Soil Preparation to Establish Healthy Turf

Transcription

1 Soil Preparation to Establish Healthy Turf Presented at the Sustainable Turfgrass Management for Landscape Professionals Workshop in Sacramento, California by Bill Baker

2 Soil Physical Problems Compaction Heavy clay Too sandy Poor drainage (percolation) Low infiltration rate Low organic matter content

3 Soil Structure Structure refers to the way soil particles clump together into larger units These large units are called aggregates Aggregates that occur naturally in soils are called peds Clumps of soil caused by tillage are called clods Structure can alter the effects of texture Compaction = reduction of aggregates

4 Soil Texture Soil texture describes the proportion of three sizes of soil particles sand (large), silt (medium), and clay (small). The three particle groups are called soil separates. Soils should also be about 50 percent open space (pores) about half of which should be filled with water and the other half air. Ideally, soils should also include about 5 percent organic matter.

5 Comparison of Particle Sizes Very coarse sand = (mm) Coarse sand = (mm) Medium sand = (mm) Fine sand = (mm) Very fine sand = (mm) Silt = (mm) Clay = < (mm)

6 Effects of Texture (particle size) Surface area - small particles have more surface area - high surface area = greater H2O capacity Number and size of pore spaces - large particles have larger pores - small particles have smaller pores - water drains rapidly through large pores

7 Sand Particles Sand is the largest soil separate Composed mainly of weathered grains of quartz Almost all sand sizes are visible to the eye Gritty to the touch Grains do not stick together Sandy soils have poor nutrient and moisture holding capability

8 Silt Particles Silt is the medium size soil separate Silk particles are silky or powdery to the touch like talc Like sand, silt particles do not stick together Silt has the best ability to hold large amounts of water in a form that the plant can use

9 Clay Particles Clay is the smallest soil separate Mostly in the form of tiny, sheet-like crystals Clay results from chemical reactions between weathered minerals to form tiny particles of new minerals Clay can bond nutrients chemically to their surfaces

10 Particle Density Refers to the weight and density of the soil without the pore spaces Think in terms of a soil being a solid block instead of a permeable mixture of particles

11 Bulk Density Refers to the mass of a volume of undisturbed, oven-dry soil Bulk density measurement includes pore space Bulk densities of mineral soils depend mostly on the pore space Organic soils are much lighter

12 Soil Porosity Soil porosity = total pore space Measure of the soil volume that holds air and water Porosity increases at finer textures The porosity of sand is less than clay

13 Permeability Refers to the ease at which air, water, roots move through soil Permeability depends partially on the number of pores, but the size and continuity of the pores is more important Large pores (macropores) occur between large particles The rate of water movement in soil (hydraulic conductivity) relates directly to permeability

14 Infiltration Rates of Different Soils Measured in inches per hour Sand-coarse Sand-very fine Sandy loam Loam Clay loam Clay

15 Site Preparation Soil Amendments ADD SOIL AMENDMENTS IF: The soil is compacted The soil is heavy clay The soil drains poorly The soil is very sandy You want to minimize irrigation You want to have superior turf for years to come

16 Mulch versus Compost Compost is an organic feedstock materials that has been decomposed and stabilized through biological decomposition Organic mulches are used as a soil cover and generally have not been decomposed - but composts can easily fill this role. 16

17 Uses of Composts in Turf Incorporate into existing soil Mix into new growing mediums Apply as component in topdressing Seed cover Mulch Cosmetic appeal 17

18 Benefits of Compost to Turf Improves soil structure Improves soil fertility Adds beneficial soil micro-organisms Reduces irrigation requirements Improves commercial fertilizer utilization Suppresses plant diseases Reduces off-site transport of pollutants

19 Composition of Composts Vegetative Based Composts improve soil structure but add limited amounts of nitrogen Animal Based Composts this category is primarily manures and they are high in nitrogen but add only minimal improvements to soil structure Biological Solids this is domestic waste and performs similarly to manures 19

20 Advantages Over Non- Composted Organics Will not draw nitrogen from the soil Will not generate unpleasant odors Will not be a carrier for weed seeds Will not support pathogenic organisms Non-composted can be defined as materials that have not gone through a decomposition (decay) process 20

21 Disadvantages of Composts Composts are generally higher in salts and ph then native soils or other amendments Compost quality is inconsistent in the marketplace and greatly depends on credibility of the supplier The soil structure improvements derived from composts are most effective in the first 5 years and diminish in following years 21

22 Selecting Quality Composts Watch for visible contaminants Should have a pleasant aroma What is the texture and appearance Is the particle size appropriate and uniform

23 Terms Associated with Composts by Successive Stages of Improvement Green Active - unprocessed or early stages - decomposition is incomplete Stabilized - completed decomposition Mature Cured - recombined into humus - colonized by beneficial org. 23

24 Compost Analysis Considerations ph of compost Salt concentration Moisture content Organic matter content Water holding capacity Trace heavy metals Nutrient content

25 FIELD GUIDE TO VERIFYING SOIL QUALITY AND DEPTH IN NEW LANDSCAPES Washington State BMP Manual

26 Sand Amendments Sands have the advantage of being permanent in altering soil structure Purchase from a reliable source sands can be very high in ph or have contaminants Sands will not retain nutrients, but this may not be a problem if the soil has an original high clay content 26

27 Sand Amendments2 Sands should be washed or double-washed to remove clays and fine sediments. Sands should also have been screened to remove pebbles and rocks Sand suppliers should be able to provide a spec sheet on the material Adding too little sand may do more harm than good 27

28 Soil Chemical Problems Alkalinity High ph Acidity Low ph (not us) High Sodium High Total Salts Low Fertility Ion Toxicity

29 Site Preparation Soil Tests CONDUCT A SOIL TEST IF: Soils in your region are known to be problematic There are identified water quality issues Other turfgrass sites and landscapes in the area are in decline or under stress You want to be sure you always putting down the correct nutrients

30 Soils and Irrigation Water Soils and irrigation water are two parts of the same puzzle. In many cases we analyze the same properties in both the soil and water. Whatever problems we see with the irrigation water we can soon expect to see in the soil. Existing issues with the soil will be compounded if similar problem are found in the irrigation water.

31 ph Definition The ph, or potential of Hydrogen is the scale that measures the relative acidity or alkalinity of a solution. Solutions are measured from zero (totally acid) to fourteen (totally alkaline) and seven is neutral. 31

32 ph Scale 32

33 How the ph Scale Works Like the Richter scale that's used to rate earthquakes, the ph scale is not linear. The intervals between numbers is logarithmic, which means every number on the scale shows ten times less H concentration than the number below. Soil with a 5 is ten times more acidic than soil with a ph of 6. 33

34 Cation Exchange Capacity (CEC) Any element or molecule with a positive charge is called a cation Basic cations include calcium (Ca+2), magnesium (Mg+2), potassium (K+1) and sodium (Na+1) Acidic cations include hydrogen (H+1) and aluminum (Al+3). The amount of positively charged cations a soil can hold is described as the CEC and is expressed in milliequivalents per 100 grams (meq/100g) of soil. 34

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36 Plant Nutrients Element Chemical Symbol Source Available Form MAJOR Nitrogen N S-F NH 4 +, NO 3 - Largest Phosphorus P S-F HPO 4 =, H 2 PO 4 - quantity Potassium K S-F K + SECONDARY Sulfur S S-F SO 4 = Medium quantity Calcium Magnesium Ca Mg S-F S-F Ca ++ Mg ++ MINOR Iron Fe S-F Fe ++, Fe +++ Smallest quantity Manganese Boron Copper Zinc Molybdenum Chlorine Mn B Cu Zn Mo Cl S-F S-F S-F S-F S-F A-W Mn ++ H 2 BO 3 - Cu ++ Zn ++ MoO 4 = Cl - Carbon Hydrogen C H A-W A-W CO 2=, CO 3 = H + Oxygen O A-W Many forms S = Soil, F = Fertilizer, A = Air, W = Water 36

37 Soil Preparation Pre-plant Fertilizers WHY USE PRE-PLANT FERTILIZERS? They are high in phosphorous an important nutrient for root development Phosphorous is difficult to infuse in the soil profile later The fertility will be almost immediately available to the new sod New turf requires 25 50% more fertility the first year

38 Site Preparation - Conditioners Add a soil conditioner if the soil test results recommends it Add a conditioner absent a recommendation if you just want to have some insurance against soil problems and improve the soil long-term A safe, and almost always helpful, conditioner is gypsum at 25 lbs. per 1,000 square feet

39 Site Preparation Incorporating amendments, conditioners, and Pre- Plant Fertilizers All materials can be mixed into the soil at the same time. Mix to a full 6 inch depth Use a roto-tiller or do it by hand with a shovel. Roll and water thoroughly after mixing to stabilize the soil and start the breakdown of the materials

40 Classifying Soils by Percentages of Sand, Silt, and Clay

41 Performing a Jar Test A reasonable estimate of the amounts of sand, silt, and clay can be determined by filling a quart-size jar half full of soil and the other half water. Add a teaspoon of soap solution to break up water and soil tension. Shake thoroughly and let it set long enough to settle out. 41

42 Performing a Jar Test2 Sand Most of the sandy particles sink and form a layer on the bottom, and the water looks fairly clear. Silt The silt fraction will settle on top of the sand and before the clay. It will be noticeably darker than the other two soil types. Clay The water is cloudy with a thin layer of particles on the bottom. The tiny clay particles take ages to settle. 42

43 Jar Test Example 43

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45 Conducting a Soil Feel Test Determining Your Soil Type The "Feel Test" can help you determine your soil type. Take just enough moist soil to rub between the thumb and fingers. Rub it back and forth several times and feel it very carefully. Clay soils will be slick and smooth, with little or no grittiness. Sandy soils will be gritty and will not stick together well. Loamy soils will stick together easily, but not like a clay soil. Loam will feel moderately gritty. 45

46 Loam Soils (or Sandy Loams) are Preferable for Plant Growth Loam soil is a mix of sand, silt or clay, and organic matter. Feel: Loam soils are loose and look rich. When squeezed in your fist, moist loam will form a ball which crumbles when poked with a finger. Infiltration: Loam is the best soil for infiltration of rainwater and for healthy vegetation. Loam soils normally absorb water and store moisture well. Loam soils can be sandy (preferable) or clay (less desirable) based, and will vary in moisture absorption and retention. 46

47 Defining Loams by Percentages of Sand, Silt, and Clay Central Ranges of Percentages for Loams as defined on the Soil Pyramid Loam = 40% Sand / 40% Silt / 20%Clay Sandy Loam = 70% Sand / 20% Silt / 10% Clay Clay Loam = 30% Sand / 30% Silt / 40% Clay 47