All fertilizer labels have three bold numbers. The first number is the amount of nitrogen (N), the second number is the amount of phosphate (P 2 O 5 ) and the third number is the amount of potash (K 2 O). These three numbers represent the primary nutrients nitrogen(N) - phosphorus(P) - potassium(K). A bag of 10-10-10 fertilizer contains 10 percent nitrogen, 10 percent phosphate and 10 percent potash. When in doubt always follow the manufacturers label for spreading and rate information.
To calculate the pounds of nitrogen in a 50-lb bag of 10-10-10 fertilizer, multiply 50 by 0.10. Do the same for calculating the amounts of phosphate and potash. A 50-lb bag of 10-10-10 contains a total of 15 lbs of nutrients: 5 lbs nitrogen, 5 lbs phosphate and 5 lbs potash. The remaining weight is filler, usually sand or granular limestone. Another Example: 8-0-24, 50 pound bag
1. To calculate the pounds of nitrogen: Multiply 50 by .08, which equals 4.
2. To calculate the pounds of phosphate: There is no phosphate in this bag of fertilizer.
3. To calculate the pounds of potash: Multiply 50 by .24, which equals 12.
A 50 pound bag of 8-0-24 fertilizer contains a total of 16 lbs of nutrients: 4 lbs nitrogen, 0 lbs phosphate, and 12 lbs potash. This would leave us with 34 lbs of filler.
The best way to select a fertilizer grade is to have your soil tested. It is always helpful to know what you are working with. Your local extension agent can provide a soil sample test kit, or you can hire a private service/lab to perform a soil analysis for you. After collecting soil samples, sending them for analysis, and receiving the results, you can amend the soil as recommended in the report. Soil samples can be taken here. Some garden supply retailers also send soil samples for analysis.
Have you ever seen a lawn that looked like it had different colored stripes? This was probably caused by spreading fertilizers the wrong way. To make sure that the color and growth of your plants are the same, fertilizers must be spread evenly. The most popular types of fertilizer spreaders are the drop spreader and the cyclone spreader. Cyclone spreaders generally provide the best results. Make sure when you spread the fertilizer that you overlap your spread pattern by applying half the material in one direction and the remainder in the opposite direction. Break up any clumps so that the fertilizer won't get clogged in the spreader. Always calibrate your spreader before each use per the manufacturers recommendations.
Soil pH is one of the most important soil properties that affects the availability of nutrients.
- Macronutrients tend to be less available in soils with low pH.
- Micronutrients tend to be less available in soils with high pH.
Lime can be added to the soil to make it less sour (acid) and also supplies calcium and magnesium for plants to use. Lime also raises the pH to the desired range of 6.2 to 6.5.
In this pH range, nutrients are more readily available to plants, and microbial populations in the soil increase. Microbes convert nitrogen and sulfur to forms that plants can use. Lime also enhances the physical properties of the soil that promote water and air movement. It is a good idea to have your soil tested. If you do, you will get a report that explains how much lime and fertilizer your crop needs.
There are 13 main mineral nutrients, which come from the soil, are dissolved in water and absorbed through a plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why we recommend the use of fertilizers to add the nutrients back into the soil. The mineral nutrients are divided into two groups: Macronutrients & Micronutrients.
The macronutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival. The secondary macronutrients are calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is usually found in sufficient amounts from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.
- Nitrogen is a part of all living cells and is a necessary part of all proteins, enzymes, and metabolic processes involved in the synthesis and transfer of energy.
- Nitrogen is a part of chlorophyll, the green pigment of the plant that is responsible for photosynthesis. - Helps plants with rapid growth, faster green-up, and help maintain vitality in cool weather.
- Levels are crucial: too little nitrogen stunts growth and causes yellowing, too much nitrogen encourages over-growth that weakens the plant, reduces carbohydrate reserves that are needed during times of stress, and increases the risk of nitrates escaping into the environment via runoff.
- Like nitrogen, phosphorus (P) is an essential part of the process of photosynthesis.
- Involved in the formation of all oils, sugars, starches, etc. Helps with the transformation of solar energy into chemical energy; proper plant maturation; withstanding stress.
- Effects rapid growth.
- Encourages root growth.
- Phosphorus often comes from fertilizer, bone meal, and superphosphate.
- Potassium is absorbed by plants in larger amounts than any other mineral element except nitrogen and, in some cases, calcium.
- Helps in the building of protein, photosynthesis, leaf quality, and reduction of diseases.
- Potassium is supplied to plants by soil minerals, organic materials, and fertilizer.
- Calcium, an essential part of plant cell wall structure, provides for normal transport and retention of other elements as well as strength in the plant. It is also thought to counteract the effect of alkali salts and organic acids within a plant.
- Sources of calcium are dolomitic lime, gypsum, and superphosphate.
- Magnesium is part of the chlorophyll in all green plants and essential for photosynthesis. It also helps activate many plant enzymes needed for growth.
- Soil minerals, organic material, fertilizers, and dolomitic limestone are sources of magnesium for plants.
- Essential plant food for production of protein.
- Promotes activity and development of enzymes and vitamins.
- Helps in chlorophyll formation. Improves root growth.
- Helps with vigorous plant growth and resistance to cold.
- Sulfur may be supplied to the soil from rainwater. It is also added in some fertilizers as an impurity, especially the lower grade fertilizers. The use of gypsum also increases soil sulfur levels.
Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities. Even though they are only needed in small amounts, they are still very important for the health of the plant. These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America. The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.