Photo by Stephanie Staton
You can determine your soil's weaknesses and amendment needs by performing regular soil tests.
The key to good soil is good soil management. Even the poorest soils can be improved to yield a productive crop by adding beneficial amendments, which will help improve plant growth and health. Below are six common soil issues and amendments that can help solve them, as well as additional steps you can take to boost the amendments' effectiveness. The amendment details below are simply guidelines. Every farm has different soil requirements, so get to know your soil and experiment to discover the best plan of action for your situation.
Soil Problem No. 1: Soil is too dry.
Common to: sandy soils
Amendments to add: compost
If your crop beds drain and dry out too quickly, they can benefit from the addition of compost, which will add both nutrients and water-retention capacity. The North Carolina State University Cooperative Extension recommends incorporating a 3- to 6-inch layer of decomposed organic material on the ground that needs amended. Be sure to use mature compost, as compost that hasn’t fully decomposed can actually deprive your growing plants of nutrients as it continues to break down.
In addition to incorporating compost into the soil, mulch crop areas to reduce water evaporation from the soil, then turn the mulch into the soil at the end of the growing season.
Soil Problem No. 2: Soil is too wet.
Common to: clay soils, low-lying areas, areas with a high water table
Amendments to add: compost, sand, 78M pea gravel
Soggy, compacted ground needs an amendment to add space between soil particles and allow better drainage. An effective way to combat this is to incorporate gravel or sand into the soil—not simply adding it as a drainage layer below the topsoil. The addition of these amendments will also require you to add organic materials to boost nutrients. Avoid adding sand to clay soils, as the mixture can set up like concrete. According to the University of Georgia Cooperative Extension, clay soils should generally be amended with 1 cubic yard of amendment (such as gravel or compost) per 100 square feet. The amendment rate for non-clay soils will vary depending on soil type and the amendment you choose to use.
In addition to using amendments, build raised beds to encourage crop areas to drain faster. Plant crops in areas away from natural water pathways. Do not work soil, particularly dense clay soil, when it’s wet, as this will only add to your soil-compaction problems.
Soil Problem No. 3: Soil is alkaline.
Common to: clay soils, arid and semi-arid climates
Amendments to add: elemental sulfur, iron sulfate
When soil test results show high soil pH levels, your crops will benefit from some balance. Apply elemental sulfur and iron sulfate at rates dependent on your soil type—your soil-testing agency should provide recommendations. Elemental sulfur reacts slowly with the soil, so apply it the year before planting. The University of Minnesota recommends that additional iron sulfate applications of more than 7 pounds per 100 square foot be spaced one to two months apart. Amounts less than 7 pounds can be applied in a single application. It is safe to apply iron sulfate to plants.
Alkaline soils require continual buffering, so monitor your soil pH every one to two years and amend as needed. For perpetually alkaline soils, grow crops that tolerate high pH, including asparagus, beets, cabbage, lettuce, parsley and spinach.
Soil Problem No. 4: Soil is acidic.
Common to: areas of high rainfall, poor drainage, heavy nitrogen-fertilizer use and high evergreen-tree population
Amendments to add: dolomitic lime, wood ash
For soils with low pH, lime is many farmers' go-to amendment. Lime is best incorporated into the soil, but if you’re applying it to an already-established area, it can be watered in by rainfall or irrigation. The application rate for lime varies based on your soil's pH and type, so follow your soil-testing agency's recommendations. If using more than 25 pounds lime per 1,000 square feet, the University of Florida suggests allowing three to four weeks between applications to minimize negative impacts on plants, such as reduced availability of nutrients in the soil due to over application. Amounts less than 25 pounds can be applied in a single application. Wood ash should be applied at a rate of no more than 2 pounds per 100 square feet, according to the University of Minnesota, as excess wood ash will raise the potassium level in the soil, preventing plants from absorbing other nutrients.
In low-pH areas, you can still grow many acidic-soil-loving crops, including radishes, sweet potatoes, potatoes, blueberries, cranberries, raspberries and apples.
Soil Problem No. 5: Soil has excess salinity (salt content) or sodicity (sodium content).
Common to: arid and semi-arid climates, low-lying areas near salt water
Amendments to add: gypsum (calcium sulfate), elemental sulfur
If you notice white salt crusts forming on your soil, excess soluble salts could be to blame. Test you soil with an electrical conductivity meter provided by your cooperative extension or a soil-testing lab to confirm your salinity or sodicity suspicions.
The application rate for gypsum and elemental sulfur vary based on soil type, so follow your soil-testing agency's recommendations. Do not apply gypsum to sandy or acidic soils, as it can cause mineral deficiencies in plants. Elemental sulfur reacts slowly with the soil, so apply it the year before planting.
Poor drainage is often a factor in sodic and salinic soils. If this is the case in your garden, you can improve the soil by incorporating compost, sand or pea gravel (see No. 2 above). Pond fresh water on the area to leach sodium out of the soil and away from the plants’ root zone.
Soil Problem No. 6: Soil lacks organic matter.
Common to: many soils, especially those that have been continually farmed using less-sustainable methods
Amendments to add: compost
Lack of soil life, failing crops and poor water retention or drainage are issues facing many crop areas and often point to an overall lack of organic matter. To remedy this, the Cornell University Cooperative Extension recommends spreading a 3-inch-deep layer of compost and incorporating it into the top 3 to 6 inches of soil. Be sure to add fully decomposed compost to prevent the decomposition process from depriving your crops of necessary nutrients. You can provide additional benefits to soil microbes by using cover crops during fallow periods, crop rotation, perennial crops and conservation-tillage practices. Avoid soil compaction by not working wet ground.
About the Author: Freelance writer Lisa Munniksma is traveling around the world to learn about sustainable living, agriculture and food systems everywhere. Follow her adventures at www.freelancefarmerchick.com.