Outline Soil: We Can t Grow without it! Clay Robinson PhD, CPSS, CCA Associate Professor of Soils Illinois State University Which nutrients do plants need? Fertilizers: Which and how much? Nutrients and sources: Fertilizer Compost. Soil biology and health Biologicals and humus. What is soil? Dynamic Ever-Changing Heterogenous Different sizes, minerals, organics 3-phase Solids, liquids, gases Porous Media Spaces between the solids Liebig s Law Plants grow in response to the most limiting factor. Adding Nitrogen is pointless if air (or water) is the most limiting Adding Iron is pointless if Potassium is the most limiting factor Plant WANTTS Water Air Nutrients Temperature (species-dependent) Toxicities (none) Strength (root support) Soil Nutrient Cycles Plant Uptake CO 2 Photosynthesis Nutrients Residues Microbes SOM 1
Plant Essential Macronutrients From air and water Carbon Hydrogen Oxygen From Soil Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur Plant Essential Micronutrients (from Soil) Iron Manganese Copper Zinc Nickel Chlorine Boron Molybdenum Soil Reaction, ph Soil Reaction, ph Affects Nutrient availability Toxicities of nutrients and elements Fertility potential Microbial activity Decomposition, nutrient cycling Bacteria 6.5-7.5 Fungi < 6.0 Soil Reaction, ph Plants vary in ph preferences Acid soils: Rhododendrons, azaleas, cranberries Neutral to acid soils: Pines, spruces, maples, sycamores, et al. Slightly acidic to neutral soils: Most vegetables, corn, soybeans Neutral soils: Alfalfa et al. Chlorosis Yellowing of plant tissues, esp. leaves sign of stress - analogous to a fever What is the source of the stress? 2
Chlorosis What is the source of the stress? Nutrient deficiencies Disease Insect damage More diagnostics needed Soil Sampling Turf and gardens: October to March Nutrients available to plants Used to recommend fertilizers Soil Sampling: Strategy? February at old home Turf Vegetable garden Soil Sampling Uniform areas (Turf, gardens, etc.) 5 to 10 subsamples Composited Mixed Turf Vegetable garden Perennial beds Perennial beds Soil Tests Use chemical processes to estimate plant available nutrients Reported in parts per million (ppm) Fertilizer and management suggestions, if requested Interpreting Soil Tests Very low to very high Based on probability of plant response Lawn or garden recommendations Pounds per thousand square feet. 3
Soil Testing Laboratories http://www.gmslab.com/lawn-garden Cropsey, IL https://www.unitedsoilsinc.com/ Fairbury, IL https://extension.illinois.edu/soiltest/ List of labs Nutrient Sources Commercial fertilizers, standard mixes Unknown amounts Compost and Manure Most nutrients Excellent P source, May need more nitrogen Difference? Decomposition Stability and availability What s in the Bag? Fertilizer grade, e.g., 20-10-5 Nitrogen Phosphate Potash (Aside: Truth in labeling) Nitrogen = 20% Phosphate, P 2 O 5 = 10% (not phosphorus) Potash, K 2 O = 5% (not potassium) What s in the Bag? Other nutrients/chemicals reported in detailed analysis Other nutrients on elemental basis, e.g., % sulfur or % iron What s in the Bag? Fertilizer Application About half nitrogen by soil test when ground thaws, growth starts Apply more in split applications during summer only if lawn color fades Apply a winterizer to turf in late fall (September/October) 4
Applying Fertilizer Recommendation: 10 lbs 28-0-0-5 per 1000 ft 2 Determine the area of your yard, garden, etc. Divide your lawn or garden into rectangles or squares Measure the length and width of each parcel Area: Example June at old home Turf area? 35 ft x 40 ft 60 ft x 30 ft Turf area: Solution Multiply length x width to find area 60 ft long x 30 ft wide = 1800 ft 2 35 ft long x 40 ft wide = 1400 ft 2 Area = 1800 ft 2 + 1400 ft 2 = 3200 ft 2 So, how much 28-0-0-5 fertilizer? Fertilizer amount: Solution So, how much 28-0-0-5 fertilizer? 10 lbs 28-0-0-5 per 1000 ft 2 Area = 1800 ft 2 + 1400 ft 2 = 3200 ft 2 10 1000 2 3200 2 = 32 lb 28-0-0-5 Most fertilizer bags come with setting instructions for common spreaders Applying Fertilizer Read the bag carefully Herbicides or insecticides? Make sure product is safe for your lawn or garden Herbicides kill target species + others: certain grasses, flowers, shrubs, etc. Applying Fertilizer Following suggested rates and spreader settings Some is good, more is better! Too much of a good thing is a bad thing! 5
2/13/2018 Soil Biology Dr. Dirt Soil organisms - residue decomposition and nutrient cycling Active portions of soil: clay and humus provide sites for nutrients, chemical bonding, reactions, and microbes DoctorDirt.org @DrD_SoilStuff Youtube.com/drdirtsoilvideos FB: Dr. Dirt: Why everyone should love soil 6