The Hippo


May 25, 2020








Healthy soil, happy plants
Having good soil will help your garden thrive


 Few things are as fundamental to gardening as making sure your soil is in good shape. Good soil depends on many factors, but without it your plants will struggle to grow and flourish. Getting your soil tested is key to figuring out what you need to do to create the perfect home for your garden.

Soil comes in many different forms with a variety of characteristics.
Karen Dudley, a soil scientist at the Natural Resource Conservation Service in Concord, said there are 19,000 soil types mapped throughout the United States and about 240 in New Hampshire alone.
She said good soil is defined by three categories: physical, chemical and biological. 
The physical makeup of your soil is determined by its compaction, texture and infiltration capacity, meaning the ability for water to get in.
Don Keirstead, the state soil scientist, said if your ground is too compacted, no amount of fertilizer is going to help your plants grow. That’s because there isn’t enough aeration and places for moisture and microbes to swim around and transport nutrients to the plant. 
A common mistake by gardeners, he said, is doing a lot of garden work when the ground is muddy and wet. By walking and wheeling over muddy terrain, you are more likely to compact the soil.
While generally he recommends very little soil disruption, ground that is already compacted may require some tilling.
An ideal balance in your soil makeup, he said, would be 25 percent water, 25 percent air and 50 percent soil particles.
The chemical makeup of your soil can be broken down into a few different categories. There is the pH balance, nutrients like nitrogen and minerals like calcium.
The first thing people should do to make sure their garden has what it needs is to perform a soil test.
Emma Erler with UNH Cooperative Extension said a standard home yard and garden test is $17 and takes about three weeks from the time the lab receives the sample to the time you get the results. April and May are the busiest months, however, and results can take longer.
To create a sample, you need to collect soil from six to eight different locations in your garden (try to avoid outlier areas with very obviously different soil types) about six inches deep and mix them together in a bucket. For trees and shrubs, dig between six and eight inches deep.
Once you’ve mixed the soil together, extract only one dry cup of soil and ship it to the lab. Don’t send more than one cup.
There’s also a questionnaire you have to fill out that will ask what kinds of crops you’re growing so the lab results can come with informed recommendations.
To find the form and instructions, go to and search ‘soil testing’ in the top bar.
“One of the first things they look for is soil pH,” Erler said.
Erler said the ideal range for most plants is between 6 and 6.5. Keirstead said garden crops in particular like it even higher, between 6.5 and 6.7, which is pretty close to neutral.
Keirstead said Granite Staters generally have to add a lot of lime to bring down the acidity.
“The soils in New Hampshire are naturally very acidic,” Keirstead said. 
For a plot of land that has never been cultivated before, he expects you’ll need about 2 or 3 tons of lime per acre. For deficiencies in minerals like calcium or magnesium, there are bags of lime sold with those minerals mixed together.
The next thing you’ll need to consider is the nutrient load of the soil. The three main nutrients you need to consider are nitrogen, phosphorus and potassium. Every bag of fertilizer is usually sold with a number associated to each under a label that reads “N-P-K” so you know how it’s balanced with one nutrient or another.
If your soil test results mark a low nitrogen figure but it’s high in phosphorus, you need to find a fertilizer that conversely provides more nitrogen and less phosphorus. 
“New Hampshire soils tend to be really high in phosphorus,” Erler said.
Each nutrient provides a different kind of aid to the plants. Sherry Diamond, the president of the Milford Garden Club, remembers what they do with a mnemonic device “up, down and all-around.” Nitrogen helps with the “up,” or green stem and leaf growth, phosphorus helps with the “down,” meaning the root system, and the potassium helps with the plant “all-around.”
Not only do you need to consider your existing soil makeup, you also need to consider what plants need.
“Every plant has its own preferences,” Diamond said.
For things like morning glories, Diamond said you generally don’t want to fertilize them because they’ll just grow their vines and not flower as much. But annuals like petunias and geraniums usually require more fertilizer. 
Keirstead said wildflowers generally don’t need fertilizer and only require a good pH balance.
Timing is also important. Keirstead said the ideal times for putting down fertilizer are when the plants just start growing in the late spring. Otherwise, nitrogen and potassium, which are water-soluble, will wash way and leach into the water table, while phosphorus, usually in salt form, will stick around.
“That’s why it’s best to fertilize your lawn in the late spring when there’s more moisture around … or late fall,” Keirstead said.
Slow-acting lime is best put down in the fall, while fast-acting lime is ideal for the spring.
Finally, your soil needs to have a rich microbial economy. The test results will give you a sense of how much organic matter is in your soil. 
Erler said 10 percent is on the high side, but 5 percent is within the normal range. 
Keirstead said organic material is essential for the nutrients to get to the plant.
“The organic matter in the soil is what feeds the microbes. The microbes are what make the nutrients in the soil available,” he said.
One of the reasons he advises against tilling the soil too much is it increases the air in the soil, which accelerates the decomposition of organic matter.
If your soil is low on organic matter, one option is to grow a cover crop, like farmers do to keep their soil healthy between harvests, or simply add compost and manure. 

®2020 Hippo Press. site by wedu