2013 Georgia Grazing School:

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1 Soil Fertility in Grazed Systems How Soil Holds Nutrients Soil Particle Organic Matter Extension Forage Specialist Crop and Soil Sciences UGA Mg K + Ca K + Al 3+ Mg Ca e.g., CEC = 10 K + K + Mg Ca Ca Mg K + K + Mg K Mg + Ca Mg K + Ca + Ca Mg Mg K Ca Ca + Mg Mg Mg Ca K Ca + K + Mg K K + + K + Mg K + Mg Ca Ca Ca Mg Ca Ca K Mg Ca + Mg K + K + Mg Mg Ca Mg K Mg K K + Ca + Ca + Ca Ca Ca K + Mg Ca K Mg + K + Mg Ca Ca K + e.g., CEC = 200 Plant Nutrients Liebig s Law of the Minimum Macro- (Primary) Element Available Form Oxygen O 2, OH - Carbon C0-2 3, HCO 3, CO 2 Micro- (Trace) Element Available Form Iron Fe +2, Fe +3 Copper Cu +2, Cu + S Mo Zn Fe Cl Mn Cu B P Hydrogen H +, OH - Nitrogen NO - 3, NH + Phosphorus HPO -2, H 2 PO - Zinc Zn +2 Manganese Mn +2, MnO - Molybdenum HMoO -, MoO -2 Ca K N Mg Potassium K + Boron H 3 BO 3, B O 7-2 Chlorine Cl - Meso- (Secondary) Element Available Form Calcium Ca +2 Magnesium Mg +2 Sulfur SO -2 Soil Test and Follow Fertility Recommendations Soil Sampling Probe, shovel Sample to inches. Discard thatch/duff. Collect samples in clean, plastic container. Mix, remove debris, split the sample if necessary. Sample hay and crop fields every year and 1/3 of your paddocks each year. 1

2 Sampling is Critical Sample Individual Paddocks A soil test is no better than the soil sample submitted for analysis. Sampling error is the most common source of error in soil test results. The goal of soil sampling is to obtain a representative sample for each paddock or management area. Courtesy: Univ. of Missouri Extension Field Average Sampling Soil Sampling in Pastures Random Composite Sample Random Composite Sample One average Soil Test level One Core Take 20-0 random samples for each 10 acres. Avoid areas near shade, troughs, trails. Fate of Fertilizer N in a Grazed Grassland 1100 lb N fertilizer Animal body 10 lb N Animal Intake 50 lb N 50 lb N Plant Organic Matter 50 lb N What s in the soil, is in the plant, is in the animal,. Microbial & Plant Stored N 2

3 50 lb N 50 lb N Plant Organic Matter 15 lb N Microbial & Plant Stored N Fate of Fertilizer N in a Grazed Grassland 1100 lb N fertilizer Animal body 10 lb N Animal Intake 50 lb N NH 3 + N 2 O 15 lb N 0 lb N Feces+Urine 5 lb N 5 lb N NO 3 Leaching Soil Inorg.N Organic N accumulation rate in upper 12 inches of soil during 12 years of haying or grazing with a yearly application of 220 lb N/acre as NH NO 3. Treatment Management Organic N accumulation Hayed High Low lb N/acre/year Monthly cuts to 2 inches 51 (23%) 1300 lb/acre 92 (2%) 2600 lb/acre 122 (56%) Franzluebbers and Stuedemann (2009) Organic N accumulation rate in upper 12 inches of soil during 12 years of haying or grazing with a yearly applications of 230 lb N/acre as broiler litter. Treatment Management Organic N Accumulation Hayed High Low lb N/acre/year Monthly cuts to 2 inches 78 (3%) 1300 lb/acre 17 (76%) 2600 lb/acre 182 (79%) Franzluebbers and Stuedemann (2009) Pasture vs. Conservation Tillage (CsT) and Conventional Tillage (CvT) Causarano et al., Soil Sci. Soc. Am. J. 72: CvT CsT Pasture Improvement in soil OM in 3 paddocks located in a pasture-based dairy in Wrens, GA. ( ) Paddock IniBal 1 year 2 years 3 years Soil Organic Ma.er, % P P P Avg years after grazing system started, averaging an inc. in soil OM of 0.35 percentage points per year!!! 3

4 Get your priorities right! How Soil ph Affects Availability of Plant Nutrients Maintaining soil ph is job #1. Nutrient availability Soil structure Soil biological activity Aluminum toxicity The difference of a soil ph of 5.6 vs. 6.2: Nutrient Amt. Used Annually Unit Price Dec. in Efficiency Value of Decrease (Lbs/acre) ($/lb) ($/acre) N 200 $ % -$9 P 2 O 5 50 $ % -$15 K 2 O 150 $ % -$8 Total -$72 Fertilization Strategies Pasture A ph = 6.2 P = 35 K = 180 OM = 3% Hayfield 2 & 3 ph = 5.5 P = 15 K = 90 OM = 1.5% Get at the Root of a Problem: Soil ph Problems Hayfield 1 ph = 6.0 P = 25 K = 120 OM = 2.5% Low Soil ph = Aluminum Toxicity Applications of lime every 3 to years are needed in Southeastern soils to maintain appropriate chemical balances in the soil.

5 Benefits of Adding Legumes Split Your Nitrogen Applications! Long-term, this can increase yields by 5-10% and increase NUE by 25-30% Especially important under extremes Ø Leaching Ø Volatilization (in the case of urea-based products) Ø Late freeze Ø Drought Reduces risk of nitrate toxicity, too. A valuable source of N (time-released). Species Annual lbs (N/acre) N value at $0.60/lb. of N Alfalfa $ Red clover $ White clover $60-90 Annual clover $30-90 Another Fertilization Trick Apply P in late summer or fall. Another Fertilization Trick Split Your Potassium Applications! P can essentially be applied any time during the year on established forage crops. Purchase P fertilizer in off-peak times of the year (i.e., summer and fall) Demand for the product is low Demand for spreading services is low Less risk of P runoff 0-50% in the Spring 50-60% in mid late season K is for Persistence Nutrients removed per acre with bermudagrass hay or 500 lb animal Leafspot Diseases Poor Winterhardiness Not Competitive Poor Stress Tolerance The Stand is Gone! Grows Very Slow Adapted from S. Forages 3 rd Ed. 5

6 Benefits of Rational Manure Distribution 1. Better utilization of forage 2. Growth rate of forage is optimized Kept in linear/exponential growth phase Higher yield of forage 3. Higher stocking rates. More animal gains/milk production per acre 5. Reduced feeding of conserved forage or supplements 6. Better persistence of desirable forages Especially clover and legume species 7. Better weed suppression 8. Better manure distribution Manure Distribution Efficiency of Four-legged Manure Spreaders Rotation Frequency Years to Get 1 Pile/sq. yard Continuous day 8 day 5 2 day 2 White et al., 2001 J. Environ. Qual. 30: :8 Efficiency of Waste Management Location Time (% of Total) Defecations (% ) Urinations (% ) Paddock Feed Area Lanes Holding Parlor White et al., 2001 J. Environ. Qual. 30: