Soil


One of my favorite plants in our yard is a large wisteria that wends its way through and around our back deck. Planted in the early 2008 this woody, non-native climbing vine was slow to flower. Although a hardy, fast-growing plant, wisteria usually doesn’t produce flowers until it establishes itself and matures so it was a few years before the first blooms appeared in May of 2011, the image on the left. The center image is from May, 2013 and the image on the right is from the same perspective but in May of 2017.

In early May, before most of the foliage leafs out, the flowers will begin to open, starting at the base and gradually working towards the tip. The 6-12” long drooping racemes of wisteria bloom from basal buds on last year’s growth of wood. It will continue to bloom through the summer when it has full sun and well-drained soil.

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Wisteria vines can become very heavy and need a strong structure such as a trellis, arbor, pergola, or in our case, a deck to provide support. The twining of the stems can be used to identify the species, depending on whether they twine clockwise or counter-clockwise when viewed from above. Our wisteria twines counter-clockwise so it is a Wisteria sinensis, Chinese wisteria. Wisteria that twines clockwise is Wisteria floribunda, Japanese wisteria.

I usually prune it in the early spring when I also give it a low nitrogen-fertilizer. If it sends out unruly new growth during the spring and summer I just break them off by hand. Likewise, with any adventitious shoots that appear at the base of the plant. It’s a low-maintenance plant otherwise with practically no pests or diseases. The bees and other pollinators love it and I saw a hummingbird visiting it this week. One of the few pests that are ever on it are Japanese beetles.

JB

As you can see by the oval white egg on the surface of its green thorax this beetle has been parasitized by a tachinid fly, Istocheta aldrichi. These tiny flies attach a solitary egg to the Japanese beetle. It will hatch a week later and then the tiny larvae will burrow its way into the body to feed. The larvae will consume the beetle from the inside causing its ultimate death, exiting the body to pupate. If you see a Japanese beetle with one of these eggs on it, let it be. It is already on death row and the new fly that it is nourishing will go on to parasitize other beetles in the future.

As I walked past the wisteria earlier this week I noticed bees among its beautiful pendulous violet flowers. I took out my phone to get a picture and as I focused on the buzzing bee I noticed how the individual blooms of wisteria are so like the blossoms of the different beans in the vegetable garden.

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Like bean and pea flowers, the blossoms of wisteria are zygomorphic. ‘Zygomorphic’ means that the flower is only symmetrical when divided along one axis, in this case vertically, unlike the radial symmetry of a flower such as a daisy which is the same on either axis. Clockwise from the top these are the blossoms of a wisteria , a purple sugar snap pea, a pole bean, and a yard-long bean.

Wisteria and beans share many traits with the almost 18,000 other species in the Fabaceae family, also known as Leguminosae, making it the third largest family of flowering plants. Grown world-wide, this group contains trees, shrubs, vines, and herbs that bear fruit called legumes. Many legumes are grown to eat, such as the edible pods of freshly-picked snow and sugar peas and beans, the edible seeds of peas and peanuts, or dried pulses such as lentils, chickpeas, soybeans, beans, and lupin.

I never connected the ornamental lupin, Lupinus polyphyllus, that grow in our flower beds with the salty lupini beans, Lupinus albus, that accompany many antipasto platters. But when you look at the seed pods of an herbaceous lupin the similarity to other legume seed pods becomes apparent. The images are, clockwise from the upper left, wisteria, lupin, purple snow pea, sugar snap peas, and yard-long beans.

Fun fact about another legume: in a method called geocarpy, the seed pods of peanuts develop underground. This gives rise to its other moniker, the groundnut. Post-fertilization, the yellowish-orange peanut bloom sends out a ‘peg’ that grows down to the soil where the ovary at the tip matures into a peanut seed pod.  Like most other legumes, peanuts have nitrogen-fixing bacteria called rhizobia in their root nodules. This capacity to take inert atmospheric nitrogen from the soil means legumes require less nitrogen fertilizer. When the plants die they can improve soil fertility for future crops by releasing that fixed nitrogen.

Scarlet runner beans blossoms

Scarlet runner beans

Any home gardener can benefit from growing legumes, whether they enjoy the beautiful blooms, the healthful benefits derived from eating these high protein and fiber foods or to enrich their garden soil for future plantings.

Susan Pelton

UConn Home & Garden Education Center, 2018

All images by Susan Pelton

This year I had the opportunity to work in the UConn Soil and Nutrient Analysis Laboratory during the ‘spring rush’. During this time the Soil lab can get up to hundreds of samples a day. These samples may come in one at a time from homeowners with established lawns or garden beds who are looking to maintain their plantings or from new homeowners who have never planted or cared for a landscape before, or dozens of samples from commercial landscapers on behalf of their clients, or from commercial growers.

For over 50 years farmers, greenhouse growers, and homeowners have been served by the UConn Soil Lab. With more than 14,000 samples coming in on an annual basis, that is a lot of soil! Soil fertility is the first building block of plant health. If a plant is not growing in soil that has the proper proportion of available nutrients then it will not grow as well as it could. Poor soil health leads to stressed plants with stunted growth and stressed plants are vulnerable to insect and disease issues.

Iron deficiency on buddleia

Buddleia with iron deficiency

There are a minimum of 16 elements that have been deemed necessary to vigorous plant health. In order by atomic weight they are: hydrogen, boron, carbon, nitrogen, oxygen, magnesium, phosphorus, sulfur, chlorine, potassium, calcium, manganese, iron, copper, zinc, and molybdenum. Some other elements that may not be used by all plants are sodium, silicon, vanadium, and cobalt. The big 3 are, of course, nitrogen, phosphorus, and potassium. Represented by their symbols from the periodic table as N-P-K, they are the prime ingredients in most fertilizers. The seedlings below show signs of nutrient deficiency and are in need of a weak solution of a balanced fertilizer.

 

Also essential to healthy plant growth is the pH of the soil. It won’t matter how much fertilizer is applied if the soil pH is not in the correct range for the host plant. pH stands for potential of Hydrogen and is represented by a scale that runs from 0-7 for acidic solutions and from 7-14 for the alkalis. The higher the concentration of hydrogen ions, the more acidic the sample is. All soil test results will recommend the addition of either limestone to raise the pH, sulfur to lower the pH, or no action required if the pH falls into the acceptable range for the plant/crop.

All standard nutrient analysis tests begin their journey in the same way. For each area to be tested one cup of soil is sent or brought to the lab along with the soil sample questionnaire. The standard test will provide soil pH, the macro and micro nutrients, the total estimated soil lead, and basic texture and organic matter content. Many homeowners and growers request additional tests or only require specific information in the form of textural analysis, organic matter content (measured by Joe in the images below), soluble salts, a pH only test, saturated media analysis (for soil-less potting media for greenhouses), or nitrate testing (for commercial growers).

 

This spring was very cool and wet, as we all know. Many samples were sent in later than usual and a good many were very much wetter than usual. It is important then that the first step requires that soils be spread onto paper toweling and allowed to dry.

1. Spread soils on drying rack

Once the soil has adequately dried out it must be sieved so that any rocks or bits of organic matter are removed. This step may also involve some pounding to break up any chunks of soil as shown by Skyley.

 

From there a small amount of each sample is placed in a paper cup by Louise to be tested for its pH. It is mixed into a slurry with a small amount of distilled water, the calibrated testing meter probe is placed in the mixture and the pH level is stored in the computer program for later retrieval.

 

In a manner similar to a coffee pour over, some of the soil is placed in filter paper that is resting in a test tube in preparation for the nutrient analysis. A Modified Morgan solution is the liquid used for this extraction method.

 

The nutrient analysis is done by a machine called the ICP which stands for Inductively Coupled Plasma. This machine would be right at home in Abby’s lab on NCIS! When I was in school back in the 70’s we were taught that matter existed in three states: solid, liquid, and gas. But matter has a fourth state and it is plasma. It doesn’t exist on Earth under normal conditions but we do witness it every time we see a lightning strike.  Plasma can be generated by using energy to ionize argon gas.

The plasma flame is hot. Really hot.  6000 Kelvin.  For some perspective, the surface of the sun is approximately 5,800 K.  The solution from the individual tube samples is passed through a nebulizer where it is changed to a mist that is introduced directly to the plasma flame. A spectrometer is then able to detect the elements that are present in the soil sample.

 

Additionally, the testing for phosphorus is done with this machine shown below, the Discreet Analyzer.

 

Some soil samples come from outside of CT and those may present a particular set of problems. The USDA has quarantines in several states to limit the spread of certain invasive insect pest species such as the imported fire ant, golden nematodes, and even a few plant species. For more information visit the Federal Domestic Soil Quarantines site.

Working at the UConn Soil Lab has been a great experience and quite an eye-opener. Who knew that there was so much behind a soil test?

Susan Pelton

All images by S. Pelton, 2108