。
Nitrogen-Fixing Plants
一些植物是“重度饲养者”，它们“吃”了大量的氮，而另一些则需要较少的氮。一些植物可以通过根部的共生细菌菌落来固定来自大气中的氮。The legume family is most well known for this, but othermany other plants, like the red alder tree, also fix nitrogen. Successful invasive species like kudzu and scotch broom thrive in all types of soil because they are prolific nitrogen fixers.
When I first started gardening, I was confused about nitrogen fixing—do the plants actually put it in the soil, where other plants can use it? The answer is no—the symbiotic bacteria convert atmospheric nitrogen to nitrate, a compound that is available to the plant, but that becomes stored in the plant matter itself, not in the soil.
So, for that nitrogen to be available to next year’s crop, you have to till in the green matter of the plant at the end of the season. For example, alfalfa is a nitrogen-fixing crop grown as animal feed. But since the whole plant is harvested and not much is left to till in, it doesn’t significantly improve soil quality for the next year. On the other hand, crops like peas and soybeans do improve soil nitrogen levels, because the seed is harvested with a combine for animal feed and the green matter is left in the field.
Micronutrients
In addition to the big three and the secondary nutrients, plants need small amounts of half a dozen or so other minerals, just like humans do. These include iron, copper, boron, and zinc, among others, Some nutrients that plants need in small amounts become toxic in large quantities. It can be hard to mix very small quantities of additives onto small pieces of land.
Boron, for example, is a mineral that helps strengthen cell walls in plants, and an acre of crops takes about ½ lb of boron as an additive. Too much boron will cause yellowing and withering and eventually stunt a plant.
这意味着，如果你的花园面积为1000平方英尺，那么整个花园只需要不到0.02磅(0.011磅)的硼。想象一下，要均匀分布会有多难!
When I was gardening small plots I never worried about micronutrients. As long as you fertilize at the beginning of your season with a balanced fertilizer like chicken manure, there should be plenty of micronutrients available to your plants all season. However, if you are having puzzling plant problems like stunted growth, discoloration, or failure to fruit, checking your micronutrients is a great troubleshooting option.
Soil pH
Knowing yoursoil’s pHis more actually more important than getting a precise read on the nutrient content, because pH dictates how available the nutrients in the soil become. Your soil could have a perfect nutrient balance, but with a pH too low or high the plants would not be able to access any of those minerals.
Most plants want slightly below a neutral pH of 7 for optimum growth, but a soil’s natural pH varies widely from place to place. Naturally-adapted varieties will have some tolerance for the indigenous pH.
在太平洋西北部我们有酸性土壤，但就在一百英里之外的喀斯喀特山脉的另一边，土壤是碱性的。这有助于了解你所在地区的土壤pH值，但你的花园可能不同。如果你刚买了一套新房子，或者打算在一个新的地方开始一个花园，最好检查一下。
Unlike nutrients, soil pH doesn’t change much unless you change it yourself. If your soil is acidic, you can add powdered lime. If soils are alkaline, you can add sulfur to create sulfuric acid, or organic material that will create acids as microbes break it down, like peat moss.
Changing soil pH is a gradual process that usually requires soil amendments over the course of many years, usually at the beginning of each growing season.
How Do I Know What Is In My Soil?
Most components of soil health, including pH and nutrient levels can be easily tested in a lab. Agricultural extension offices almost always offer soil testing services for low or no cost.
They will give you instructions on how to take a sample and submit it. You can expect your results within a couple of weeks, and if you need help interpreting the results, extension agents are the best people to help. You can buy home test kits, but they offervariable and unreliable results.
You can also have your soil tested for micro-organisms in the soil, but these tests are more specialized and expensive. In Washington, our state extensions do not perform those tests, but private labs in our area do.
Since soil is so unique, labs work regionally rather than nationally. If you want to go this route, ask your extension agent for recommendations, or trythis database on soil labs maintained by the National Center for Appropriate Technology.
Some indicators of soil health that don’t involve testing at all. People have been caring for soil in agricultural societies for thousands of years and there are many factors that help a gardener understand what is happening in their soil.
作物的生长状况是土壤健康状况的首要指标。营养缺乏的症状通常开始于叶片变色或发黄、果实产量差、萎蔫、下垂或枯萎，有时还包括水泡和其他畸形。
It is not always easy to tell the difference between a soil problem and aplant disease, but if it has affected your whole crop at once, rather than starting in one place and spreading, it is likely to be a soil issue.
Other indicators that you can see and feel include soil texture, organic matter, organism diversity and water penetration. When you water your plants, watch to see if it sheets off the surface or if it penetrates readily. Poor water penetration can be a sign of compacted, heavy soil, low organic material, or drought.
The soil should be as light as possible for the type of soil you have. Clay soils will never be as light as sandy soils, but incorporating organic matter like grass clippings or manure will help make your soil more airy. Healthy populations of worms and other macro-organisms will also help aerate the soil, and diverse, abundant populations of worms and other bugs are a great indicator that you also have healthy microorganisms.
Soil Toxicity
Unfortunately, in parts of most cities, and even in some rural areas,the soil is contaminated with toxic metals and chemicals, like lead, mercury, petroleum and solvents. If you live in an industrial neighborhood, near a highway, or in a rural area near or downriver from industry, consider testing your soil for toxins.
If you are unsure about the history of your property or garden, do some digging! (Get it?) Look into county records, find out what uses your land is zoned for, talk to previous owners or neighbors who have been around longer. And when in doubt, get out a trowel and take some soil samples. To find a local lab that will run these tests, ask your extension office. They most likely do not do toxicity tests themselves but will know who to ask.
If you find that your soil contains one or more industrial pollutants, build raised beds to fill with imported soil, or look for a different garden location. Always wash your food before cooking. Cornell University has compiledthese guidelines on common metallic contaminants, including some potential risks and recommendations for safety.
Polluted soil is a reality of life for many people, and by being informed about what your soil contains, you can takesimple stepsto limit exposure and still grow a garden.
A Note On Buying Soil
It is possible to buy topsoil, and many people choose to. It is a good option if you are overwhelmed by the idea of restoring very acidic, alkaline, rocky, or depleted soils, or if you are building raised beds and need to fill them, and especially if you suspect toxic contamination of any kind.
Buying soil can put your mind to rest that your plants are growing in clean soil with a good balance of nutrients, organic matter and pH. But it can get expensive if you have a large garden.
As always, check the labels on products you buy—the more information they provide the better. Reputable companies should tell you the percent organic matter, the nitrogen levels, and pH. Look for a mix that includes lots of organic materials. Check outthis guidefor more details on buying topsoil.
然而，虽然购买表土会让你更容易开始种植花园，但每年你的土壤在整个季节仍然需要呵护，就像你呵护你的庄稼一样。
Ongoing Soil Care
Without care, even the best soil will get nutrient-depleted and stop producing great food. Depending on your climate and what you are growing, this may take years, or months. Throughout the growing season, watch your plants, and amend with fertilizer like compost orworm tea如果你的植物看起来是黄色的，给它们一个刺激。
After the season every year, you need to do a few things to keep your soil healthy.
让土壤休息是很重要的。通过在花园的不同区域轮种作物，你可以帮助植物本身支持土壤健康。旋转固氮剂与重饲料，就像豆类与玉米，创造了一个共生关系在几个生长季节。
轮作对防治病虫害和养分管理至关重要。对你来说，害虫越少意味着头痛越少，收获越好，但它会让你的土壤更健康。While organic pesticides in moderation can help a gardener, applying too much, or usingharsh chemicals like Roundup会危害土壤中的有益微生物群落。
如果你住在气候凉爽的地方，每年冬天都是土壤休息的好机会。为了从冬季休耕中获得最佳效益，在春季种植覆盖作物以保护土壤并增加有机质。
如果你足够幸运，住在一个可以全年种植的地方，你仍然需要让你的土地休息，要么种植覆盖作物，要么每隔1到3年作为牧场，这取决于你种植的作物以及它们的食用量。
Soil Science Is Not Rocket Science
Soil science is a complex and technical field of study in its own right, that people spend lifetimes studying. Don’t let the chemistry and measurement overwhelm you. The bottom line is that by trial and error you will learn a system of amendments and soil care that works for your garden.
Pay attention to your plants and they will tell you if they need something different. Soil tests and pH are tools to help get clarity and troubleshoot when things go wrong, but they are not the law of the garden.
With a basic understanding of what is in soil and how it helps plants, you can navigate most problems and support healthy soil for many years in your garden. As always, don’t be afraid to ask for help, from extension agents, other gardeners, even university professors. If there’s one thing I know, it’s that soil science nerds are always happy to talk about dirt.
This is a great article. Very informal! Thanks for putting this together.