List of Resources

Most multivitamins and many dietary supplements contain Vitamin K. Both types, K1 and K2 are used, but K3 is not allowed in humans because it has been shown to damage hepatic cells in laboratory studies. However, Vitamin K3 is allowed in certain animal feed formulations. ...

If a product has more than five ingredients, it's almost a necessity to have it be analyzed analytically to calculate calories.

Vomitoxin is a mycotoxin that can occur in small grains such as wheat, barley and oats.

The Agronomy Handbook is a comprehensive resource that discusses soil properties, plant essential nutrients, as well as soil test results and recommendations. It also covers soil sampling, fertilizer application methods, nutrient deficiency symptoms in plants, plant tissue analysis, nutrient uptake and removal in crops, and ...

Alfalfa is superior to other forage crops and understanding how alfalfa grows and its relationship to forage yield & quality is critical to high quality production.

The quality of alfalfa hay used as feed, can be determined from the ADF, NDF, Relative Feed Value, TDN and crude protein levels.

The final step to profitable alfalfa production is to set goals for forage quality and use the appropriate harvest techniques.

Amino Acids play a vital role in metabolism, immune function and maintaining a healthy nervous system.

Determining if a supplement is needed for beef cows is based on forage quality and can be guided by a forage analysis which measures several components.

Starch analysis involves two basis steps. The first is the enzymatic hydrolysis of starch in glucose. The second is the measurement of glucose levels.

Analytical conversion factors are useful in interpreting your analysis.

Here is a comprehensive listing of the analysis options provided by Midwest Labs to the Animal Feed industry. It includes tests, methods, prices, descriptions, warnings, recommendations, suggestions, instructions, and reporting options.

Whether you band or broadcast your application, you should consider the pros and cons of each application method.

Biochemical oxygen demand (BOD) is a common test usually performed on influent or effluent water samples.

A biogenic substance with one or more amine groups is called a biogenic amine.

When sampling sludge, extra precautions should be taken to ensure safe handling and accurate sampling.

Instructions for Collection, Handling, and Storage of Biosolid Samples (Referenced directly from EPA Methods 1681 and 1682)

"The U.S. Food and Drug Administration began requiring additional information about the source of store-bought water."

A soil's buffer index measures how much reserve acidity is present and qualifies acidic soil pH's by determining how much lime material to apply.

How to calculate the Cation Exchange Capacity (CEC) is a calculation based on soil analysis results of Ca, Mg, K, Na, and H.

Calories in foods can be calculated using the grams of protein & carbohydrates in a serving and the grams of Fat.

Chlorine (Cl2) is a diatomic gas, whereas Chloride (Cl-) is the negative charged ionic form of Chlorine.

Fiber can be broken out into three different fractions, Crude, Neutral Detergent and Acid Detergent. Each of these fiber fractions are made up of different components.

Introduction: Confined spaces such as manholes, vaults, pits, tanks, storage bins, hoppers and silos need special consideration.

This document will allow you to convert a Midwest Labs lime recommendation based on pounds of 90% ECCE lime to a recommendation in tons of ag lime using your lime product's % Effective Calcium Carbonate Equivalent or Effective Neutralizing Material.

Throughout the months of the year, management of grasses depends upon the production goal of your cool season grass.

When adjusting corn yields, consider the final population of corn.

This guide will reference if your corn plant nutrient uptake is within the normal ranges for the current stage of growth.

Corn plant development is broken into four (4) stages of development based on week of emergence, and leaf count.

This memo shows how corn's nutrient uptake varies through the growing season.

There are basic principles of crop observations that will assist in the management and identifying some variations that will influence plant stands.

The residue remaining after a dried & ground sample is extracted and ether has evaporated is weighed and referred to as ether extract or crude fat.

Crude fat is more of a screening method because the test procedures don't identify a specific fat.

This Memo helps you understand the challenges associated with cyst nematodes. We cover how to sample a field or area, how to submit samples for cyst analysis, and how to interpret results and manage cyst nematode affected fields.

A detection level shows a relationship between levels of analyte and some sort of a response. The response could be no observable response, a maximum response, and the standard curve.

Before sampling, freeze cool pack enclosed in kit. This will allow the sample to remain cool until it reaches the laboratory. Open the cold water faucet and allow the water to run for several minutes. Fill the enclosed bottle(s). If purity (total coliform) is to ...

Analyzing your water for domestic suitability at Midwest Laboratories will provide information about your water's hardness, fluoride levels, pH levels, and possible bacteria contamination.

The organism, Escherichia coli 0157:H7, also known as hemorrhagic E. coli, causes an illness known as hemorrhagic colitis.

The organism, Escherichia coli 0157:H7, also known as hemorrhagic E. coli, causes an illness known as hemorrhagic colitis.

The pH level of our soil can play a part in the relative yield of crops.

Here is a comprehensive listing of the analysis options provided by Midwest Labs to the Environmental industry. It includes tests, methods, prices, descriptions, warnings, recommendations, suggestions, instructions, and reporting options.

Fallow syndrome is a result of population reduction of fungi. The syndrome can often be confused with a phosphorus deficiency.

Nitrate in plants are usually converted to proteins, amino acids and other compounds. However some stresses to the plant can cause toxic levels of nitrates.

Applying fertilizer solutions through irrigation water is not a recent development; the first agricultural use of anhydrous ammonia was through application in irrigation water in the early 1930's. With the mechanization of irrigation, particularly with the development of center pivot sprinkler systems, new application techniques ...

This memo explains how the salt index is measured and how to interpret these values when compared to common fertilizer products.

Guides based on the manure source and facility, are available to assist in handling and spreading manure.

Silage and hay are the most common forms of storage for forages. Silages are usually preferred by livestock to hay.

Foliar feeding, a term referring to application of essential plant nutrients to above-ground plant parts, has been documented as early as 1844, when an iron sulfate solution was sprayed as a possible remedy for "chlorosis sickness." More recently, foliar feeding has been widely used and ...

Here is a comprehensive listing of the analysis options provided by Midwest Labs to the Food & Ingredients industry. It includes tests, methods, prices, descriptions, warnings, recommendations, suggestions, instructions, and reporting options.

Over time, food products will begin to deteriorate. One critical aspect of this process is to monitor the degradation processes using a variety of analyses including peroxide value, iodine number, p-anisidine value, biogenic amines, thiobarbituric acid (TBA), and free fatty acids. Download our White Paper ...

Knowing the foods implicated in outbreaks and the preventative measures, you can avoid food poisoning.

You’ve got a great recipe and want to bring it to the marketplace. Here are some useful links to help you start a food business. What food regulations affect my recipe? Food production is regulated by federal, state and local agencies to ensure that our ...

Brian Hodges discuss a frequent question he receives in the lab. 1. What is a Genetically Modified Organism (GMO) Analysis?

Glycerin is odorless, colorless, water soluble, and has a sweet taste. And the feed value in terms of energy could be equal to corn.

Glycols are most commonly associated with antifreeze, but has other uses such as deicing fluid, food additives, food solvent, humectants and moisturizers.

Plants, animals or microbes which are changed at the DNA level are called genetically modified organisms or GMOs.

Considerations such as planting rates, planting dates and relationships between seed size and field performance can assist with plant development of grain sorghum.

Heavy Metals Both plants and animals require certain minerals to grow and thrive. These essential minerals are acquired through food and water. However, some minerals are poisonous, even in minute amounts. Heavy metals; named because they are dense elements found in the metal portion of ...

There have been several changes made to the FDA/USDA Nutrition Facts Label: Servings are in larger, bolder typeface. Serving sizes have changed to reflect reality. Calories use a larger typeface. Percent Daily Values have been updated. A new category has been created: Added Sugars. There ...

Here is a comprehensive listing of the analysis options provided by Midwest Labs to the Home & Small Business industry. It includes tests, methods, prices, descriptions, warnings, recommendations, suggestions, instructions, and reporting options.

When determining herbicide rates, remember that only those herbicide molecules dissolved in soil solution are available for control of weeds.

Converting your fertilizer recommendation from pounds per acre to measurements compatible with smaller areas such as flower pots, or lawn & garden use.

Tim Mundorf, CPAg walks you through taking a grid soil sample. Tools you will need for sampling: Grid Sampling Software Plastic 5-gallon bucket Soil Probe – marked for appropriate depth for consistency Midwest Labs soil sample bags Sharpie or another permanent marker Questions about soil ...

Angela Johnson walks you through taking an environmental swabbing sample. Questions about Environmental Swabbing? Contact Jamie Wood at  jwood@midwestlabs.com, 402-590-2964. 

Food spoilage can be triggered by many factors and can be indicated by a combination of odor, appearance, texture and color.

There are two (2) types of ICPs, and optical emission and a mass detection. The difference between the two (2) is how the element level is measured.

There are two (2) types of ICPs, and optical emission and a mass detection. The difference between the two (2) is how the element level is measured.

Public Water Systems (PWS) who provide water for human consumption to the public, must report their results. This guide walks through reporting chemical results.

Public Water Systems (PWS) who provide water for human consumption to the public, must report their results. This guide walks through reporting bacterial results.

This permit is for the movement of live plant pests, noxious weed, and soil. Plant Pathogenic Nematodes of any life stage can be sent to Midwest Laboratories from Argentine, Bahamas, Bermuda, Brazil, Chile, Colombia, Costa Rica, Ecuador, Nicaragua, Panama, Virgin Islands, British, Canada, Mexico, North ...

This video looks at manure report information data and how the data should be interpreted.

Midwest Labs will use distilled deionized water to measure pH on routine soil samples. Upon customer requests, we will run a salt pH by adding calcium chloride to the water.

This video provides an overview of the plant tissue analysis and reporting process.

Interpreting Soil Analysis is one of Midwest Laboratories' most popular publications. This brochure will walk the reader through how to read the soil test. We explain the individual analysis and calculations. We also discuss the desired levels of different nutrients and soil properties.

This video will give you more insight into understanding your soil test results from Midwest Laboratories. Call 402-334-7770 for more information on soil testing.

This video will give you insight into understanding your soil test results regarding Phosphorus, Potassium, Cations, and Percent Base Saturation.

This video will give you more information on how to interpret your soil test results from Midwest Laboratories, Inc. regarding Nitrate, Sulfur and Micronutrients in soil.

Lecithin is a commonly used ingredient in the food industry. It is a mixture of phospholipids naturally found in animal and plant cells. Commercially available lecithin is generally extracted from soybeans.

The purpose of liming is to neutralize acid. Midwest recommendations are based on an assumption of 90% neutralizing power.

Limestone is a soil additive that is used to increase the pH of acidic soil and improves the uptake of major plant nutrients.

First described as a pathogen in the late 1920's, it was not until the early 1980's that Listeria monocytogenes emerged as a food-borne pathogen. These hardy, nonspore-forming bacteria are capable of growing over a temperature range of 1-45o C (34-113o F), growing best at 30-37o ...

Tim Mundorf, CPAg explains how lubricating your soil probe helps break the tension of the soil without impacting results. Additional resource Soil Probe Lubrication: To Lubricate or Not Questions about soil sampling? Call client services 402.334.7770 or your  account manager Stacie Nelson 402.829.9840

When it comes to water quality, there are many treatments available. The best procedure is to have Midwest Laboratories test your water and make recommendations for corrective action.

Understanding the value of manure fertility can assist in improving soil fertility.

The accuracy in which a manure sample is taken is imperative to adhere to requirements for manure management plans.

There are three (3) types of manure used agronomically. The composition of the manure will vary with the type of manure and class of livestock.

Forages must match livestock needs, and production dates may vary to the North and the South.

"Salt" is composed of sodium and chloride. Measuring the "salt" level is an estimation, as there is no method that is specific for measuring "salt".

by Dr. Jane Caldwell & Brian Hodges Twenty-first-century consumers, processors, co-packers and regulators need to verify the identity of meats for a variety of nutritional, personal, religious, safety, regulatory, and ethical reasons. Many consumers have taboos and religious laws concerning species fit for consumption. Download ...

Mehlich-3 Phosphorus analysis is suitable for removing P and other elements in acid and neutral soils.

When sampling sludge, extra precautions should be taken to ensure safe handling and accurate sampling.

Download a copy of Food Label Consultant, Michelle Wright’s, presentation. She came and spoke at our 2017 & 2018 Voices in Food Production Symposium. In her presentation, she spoke about that new proposed GMO labeling requirements from FDA & USDA.

Midwest Laboratories offers the soil health assessment in two packages. The Soil Health Basic, and the Soil Health Complete.

Manure fertiltiy values are affected by diet and water composition and class of livestock.

Mycotoxins are not produced all the time, but can present under specific growing conditions and colonize crops.

Mycotoxins are an ongoing concern when feeding livestock and companion animals since minute amounts can greatly effect animal health and productivity.

Trends in Pet Food Dogs, cats, birds, and exotics provide emotional support, unconditional love and steady companionship to their owners. Pet owners, in return, love their pets like family and want to feed them high-quality products. They also like to discover new ways to interact ...

Mirroring Trends Dogs, cats, birds, and exotics provide emotional support, unconditional love and steady companionship to their owners. Pet owners, in return, love their pets like family and want to feed them high-quality products. They also like to discover new ways to interact with their ...

Nitrate-nitrogen is the most abundant form of nitrogen in the soil and uptake is easily accomplished through water absorption. The influence of ammonium nitrogen on the soil-plant system is also beneficial.

End of season cornstalk tests should be done approximately 1-3 weeks after black layer has formed on 80% of the kernels of most ears.

Forage diets high in nitrates could cause nitrate toxicity when the conversion of nitrite to ammonia becomes the limiting factor.

Profitable crop production largely depends on adequate amounts of available nitrogen. In continuous corn, for example, the dollar return per one dollar invested in nitrogen fertilizer can be as high as eight to one. However, as beneficial and profitable as nitrgoen fertilizer is to crop ...

Nutrients play an important role in plant development.

Organic soils have some specific micronutrient problems, but with testing and more specific information about your sample(s), Midwest Laboratories will assist you in further interpretation.

Midwest Laboratories run the standard Bray phosphorus tests, also known as the P1 and P2 tests on soil.

A general guideline for particle size interpretation shows an average particle size of 700-800 microns is considered acceptable for all classes of swine.

Patulin is a mycotoxin associated with the spoilage of grains, fruits, cheeses, and breads. It is considered the most significant mycotoxin in fruit and fruit juices; important because high-risk populations such as infants, children and the elderly consume these products. Download white paper to read ...

Evidence of rancidity in fats and oils can be evaluated by the detection of peroxide. The Peroxide value analysis is the most widely used.

Here is a comprehensive listing of the analysis options provided by Midwest Labs to the Pet Food industry. It includes tests, methods, prices, descriptions, warnings, recommendations, suggestions, instructions, and reporting options.

Protect your brand and bottom line with Midwest Laboratories pet food testing. Download our pet food resource or call our account manager Jamie Wood at 402-829-9892.

The pH scan is based on values between 0 and 14, with 7 being neutral. Readings above 7 are considered to be basic or alkaline, where reading below 7 are considered to be acidic.

The abundance of phosphorus is minor compared to oxygen, sodium, or aluminum, But the importance to life, phosphorus is a crucial element.

Soil structure can influence pore space in soil and the ease in which air, water and roots can move through the soil.

Some differences in analytical results could be due to the methods used for the analysis. These are the methods used by Midwest Laboratories.

A plant parasitic nematode assay result will be reported by genus and will also show numbers of all nematodes recovered.

This document should accompany soil samples that are being sent in for plant parasitic nematode testing.

Analysis This publication provides general information on how to best utilize plant tissue analysis. We combine information gained from plant and soil analysis data to better our decisions for soil and plant nutrients. Plant tissue nutrient analysis has been used for decades to diagnose plant ...

Modern agriculture demands top yields... and quality yields. Additionally, you demand profitable yields. In satisfying these demands, plant tissue analysis has become a valuable crop production tool. Top quality and profitable yields, unfortunately, don't just happen. Many factors need to be considered... like adequate moisture ...

Potable (drinking) water samples for human consumption must adhere to current regulations for analyzation, including sample bottle type, and time.

The late Spring PSNT test on soils is used to aid with profitable corn production and nitrogen management.

Landfills are no longer the first choice for disposal so composting has become a renewed interest.

Taking precautions when grazing sorghums and sudangrass will provide safety against hydrocyanic acid or prussic acid poisoning or nitrate toxicity.

Purpling in corn is only one outward indicator of stress, and determining what caused the purpling can be difficult to sort out.

Midwest Laboratories implements quality control in our labs to maintain standards in testing.

Download our free resource to learn more about composting and what Midwest Laboratories analysis can do to support sustainable composting. Additional questions about composting? Contact Midwest Laboratories Rob Ferris at 429-829-9871 to learn more.

Following is a brief introduction to the Interpretation of pastling curves for starch-based samples testing using your RVA 4500. A heat-hold-cool cooking cycle is assumed. A good textbook covering polymer hydrocolloids should provide further information on these processes and on starch chemistry, modification and uses.

The Rapid Visco Analyzer is a tool used to determine the cooked viscosity of products such as grain, flour, cereal-based, and starch.

Phosphate and Potash recommendation guide for Midwest Laboratories soil tests.

Comparison of corn, soybeans, alfafa, sunflowers and sugar beets.

Download a copy of Dr. Jane Caldwell’s presentation from our 2018 Voices in Food Production Symposium. Dr. Caldwell is our Assistant Technical Manager here at Midwest Laboratories, and she spoke in depth on Refrigerated Shelf Life. Check out her presentation for information on the types ...

Relative Feed Value (RFV) can be calculated on any set of feed analysis data that includes ADF and NDF, however the equations were developed specifically for alfalfa hay fed to Dairy cows.

The existing science and instrumentation for residual antibiotic analyses is leaning toward the LC/MS or LC/MS/MS methods because of the versatility.

Download a copy of Risk Assessment and Food Quality consultant, Julie Neuhalfen’s, presentation from our 2018 Voices in Food Production Symposium. Julie spoke in depth about the procedures and practices one must go through when applying for risk assessment.

Since Salmonella bacteria are common in the intestinal tract of many animals, contamination of the meat is common. Good sanitation and food preparation practices are important in preventing salmonellosis.

Salmonella can be transferred from birds & mammals defecating, and then having that raw or unprocessed manure spread onto fields.

Shelf-life refers to the amount of time a product can be stored and, when taken off the shelf, can still perform its intended function. When a product is degraded to the point where it can no longer perform or its quality is deemed unacceptable to ...

New Rates Effective March 1, 2019 __ FedEx $25 Flat-Rate | Overnight Time-Critical Shipping Weight – Up to 50 pounds Check drop off locations and times for next day delivery on the FedEx site. Click the download link below for details on our new FedEx ...

Silicon has not been defined as an essential substance; it may have been overlooked as essential since it is difficult to have a growing situation without silicon present in either soil or hydroponically. For the complete story click the download link below.

When sampling sludge, extra precautions should be taken to ensure safe handling and accurate sampling.

Understanding plant nutrient uptake during plant development stages can assist with better yield production.

Several factors can influence irregularities in soil analysis. Depth variations, combining samples with different soil areas or different historical liming are just a few of the factors.

Some differences in analytical results could be due to the methods used for the analysis. These are the methods used by Midwest Laboratories.

Soils excess in magnesium may limit potassium uptake, and certain soil management

The lightness or heaviness of a soil, or soil texture, can be learned from the cation exchange capacity of the soil.

Compaction can have many effects on soil. While a compacted condition can be naturally occurring, management is the cause of most compaction.

The biggest risk of lead exposure is through eating or swallowing contaminated dirt. Young children are at the highest risk for this exposure.

Taking soil samples can be made easier by lubrication of the probe, especially for wet soils and high clay content soils. The soil can stick to the probe and stop the soil from being released from the probe or make it difficult for the probe ...

Efficient soil sampling will cut your sampling time and improve accuracy.

Properly collecting soil samples is the most important step in any nutrient/soil amendment management program. Soil sampling should reflect tillage, past fertilizer/soil amendment placement, cropping patterns (and correcsponding irrigation requirements), soil type (including drainage and slope characteristics) and perhaps old field boundaries (such as old ...

1. Divide your field into areas which have the same soil type. 2. Sampling areas may range from 20-60 acres depending upon the consistency of the ground. 3. Smaller areas can be used for trouble spots ...

Correct sampling procedures will aid in providing an accurate soil analysis.

Soil sampling strategies can effectively deal with a history of bands applied to the soil.

Understanding your soil analysis can be achieved with the basic soil test interpretation guide.

Soil naturally presents trace amounts of lead. But contamination results from peeling of lead based paint from the exterior of older homes, as well as from emissions from vehicles that once used leaded gasoline.

Protect your brand and bottom line with Midwest Laboratories pet food testing. From pet food manufacturers and in-home treat makers to veterinarians and zoologists, animal lovers across the country rely on Midwest Laboratories to keep their pet food safe and nutritious. Our suite of analytical ...

Using the plant food uptake guide for sorghum, you can use the information to guide upcoming growth stage expectations.

Oil seed crops generally follow a different nutrient uptake pattern than grass crops like corn.

A domestic water analysis could indicate the source of stains in your laundry, bathtubs, showers and sink surfaces.

Most workers agree that sulfur is both beneficial and profitable on sandy soils. Several soil conditions affect crop responses to micronutrients.

Midwest Laboratories uses ASTM D 5453 – Sulfur analysis as the reference method for Sulfur TIER III Analysis and have carried out the required quality validation. Supporting clients is our biggest focus and through this process, we have tried to deliver a high-quality program that ...

Sulfur is an essential nutrient for crop production and yield response to sulfur fertilizer varies greatly.

Soil Sulfur levels can be affected by differences in soil texture, irrigation water, types of irrigation, soil drainage, sodium levels, and history of sulfur fertilization.

A guide showing the ratings used on soil analysis reports and the levels for each rating.

Thiobarbituric acid can be performed directly on food products (wet or dry) while peroxide value testing can only be accurately performed on oils.

Texture analysis is an important component for evaluation of select products. Texture, in this application, deals with the integrity of a sample and a change in the resistance to pressure.

Soil texture can be estimated from the cation exchange capacity, however for a more accurate determination, run a soil texture by hydrometer.

If your forage legumes are stunted and yellow and generally exhibit signs of nitrogen deficiency, the problem may be nodulation failure.

TCLP- Toxic Characteristics Leachate Procedure, is an extraction or sample preparation procedure.

Forages provide the nutritional base of cow-calf operations. Mineral supplementation decisions pivot around the quanitity and quality of the forage-base.

If an underground storage tank has been removed due to damaged or leaking tanks, an analysis of the surrounding soil and water

Understanding your manure analyses is necessary to determine the rates of application to increase yields.

Part 1: CEC, Organic Matter, Soil pH, & Buffer Index Part 2: Phosphorus, Potassium, Other Cations, & %Base Saturation Part 3: Nitrate, Sulfur, & Micronutrients

USDA Plant Protection & Quarantine Permit to Move Live Plants Pests, Noxius Weeds, and Soil. Plant Parasitic (pathogenic) Nematode Testing USDA International Permit for Live Pests  

Midwest Laboratories  USDA Plant Import Permit Controlled Import Permit to Import Restricted or Not Authorized Plant Material. This permit is to be used: To Test Plant Material and process plants (feeds, hay, etc.) for nutrient analysis for minerals, fiber, ash, and energy levels for feed ...

Midwest Laboratories USDA Soil Import Permit. The USDA permit to import soil is for use under the following guidelines: For hand carry of soil, an official of CBP Agricultural Programs and Trade Liaison (APTL) would have been notified to document and facilitate the entry of ...

For questions on where to obtain activated charcoal, contact your local chemical supplier, or the agronomic staff at Midwest Laboratories.

An agricultural testing laboratory offers many different types of analyses to help growers, ag retailers, and crop consultants maximize yields and economic returns. This document provides an overview of the types of analyses useful for crop production in a typical Midwestern corn-corn or corn-soybean rotation ...

Vitamin C (Ascorbic Acid) is necessary for maintaining healthy gums and for formation of connective tissue. Vitamin C can prevent Scurvy.

Vitamin E plays a role as an antioxidant in the body and can be found naturally in some foods, added to others, and is also available as a dietary supplement.

Differences with the water's association with the nonaqueous components of the food products can affect the rate of spoilage.

Rancidity is a sensory term which describes off-flavors and unpleasant aromas associated with certain foods, feeds or ingredients. Rancidity is usually the limiting factor in shelf-life, being the first reason for a consumer to find a food product unacceptable. Read More

Knowing the growth stage of your wheat plant can assist in proper plant tissue sampling and soil management practices.

Grid sampling is used to identify areas that need additional fertility as well as those areas that do not.

Shelf-life studies Food producers are constantly creating and updating product formulations to meet consumer’s shifting preferences. Enter any grocery store and you will see a produce section which looks like an oriental bazaar. Browse the shelves and note the new sections which stock trending categories ...

When is the best time of the season to collect soil samples? Here we discuss the advantages and disadvantages of winter soil sampling.