Using Fertilizers: Feeding plants Lydia Clayton UAF Cooperative Extension Service Kenai Peninsula District
What to know before you grow? Proper fertilization is essential for: Disease control Weed control Water quality Healthy plants Production
What to know before you grow? Soil sampling is helpful for determining nutrient deficiencies and requirements. UAF CES Publication, FGV-00044, Soil Sampling
What a soil test is and is not A soil test is Evaluation of nutrient supplying capacity of the soil A measure of a certain portion of the total soil nutrients A soil test is not A measure of total nutrient amount A measure of amount of plant-available nutrients (generally)
When to take a soil sample Generally.. When soil is not frozen, very wet, or very dry The same time every time As close to time of planting or when nutrients are needed Specifically Prior to planting To diagnose problems Every 2-3 years
Sampling the Soil Sample areas that appear differently, have different soils, or are managed differently separately multiple samples for the home and landscape
Sample depth depends on the crop or plants, cultural practices, tillage depth and nutrients to be analyzed The recommended sampling depth for most nutrients is 12 In turf a depth of 6 is usually adequate Sampling the Soil
We ve sent it off to the lab now what? General Soil Test includes the following: Soil ph Organic Matter (%) Various nutrient analyzes Most often N, P, and K UAF CES publication, FGV-00045, Factors to Consider in Selecting a Soil Testing Laboratory
We ve sent it off to the lab now what? 18 essential nutrients Macronutrients (large quantities): oxygen nitrogen phosphorus hydrogen potassium sulfur carbon calcium magnesium Micronutrients (small quantities): zinc iron cobalt copper manganese chlorine molybdenum boron nickel HGA-00338, Soils and Fertilizer Management for Healthy Gardens
We ve sent it off to the lab now what? Soil ph: the degree of acidity or alkalinity of soil Affects 3 thing: nutrient availability, toxic metal availability, and soil micro-organisms The ph scale: 2 4 6 8 10 12 acidic Neutral (7.0) alkaline
We ve sent it off to the lab now what?
Deficiencies
We ve sent it off to the lab now what? Major ph problem: aluminum FGV-00043, Managing Alaska Soils
We ve sent it off to the lab now what? Adjusting soil ph For soil ph less than 5.5 amendments to raise ph are helpful: Applying dolomitic lime in the fall at 50 lbs/1000 sq. ft Also supplies calcium and magnesium For soil ph greater than 7.5 amendments to lower ph are helpful: Elemental sulfur (S) or Aluminum sulfate at 50 lbs/1000 sq ft. Organic matter, peat moss, evergreen tree residues
We ve sent it off to the lab now what? Organic matter: builds and stabilizes soil structure, thus reducing erosion and improving soil porosity, infiltration, and drainage. holds water and nutrients for plants and soil organisms. is a long-term, slow-release storehouse of nitrogen, as well as, phosphorus and sulfur
We ve sent it off to the lab now what? Soil Test OM (%) 7 or higher 5 to 7 3 to 5 1 to 3 Under 1 N supplying capacity (generally) of soil: Very High High Moderate Low Very Low What about in cold Alaskan soils?
We ve sent it off to the lab now what? The key to fertilizing is to meet plant needs without creating excesses that can harm plants or the environment: Toxic to plants Limit other nutrient uptake Excessive foliage production Increased risk of disease/wind damage Delay in flowering, fruiting, and dormancy Contamination of drinking water
We ve sent it off to the lab now what? Major problem: magnesium deficiency
We ve sent it off to the lab now what? Buffer ph in acid range Aggravating factors Cold soils Over-irrigation Soil compaction Over-fertilization- potassium fertilizer
We ve sent it off to the lab now what? Sources for Nutrients: Inorganic fertilizers Organic fertilizers Manures, composts, and commercial materials Green manures (legumes and others) Peas, vetch, other legumes fix nitrogen Oats, wheat, barley and other non-legumes recycle nutrients
We ve sent it off to the lab now what? Organic Processed Source Natural materials Manufactured Nutrients Slow-release Immediately Content Usually Low Usually High Examples Manure, Seed meals, Ammonium Rock phosphate, sulfate, Urea, Fish by-products, Potassium Limestone chloride
Three primary nutrients: Fertilizer Labels N (nitrogen):p (phosphorous):k (potassium) Expressed as a % of total fertilizer weight HGA-00131, Make Your Own Complete Fertilizer
A few N-P-K labels out there Inorganics 34-0-0 21-0-0 29-3-4 26-3-3 28-4-4 25-3-5 20-2-4 26-3-3 25-3-5 32-3-5 Inorganics 24-6-12 16-4-8 16-16-16 12-12-12 22-4-11 22-4-14 20-27-5 18-5-9 5-10-10 9-17-9 Organics 3-2-2 0.5-0.2-0.6 1.5-1-1 6-2-1 12-1-1 10-4-0 1-15-0 2-0.5-2 0-0-6 0-25-0 FGV-00348, Fertilizer Nutrient Sources and Lime
Fertilizing with Manures Aged Manures Low nutrient content Good sources of OM Can be applied at higher rates Fresh Manures Higher nutrient content May burn young plants May cause accumulation of salt to toxic levels Disease pathogens Apply sparingly LPM-00340, Animal Manure As Fertilizer
General Fertilizer Guidelines Intensity or plant requirement Low = 1 to 2 lb nitrogen/1000 sq feet Low maintenance turf Low intensity vegetables (peas, beans) Medium = 2 to 4 lb nitrogen/1000 sq feet Medium maintenance turf Medium intensity vegetables (most vegetables) High = 4 to 6 lb nitrogen/1000 sq feet High maintenance turf High intensity
Vegetable Gardens In general Heavy, Medium, or Light feeders Heavy feeders: Brassica crops Melons Corn Cucurbits Solanaceous crops Greens Light feeders: Carrot Garlic Allium crops Peppers Potatoes Soil Builders: Beans Peas In containers: A water soluble, slow release or organic fertilizer every 2-3 weeks with an occasional dose of fish emulsion or compost for trace minerals should be adequate
Ornamental Trees and Shrubs Only use slow release types of fertilizer at planting After planting apply a low rate of N in a 3 x 3 foot area Once established they need very little fertilizer 2-6 lbs of N/1000 sq ft annually When to fertilize: Deciduous Trees Spring Split application of slow release Evergreen Trees Winter Slow release
Fruit Trees Best way to gauge whether fertilization is needed is to watch new annual growth 12-18 of new growth = healthy tree and soil If new growth is lacking a low rate of N fertilizer (no more than 2 lbs/1000 sq ft) may be applied Over-application of N can cause excessive vegetative growth at the expense of flowering and physiological problems in fruit
Calculating Area How to fertilize a tree Find the square area underneath a tree or shrub that extends just past the drip line Divide by 1000 sq ft Multiply by the lbs of fertilizer need per 1000 sq ft The result is the amount needed for the tree
How to fertilize a tree Calculating Area Example: Want to fertilize using a 21-4-4 fertilizer at 3 lbs/1000 sq ft 20 x 20 tree area = 400 ft sq 400 ft sq/ 1000 sq ft = 0.4 3 lbs of N/ 0.21 (N) = 14 lbs of fertilizer/1000 sq ft. 14 lbs x 0.4 = 5.6 lbs of fertilizer for tree area
Resources UAF CES Publications Catalog www.uaf.edu/ces/pubs/catalog/
HGA-00026
Fertilizing new garden soil in raised beds -Julie Riley, UAF CES Extension Unexpected Transmitters of Herbicides -by Steven Seefeldt, UAF CES Extension January 30 - Aminopyralid and Clopyralid in unexpected places: a discussion of herbicide persistence and how to avoid consequences. www.uaf.edu/ces/pests/cnipm/k12/webinars/
National Sustainable Agriculture Information Service https://attra.ncat.org/
Alternative Soil Amendments Alternative Soil Testing Laboratories Biochar and Sustainable Agriculture Foliar Fertilization Introduction to Permaculture Manures for Organic Crop Production Notes on Compost Teas Organic Matter Series: Protecting Water Quality Overview of Cover Crops and Green Manures Soil Management for National Organic Program Regulations Sustainable Management of Soil-Borne Plant Diseases Sustainable Soil Management Worms for Bait or Waste Processing (Vermicomposting)
SARE, www.sare.org