Nutient Application Basics
Written By Jason Streubel and Chad Kruger
We all know our plants need food (nutrients) to survive and produce a bountiful crop for our family nutritional and economical needs. When this type of discussion about nutrient application to soil arises the first questions quickly to revolve around why and what types of nutrients, when and how much do I apply, and it sounds like math is involved so help. The answers to these questions are going to vary depending on location, crops, and nutrient type but here are some suggestions to guide you.
Deep down everyone knows plants need nutrients to grow but understanding the nutrients can run out is not always second nature. Plants need macro and micronutrients to survive and grow. In the agriculture setting the most common addressed nutrients are Nitrogen (N), Phosphorus (P), and Potassium (K), however the others should not be ignored. These nutrients determine whether or not the plant can produce seed, roots, flowers, and how much of each. Each of these components are essential for the production of the vitamins and minerals needed for human nutrition and must be provide by the plant via the soil. The plant takes the nutrients from the soil and if one of the nutrients is deficient the full potential is not going to be reached, furthermore if nutrients are not replaced back to the soil ones yield will decrease year after year. The starving of your soils nutrient bank account will only give you headaches. You starve the soil you starve your garden!
WHAT TYPES OF NUTRIENTS:
In modern gardening there are two primary categories of nutrients traditionally added to soils, organic material and synthetic fertilizers.
- Organic materials are anything that was once living (or in something living). In the common garden these are animal manures and compost. The benefits of organics including long term soil health (building the soils nutrient savings account) and supplying the much needed micronutrients. When using organics it is important to remember you will not get all the nutrient value during the first year, like synthetics but will draw them out over a 3 year or more period.
- Synthetic fertilizers are manufactured nutrients you can buy at your local home store or garden shop. These can come in single nutrients or in blends. For example one can buy a 50lb bag of Urea (Nitrogen) or Triple 16 that is a blended equal parts Nitrogen, Phosphorus, and Potassium. Synthetics give you a quick supply of nutrients for the one season but do not address the micronutrients or overall soil health. The decision to use synthetics over organic is a personal one and where you are starting in the process. If you need a garden this season then using synthetic might be your best option as long as you are planning of addressing your long term soil health.
Synthetic nutrients can be a critical factor in helping to ‘boost yields’ and getting a quick ‘bang for the buck’ for increasing overall food production is important. However, without a long-term “health” of a soil / crop system management plan using manures, compost, and other organics in the system you will find yourself doing more damage to your yield and soil than good.
On a common fertilizer bag there are usually three numbers which show the nutrient value of the material in the bag. They are always written in the standard order of N, P, and K. For example the 50lb bag of Urea will read 52-0-0 and Triple 16, 16-16-16. The number give is the percentage of the nutrient in the fertilizer, therefore Urea is 52% nitrogen. There are several universities with available resources on how to make the calculations based on the nutrient values of different organic amendments. Oregon State University’s “compost calculator” is one of the best. It can be found at http://smallfarms.oregonstate.edu/calculator.
When someone applies nutrients to the field depends on type and crop but here are some general principles.
- When applying organic material to the field it is best applied in late fall or in winter to allow maximum time for the microbes in the soil to break down the material releasing the nutrients. If apply liquid organics early spring is ideal after the ground has thawed making penetration possible instead of running off from the frozen soil.
- Synthetics fertilizers can be applied to perennials (lawns, cover crops) in the fall. A fall application allow roots to take up the nutrients in storage prior to going dormant giving them energy for start up in the spring. In the traditional garden setting one should apply the nutrients just prior to turning the soil under before planting. Incorporating the fertilizer into the soil close to application will keep the nutrients in the soil instead of dissolving into the air (volatilization).
A word of caution when planting seeds into soil that has been fertilized with synthetics do not plant the seed directly on or close to a piece of fertilizer as it could burn the roots during germination.
This is a question without a general answer and does take a little research because different plants have different nutrient needs. The best possible scenario for anyone wanting to plant a garden is to have their soil tested for its current nutrient value before one starts. A soil test will give you all the information necessary for answering the HOW MUCH question. Growing a garden without a soil test is nothing but a guessing game. The soil test can be conducted by a commercial lab, usually found in a phone book or internet, which cost roughly 60 dollars. If however money is short a basic N, P, K soil test kit can be purchased at a store giving you a rough estimate of your content. If there is no current soil test most garden vegetables will do nicely with 150-200lbs N & K, and 60lbs P (per acre basis). The cost of soil testing is actually very small and the value is nearly always recovered through either improved yield in the case of nutrient deficiencies or reduced fertilizer cost in the case of nutrient excess.
The worse thing one can do for long term soil and environmental health is to continually add synthetic fertilizers to a lawn or garden if the nutrients are not needed. The overloading of N and P can cause fish kills in our streams, rivers, and oceans and is the leading cause of governments regulating phosphorus in cleaners. GET a Soil Test.
THE MATH: (BRACE YOURSELF)
Once you have determined the amount of nutrient (how much) you want to apply to your area there is some simple math which will assure you are adding the correct amount giving you the best chances of success. We will look at examples for Urea (52-0-0), Triple 16 (16-16-16) and cow manure (2-.05-2) In our example we will use a 60ft by 90ft garden plot that we want to add 150 lbs of N per acre (RATE) at the beginning of the season. These same calculations can be done for each nutrient element, but below is for N.
Step 1: Figure out the square foot area of your area.
So 60ft X 90ft = 5400 sq ft
Step 2: Determine the acreage of your area
So your plot is 5400 sq ft and 1 acre is 43560 sq ft
5400 sq ft \ 43,560 sq ft = .124 Acres
Step 3: Determine how much material you need to apply.
RATE PER ACRE / % nutrient of material = Material per Acre
Material Per Acre X Plot Size = Material Needed
Example 1: Urea 52-0-0
150lb N \ .52 = 288lbs Urea X .124 acres = 35lbs of Urea for you area
Example 2: Triple Sixteen 16-16-16
150lb N\ .16 = 937.5 lbs Triple 16 X .124 acres = 116lbs of Triple 16 needed
Example 3: Dried Cow Manure 2-.05-2
150lbs N \ .02 = 7500lbs manure X .124 acres = 930 lbs of manure needed
Remember only 65-80% of the nutrients are available in the first year so you may need to have a higher rate at year 1.
This is a baseline for information on nutrient applications and there are several resources on the internet, your local bookstore and most importantly your state extension office. The extension system in your area is a value resource for going beyond the basics and getting one on one personal help with their master gardener programs.