Soils and Soil Fertility Management

Transcription

1 Soils and Soil Fertility Management Mark L. McFarland Professor and Soil Fertility Specialist Texas A&M AgriLife Extension Service College Station, Texas Four Principal Components of Soil Air Mineral Solid Soil Water Organic Material Variation in Soils - Geology - Climate - Vegetation 1

2 Soil Properties Physical properties Texture Structure Chemical properties Cation exchange capacity (CEC) Soil reaction (ph) 2

3 Soil Texture (Diameters of individual soil particles) SAND Very Coarse Coarse Medium Fine Very Fine mm mm mm mm mm SILT CLAY mm Less Than.002 mm 3

4 Soil Physical Properties Soil Texture Sand Loam Silt Clay Permeability High Medium Low Low Water Retention Low Medium High High Soil Structure Formation of soil aggregates (clods) Opens soil surface to allow water, air, nutrients, and roots to move. 4

5 Expected ph Range in Soils Neutral k Acidic Basic 5

6 Effect of ph on Plant Nutrient Availability Preferred ph Ranges of Various Plants Crops: Asparagus Beets Cabbage Sweet Corn Pumpkins Tomatoes Blueberries Strawberries Optimum ph Range for Vegetable Crops

7 Cation Exchange Capacity (The Nutrient Supplying Power of Soil) Ca ++ Na + Likes repel Unlikes attract Mg ++ Clay particles Organic matter SO 4 = NO 3 - K + H + Ca ++ Cl - Soil Water NO 3 - Plant Nutrition Factors Affecting Fertilizer Management Plant species Type and intensity of use Soil characteristics (texture) Residual nutrient status Essential Elements for Plant Growth Boron Calcium Carbon Chlorine Cobalt Copper Hydrogen Iron Magnesium Manganese Molybdenum Nitrogen Oxygen Phosphorus Potassium Silicon Sulfur Vanadium Zinc 7

8 Essential Elements Found to Limit Plant Growth in the Field Primary Nutrients: Nitrogen, Phosphorus, Potassium Secondary Nutrients: Calcium, Magnesium, Sulfur Micronutrients: Boron, Chlorine, Copper, Iron, Manganese, Zinc Annual Nutrient Removal in Clippings (lbs./1,000 ft 2 ) Nutrient Bermuda St. Augustine Primary Secondary Micro s Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur Zinc Manganese

9 Soil Testing The Key to Nutrient Management A soil test is a chemical extraction that provides an index to estimate the nutrient supplying power of a soil Identifies the degree of deficiency or sufficiency of a nutrient The Best and Proper Fertilizer to Use is the One Based on a Soil Test! There is no standard fertilizer product, nutrient ratio or rate of application for yards, gardens, etc. Each crop, location and year can and often will be different. 9

10 Types of Fertilizers Single Nutrient Simple Fertilizers Multinutrient Mixed Fertilizers or Complexes Fertilizers Must Always Be Used Properly Nutrient Contamination of Water Nitrogen and Phosphorus: Needed by all plants for optimum growth and production. Runoff into creeks, streams, lakes can cause excessive plant growth (eutrophication). 10

11 Plum Creek IMPAIRMENT: Bacteria Water quality does not support designated use of contact recreation. Lockhart CONCERNS: Nutrients (nitrogen and phosphorus) Portions exhibit elevated nutrient levels. Impairments in Texas 1,214 water bodies surveyed for the 2010 report 11

12 Fertilizer Analysis State Law commercial fertilizers must have a label identifying the materials guaranteed analysis (grade) Guaranteed Analysis minimum weight (%) of each nutrient contained in the fertilizer Fertilizer Grade % Nitrogen % Phosphate % Potash (N) (P 2 O 5 ) (K 2 0) Fertilizer Grade & Ratio Grade: Ratio: 3 : 1 : 2 12

13 Primary Nutrients Nitrogen Phosphorus Potassium The Nitrogen Cycle Atmospheric Nitrogen Atmospheric Fixation Industrial Fixation Protein Biological Fixation Plant & Animal Wastes Nitrate Reduction Denitrification Ammonium Nitrite Nitrate Leaching Loss Nitrogen Characteristics and Functions Available Forms: Nitrate (NO 3- ), Ammonium (NH 4+ ) Movement in Soil: NO 3- can leach NH 4+ won t leach Functions in Plant: Part of Amino Acids Proteins Part of chlorophyll molecule 13

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15 Excess Nitrogen Reduced root growth. Excess water use. Reduced cold tolerance Thatch accumulation. Disease and insect susceptibility. Brownpatch Nitrogen Fertilizer Sources Inorganic, soluble sources Inorganic slow release Organic (slow release) 15

16 Soluble Nitrogen Sources Material % N Urea Ammonium sulfate Potassium nitrate Slow Release Nitrogen Sources Coated Products Sulfur coated urea Polymer coated urea Polymer/sulfur coated urea Reacted Products IBDU Ureaformaldehyde Methylene Urea Ureaform Organic Products Municipal biosolids Food processing by products Composts Animal manures Growth Response 10 Color Rating Weeks After Fertilization 16

17 Phosphorus Characteristics and Functions Available Forms Primary orthophosphate (H 2 PO 4- ) Secondary orthophosphate (HPO 4 2- ) Movement in Soil: Very immobile; Will not leach or volatilize Tends to accumulate/build up in soils. Functions in Plant: Stimulates early growth & root formation Hastens maturity and promotes seed production 17

18 Excessive Phosphorus * phosphorus induced zinc deficiency Phosphorus Fertilizer Sources Inorganic % P 2 O 5 Triple superphosphate (TSP) 46 Monoammonium phosphate (MAP) 48 Diammonium phosphate (DAP) 46 Organic Biosolids 3 4 Animal manures < 1 3 Bone meal Potassium Characteristics and Functions Available Forms:Potassium ion (K + ) Movement in Soil: Does not leach/volatilize Functions in Plant: Increases water use efficiency Increases disease resistance Improves cold hardiness 18

19 Potassium Fertilizers Grade Source Formula (% K 2 O) Potassium chloride KCl Potassium sulfate K 2 SO Potassium nitrate KNO K Mag KMgSO Secondary Plant Nutrients Calcium (Ca) Magnesium (Mg) Sulfur (S) 19

20 Essential Micronutrients Zn Fe Cu Mn B Cl Mo Needed in very small amounts Most micronutrients come from decomposition of O.M. Increase in soil ph decreases micronutrient availability (Except Mo and Cl) 20

21 Name That Deficiency? Taking Soil Samples Soil tests are only as accurate as the samples on which they are based. Samples must be representative of the area to be cropped. 21

22 Taking Good Soil Samples Take cores for each management area (yard, garden, flower beds). Place cores in clean plastic bucket, and mix thoroughly. Put 2 pints in bag and mail immediately to laboratory. sandy spot X X X X X X X X X drainage 22

23 Non-Traditional Products 23

24 Categories of Non-Traditional Products Soil conditioners Soil activators (biological inoculants) Wetting agents Plant stimulants and growth hormones Mineral nutrient sources used in an unconventional manner Effects of Two Soil Activators on Crop Yields Fertility Soybean Peanut Corn Bermuda Rice Tomato Treatment KY LA FL OK Al KY TX Unfertilized Check Medina Supernate Fertilized Check Medina Supernate * Weaver et al.,