Objectives To understand the importance of fertilizers and pH To distinguish fertilizer types To calculate fertilizer rates for their home gardens Apply fertility concepts to a vegetable experiment Soil Fertility and Fertilizers What is a fertilizer? Definition - a material added to the garden that supplies essential nutrients plants need for vegetative and reproductive growth. Why are fertilizers important? Build-up - increasing the level of minerals and OM in the soil. Maintenance - replenishing nutrients lost through leaching, removal during plant growth, and harvest Macronutrients Nitrogen (N) Most mobile nutrient; subject to loss by leaching Used to form proteins and pigments (chlorophyll) Phosphorus (P) Immobile nutrient; must be incorporated into soil Important for energy transfer (ATP) in plants Potassium (K) Immobile nutrient; must be incorporated also Important for cell wall formation and cell liquid balance Fertilizers and pH Optimum soil pH is plant species dependent Most plants will grow well at pH 6.2-6.8 Slightly Moderately Very IL soils slightly acidic Tolerant Tolerant Tolerant - 5.8-6.8 (pH 6.5-6.8) (pH 5.5-6.8) (pH 5.0-6.8) Asparagus Bean Potato Beet Carrot Rhubarb Broccoli Corn Sweet Cabbage Cucumber Potato Watermelon Fertilizers and pH pH influences nutrient availability Determines nutrient form in soil How strongly nutrients are bound to soil particles Nutrients deficient in acid soils Ca, P, Mg, Mo Nutrients deficient in alkaline soils Cu, Fe, Mn Nutrient availability by pH Adjusting pH Lime replaces H+ ions with Ca2+ ions Amount applied depends on soil type and pH change desired Desired pH ∆ Sand Loam Silt Loam Clay Loam ----------------------Lbs/Acre of limestone------------------------ 4.5 6.5 2200 5800 7000 8400 5.5 6.5 1200 3400 4000 4600 6.0 6.5 600 1800 2200 2400 Types of Fertilizers By form Synthetic - Miracle Grow®, Osmocote® Organic - manure, fish meal, bone meal By physical state Solid - manure, compost, granulated Liquid - seaweed extract, anhydrous By rate of release Fast release - mostly synthetic types Slow release - carbon-based (organic), Osmocote® Fertilizer Grade Definition - guaranteed minimum % of total N, available P, and water-soluble K 10-10-5 = 10% total nitrogen 10% available phosphoric acid 5% water-soluble potash Determining Fertilizer Needs Soil Testing Must collect representative samples Professional labs analyze soil for a fee Also provide fertilizer recommendations Home testing kits available Indicates levels of P, K, Mg, pH, and CEC Poor indicator of nitrogen levels due to Leaching losses Mineralization Calculating Fertilizer Rates Measure area to be fertilized 10ft x 40ft = 400ft2 Determine amount applied/Acre using soil test recommendations Need - 100lb/A total N 100lb/A available P 50lb/A water-soluble K Calculating Fertilizer Rates… Use fertilizer grade to convert amount of nutrients/A to amount fertilizer/A 100lbs/A total N = 1000lbs fertilizer/A .10 100lbs/A available P = 1000lbs fertilizer/A .10 50lbs/A water-soluble K = 1000lbs fertilizer/A .05 Calculating Fertilizer Rates… Determine amount fertilizer for your garden space - 400ft2 43,560 ft2 in an acre Set up a proportion 1000lbs fertilizer = x__ 43,560 ft2 400ft2 x = 9.18 lbs fertilizer 9.18 lbs x 454.6g/lb = 4,172g fertilizer!
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