Soil Fertility and Nutrient Management Hailin Zhang Department of Plant and Soil Sciences
C H O P N K 16 ESSENTIAL ELEMENTS Ca S Mg B Cl Cu Fe Mn Mo B
NON-MINERAL NUTRIENTS Carbon (C) Hydrogen (H) Oxygen (O) (O) Used in photosynthesis
MINERAL NUTRIENTS Major nutrients Nitrogen (N) Phosphorus (P) Potassium (K) Secondary nutrients Calcium (Ca) Magnesium (Mg) Sulfur (S) Micronutrients Boron (B) Chloride (Cl) Copper (Cu) Iron (Fe) Manganese (Mn) Molybdenum (Mo) Zinc (Zn)
Positively Charged Ions Are Called Cations Chemical Ionic Nutrient symbol form Potassium K K + Sodium Na Na + Ammonium NH 4 NH + 4 Hydrogen H H + Calcium Ca Ca ++ Magnesium Mg Mg ++
NEGATIVELY CHARGED COLLOIDS ATTRACT CATIONS K + - - - Ca ++ - - - Ca ++ Na + Soil Colloid - - Mg ++ - H +
Negatively Charged Ions Are Called Anions Chemical Ionic Nutrient symbol form Chloride Cl Cl - Nitrate N NO 3 Sulfate S SO 4 = Borate B BO 3 3- Phosphate P H 2 PO 4 -
Manage Saline and Sodic Soils EC (umhos/cm) 0 4000 8000 12000 16000 ESP % 15 Normal Sodic Saline Increased salt hazard Leaching Gypsum Leaching Saline-Sodic 30
9.0 ph value defines relative acidity or basicity Most productive soils 8.0 7.0 6.0 5.0 Strong Medium Slight Slight Moderate Medium Strong Basic Acid Pure water 4.0 Very strong
Soil ph affects nutrient availability to plants
Active Al Increased by Soil Acidity % Al saturation 50 45 y = 3E+07x -9.6 40 R 2 = 0.86 35 30 25 20 15 10 5 0 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 ph
Mobility of Nutrients in Soil Mobile Nutrients Nitrogen Sulfur Boron Chlorine Immobile Nutrients Phosphorus (P) Potassium (K) Calcium (Ca) Mg, Fe, Mn, Cu, Zn, Mo (Fuel Tank) (Crankcase)
Characteristics of solid-p? Phosphate ions form Al and/or Fe phosphate at low soil ph Phosphate ions form Ca phosphate at high soil ph Neither forms are plant available P- H Retention M Al, Fe Ca phosphates phosphates L 3 5 7 9 Soil ph
Dynamics among Various Forms of Soil K K K K Soil minerals K Unavailable K + K + K + K + K + Soil colloid K + K + K + K + Soil colloid K + K + Soil water K + K + Readily Available Trapped K Soil colloid Slowly available
Soil Test-P is like Dip Stick for engine l Dip Stick l Soil Test (wheat) Test Rec. (add) Test Rec. (add) Full None 65 None 1/2qt. 0-1/2 qt. 40 20 lb 1 qt. 1 qt. 20 40 lb
Processes to Make Fertilizer Recommendation q Soil Test Correlation --- to select the best soil test method for a particular nutrient of the area q Soil Test Calibration --- to describe soil test results in easily understood terminology q Fertilizer recommendation
Nitrogen Requirement Crop to be grown Yield goal N requirement N needs = N requirement - Soil NO 3 -N Credits for subsurface and manure N
Phosphorus Requirement Soil test P index (Mehlich 3 method) Percent sufficiency P requirement (P 2 O 5 lbs/acre)
Relative Crop Yield (%) 100 80 60 40 20 0 Potential Environment al Problems Low Medium High Excessive Soil Test P
P Recommendation P soil test index 0 10 20 40 65+ Sufficiency (%) 25 45 80 90 100 P 2 O 5 (lbs/a) 80 60 40 20 0
Soil Tests Serve Two Basic Functions Provide a starting point for developing fertilizer and liming program Monitor nutrient level to keep the fertilizer program on track
The greatest potential for error in soil testing is in taking the sample
Recognize Field Nutrient Variability Nitrate - Nitrogen lbs/acre 0-30 31-40 41-50 51-60 61-80 >80 (Nitrate-N within a 75 x 75 plot)
P Changes with Depth (no-till) Depth 0 2 6 12 P (ppm) 120 55 35 24 31
Get a Useful Sample 15-20 cores Soil Probe Right Depth (plow layer or 6 inches Clean Bucket OSU Cooperative Extension
Soil Tests at OSU Routine ph Buffer Index Nitrogen Phosphorus Potassium Subsoil Nitrate Secondary Nutrients Sulfate-Sulfur Magnesium Calcium Micronutrients Iron Zinc Boron Soil Organic Matter, Soil Texture, Soil Salinity
Animal Manure
Land Manure Recycling nutrients Poultry Livestock Crop
N to P 2 O 5 Ratio Plants Manure 1 to 1 4-8 to 1 1 to 1 Need to consider both N and P when deciding how much manure/compost to use
Sharpley et al., 1998
Factors Considered for P Management Source factors Soil test P level, manure, fertilizers Rate and method of P application Transport factors Monthly runoff volume, erosion potential Receiving water body sensitivity? TMDL (total maximum daily load) or state water quality standard BMPs (best management practices) Distance to water bodies, cattle exclusion, alternative watering sources Buffer strips, riparian establishment and restoration Soil and/or amendments
Summary There are 16 essential plant nutrients The chemistry of nutrients determines their mobility in the soil and how they are recommended to certain crops Soil ph is a very important soil property Soil testing is important for a successful nutrient management program Consider soil and water quality when managing manure nutrients