Pasture Management- Fertility Brie Menjoulet Agronomy Specialist Hermitage, MO
Goals of Pasture Fertility To establish and maintain desired species Requirements and application timing of some nutrients can vary depending on species Reduce weeds and some undesirable species Distribute forage growth more evenly
Plant Nutrients A mineral element is considered essential to plant growth/development if: 1) The plant can not complete its life cycle without it 2) The element is involved in metabolic functions 3) Another element may not substitute or replace its function 16 Essential Plant Nutrients 3 Most Abundant Carbon (C) Hydrogen (H) Oxygen (O)
6 Macronutrients Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulfur (S) Plant Nutrients 7 Micronutrients Boron (B) Chlorine (Cl) Copper (Cu) Iron (Fe) Manganese (Mn) Molybdenum (Mo) Zinc (Zn) Plants uptake large amounts Plants can only use certain forms of each nutrient
Law of the Minimum: It only takes one scarce nutrient or one other limiting factor to affect plant growth and vigor!
Phosphorus (P) and Potassium (K) Chemical forms change in soil Plants uptake: Phosphorus as phosphate - P 2 O 5 Potassium as potash - K 2 O Not prone to leaching Clings to soil particles and organic matter Can be built up in the soil over time
Stand Improvement 3 years after applying 30#/A of P to the right half
Complex cycle! Nitrogen (N)
N 2 O NO N 2 N 2 O N 2 NO 3 - NO NO 2 - NO 3 - NH 4 + & NO 3 - NO 3 - NH 4 + NO 2 -
Nitrogen (N) Complex cycle! Forms in soil change frequently Soil moisture level, organic fraction, temperature We usually don t soil test for N levels Little attraction to clays and organic matter Primary uptake forms: Nitrate-Nitrogen NO - 3 Ammonium-Nitrogen NH + 4
Nutrient Movement & Retention Is dependent on: The nutrient itself Overall soil health & depth Soil texture (sand, silt and clay composition) Organic matter fraction Fertilizer type Application method
Nutrient Removal Crop N P 2 O 5 K 2 O Ca Mg S --------------------------- Lbs/ton -------------------------- Alfalfa* 60.0 15.0 60.0 28.0 50.0 5.0 Red Clover* 56.0 12.5 45.0 24.0 6.0 5.0 Sorghum-Sudan 40.0 15.0 55.0 10.0 6.0 4.5 Cool-Season Grass 45.0 12.0 50.0 10.0 5.0 4.5 Warm-Season Grass 35.0 10.0 35.0 10.0 5.0 4.5 Grass Pasture (per 100 cow days = ~1.5 ton/acre) 60.0 5.0 17.0 4.0 2.0 2.0 *Most of the nitrogen is obtained from the atmosphere More than 90% of P and K are returned About ½ of N is returned
Nitrogen Requirements (no clover) Generally- 40 to 90 lb/acre At $0.71/lb = $28.40 to $63.90 an acre Higher rate: Fields with high water holding capacity, few weeds, little legume, low endophyte Split application is usually better Lower rate: Fields with low fertility, little soil depth, weedy, high legume content, high endophyte
Legumes ~ 80% of atmosphere is N-gas (N 2 ) Remember the uptake forms Nodules are home to nitrogenfixing bacteria Bacteria convert N 2 to NH 3 Most fixed N goes to host plant They will save you $$$$$$ Need ~ 20 to 30%
Nodulated Plants Produce Nitrogen Seeds should be inoculated to ensure fixation Rhizobium bacteria Presence in soil Not inoculated Inoculated
Legumes Dry matter yields of tall fescue-red clover vs tall fescue with N fertilizer (Lexington, KY, 2-yr average) Treatments Yield, lb/a Tall fescue-red clover 11,100 6 lb seed/a Tall fescue + nitrogen 0 lb N/A 3900 90 lb N/A 6700 180 lb N/A 9900 Adapted from Southern Forages
Nitrogen Fertilization of Grass/Legume Mixes 35 30 % Lespedeza 25 20 15 10 5 0 0 25 50 100 Nitrogen lb/acre
Nitrogen Fixation by Legumes Legume N Fixed (lb/a/yr) Alfalfa 150-250 Red Clover 75-200 Ladino Clover 75-150 Annual Lespedeza 50-150 Adapted from Southern Forages At $0.71/lb for ammonium nitrate: Legumes fix between $35 and $177 of N/ac/yr
Nitrogen Sources Source N P 2 O 5 K 2 O S Anhydrous Ammonia 82 - - - Ammonium-Nitrate 34 - - - Ammonium-Sulphate 21 - - 24 Diammonium Phosphate (DAP) 18 46 - - Potassium Chloride - - 60 - Example 18-46-0
Nitrogen Application Timing Perennial Ryegrass Forage Growth Rate Tall Fescue Orchardgrass Feb Apr Jun Aug Oct Dec
Manures The good: Adds organic matter Helps improve many aspects of soil health Adds micronutrients Current price = $24 to $35/ton dumped The bad: The smell Transportation costs Availability Nutrient variability
Nutrient Concentration of Manures Grass Pasture (per 100 cow days = ~1.5 ton/acre) 60.0 5.0 17.0 Source Units N P 2 O 5 K 2 O Poultry Litter lbs/ton 69 82 37 Beef Feedlot lbs/ton 24 23 30 Dairy Slurry lbs/1000 gal 25 25 40 Pig Slurry lbs/1000 gal 58 40 24 Pig Effluent lbs/acre-in 135 102 192 Research adapted from Dr. John Lory, University of Missouri
A CD/A is a pasture yield goal that means "cow day per acre." This is enough forage dry matter for a 1,000-pound cow with a calf less than 4 months old for one day. In Missouri this is considered to be 30 pounds of forage dry matter per day. For example, a yield goal of 200 CD/A is roughly equivalent to 3 tons of forage dry matter per acre.
Yield Response Curve 100% 95% % Yield Apply Buildup + Maintenance Fertilizer Economic Optimum Yield Apply Maintenance Fertilizer Apply No Fertilizer Maximum Yield Detrimental 50% VL L M H VH EX Soil Test Level
Minimum Soil Fertility Species ph(s) P K - lb / acre - Cool-season grass 5.0 20 200 Warm-season grass 5.0 20 200 Alfalfa 6.5 40 300 Red Clover 6.0 25 250 White Clover 5.5 25 250 Birdsfoot Trefoil 5.5 20 225 Lespedeza 5.0 20 200
Evening Out Nutrient Distribution Consider how you feed hay... Unrolling, stationary bale rings, move bale rings Dragging
Evening Out Nutrient Distribution Dung Beetles Speeds up manure pat removal 24 hour removal documented Manure left behind can take 5-10% of the grazing area Dung beetles can enhance grazing efficiency Increases nutrient cycling Tunneling improves OM Quick removal means less N loss to volatilization Dwellers Buriers - Rollers
Evening Out Nutrient Distribution Pasture size- Continuous Grazing 1800 ft. Water High Medium Low
Evening Out Nutrient Distribution Pasture size- Rotational Grazing 600 ft. Water High Medium Low
Liming The poor man s fertilizer For cool-season grass: 5.5 to 7.0 For legumes: 6.0 to 7.5 Limit application to 2 to 3 ton/acre/year Applying 2 ton/ac every now and then is NOT a good practice
Soil ph ph scale = 0 to 14 0=Strong Acid 7= Neutral 14= Strong Base For best plant growth and nutrient availability: ph= 6.2 to 6.5
Lime Takes a While % of Lime Broken-down 100 80 60 40 20 0 0 3 6 9 12 Months After Lime Application
Quality Sampling BE CONSISTENT Sample every 3 to 5 years Sample at the same time every year Depth Avoid sampling soon after applying fertilizer, lime, compost or manure Best to wait 1 year (at least 4-6 months) Avoid sampling hot spots
Soil Core Variability Soil test P (Bray I, lbs./acre) 200 180 160 140 120 100 80 60 40 20 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 Core number Mean: 44 STD: 48
Increasing Accuracy by Dividing Fields Based on Known Variability Soil test P (Bray I, lbs./acre) 200 180 160 140 120 100 80 60 40 20 0 Pasture Overall Mean: 44, STD: 48 Old manure piles Pasture mean: 20, STD: 17 Feeding area mean: 114, STD: 52 Feeding areas 4 8 11 14 19 22 25 28 31 36 40 45 48 51 54 57 60 63 3 16 38 Core number
Quality Sampling Divide primarily by management Sections 20 acres or less Use a zigzagging pattern
Questions? Brie Menjoulet Agronomy Specialist Hermitage, MO 417-745-6767