Easing the Soil’s Temperature

Soil characteristics like organic matter content and moisture play a vital role in helping plants flourish. It turns out that soil temperature is just as important. Every plant needs a certain soil temperature to thrive. If the temperature changes too quickly, plants won’t do well. Their seeds won’t germinate or their roots will die.Miscanthus roots break up the soil.

The roots of miscanthus break up the soil, keeping it from becoming compacted. Photo credit Timothy Reinbott.

“Most plants are sensitive to extreme changes in soil temperature,” said Samuel Haruna, a researcher at Middle Tennessee State University. “You don’t want it to change too quickly because the plants can’t cope with it.”

Many factors influence the ability of soil to buffer against temperature changes. For example, when soil is compacted the soil temperature can change quickly. That’s because soil particles transfer temperatures much faster when they are squished together. When farmers drag heavy machinery over the soil, the soil particles compact.  Soil temperature is also affected by moisture: more moisture keeps soils from heating too quickly.

Research has shown that both cover crops and perennial biofuel crops can relieve soil compaction. Cover crops are generally planted between cash crops such as corn and soybeans to protect the bare soil. They shade the soil and help reduce soil water evaporation. Their roots also add organic matter to the soil and prevent soil erosion. This also keeps the soil spongy, helping it retain water.

But Haruna wanted to know if perennial biofuel and cover crops could also help soils protect themselves from fluctuating temperatures.  Haruna and a team of researchers grew several types of cover and perennial biofuel crops in the field. Afterwards, they tested the soils in the lab for their ability to regulate temperature.

Taking soil samples in field

Soil scientist Samuel Haruna samples the soil in order to determine how cover and perennial biofuel crops affect soil temperature. Photo credit Samuel Haruna.

“I was amazed at the results,” Haruna said. He found both perennial biofuel and cover crops help soils shield against extreme temperatures. They do this by slowing down how quickly temperatures spread through the soil. Their roots break up the soil, preventing soil molecules from clumping together and heating or cooling quickly.  The roots of both crops also add organic matter to the soil, which helps regulate temperature.Additionally, perennial biofuel and cover crops help the soil retain moisture. “Water generally has a high ability to buffer against temperature changes,” said Haruna. “So if soil has a high water content it has a greater ability to protect the soil.”

Although Haruna advocates for more use of cover crops, he said it’s not always easy to incorporate them into farms. “These crops require more work, more financial investment, and more knowledge,” he said. “But they can do much for soil health.” Including, as Haruna’s research shows, shielding plants from extreme temperature changes.

“Climate change can cause temperature fluctuations, and if not curtailed, may affect crop productivity in the future,” he said. “And we need to buffer against these extreme changes within the soil.”

Haruna hopes to take his research from the lab and into the field. He says a field experiment will help him and his team collect more data and flesh out his findings.

(Source -http://www.farms.com/news/easing-the-soil-s-temperature-128931.aspx)

 

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Farmers advised on water and soil management

While no one knows exactly which mix of factors and to what extent those factors are causing algal blooms on Lake Erie, it’s clear among the scientific community that, in the western basin, farmers are at the very least playing a significant role.

Along with sunlight, the release of soil nutrients like phosphorus and nitrogen through farm field runoff helps create environments in waterways where harmful algal blooms can form, threatening health outcomes in the area and putting a major damper on the region’s tourism and fishing industry dollars.

That’s why former Kentucky farmer, Dr. Kevin King, research leader and supervisory research agricultural engineer with the U.S. Department of Agriculture’s Agricultural Research Service-Soil Drainage Research Unit was on hand at the Williams Soil and Water Conservation District’s Field Technology Day to discuss possible solutions and to enlist farmers’ help in further understanding the problem.

According to King, testing at 80 fields across 40 sites has revealed that drainage from tiles contains a phosphorus concentration of about .05-.06 parts per million (ppm), right at the level accepted through an agreement between the U.S. and Canada.

“Our tile is just about there,” King said, noting that some individual sites rich in phosphorous do contain much higher concentrations.

However, surface flow drainage contains concentrations of about 0.2 ppm on average.

While tile drainage accounts for anywhere from 40 to 95 percent of annual discharge, surface drainage’s higher concentration remains a bigger issue, according to King.

“Concentration is what really feeds the algal bloom,” he said.

King noted that the region has had 4,500 rainfall events since 2010 and that individual rainfall events totaling 1.5 to 2 inches or more cause the loss of 60 to 70 percent of all nutrients leaving test sites.

“If we can store 1.5 to 2 inches of rain in our landscape or at the edge of the field, then we can go a long way to reduce the amount of nutrients going downstream and eventually in the lake,” King said, listing possible solutions like elevating tiles at certain times of the year and planting cover crops, though he noted those ideas may not work for everyone.

King said for every 1 percent of organic matter in soil, 3 quarters of an inch of water can be stored. Organic matter can be restored through no-till practices and manure application.

When informally polled by King about who had water management plans, of the dozens of farmers in attendance only several raised their hands. A group of farmers estimated less than 50 percent of farmers practice water management.

However, King said 93 percent of farmers in the region test their soil at least once per crop rotation. Over-application of phosphorous-containing manure over many years is believed to be a contributor to the issue. Some 5 percent of farmed acreage in the western Lake Erie basin contains phosphorous levels of 150-200 ppm.

King mentioned a farmer who hasn’t applied phosphorous in five years who haven’t seen a drop in yield.

“It’s not a large percentage of the land, but we definitely don’t (need) to be putting fertilizers on those areas,” King said. “We can’t just look at our soil tests and say, “That’s what my level is.’ We’ve got to look at what the historical crop rotation is and start taking a more holistic approach, looking at the microbial biomass as well.”

He talked about the level of nutrient loss per acre the scientific community is asking farmers to achieve.

“It’s about a quarter-pound per acre, that’s what we’re striving to get to,” King said. “That ought to scare you. If we think about what you’re applying right now, you’re applying 15, 20 pounds an acre and we’re asking you to get down to a quarter of a pound loss.

“Right now, your losses are somewhere in the 1 to 1.50 pounds (range) an acre of loss.

“We’re already doing 90 percent recovery efficiency, so what do we do now to get us down 0.25 of a pound?” he said. “That’s the margin we’re working with … It’s that quarter of a pound an acre that’s causing the lake to be green.”

He recommended putting fertilizer on just before planting, if possible.

“What I would encourage you to do is turn off the hoppers when you fertilize for 100 yards in two or three spots,” King said. “Don’t wait on the science, it’ll be four, five, six years before we figure out and get those recommendations. Convince yourself that you don’t need that much phosphorous. There’s a lot in the soil.”

Joe Nester, owner of Bryan-based Nester Ag, as well as the test field where Thursday’s Tech Day was held, encouraged independent research among farmers and stressed the importance of organic matter and the use of gypsum which has been proven to effectively create bonded phosphates which don’t leave the field as easily in drainage.

“Gypsum’s not the silver bullet — There are no silver bullets and there are no smoking guns,” King said. “We don’t know what’s causing this problem. We know that in this watershed we see dissolved phosphorus going up. We don’t know why. It’s not just an Ohio issue, it’s a world issue.”

He provided the example of algal blooms in once-pristine Colorado streams.

“In this watershed, agriculture absolutely has a role in what’s happening, but it’s not explanatory for what’s happening around the globe,” King said.

“We have to keep taking a chance of failing and put yourself out there,” Nester said. “Find that breaking point on phosphorous on you operation under your management. Find that breaking point on nitrogen so we’re not contributing.

“The answer will come from farmers, not the legislature. We have to bring the answers,” Nester said.

A few farmers present at the discussion voiced their belief that factors like animal waste, human waste from cities and the changing chemistry of (acid) rain play roles that are not commonly acknowledged by the scientific community.

Currently, there are no tangible incentives from state or federal governments for farmers to implement best practices determined by research to limit algal blooms.

When asked, several other farmers indicated by-acre incentives for best practices would help more quickly increase implementation.

(Source -http://www.willistonherald.com/national/agriculture/farmers-advised-on-water-and-soil-management/article_6988f96a-ec54-58ba-be9a-71773b9fb6ae.html)

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Soil Health Evaluation

Sorting through some of the differences between soil health tests can be challenging. Penn State offers a Soil Quality Assessment Worksheet that may be beneficial.
It is very encouraging that soil health is receiving a lot of attention lately from many different quarters, such as innovating farmers, crop consultants, USDA-NRCS, the agricultural industry, conservation community, water quality experts, and Cooperative Extension. It was a concept that was ignored for too long and we realize that soil biology needs to be integrated into our agronomic tool kit. However, we are still struggling to find the best information to use. Evaluation tools of soil health are still in their infancy and we are still trying to sort out which ones are the most suited and cost effective.
Laboratories are developing tests and are already offering them. Some tests we have evaluated are the Soil Nutrient and Health Tool (Woods End Lab), Phospholipid Fatty Acid Analysis (Ward Lab), Food Web Analysis (Soil Foodweb Inc), and the Cornell Soil Health Test (Cornell University). All these labs ask for is just a sample taken similar to what you would take for a soil fertility test. The only exception is the Cornell test which also asks you to take penetration resistance measurements with a penetrometer (soil compaction tester) in the field. This makes the tests convenient for the farmer.
The Soil Nutrient and Health Tool gives you Solvita CO2 burst, water extractable nitrogen and carbon, nitrate-N, Soil Labile Amino Nitrogen, mineralized carbon, aggregate stability, P-saturation and Calcium saturation. The Phospholipid Fatty Acid Analysis is a chemical footprint of the microbial cell membranes which gives a measure of microbial biomass and community composition. Food web analysis is an analysis of bacteria, fungi, protozoa, nematodes and mycorrhizae (obtained by looking at samples under a microscope). The Cornell Soil Health Test gives aggregate stability, available water capacity, surface and subsurface hardness, organic matter, active carbon, potentially mineralizable carbon, root health rating, pH, extractable P, K and minor elements. It will be clear that the tests evaluate different things and therefore give different results.
The costs of the tests were $49.50 for the Soil Nutrient and Health Tool, $39.50 for the PFLA test, $144 for the Soil Food Web Analysis, and $45 for the basic Cornell test (in 2013, prices may have changed since then). We found that the Soil Nutrient and Health Tool and the Cornell Test were able to pick up major soil health differences (like a visually very degraded, continuously moldboard plowed field with very limited organic matter inputs compared with a field next to it that had been in continuous no-tillage with a diverse crop rotation and regular cover crop use). The PFLA and Soil Food Web didn’t show clear differences between these. However, even the Soil Nutrient and Health Tool and Cornell Test did not show clear differences between fields that had more subtle management differences that should have resulted in soil health differences (such as corn-soybean rotation with chemical fertilizer and no cover crops versus alfalfa/canola/rye/soybean rotation with manure inputs or a 30+ year continuous no-tillage versus chisel/disked field).
We recently took more samples from contrasting fields from grazing farms that we had analyzed with the Soil Nutrient and Health Tool but had difficulty finding clear differences based on the test results. Therefore, we went back this spring to taking an infiltration ring and a shovel to do a qualitative evaluation of some fields. In one field, one inch infiltrated in 10-22 seconds, while in another field an inch had not infiltrated after 55 minutes! We dug up some soil and observed large differences in soil structure and color. The field with extremely high infiltration capacity had been in perennial warm season grass for over one year. Its structure was extremely mellow and one could see the dark color. Another field where an inch of water infiltrated in about 2 minutes had been severely compacted last spring but its structure had been restored significantly by the use of a multi-species cover crop of hairy vetch, alsike, red and yellow clover, and annual ryegrass. The field with the lowest infiltration showed greyness and orange mottles near the surface while the subsurface was bright orange. It had a weak cover of crimson, alsike and yellow clover. We saw that an area in the same field where perennial ryegrass had been planted a year ago showed significant improvement with higher infiltration and better soil structure. These results provided us with food for thought about practices that could help improve soil health on this farm. The moral of the story is to keep the pulse on new information on soil health tests, but in the meantime, use a qualitative assessment which is free of charge. A resource that is available from Penn State Extension to help you with this is the Soil Quality Assessment Worksheet. Another good piece of information to have is the organic matter content which you can get with your regular soil fertility analysis (Penn State Ag Analytical Lab offers it for $5, just check the box on the sheet that goes with the sample).
By performing a qualitative soil health evaluation every year and organic matter content every three years or so you have valuable information to assess whether your practices are helping to improve your soil.
(Source – http://www.farms.com/news/soil-health-evaluation-106195.aspx)
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