Plants need to be nurtured like humans and animals in order to grow and bear. Substances which plants use in the formation of their own roots, branches, leaves, fruits and crops are called “plant nutrition substances”. Plants take their nutrients from under the soil through their roots and from atmosphere through their leaves called green parts.
The process of adding nutrients to soil, which does not contain sufficient nutrients, in order to increase soil productivity and the quality and quantity of agricultural products is called fertilization and the matters which contain these nutritional elements are called fertilizers .
All the animate and inanimate creatures in the world consist of about one hundred small and different units we call elements. The 17 of them are essential for the plant growing, namely : carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, ferrous, manganese, boron, zinc, copper, molybdenum, chloride and sodium. The first ten elements are called macro elements, which are added to soil in more proportions while the remaining 7 elements are micro elements, which are sufficient in small quantities.
Fertilizers are divided into two groups :
- 1. Organic fertilizer contains plant nutrients organically. Stall fertilizer and green fertilizer are two examples. Stall fertilizer is the mixture of animal manure and matters which are used as bedding. There are approximately 0.5-0.7% nitrogen, 0.2-0.3% phosphorus and 0.4-0.6% potassium in stall fertilizer. In addition to these elements, it contains calcium, magnesium and sulfur as well as little amount of micro elements such as manganese, zinc, copper and ferrous. Stall fertilizer increases the amount of organic matters in the soil and the soil’s capacity to hold water, which improves soil’s tolerance against droughts and helps soil processing.
Green fertilization, which is conducted by mixing leguminous seeds into soil when they are green, regulates the nature of soils poor in organic matters and increases the water holding capacity.
- 2. Chemical, mineral, commercial and artificial fertilizers contain one or more nutrients and are produced by chemical methods. These are fertilizers with nitrogen, phosphorus, potassium and calcium. Nitrous fertilizers contain ammonium sulfate, ammonium nitrate, urea; phosphorous fertilizers contain superphosphate, triple superphosphate; potassium fertilizers contain potassium sulfate, potassium chloride; and composite fertilizers contain particular amount of N, P and K, which are fertilizers such as 20-20-0, 15-15-15, 18-46-0 and 26-13-0.
Nitrogen, phosphorus and potassium are nutrients which plants need most and thus required to be given to plants through fertilization. In countries like United States, Canada and Australia, most of soils are poor in nitrogen and phosphorus while the amount of potassium is more than the plants require in most of the agricultural fields. In order to increase the productivity of agricultural fields, fertilization should be done in the appropriate amount in accordance with the results of soil analysis if possible.
Within the framework of fertilizers and fertilization , nitrous and phosphorous fertilizers which are mostly used in agriculture will be emphasized.
The source of nitrogen of our world is atmosphere. The %79 of the atmosphere consists of nitrogen gas. Nitrogen is added to soil through bacteria in the roots of plants such as lentil, chickpea, alfalfa and sainfoin and through the merging of nitrogenous bacteria, clostridiums and algae with the nitrogen in the air. Other plants such as wheat, maize and sugar beet use this nitrogen. Therefore the source of nitrogen in the soil is the wastes of plants and animals. We call these wastes organic substances. As the amount of organic substances in the soil increases, so does the amount of nitrogen in that soil. Organic substance decomposes and disintegrates in time, which leaves behind nitrogen good for the plant growing.
If we carry the animal wastes in our stalls to our fields and mix them into the soil, it is a kind of nitrogen fertilization. However, as the stall fertilizer is not sufficient in amount and as it is expensive to carry it from the stall to the field, we generally use artificial fertilizers called commercial fertilizers.
The commercial fertilizers, which contain nitrogen, are called nitrogen fertilizers. Nitrogen is an element which needs to be in all the cells of the plant. It encourages vegetative growing, in other words, stem and leaf growth. It rapids growing and increases the green color in the plants. Nitrogen increases the protein in the various parts of the plant and encourages grain production. Plentiful nitrogen in a soil helps leaf and stem growing. The remarkable increase in the leaf part of the plant is the indicator of nitrogen abundance in the soil.
In addition, abundant nitrogen increases the amount of water. Excessive nitrogen may have negative impact on the sensitivity of plants against droughts, diseases and frosts. Excessive nitrogen also slows flower and fruit growing and thus causes the development of leaves and stem. Excessive amount of nitrogen in soil, on the other hand, burns or kills the plant. While the nitrogen abundance in soil is not so effective in productivity, excessive amount of nitrogen delays ripening and seeds require harvesting before they are completely ripened.
Light green or yellowish color in the plant is an indicator of nitrogen deficiency. Symptoms of nitrogen deficiency include small and old plants, reduced tillering in single year plants such as barley, wheat and lentil, small and bad looking flowers or fruits. In nitrogen deficiency, lower leaves dry and fall earlier than usual. There is also remarkable decrease in yield.
There are a few points which require attention in nitrogen fertilizer practices. As nitrogen is an active nutrient in soil, water removes nitrogen from the root part of the plant in rainy climates and thus nitrogen deficiency occurs in the plant. !n such regions, instead of nitrogen fertilizers, ammonium fertilizers such as ammonium sulfate should be preferred. One of the other solutions would be dividing and giving fertilizers in portions.
The second important point in nitrogen fertilization is to fertilize as early as possible. The yield potentials of some plants which are grown for their seeds depend on their development in seedling phase. If there is nitrogen fertilizer, the first development in these plants is better and healthier as well as high grain yield is achieved.
Now, let’s get to know the nitrogen fertilizers which are commonly sold in our country.
It is the oldest artificial fertilizer. It creates a strong acidity in the soil. The ammonium is taken directly by the plant roots. Contrary to nitrate, ammonium is held by the clays and organic substances in the soil and thus its activity is low. However, in time, ammonium may turn into nitrate. When it does, it becomes very active.
Ammonium nitrate. This fertilizer contains both nitrate and nitrogen in ammonium form. Nitrate is washed and removed from the soil in the rainy regions.
This fertilizer gains more importance day by day. Urea is active in soil as much as nitrate. This organic fertilizer disintegrates in time and turns into ammonium, which is good for the plants. It the air is dry and soil texture is sandy during the disintegration, nitrogen may be lost in the form of ammoniac gas.
After this introduction of the fertilizers, we need to pay attention to another issue regarding the economy. This is important because there are many mistakes made by our farmers. In each fertilizer, there is a particular amount of nitrogen. And this amount is written on the fertilization bags in %. After learning the pure nutrient amount we need to give our plants, this is turned into fertilizer. After this process, there are different amounts for each fertilizer. Pay attention to this difference in types of nitrogen fertilizers we call turfgrass fertilizer.
The second important point is related to costs. If we don’t have a special obligation in fertilization, there is no difference between the types of fertilizers. Therefore, we need to prefer the one with the lowest cost.
Phosphor and phosphor fertilization
Phosphor is in the form of organic phosphor salts in livings and they are essential for the livings. Plants take phosphor from the phosphate solution in the form of phosphate ions. In our country’s soils, the amount of phosphor would be enough to last for centuries if all the phosphor were good for the plants. However, the clays, calcium and ferrous components in the soil attach phosphate to themselves, which makes it useless for the plants. Phosphor plays an important role in transferring genetic characteristics and the protection and carriage of energy.
Symptoms of phosphor deficiency include dark green, violet and bronze chlorosis of old leaves, late flowering of plants and few number of flowers. Root and stem development is considerably reduced. Beginning with the old leaves, all leaves start to curl before ripening. There are only few lateral shoots, and buds die or do not flower. Flowering is reduced. In spring, the leaf and flower buds emerge late. The leaves become violet or the color becomes brown in the center with bluish green spots. Leaf sides turn into brown. Plants need phosphor fertilizer more in the beginning phase of their development. In this phase, root system covers a smaller area. Therefore, more fertilizer is needed. Generally, the 50% of the phosphor is consumed in the first 20% of the total development.
Now, let’s take a look at the types of phosphor fertilizers used in phosphor fertilization and their characteristics. Triple super phosphate. There is 44-46% water dissolvable phosphate in its components. It is produced in the form of off white and grey granules. Diammonium phosphate. It is a fertilizer containing two nutrients together. It contains 16-18% nitrogen and 46-48% phosphor. It is in the form of grey granules. It is an appropriate fertilizer when these two nutrients are needed.
As it contains high amount of nutrients and as it does not get lumpy quickly, it saves transportation and labor costs.
It contains both nitrogen and phosphor like dap fertilizer. As can be understood from the name, it contains 20% nitrogen and 20% phosphor. In the selection of phosphor fertilizers, their availability and costs should be taken into consideration. Other than that, there is no difference between fertilizers regarding their usefulness for the plants. Another important point in using phosphor fertilizers is that phosphor is relatively inactive in the soil. Because of this inactivity, the fertilizer should be dispersed onto the plant roots in the form of granules or applied just next to the seed in the depth of plantation. As it is seen in the common fertilizer practices, many farmers place all the fertilizers on the same footing, with the expression of TSP, i.e. triple superphosphat, and use them in the amount they are accustomed to, without considering the differences between phosphor fertilizers regarding their nutrients. Selecting the amount of fertilizer according to own discretions is a misapplication.
After learning about nitrogen and nitrogen fertilizers, leaf fertilizers can be used to make up for the deficiencies of other nutrients. Besides being used in soil like organic and mineral fertilizers, leaf fertilizers can also be applied to plant parts over soil, particularly plant leaves. The main nutrient storage organ for the plants is roots. Then comes leaves and other plant parts over soil even though they can only take limited amount of nutrients.
Applying fertilizers in liquid form or spraying them onto plant parts over soil is called leaf fertilization. Solutions which are sprayed onto plant leaves and which contain one or more plant nutrients are called leaf fertilizers. The production of leaf fertilizers are made in the solid (powder) and liquid form in packages.
The following should be taken into consideration during leaf fertilization:
- Licensed leaf fertilizer, which contains the particular nutrient lacking in the plant, should be preferred,
- The fertilizer should be dissolved well in the chemical application tank.
- Application should be made early in morning or late in the afternoon when there is no direct sunlight,
The fertilizer should be sprayed with chemical sprayer in very thin particles.