Soil Health Tool (SHT) ver 4.4 

An Integrated approach to soil testing  

Soil Testing in Nature’s image 

Rick Haney USDA-ARS 

The soil health tool is an integrated approach to soil testing using chemical and biological soil  test data; it is designed to mimic nature’s approach to soil nutrient availability as best we can in  the lab. This tool is the culmination of nearly 20 years of research in soil fertility and I believe it  represents the next step in soil testing for the 21st century. 

This tool is designed to answer some simple questions: 

1. What is your soil’s condition?  

2. Is your soil in balance?  

3. What can you do to help your soil?  

The Soil Health Tool is designed to work with any soil under any management scenario because  the program asks simple, universally applicable questions. The methods use nature’s biology  and chemistry by using a soil microbial activity indicator, a soil water extract (nature’s solvent), and the H3A extractant, which mimics the production of organic acids by living plant roots to  temporarily change the soil pH thereby increasing nutrient availability. These organic acids are  then broken down by soil microbes since they are an excellent carbon source, which returns the  soil pH to its natural, ambient level. The tool uses an integrated approach to soil testing,  reflecting the complex ecosystem of the soil, instead of depending upon the narrow  measurement of inorganic N, P, and K. The integrated approach is naturally controlled so that  N or P will not exceed what is available from the organic N and organic P pools.  

Procedure for soil analysis: 

Each soil sample received in the lab is dried at 50oC, ground to pass a 2 mm sieve and weighed  into two 50 ml centrifuge tubes (4 g each) and one 50 ml plastic beaker (40 g) that is perforated  to allow water infiltration. The two 4 g samples are extracted with 40 ml of DI water and 40 ml  of H3A. The samples are shaken for 10 minutes, centrifuged for 5 minutes, and filtered through  

Whatman 2V filter paper. The water and H3A extracts are analyzed on a Seal Analytical rapid  flow analyzer for NO3-N, NH4-N, and PO4-P. The water extract is also analyzed on a Teledyne-

Tekmar Apollo 9000 C: N analyzer for water-extractable organic C and total N. The H3A extract  is also analyzed on a Varian axial ICP-OES instrument for Al, Fe, P, Ca, and K. 

The 40 g soil sample is analyzed with a 24 hour incubation test at 25oC. This sample is wetted  through capillary action by adding 25 ml of DI water to an 8 oz. glass jar and placed in the jar  along with a Solvita® paddle and then capped. At the end of 24 hour incubation, the paddle is  removed and placed in the Solvita® digital reader for CO2-C analysis. 

Following lab analysis, the raw data are placed in the Excel file that uses macros for various  calculations, and the results are placed in the NPK tab for delivery to the user. In the Excel file  you will find the following: 

NPK TAB 

Fertilizer Recommendations 

N, P2O5, and K2O (lbs/acre): 

These numbers represent the amount these nutrients presently in your soil in lbs/ac. 

Nitrogen: From the water extractable NH4-N + 60% of NO3-N + MAC * WEON *4 where;  MAC = microbially active C and WEON = water extractable organic N. The number 4  represent a conservative estimate of the number of significant rainfall events (>1 in.) over  the course of a growing season.  

Phosphate: From the H3A extractable ortho-phosphate and organic P based on a sliding  scale C: N ratio. 

Potassium: H3A extractable K. 

Nutrient value per acre: 

Current fertilizer prices are multiplied by the nutrients present in your soil. This is the value  in dollars per acre of nutrients currently in your soil. 

N, P2O5, and K2O needed calculator (Run button): 

In the crop column, type in your crop type. In the yield goal column, type in your yield goal.  Click on the Run button and the next three columns will calculate your N, P2O5, and K2O needed in lbs per acre to produce your stated yield goal. You must put a crop and yield goal  for each sample or you will get an error.

The method used to calculate fertilizer requirements is based on a simple concept: NPK  needed for your yield goal minus NPK you have in the soil. However, it is your money; if you  think these numbers are too high or too low adjust them accordingly. We are giving you the  best numbers we can based on our current understanding of soil and the limits of  technology.  

NO3-N Only (traditional testing) lbs per acre: 

This column represents testing for nitrate in lbs/acre. This is the only form of nitrogen that  most soil test labs measure. We only credit 60% of this measurement due to leaching and  denitrification over the growing season.  

Additional N (SHT) lbs per acre: 

This column represents the amount of nitrogen present in your soil in addition to the nitrate  described above. This number is attained by incorporating contributions from the biological  component in the soil plus NH4-N from the water extract. In other words, this value is the biologically available N value and NH4-N as compared to the inorganic N measured by most  commercial or university labs. 

$ Nitrogen saved per acre: 

This column represents the amount of nitrogen saved in dollars per acre by accounting for  the biologically available N as compared to the nitrate only approach.  

Soil Health 

Solvita 1-day CO2-C:  

This result is one of the most important numbers in the soil test procedure. This value is the  amount of CO2-C (ppm) released in 24 hr. from soil microbes after your soil has been dried  and rewetted (as occurs naturally in the field). This is a measure of the microbial activity in  the soil and is highly related to soil fertility. In most cases, the higher the number, the more  fertile the soil. 

Microbes exist in soil in great abundance. They are highly adaptable to their environment.  Their composition, adaptability, and structure are a result of the environment they inhabit.  They have adapted to the temperature, moisture levels, soil structure, crop and  management inputs, as well as soil nutrient content. In short, they are a product of their  environment. If this were not true they most likely would have died out long ago, but they  didn’t. Since soil microbes are highly adaptive and are driven by their need to reproduce  and by their need for acquiring C, N, and P in a ratio of roughly 100: 10: 1 (C: N: P), it is safe

to assume that soil microbes are a dependable indicator of soil health. It is clear that C is the  driver of the soil nutrient-microbial recycling system. This consistent need sets the stage for  a standardized, universal measurement of soil microbial activity. Since soil microbes take in  

oxygen and release CO2, we can couple this mechanism to their activity. It follows that soil  microbial activity is a response to the level of soil quality/fertility in which they find  themselves. 

Water extractable organic C (WEOC): 

This number (in ppm) is the amount of organic C extracted from your soil with water. This C  pool is roughly 80 times smaller than the total soil organic C pool (% Organic Matter) and  reflects the energy source fueling soil microbes.  

A soil with 3 % soil organic matter (SOM) when measured with the combustion method at a  0-3 inch sampling depth produces a 20,000 ppm C concentration. When we analyze the  water extract from the same soil, that number typically ranges from 100-300 ppm C. The  organic C in the soil water extract reflects the quantity of the C in your soil that is readily  available to the microbial population; whereas % SOM is reflective of the entire organic C pool that may become available over the lifetime of the soil. The amount of WEOC reflects the quality of the soil. In other words, % SOM is the house that microbes live in, but what  we are measuring is the food they eat (WEOC and WEON). 

Water extractable organic N (WEON): 

This number is the amount of the total water extractable N minus the inorganic N (NH4-N +  NO3-N). The WEON pool is highly related to the water extractable organic C pool and will be  easily broken down by soil microbes and released to the soil in readily plant available inorganic N. 

Organic C: Organic N: 

This number is the ratio of organic C from the water extract to the amount of organic N in  the water extract (WEOC: WEON). This C: N ratio is a critical driving factor in the nutrient  cycle. Soil organic C and N are highly related to each other as well as the water extractable  organic C and N. We assess the organic C: N ratio of the water extract since this relationship  reflects the portion of C and N that are readily available to soil microbes and is a more  sensitive indicator of soil health than the total soil C: N ratio. A soil C: N ratio above 20:1  generally indicates that no net N and P mineralization will occur, meaning the N and P are  “tied up” within the microbial cell until the ratio drops below 20:1, as the ratio decreases  the more N and P are released to the soil solution which can be taken up by growing plants. 

Note: water extractable organic C and N are not separate entities in the soil, the C and N are actually from the same molecule, although we separate C and N in analysis because of the  nature of the instruments we use to analyze them.  

Soil Health Calculation: 

This number is calculated as 1-day CO2-C / 10 + WEOC/100 + WEON/10 to include a  weighted contribution of microbial activity, water extractable organic C and N. It represents the overall health of your soil system. It combines 5 independent measurements of your  soil’s biological and chemical properties. The calculation looks at the balance of soil C and N and their relationship to microbial activity. This soil health calculation number can vary from  0 to more than 30. We like to see this number increase over time. This number indicates the  current soil health and helps us identify what it needs to reach its highest sustainable state.  Keeping track of this Soil Health number will allow you to gauge the effects of your  management practices over the years. 

Cover Crop Mix: 

This is a suggested cover crop planting mix based on your soil test data. This is a  recommendation of what you can do to increase your Soil Health number; it is not what you  have to do. It is designed to provide your soil with a multi-species cover crop to help you  improve soil health and thus improve the fertility of your soil. 

Nitrogen 

Total N:  

This number is the total N from the water extract from your soil (in lb/ac). It contains both  inorganic N and organic N, which are shown in the next two columns.

Inorganic N: 

This is the combined amount of plant available forms of inorganic N (NO3-N (nitrate N) plus NH4-H (ammonium N)). NO3-N is the form of N that is easily lost from soil through surface  runoff, subsurface leaching, erosion, and in water logged conditions, it can revert back to a  gas. NH4-H is usually quickly converted to NO3-N by soil microbes but is less susceptible to  leaching.  

Organic N:  

Organic N is the total water extractable N minus the total water extractable inorganic N in  lbs. per acre. This form of N should be easily broken down by soil microbes and released to  the growing plant providing minimal chance of loss since the N is bound in large organic  molecules. This pool represents the amount of potentially mineralizable N in your soil.  

Phosphate 

This lists the same type of results as nitrogen but for inorganic P and organic P. Remaining columns 

Columns to the right of the phosphate column on the NPK TAB are used for the GRAPH IT TAB where you can click on a sample, click the Graph it button and see the results from that sample in pie charts and bar graphs. 

Al H3A: the amount of H3A extractable aluminum in ppm 

Fe H3A: the amount of H3A extractable iron in ppm 

Ca H3A: the amount of H3A extractable calcium in ppm 

Organic N release: This is the portion of the water extractable organic N that we credit as plant  available based on the microbial activity, WEOC, WEON and the balance of the two (C: N).  

Organic N reserve: This is the amount of organic N that is not credited as plant available usually  due to lower microbial activity relative to the WEOC and WEON pools. If this number is 0 then  the entire WEON pool is considered plant available.  

Organic P release and organic P reserve: the same as described above for nitrogen except  phosphate uses the H3A extractant.  

%P saturation: The amount of H3A extractable P/the amount of H3A extractable Al and Fe  expressed as a percentage. This is an index of the P associated with Al and Fe in your soil, a 

number below 5 usually indicates a need for P fertilizer and a number above 20 usually  indicates excess P in soil. These numbers can be misleading if you have high P and low AlFe but  high Ca, these numbers are just indicators of some of the chemical properties of the soil but can  reflect P fertilizer additions. 

Ca/AlFe: the H3A extractable calcium/H3A extractable Al and Fe, this ratio is used to indicate  the balance of some of the drivers of soil pH. A number less than 1 may indicate a need to add  lime, numbers greater than 20 usually indicate a high pH soil (>7.7). 

SHC is the soil health calculation and $ saved per acre is nitrogen. 

References: 

Franzluebbers, A.J., Haney, R.L., Hons, F.M., and Zuberer, D.A. Active fractions of organic matter  in soils with different texture. Soil Biology and Biochemistry 28:1367-1372. 1996. 

Franzluebbers, A.J., Haney, R.L., Hons, F.M., and Zuberer, D.A. Determination of soil microbial  biomass and nitrogen mineralization following rewetting of dried soil. Soil Science Society of  America Journal 60:1133-1139. 1996. 

Franzluebbers, A.J., Haney, R.L., Hons, F.M., and Zuberer, D.A. Assessing biological soil quality  with chloroform fumigation-incubation: Why subtract a control? Canadian Journal of Soil  Science 79:521-528. 1999. 

Franzluebbers, A.J., Haney, R.L., and Hons, F.M. Relationships of chloroform fumigation incubation to soil organic matter pools. Soil Biology and Biochemistry 31:395-405. 1999. 

Franzluebbers, A.J., Haney, R.L., Honeycutt, C.W., Schomberg, H.H., and Hons, F.M. Flush of CO2  following rewetting of dried soil relates to active organic pools. Soil Science Society of America  Journal 64:613-623. 2000. 

Franzluebbers, A.J., Haney, R.L, Honeycutt, C.W., Arshad, M.A., Schomberg, H.H., and Hons,  F.M. Climatic influences on active fractions of soil organic matter. Soil Biology and Biochemistry  33:1103-1111. 2001. 

Haney, R.L., Franzluebbers, A.J., Hons, F.M., and Zuberer, D.A. Soil C extracted with water or  K2SO4: pH effect on determination of microbial biomass. Canadian Journal of Soil Science  79:529-533. 1999.  

Haney, R.L., Senseman, S.A., Hons, F.M., and Zuberer, D.A. Effect of glyphosate on soil microbial  activity. Weed Science 48:89-93. 2000.

Haney, R.L., Franzluebbers, A.J, Hossner, L.R., Hons, F.M., and Zuberer, D.A. Molar  concentration of K2SO4 affects estimates of microbial biomass. Soil Biology and Biochemistry  33:1501-1507. 2001. 

Haney, R.L., Franzluebbers, A.J., and Hons, F.M. A rapid procedure for prediction of N  mineralization. Biology and Fertility of Soils 33:100-104. 2001. 

Haney, R.L., Senseman, S.A., and Hons, F.M. Effect of roundup ultra on soil microbial activity  and biomass on selected soils. Journal of Environmental Quality 31:730-735. 2002. 

Haney, R.L., Senseman, S.A., Krutz, L.J. and Hons, F.M. Soil carbon and nitrogen mineralization  as affected by atrazine with and without glyphosate. Biology and Fertility of Soils 35:35-40.  2002. 

Haney, R.L., Franzluebbers, A.J., Porter, E.B., Hons, F.M., and Zuberer, D.A. Soil carbon and  nitrogen mineralization: Influence of drying temperature. Soil Science Society of America  Journal 68:489-492. 2004.  

Haney, R.L., Haney, E.B., Hossner, L.R. and Arnold, J.G. A new soil extractant for simultaneous  phosphorus, ammonium, and nitrate analysis. Communications in Soil Science and Plant  Analysis 37 (11-12):1511-1523. 2006. 

Haney, R.L., Hossner, L.R., and Haney, E.B. Soil microbial respiration as a program to assess  post mine reclamation. International Journal of Mining, Reclamation, and Environment 22(1):  48-59. 2008. 

Haney, R.L., Brinton, W.H., and Evans. E. Estimating Soil C, N, and P mineralization from short term CO2 respiration. Communications in Soil Science and Plant Analysis 39:2706–2720. 2008. 

Haney, R.L., Brinton, W.F., and Evans, E. Soil CO2 respiration: Comparison of chemical titration,  CO2 IRGA analysis and the Solvita gel system. Renewable Agriculture and Food Systems 23(0);  1–6. 2008. 

Haney, R.L. and Franzluebbers, A.J. CO2 Evolution: Response from arginine additions. Applied  Soil Ecology 42:324-327. 2009. 

Haney, R.L. and Haney, E.B. A simple laboratory method for rewetting dry soil. Communications  in Soil Science and Plant Analysis 41: 12, 1493-1501. 2010. 

Haney, R.L., Haney, E.B., Hossner, L.R., and Arnold, J.G. Modifications to the new Soil  Extractant H3A – A Multi-Nutrient Extractant. Communications in Soil Science and Plant  Analysis 41:12, 1513-1523. 2010.

Haney, R.L., J.R. Kiniry, and M.-V.V. Johnson. Soil microbial activity under different grass  species: underground impacts of biofuel cropping. Agriculture, Ecosystems and Environment 139:754-758. 2010. 

Harmel, R.D., Smith D.R., Haney R.L., and Dozier M. Nitrogen and phosphorus runoff from  cropland and pasture fields fertilized with poultry litter. Journal of Soil and Water Conservation  64(6):400-412. 2009. 

Harmel, R.D., Haney, R.L. and Smith. Effects of Annual Turkey Litter Application on Surface Soil  Quality of a Texas Blackland Vertisol. Soil Science. 2011. 

Jin, V.L., M.-V.V. Johnson, R.L. Haney and J.G. Arnold. Potential carbon and nitrogen  mineralization in soils from a perennial forage production system amended with class B  biosolids. Agriculture, Ecosystems & Environment. 141:461-465. 2011. 

Krutz, L.J., Senseman, S.A., and Haney, R.L. Effect of glyphosate on atrazine degradation. Biology  and Fertility of Soils 38:115-118. 2003. 

Lancaster, S.H., Haney, R.L., Senseman, S.A., Hons, F.M., and Chandler, J.M. Soil microbial  activity is affected by roundup WeatherMax and pesticides applied to cotton (Gossypium  hirsutum). Journal of Agricultural and Food Chemistry 54(19):7221-7226. 2006. 

Lancaster, S.H., Haney, R.L., Senseman, S.A., Kenerley, C.M., Hons, F.M., and Chandler, J.M.  Microbial degradation of fluometuron is influenced by Roundup Weathermax. Journal of  Agricultural and Food Chemistry 56:8588-8593. 2008. 

Richard L. Haney, Alan. J. Franzluebbers, Virginia. L. Jin, Mari-Vaughn. Johnson, Elizabeth. B.  Haney, Mike. J. White, Robert. D. Harmel. Soil Organic C:N vs. Water-Extractable Organic C:N.  Open Journal of Soil Science 2: 269-274: 2012 

Virginia L. Jin , Richard L. Haney, Philip A. Fay, H. Wayne Polley. Soil type and moisture regime  control microbial C and N mineralization in grassland soils more than atmospheric CO2-induced  changes in litter quality. Soil Biology and Biochem. Online Nov 30 2012. 

R. Daren Harmel and Richard L. Haney. Initial Field Evaluation of the Agro-Economic Effects of Determining Nitrogen Fertilizer Rates with a Recently-Developed Soil Test Methodology Open Journal of Soil Science 3: 91-99: 2013