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Fertilizer Application Rate Calculator & Reference Guide
Calculate how much fertilizer to apply per square foot, per acre, or per container. Application rate tables and formulas for every situation.
What Is It ?
Applying the right amount of fertilizer is just as important as choosing the right type. Too little and your plants underperform — pale leaves, weak stems, and disappointing harvests. Too much and you risk burning roots, polluting waterways, and wasting money on nutrients that leach away before plants can use them. The math behind fertilizer rates is straightforward once you understand how it works: the NPK numbers on the bag tell you the percentage of each nutrient by weight, so a 50-pound bag of Wicked Growth 10-10-10 contains 5 pounds of nitrogen, 5 pounds of phosphorus, and 5 pounds of potassium. If your soil test says you need 1 pound of nitrogen per 1,000 square feet, you need 10 pounds of 10-10-10 to deliver that amount. The formula is simple: pounds of product needed equals pounds of nutrient needed divided by the nutrient percentage expressed as a decimal. So 1 pound of nitrogen divided by 0.10 equals 10 pounds of product. This same formula works for any Old Cobblers Farm fertilizer and any nutrient. To deliver 1 pound of nitrogen using Wicked Growth 46-0-0 Urea, you need only 2.17 pounds of product — making it the most economical nitrogen source by weight. This guide provides application rate reference tables for every major Old Cobblers Farm product across garden beds, lawns, containers, trees, and agricultural acreage, plus the formulas to calculate custom rates for any situation.
Wicked Growth Garden Bed Rates
For a standard vegetable garden, most crops need 1-2 pounds of actual nitrogen per 1,000 square feet per growing season. Heavy feeders like corn, tomatoes, brassicas (broccoli, cabbage, cauliflower), and peppers lean toward 2 pounds. Moderate feeders like squash, cucumbers, and lettuce need about 1.5 pounds. Light feeders like beans, peas, and root vegetables need closer to 1 pound — and legumes like beans and peas fix their own nitrogen, so they may need none at all.
Using Wicked Growth 10-10-10, that means 10-20 pounds of product per 1,000 square feet for the full season, typically split into a pre-plant application and one or two side-dressings during the growing season. Split applications are more efficient than dumping everything at once because plants cannot absorb a season's worth of nitrogen in one feeding — the excess leaches or volatilizes before the plant can use it.
Wicked Growth 5-10-10 at 10-20 pounds per 1,000 square feet provides extra phosphorus and potassium for fruiting crops and bulbs. Use this ratio for tomatoes, peppers, squash, cucumbers, and any crop where fruit production is the goal. The lower nitrogen relative to P and K prevents the common mistake of over-fertilizing fruiting crops with nitrogen, which produces spectacular foliage but disappointing harvests.
Wicked Growth 8-16-16 Seed Potato Fertilizer at 6-12 pounds per 1,000 square feet delivers the heavy phosphorus and potassium that root crops demand. This formula works for potatoes, carrots, beets, turnips, and other crops where the harvest is underground. The high P and K ratio supports tuber and root development without pushing excessive top growth.
Wicked Growth 16-10-13 at 6-12 pounds per 1,000 square feet is ideal for leafy crops like lettuce, spinach, kale, and Swiss chard where abundant foliage IS the harvest. The nitrogen-forward ratio pushes vigorous leaf production.
Wicked Organics Garden Bed Rates
For organic programs, application rates are higher by volume because organic nutrient percentages are lower — this is normal and expected, not a disadvantage. You are applying more bulk material per unit of nutrient, but that extra bulk is organic matter that feeds soil biology and improves soil structure. It is not waste — it is a secondary benefit.
Wicked Organics 5-3-4 at 20-40 pounds per 1,000 square feet delivers equivalent nitrogen to 10-10-10. Apply at bed preparation in spring and side-dress heavy feeders mid-season. This is the workhorse organic blend — versatile enough for any vegetable garden. Wicked Organics 8-3-5 at 12-25 pounds per 1,000 square feet provides higher nitrogen for heavy-feeding crops.
Wicked Organics Blood Meal (12-0-0) at 4-8 pounds per 1,000 square feet provides a concentrated organic nitrogen boost. Because it releases faster than most organics (2-4 weeks), it works well as a mid-season side-dressing when crops show nitrogen hunger. Wicked Organics Feather Meal (12-0-0) at the same rate releases more slowly (3-4 months), making it better suited for pre-plant incorporation where you want sustained feeding.
Wicked Organics Bone Meal (3-15-0) at 5-10 pounds per 1,000 square feet supplies phosphorus for root establishment. Mix into the top 4-6 inches of soil at planting time for bulbs, transplants, and root crops. Wicked Organics Rock Phosphate (0-12-0) at 5-10 pounds per 1,000 square feet builds a multi-year phosphorus reserve — apply once and it releases for 3-5 seasons.
How To Store
Established lawns typically need 2-4 pounds of actual nitrogen per 1,000 square feet per year, split across 2-4 applications during the growing season. Cool-season lawns in New England perform best with the heaviest feeding in early fall (September) and a lighter application in late spring (May). Avoid heavy nitrogen in summer heat — it stresses grass and encourages disease.
Using Wicked Growth 16-10-13 at 6 pounds per 1,000 square feet delivers about 1 pound of nitrogen per application — a standard rate for one feeding. Apply 3-4 times per year for total season coverage. This balanced formula provides the potassium that strengthens grass for traffic, heat, and cold stress.
For straight nitrogen greening, Wicked Growth 46-0-0 Urea at 2.2 pounds per 1,000 square feet delivers 1 pound of nitrogen at the lowest cost per unit. Critical rule: always water in urea within 24-48 hours of application. Urea converts to ammonia gas through a process called volatilization — in warm weather on dry turf, you can lose 30-40% of the nitrogen to the atmosphere before it ever reaches the roots. Watering dissolves the urea into the soil where roots can access it.
Wicked Growth 21-0-0 Ammonium Sulfate at 4.75 pounds per 1,000 square feet delivers 1 pound of nitrogen while acidifying the soil. This is the preferred nitrogen source for lawns on alkaline soil or anywhere you want to simultaneously lower pH. It has a lower volatilization risk than urea and provides sulfur as a secondary nutrient.
For organic lawns, Wicked Organics 10-2-8 at 10 pounds per 1,000 square feet provides steady slow-release feeding that sustains color for 6-8 weeks per application. The slow release means no flush of excessive growth followed by a crash — just consistent, even greening.
Lawn Application Rates
Container plants live in a limited soil volume that leaches nutrients quickly with every watering. Rates are measured per gallon of soil rather than per square foot, and feeding frequency must increase to compensate for constant nutrient loss through drainage.
A general guideline for granular fertilizer: 1-2 tablespoons of Wicked Growth 10-10-10 per gallon of soil, mixed in at planting and reapplied every 4-6 weeks during active growth. For organic container growing, mix 2-4 tablespoons of Wicked Organics 5-3-4 per gallon of potting mix at planting, with additional top-dressings monthly.
Wicked Growth 19-19-19 dissolved at 1 tablespoon per gallon of water provides an immediately available feeding for containers. Use every 1-2 weeks during active growth for consistent nutrition. This water-soluble approach is the most precise way to feed containers because you can adjust concentration and frequency based on plant response. Start at half-strength for seedlings and newly transplanted plants, working up to full strength as they establish.
Wicked Growth Hanging Plant Fertilizer (10-10-10) at 1-2 tablespoons per gallon works specifically for hanging baskets and window boxes. These dry out and leach nutrients faster than standard containers because of increased air exposure, so feeding every 2-3 weeks is typical.
Container and Raised Bed Rates
Tree fertilization rates are based on trunk diameter measured at 4.5 feet above ground (DBH — diameter at breast height). The standard guideline is 0.1-0.2 pounds of actual nitrogen per inch of DBH, broadcast evenly over the drip line area where feeder roots are most active. Never pile fertilizer against the trunk — feeder roots are at the outer canopy edge and beyond.
For a 4-inch diameter apple tree using Wicked Growth Apple Tree Fertilizer (8-0-16), you would apply approximately 5-10 pounds of product spread in a ring from halfway between trunk and drip line to 2 feet beyond the drip line. The zero-phosphorus formula is ideal for established trees in soils with adequate phosphorus. For organic orchards, Wicked Organics Fruit Tree Fertilizer (12-2-8) at 4-8 pounds provides concentrated slow-release nutrition.
Wicked Organics 4-3-3 Trees and Shrubs formula at 5-10 pounds per tree provides balanced organic nutrition for general landscape trees and ornamental shrubs. For shade trees, Wicked Growth Shade Tree Fertilizer (20-10-10) provides the higher nitrogen that drives canopy development. For nut trees, Wicked Growth Nut Tree Fertilizer (5-5-10) delivers extra potassium for nut development and winter hardiness.
Fruit trees should be fertilized based on annual shoot growth measurements rather than calendar schedules. Measure the length of new growth on several branches in late summer. If growth meets or exceeds targets for the tree type and age, reduce or skip fertilization — over-fertilizing fruit trees produces excessive vegetative growth at the expense of fruit quality.
Agricultural Acre Rates
For field-scale applications, rates scale up from per-1,000-square-feet to per-acre (1 acre = 43,560 square feet, roughly 43.5 times the 1,000 sq ft rate). Wicked Growth 10-10-10 at 100-200 pounds per acre provides general fertility for hay fields, pastures, and mixed-use agricultural land.
For targeted nitrogen: Wicked Growth 46-0-0 Urea at 100 pounds actual nitrogen per acre requires 100 divided by 0.46 = 217 pounds of product per acre. For potassium: Wicked Growth 0-0-60 at 80 pounds actual K per acre requires 80 divided by 0.60 = 133 pounds of product per acre. For phosphorus: Wicked Growth 0-46-0 at 60 pounds actual P per acre requires 60 divided by 0.46 = 130 pounds per acre.
Wicked Growth 19-19-19 Food Plot Fertilizer at 150-200 pounds per acre provides balanced nutrition for wildlife food plots. Wicked Growth Cover Crop Fertilizer (10-10-10) at 100-200 pounds per acre gets cover crops established quickly.
Avoiding the Most Common Application Mistakes
The most frequent rate error is confusing pounds of product with pounds of nutrient. When a guide says to apply 1 pound of nitrogen, it does not mean 1 pound of fertilizer — it means enough fertilizer to deliver 1 pound of actual nitrogen. With Wicked Growth 10-10-10, that is 10 pounds of product. With Wicked Growth 46-0-0, it is only 2.17 pounds. This distinction is the single most important concept in fertilizer math.
The second most common mistake is not watering in after application. Urea loses up to 40% of its nitrogen to the atmosphere through volatilization if not watered into the soil within 48 hours. Ammonium sulfate is more resistant to volatilization but still benefits from watering in. Organic fertilizers like Blood Meal and Feather Meal need soil moisture to activate the microbial decomposition that releases nutrients — a dry application on dry soil just sits there doing nothing until it rains.
The third mistake is applying the full season's fertilizer in one shot. Plants cannot absorb three months of nitrogen in one feeding. The excess sits in the soil where it can leach into groundwater or run off into waterways. Split your total seasonal rate into 2-4 applications spaced 4-6 weeks apart for maximum efficiency and minimum environmental impact. This is true for both Wicked Growth and Wicked Organics products, though organics are inherently more forgiving because their slow-release nature acts as a built-in split application.