Understanding How Nitrogen Fertilizer is Lost from Soils Can Minimize Nitrogen Loss

Soil can provide plants with nitrogen through organic matter mineralization, deposition during rainfall events, and residual inorganic nitrogen in soil. However, plants often need more nitrogen than soil can provide to produce a crop yield of desired quality. As such, nitrogen fertilizers need to be applied.

When you purchase nitrogen fertilizers, you will notice that the guaranteed analysis for essential nutrients contained is provided on the bags or containers. For nitrogen, usually guaranteed analysis for percent of total nitrogen, urea nitrogen, nitrate nitrogen, ammoniacal nitrogen, water soluble nitrogen, water insoluble nitrogen, or slowly available nitrogen is provided. Depending on the fertilizer product, one or more of these forms may be contained. It is important that you read the guaranteed analysis label to understand the percentage and forms of nitrogen fertilizer because different forms of fertilizers behave differently in the soil and are lost from soils in different ways.

Ammoniacal nitrogen undergoes a series of transformations after being applied to soils. For example, ammoniacal nitrogen can be converted to a nitrate form, gaseous form (ammonia), or organic form. If you apply ammoniacal nitrogen on the soil surface when the soil is dry or high in pH, you will lose a significant portion of nitrogen to the atmosphere in the form of ammonia. Windy conditions also favor such loss. With dry or high pH soil conditions, the nitrate, slow release, or controlled release forms of fertilizers are better choices. If you inject ammoniacal fertilizers deep into the soil, then nitrogen loss to the atmosphere in the form of gaseous ammonia is very little. Under optimum soil temperature and moisture conditions, ammoniacal nitrogen can be converted to nitrate nitrogen quickly.

Injecting anhydrous ammonia into the soil. Photo credit: Haiying Tao

Nitrate nitrogen, either converted from ammoniacal nitrogen or being applied as a nitrate form of fertilizer, also undergoes a series of transformations in soil. Nitrate is water soluble, therefore, leaching is the major loss pathway – often during heavy irrigation, heavy rainfall, and snowmelt events. If your fertilizer product contains mainly a nitrate form of nitrogen, you should avoid applying the fertilizer before heavy rainfall to avoid leaching loss. If you have soil with poor drainage, applying a nitrate form of fertilizer in water logging condition should be avoided because significant portion of nitrate nitrogen can be converted to other gaseous forms of nitrogen and be lost (e.g. nitrous oxide or molecular nitrogen which makes up most of earth’s atmosphere).

Liquid fertilizer application equipment setup. Photo credit: Haiying Tao

Once applied in soils, urea is converted to ammoniacal nitrogen. If urea is applied on the soil surface, it is best if you apply urea fertilizer before rain or irrigation, so that urea is carried into the soils by water. By doing this, you can avoid nitrogen loss to the atmosphere in the form of ammonia gas. In general, it takes about 0.5 inch of rainfall within 24 to 48 hours after surface application to transport urea to the depth that will minimize volatilization loss.

Slow release or controlled release fertilizers reduce nitrogen loss by delaying nitrogen release into the soil. They gradually feed crops during the growth period. Generally, slow-release nitrogen is most beneficial when fertilizer is applied in cold temperatures, on the soil surface, in soil with high leaching potential, or at hillslope locations with poor drainage/high water ponding risk. Carefully managing application rate is still necessary for these fertilizers because excessive application can cause nitrogen loss. The portion of nitrogen that is converted to ammoniacal and nitrate forms but not taken up by plants can still be lost to the environment.

Knowing that nitrogen is not held by soil and can be lost if not taken up by plants, the timing of nitrogen application is important to minimize nitrogen loss from your soil. It is best that you synchronize nitrogen availability with plant requirements and look at weather forecasts before fertilizer application.

For questions on fertilizers, contact the UConn Soil Nutrient Analysis Laboratory (email soiltest@uconn.edu or call 860-486-4274) or contact your local Cooperative Extension Center. For any other gardening questions, contact the UConn Home & Garden Education Center (email ladybug@uconn.edu or call 877-486-6271).

Haiying Tao, PhD

 

Hidden in the Soil

It is harvest time in the vegetable garden, doing end of season gathering of squash this week. The vines of the honeynut butternut and spaghetti squash have all withered and dried signaling the squashes are ready to be picked. Once the color deepens and skins toughen the fruit should be cut from the vines and cleaned up. I wash them in a slight bleach solution to remove any fungi and bacteria that might cause rot once they are placed in storage in my cool hatchway to the basement where they will not freeze. Wrapping each in a sheet of newspaper to keep them from touching is an added measure to help retard decomposition.

Back in the garden I pulled all of the vines to add to the compost or burn any diseased plant remains. Insect problems from this year might over winter in the plant debris so cleaning up the beds is recommended. While I am there, I scrape the soil with my 20 year old CobraHead hand-weeder, my favorite tool. When held horizontally it only disturbs the top inch or so of soil while I remove any weeds without bringing up many weed seeds from deeper in the soil which might germinate next year. Even though I am only disturbing shallow depths of the ground, some insects come crawling, wiggling and moving out of what they thought was a safe place to spend the winter. It is amazing to sit on my little garden stool and watch the life emerge from what at first glance, appears to be lifeless or dormant.

First to emerge from the soil was a crazy snake worm, (Amynthas agrestis). They are an invasive species from distant lands of Korea and Japan, and do not belong in my New England garden. They move in an ‘S’ pattern and rather quickly, but they are no match for my fast, gloved hand to grab and toss into a repurposed ricotta container rescued from the recycle bin to live another life as a worm container of death. A few more swipes of the CobraHead and several more make an appearance only to be promptly deposited to the dreaded, dry plastic vessel too tall from them to slither out.

Normally worms are considered a beneficial being in the soil, but not snake worms. They damage the soil by eating large amounts of organic matter and leaving behind their castings (poop) which resembles Grapenuts cereal, small granules of black matter. Their castings change the micro biome of the soil making plants less likely to survive. There are not legally allowed control measure for obnoxious invaders except for hand removal of them. There is some research work being done at the University of Vermont and more around the Great Lakes as the snake worms are having a very large detrimental effect on the forest floor in those areas. Crazy snake worm adults will die when the ground freezes, but they leave behind their eggs, called cocoons, which will survive the cold to hatch next spring.

The next critter that made an appearance was an earwig. My gardens have always had a lot of these brown decomposers of dead plant material, but occasionally I they will feed on live leaves, flowers and fruit. Normally they do very little harm, despite their fierce looking pinchers on their butt end. They use their forceps for defense and offense, and will pinch skin if you hold one in your hand. Earwigs overwinter in the adult stage, coming out of their dormant period in the spring to ensure their population continues yet another year.

Grubs are the larval stage of beetles. There are many beetles which inhabit soil and above ground spaces. Most lays eggs in or on the soil, which hatch into grubs that feed on plant roots. Grubs in the lawn can cause significant damage, so do grubs in the vegetable garden when they feed on the roots of my vegetable plants. As a general rule, I squish grubs when I find them in my vegetable beds, even though some adult beetles may be considered beneficial by feeding on other pests. In my garden, the Asiatic garden beetle is the predominate one, causing lots of feeding damage on my leaf crops. They love basil, effectively stripping plants seemingly overnight.

The vibrations of my scraping the soil seemed to bring armies of squash bug nymphs and adults to surface where I was working and to adjacent areas yet to be disturbed. This was the squash bed and I expected the squash pests to be where the cucurbit crop was grown, but I didn’t anticipate the crowd that came to see why I was unearthing their winter abode. Only the adult stage is listed as overwintering, but I found many nymphs not yet developed to their mature adult stage. I hope the cold will kill them so I don’t have to squish many more.

Adult Squash Bug

Squash bug nymph

Squished squash bug nymph

 

The final insect I found while digging wasn’t crawling or moving. It was the resting stage of a moth, which species, I do not know. It was the pupa without many identifying features. I have yet to find a book just on moth pupae, but I am still looking. Once I found the pupa of a tomato hornworm, identifying itself by the hookshaped ‘horn’ on the end of the pupal case. I wish I had taken a photo of that one!

-Carol Quish

 

 

 

Things I See Outside This Week

The gorgeous flowers of the  horse chestnut are blooming this week. Aesculus hippocastanum is commonly called European Horsechestnut or Common Horsechestnut. The massive trees are fast growers and need plenty of room to spread out and reach high. Never plant one near or under power lines. The panicle flowers are normally white with parts of pink and yellow. There is another variety with pink flowers as shown below. Horsechestnut fruit is not edible for humans and are called conkers. The shiny nuts look nice displayed in a dish for nature lovers, just don’t try to crack and eat them!

Red Horsechestnut Flower

Luna moth sighting have been reported around the state this week. They are a strikingly large and beautiful, with only a brief seven days of life in its adult stage. They are nocturnal spending the night seeking a mate with females laying eggs for next year’s generation. Occasionally they will fly towards a light even landing on a screen door with lights on inside. Host trees providing leaves for caterpillars to eat are walnut, hickory, sweet gum, and paper birch.

Luna Moth

In the vegetable garden asparagus beetles are very active, feeding, mating and laying eggs. As can be seen in the lower photo, eggs are laid on on point sticking horizontally at a 90 degree angle to the stem and off of the flower bud stem. Crush all eggs by running you hand up and down each stalk. Catch adults beetles and crush or drop into a container of soapy water to rid them from the asparagus patch.

Asparagus Beetle

Asparagus Beetle Eggs

Another oddity was sent to my office this week. This is an Apple Oak Gall produce by a developing tiny, cynipid wasp. The adult female wasp injects the egg and a chemical into leaf tissue, causing the leaf to distort and makes a home and food for the newly hatched larva. Once the larva is big enough, it pupates inside the gall, only coming out once the gall is empty and dry. There are not enough wasp and galls to cause harm to the tree, so they are only considered cosmetic not a pest.

Apple Oak Gall

Another gall I found this week was the Wool Sower Gall on a white oak tree.  The gall is caused by secretions from the developing wasp larva, secretions of , (Callirhytis seminator). These galls and wasp damage are also not harmful to the tree. The wasps are not dangerous to humans as they do not sting.

Wool Sower Gall on white oak.

Other galls we have seen in past made by insects are the grape tube gallmaker galls on grape leaves, (Schizomyia viticola). Grape tube gallmaker is a species of mite that forms a gall on New World grape leaves. Larvae feed inside the tubes and are free from predators as they feed on the deformed plant tissue. Again only cosmetic to the plant.

Grape Tube Galls on grape leaf.

Finger galls form on a cherry leaf below. Eriophyid mites are the gall makers here. They are microscopic mites developing inside the raised, malformed tissue. Mites can be identified by the structures they create on their host plant.

Finger Galls on a cherry leaf.

Velvetleaf galls on sweet birch develop from the feeding of the  velvet eriophyid gall mite.  Reddish-patches are called an erinea, can also occur on silver maple. (JLaughman photo).

The soil bacterium, Agrobacterium tumefaciens, can cause galls, tumors in this case, on the crown, roots and sometimes branches of susceptible host plants. Euonymus is commonly infected. The bacterium can enter a plant via any tissue damage that normally happens during pruning or transplanting. Agrobacterium tumefaciens is also used as a tool in the laboratory in genetic engineering to introduce genes into plants in a natural way.

Crown Gall, Agrobacterium tumefaciens.

-Carol Quish

 

Come See Us at the CT Flower Show!

This Thursday through Sunday (February 21^st-24^th) is the 38^th Annual Connecticut Flower & Garden Show. The UConn Home & Garden Education Center along with the Master Gardener Program and the Soil Nutrient Analysis Lab will be staffing an exhibit and giving seminars. The UConn Horticulture Club will also set up a landscape display. For those of you unfamiliar with the Show, it takes place at the Connecticut Convention Center in Hartford. There are going to be hundreds of exhibits and dozens of seminars and talks devoted to different topics pertaining to flowers, plants, and gardens.

Our exhibit is located at booths 419 and 421, across from the Federated Garden Club. We will be providing free soil pH testing along with limestone recommendations, so be sure to bring a small bag of your soil! Soil Test Kits will be on sale for $12.00 (cash or check only). There are also tons of handouts on composting, gardening, lawn management, and pest & weed control. We will be available to answer any questions you may have, provide useful tips and pointers, or just chat about any of the services we offer.

Final-Floorplan-2019-Flower-Show

(Setting up our booth. Image by Joe Croze.)

(The theme for The Federated Garden Clubs of CT, Inc is April in Paris. Image by Joe Croze.)

Dawn Pettinelli, an Assistant Extension Educator as well as the manager of both the UConn Soil Nutrient Analysis Lab and Home & Garden Education Center, will be presenting two seminars on Thursday. The first is at 11:00 am and is about When Good Worms Go Bad, and the second is at 2:00 pm on Garden Ornaments.

(Dawn Pettinelli. Image by https://ctflowershow.com/seminars-demos/)

Pamm Cooper’s seminar, Gardening to Support Native Pollinators and Butterflies, is on Friday at 12:30 pm. Pamm was an assistant superintendent at a golf course for over 20 years, teaches entomology and turf portions in the Master Gardener Program, and worked with Dr. David Wagner studying caterpillars in a bio-survey for the Tankerhoosen DEEP property and Belding Wildlife Management Area. She now works in the Home & Garden Education Center office using her insight to help guide others and answer questions on better lawn and garden management practices.

(Pamm Cooper. Image by https://ctflowershow.com/seminars-demos/)

Carol Quish will be speaking about Healthy Gardens on Saturday at 2:00 pm. Carol earned a degree in Ornamental Horticulture and Turfgrass Management from UConn, is an Advanced Master Gardener and Master Composter, and is a CT Nursery and Landscape Association Professional. Carol works as a horticulturist at the Home & Garden Center where she identifies pests, insects, and plant disease.

(Carol Quish. Image by https://ctflowershow.com/seminars-demos/)

(Various exhibits throughout previous years. Images by Dawn Pettinelli.)

More information about the Connecticut Flower and Garden Show (ticket pricing, parking, additional vendors, booths, speakers, etc…) can be found online on their website or Facebook page:

https://ctflowershow.com/

https://www.facebook.com/CTFlowerGardenShow/

We look forward to seeing you there!

-Joe Croze

 

Soils Are Cool.

With the encroaching winter storm and dropping temperatures, I thought it would be appropriate to talk about a very interesting and unique soil order, the Gelisol. Soils are dynamic systems that are essential to life as we know it, and are nonrenewable resource that vary in physical and chemical composition throughout the world. Parent material (underlying bedrock, glacial deposits, wind-blown sediment, etc…), climate, topography, biological activity/factors, and time are the 5 soil forming factors. Different places on the planet will produce a wide variety of variations of these 5 factors. To help understand and classify soils, 12 different orders were formed. The 12 different Soil Taxonomy Orders are: Alfisols, Andisols, Aridisols, Entisols, Gelisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, and Vertisols. Each order has unique properties that are a result of 5 soil-forming factors.

Figure 1: Global Distribution of Gelisols (NRCS https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/class/maps/?cid=stelprdb1237761)

Gelisols are, in my opinion, the most interesting and important soil orders. The Soil Science Society of American defines Gelisols as soils that are “permanently” frozen containing permafrost within 100 centimeters of the soil surface, and/or gelic materials within 100 centimeters and permafrost within 200 centimeters of the soil surface. Permafrost is soil and rock that remains below 0 degrees Celsius for a minimum of 2 years; and “gelic materials” are soil components that show evidence of cryoturbation, or frost churning, a mechanism unique to gelisols. Cryoturbation is the irregular breaking and mixing of soil horizons (think different segmented layers of soil) via the movement of water caused by seasonal melts and thaws. To clarify, just because your front yard is frozen for a few months in the winter is not enough to classify the soil within as a gelisol.

Figure 2: A Gelisol (SSSA https://www.soils.org/discover-soils/soil-basics/soil-types/gelisols)

According to the United States Geological Survey, around 9% of global ice-free land area contain gelisols. They are found in tundra and cold-weather environments, which has made them a hot topic of conversation as the effects of climate change are becoming more obvious. Trapped within the permafrost, contained within gelisols are large amounts of preserved carbon. Over thousands of years, during the last ice age, carbon was deposited in permafrost as ice sheets advanced and retreated. Bedrock was ground into fine silts and dust via glacial movement. This glacial flour was blown across the world and deposited, covering everything in sight, including plants and animals. Quick burial in cold environments doesn’t allow for decomposition of organic material. So as a result, modern day gelisols are a giant carbon reservoir. As climate change continues, the environments containing gelisols are more at risk of melting. Melting gelisols means that the organic material within them are now subject to rapid degradation. The decomposition of organic matter releases carbon in various forms, the most dangerous being methane. Methane is a very powerful greenhouse gas that acts to trap light in heat within our atmosphere. Hopefully you can see the problem: increasing climate change has the potential to thaw gelisols, releasing large reservoirs of methane into the atmosphere, effectively increasing the rate of climate change exponentially. Quite literally adding fuel to the fire.

Figure 3: Babe, the bison was found in thawing permafrost is estimated to be around 36,000 years old. (Photo by: Bill Schmoker (PolarTREC 2010), Courtesy of ARCUS)

-Joe Croze, UConn Soil Lab

 

Wisteria

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.

May, 2011

May, 2013

May, 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.

 

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.

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.

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

Yard-long bean

Pole bean

Snow pea

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.

Wisteria

Lupin

Purple snap pea

Yard-long bean

Sugar snap pea

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

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

 

A Day in the Life of the Soil Lab

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.

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.

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