Making Sense of Soil Tests

Transcription

1 Making Sense of Soil Tests URI Master Gardener Program September 17, 2016 Dawn Pettinelli, UConn Soil Nutrient Analysis Lab

2 4R Nutrient Stewardship Biodiversity Soil erosion Resource use efficiencies SYSTEM OBJECTIVES Healthy environment Nutrient loss Water & air quality Nutrient balance Soil productivity Net profit Productivity Durability Aesthetics Profitability Return on investment Quality Working conditions

3 SOIL TESTING From Nutrient Management Perspective: 1. Optimizing nutritional/ ph conditions for plant growth 2. Maximize return on fertilizer investment (don t waste $) 3. Minimize negative environmental impacts (especially P & N)

4 SOIL TESTING Consider your soil a storehouse for plant nutrients, a pantry of sorts. A soil test is a means to take a chemical inventory of the available nutrients in your soil. Can tell if you need more nutrients or if the shelves are overstocked.

5 WHAT IS SOIL TESTED FOR? 1. ph measure of acidity/alkalinity is limestone/sulfur necessary if so, how much? 2. Nutrient levels how much N, P & K to add, if any 3. Lead Screening

6 SOIL TESTING 4 SEPARATE ACTIVITIES 1. Taking a Sample 2. Analyzing Sample 3. Interpreting Results 4. Making limestone & fertilizer recommendations Most limiting factor

7 SOIL SAMPLING How Many Samples? Depends on Sampling Area Soils that look different or on different parts of the landscape, ie. top of hill, poorly drained spot, etc. sampled separately Soils treated differently in terms of limestone &/or fertilizer application sampled separately Soils which should be similar but drastic differences in plant growth sampled separately

8 Hedge Flower Bed SOIL SAMPLING low spot x x x x x x House x x x Garden x x x x Trees Example of proper sampling technique for lawn. Individual samples were collected at each spot marked with an X. The samples were then mixed together to make a composite sample.

9 SOIL SAMPLING Sampling Tools: Soil probe best, augers OK, with spade take a uniform slice

10 Soil test P values for three sampling depths from two locations in New York Site Sampling depth Morgan Soil Test P UMass Recommended P 2 O 5 inches ppm lbs / 1000sf Lake Placid Farmingdale Soil test data adapted from Soldat et al. 2009, Slide courtesy of UMass 10

11 SOIL SAMPLING When To Sample? Fall is best but for comparison purposes use same time of year How often? Usually every 3 years or to help diagnose a problem Murrell, 2009 Slide courtesy of UMass

12 SOIL ANALYSIS Routine Soil Analysis ph & Buffer ph (Lime req) Extractable P, K, Ca & Mg using Modified Morgan Extractant Extractable Micros + S Estimated CEC & BS Estimated Total Lead Additional Tests Organic Matter Soluble Salts Texture Nitrate-N

13 WHERE S THE NITROGEN? Nitrogen is generally the most limiting nutrient for plant growth The dynamic nature of the N cycle makes it difficult to test and manage In humid environments, the value of routine soil testing to predict available N is limited by our ability to predict the weather. PSNT for some crops

14 SOIL ANALYSIS Drying soil samples Analysis of soil extract (ICP-OES) Addition of extraction solution Filtration of extraction solution 14

15 SOIL ANALYSIS A discrete fraction of available nutrients does not exist, Unavailable Available.rather, nutrient availability is more a continuum in soil based on specific conditions affecting solubility of different nutrient pools. Increasing availability Soil test extractable

16 SOIL ANALYSIS Because so many factors influence quantity-intensity relationship, soil testing can only provide an index of nutrient supplying capacity of a soil. SOIL MINERALS ORGANIC MATTER SOIL SOLUTION EXCHANGEABLE CATIONS ON SOIL COLLOIDS Stored nutrients (quantity) Available nutrients (intensity)

17 SOIL TEST INTERPRETATION Extractable or available nutrient values have little meaning unless they are shown to be related to both: 1. A plant response to addition of that nutrient (correlation) 2. A soil test level at which that response occurs (calibration)

18 SOIL TEST INTERPRETATION Critical soil test level Environmental critical level? Below optimum Optimum Above optimum General concept of interpretation based on Sufficiency level of available nutrients

19 SOIL TEST INTERPRETATION To develop these correlations and calibrations, regional research is performed with representative soils ranging from deficient to adequate for a particular nutrient. Why best to use local lab.

20 For example SOIL TEST INTERPRETATION Relative yield of alfalfa (w/ or w/o P 2 O 5 ) in 31 Vermont soils with a range in soil test P. Critical soil test P = 4 ppm Results from similar research conducted throughout New England over the last 60+ years provides our basis for interpretation. Magdoff et al., Soil Sci. Soc. Am. J. 63:

21 PHOSPHORUS NECESSARY FOR PHOTOSYNTHESIS, FLOWERING, FRUITING AND MATURATION ENCOURAGES ROOT GROWTH COMPONENT OF DNA (Genetic material) P important for plant growth, often deficient in native NE soils but doing poor job managing this nutrient so now P regulations in some states CT, MA.

22 SOIL SATURATED WITH P WHAT S THE PROBLEM? No plant growth problems from excess P Water quality problems with excess P Fresh water bodies can become eutrophic with additions of P Additions in parts per billion can cause problems Lost by runoff and leaching Algae bloom in stream next to Amherst College athletic fields

23 PHOSPHORUS CONCERNS When soil test P levels are optimum or greater, don t apply more. Zero P fertilizers are readily available. P Law in Nutshell no P to est. lawns unless soil test within last 2 years says so. Can use P when seeding, overseeding & sodding. Organics not exempt in CT. 23

24 EXAMPLE REPORT & INTERPRETATION Measuring extractable not total nutrients (index) Categories based on field experiments want to be in OPTIMUM ph/buffer ph Estimated CEC % Base Saturation Micros & Sulfur Lead Recommendations

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26 Photo by Nora Painten

27 POTATO SCAB CORKY SCABS OR BROWN SUNKEN SPOTS POTATOES DO NOT STORE WELL THOUGH TASTE IS NOT AFFECTED SOILBORNE AFFECTS POTATOES, BEETS, CARROTS, TURNIPS, PARSNIPS MAINTAIN A SOIL ph OF 5.2 OR BELOW

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29 INTERVEINAL CHLOROSIS Photo by Carol Lambiase, MG INTERVEINAL CHLOROSIS IN RHODODENDRON CAUSED BY IRON DEFICIENCY. THIS MAY ALSO INDICATE OTHER MICRONUTRIENT DEFICIENCIES LIKE ZINC OR MANGANESE AS WELL AS DEFICIENCIES IN MACRO NUTRIENTS.

30 CHANGING SOIL ph To Lower ph: To Raise ph: Apply Sulfur Apply Acidic Salts of Iron, Aluminum or Ammonium Peat Moss Apply Limestones or Hydrated Lime Soluble Calcium Products Apply Woodashes Compost

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33 Amount of Lime Needed Depends Upon: Necessary Change in ph Chemical Composition of Liming Material Buffering Capacity of Soil

34 LEAD CONTAMINATION IS CAUSED BY: Lead-based Paints Leaded Gasoline Use of Lead Arsenate as a Pesticide Pb

35 GARDENING PRACTICES THAT REDUCE LEAD CONTAMINATION Locate Gardens Away From Old Painted Buildings and Heavily Traveled Roads Give Planting Preference to Fruiting Crops (tomatoes, peppers, squash, beans, corn, etc.) Adjust soil ph to 6.5 Incorporate Organic Matter Maintain Phosphorous Fertility Keep Dust at a Minimum by Mulching Discard Outer Leaves Wash Thoroughly

36 THANKS! That s all folks! QUESTIONS?