Soil Fertility and Pasture Fertilization. Les Vough Forage Crops Extension Specialist Emeritus. INAG 116. Causes of low pasture productivity:. Lack of adequate fertilization. Poor grazing management. Unproductive species. Adequate Fertilization. Soil test every 2-3 years.
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Soil Fertility and Pasture Fertilization Les Vough Forage Crops Extension Specialist Emeritus INAG 116
Causes of low pasture productivity: Lack of adequate fertilization. Poor grazing management. Unproductive species.
Adequate Fertilization Soil test every 2-3 years. Lime and fertilize according to soil test recommendations.
Soil Testing If no-till seeding, sample from 2 depths -- surface to 2 inches and surface to 8 inches or normal plow layer if pasture has ever been plowed. If tilled soil seeding, sample from surface to 8 inches or the plow or tillage depth.
Correct Fertility Deficiencies Do not attempt seeding unless willing to apply the recommended amounts of lime and fertilizer. pH affects availability and plant utilization of minerals. P critical for seedling development. • K critical for maintaining legumes. • Apply 1 – 3 years before seeding.
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pH Basics • Soil acidity or alkalinity is measured by pH • The pH scale is from 0 to 14 • 7.0 = Neutral • < 7.0 = acidic • > 7.0 = alkaline or basic • Crops have specific soil pH requirements for optimum growth • Most pasture grasses and legumes prefer a pH range of 6.5-7.0
pH Basics • Low pH conditions can cause: • Aluminum toxicities • Reduced availability of soil nutrients • Poor conditions for soil microbes • Deficiencies of calcium and/or magnesium • Poor soil structure
pH Basics: Limestone • Limestone is an amendment used to reduce soil acidity (raise pH) • Limestone contains carbonates and oxides of calcium and magnesium • Expressed as CaCO3 or MgCO3
pH Basics: Limestone • Quality and neutralizing ability • Depends on origin or source of limestone • Limestone recommendations are based on Calcium Carbonate Equivalent (CCE) • Can vary from less than 60 to more than 125 CCE • The actual amount of limestone to be applied will differ from material to material due to different CCE values for each
pH Basics: Limestone • Limestone particle size affects rate of neutralization • Finer materials react faster • Pulverized > ground > granular • Ag lime must meet minimum standards and the label must provide a guaranteed analysis
Fertilizer Basics • Most fertilizers are products that supply: • Nitrogen (N) • Phosphorous (P) • Potassium (K)
Fertilizer Basics: Grades • Grades of fertilizer are identified by three numbers, for example: • 10-10-10 • 5-10-5 • 46-0-0 • Numbers represent the percentage, by weight, of N, P2O5, and K2O, respectively
Fertilizer Basics: Nitrogen • Nitrogen is abbreviated as “N” • Listed as the first number in fertilizer grade • 10-10-10 • Critical component of plant proteins • Required for vegetative growth • Produces lush, dark green coloration • Most forms do not remain in the soil, rather they have high soil mobility • N must be annually applied and in methods that reduce environmental problems • Can be fixed by legumes
Fertilizer Basics: Phosphorous • Phosphorus is abbreviated as “P” • Listed as the second number in fertilizer grade • 10-10-10 • Vital role in plant reproduction • Essential for root growth and seedling development • Supplied as P2O5 • Limited soil mobility
Fertilizer Basics: Potassium • Potassium is abbreviated as “K” • Third number in fertilizer grade • 10-10-10 • Important in many chemical processes in plant growth • Important for disease resistance, overall plant health, and winter hardiness • Supplied as K2O • Little soil mobility
Fertilizer Basics: Grades • Multiply the total weight of fertilizer material by the percentage for each nutrient to determine actual nutrient content • For example, an 80-pound bag of 10-10-10 fertilizer contains • 8 lb. of N • 8 lb. of P2O5 • 8 lb. of K2O
Fertilizer Basics: Grades • Fertilizer recommendations are provided based on pounds of nutrients needed for the given crop based on the soil test levels and expected yields • Application timing and method will be provided in the recommendation
Fertilizer Basics: Manures • Manures are a source of nutrients • Typical nutrient composition of horse manure (per ton) • 12 lb. of N • 5 lb. of P2O5 • 9 lb. of K2O • A manure analysis will provide data on specific nutrient concentrations
Fertilizer Basics: Manures • Manure should be applied to fields only if fertility levels justify their application. • Manures can be composted to reduce their volume as well as any pathogens contained within.
Pasture Fertility Management • Soil testing data and recommendations should be followed to develop a fertility and pH management plan • Recommendations differ, depending upon: • New seeding or established stand • Grass and legume species • Current fertility levels
Pasture Fertility Management • Establishing New Seedings • Last chance to build nutrient levels into the optimum range throughout the rooting zone • At this time, tillage may be used to incorporate and mix lime and fertilizer into the soil • This is particularly important if the soil pH or phosphorus level is very low • Fertilizer and lime usually broadcast onto the field and disked or tilled into the soil prior to seedbed preparation
Pasture Fertility Management • Establishing New Seedings • Different application procedures are used depending on the amount of lime or fertilizer to be applied • If large amounts are recommended, apply as a split application -- plow down ½ the amount and surface apply the remaining ½ • If small amounts are recommended, apply the entire amount on surface
Pasture Fertility Management • Maintenance of Established Pastures • Amount of N, P2O5, and K2O recommended depends on current soil fertility levels and the type of pasture species being grown. • N not recommended for pastures containing >25% legumes. • Heat sensitive grasses such as Kentucky bluegrass and timothy require different fertilizer rates and application times than less sensitive grasses such as tall fescue and orchardgrass.
Pasture Fertility Management • N -- Established Grass Pastures • Rate based on expected yield • Generally 40 lb N/acre/ton of expected yield is recommended • Equivalent to approximately 100 to 250 lb N/acre annually • Timing – split applications • Late winter/early spring (green up) • Mid- to late May • Late Aug/early Sept
Pasture Fertility Management • P and K --Established Grass Pastures • Application rates based on soil nutrient levels and expected yields • Generally 10 - 20 lb P2O5 and 45 - 60 lb K2O removed/ton of forage • Timing • For low fertilizer rates, timing not critical • High rates should be split for maximum efficiency • ½ in mid- to late May • ½ in late Aug/early Sept
Pasture Fertility Management • Long-Term Management • Recommended fertilizer applications should be followed for a 2- to 3-year period. • Soil should be retested every 2 to 3 years to determine: • Soil pH and fertility status • If any change in fertilization and pH management is necessary
Pasture Fertility Management • Long-Term Management • All soil test reports should be kept on file for historic reference • All application records should be retained for future reference • Include a field-by-field inventory • Record lime and fertilizer analyses and rates • Record manure applications • Reference this information and follow the recommendations to improve and maintain soil fertility
Conclusions • Optimum production of pasture plants depends on optimum pH and fertility management • Soil testing is the foundation for sound soil fertility management • Timely applications of necessary lime and plant nutrients will provide pasture plants with optimum fertility conditions • Proper management is essential to reduce environmental risks or degradation