Fertilizers

There is no doubt that plants need many mineral elements for their growth and activity and to obtain a balanced production in terms of quality and quantity. The most important of these elements are approximately 13 essential fertilizer elements, some of which the plant needs in large quantities such as: Nitrogen (N) - Phosphorus (P) - Potassium (K) - Calcium (Ca++) - Magnesium (Mg) - Sulfur (S) and others that the plant needs in small quantities such as: Iron (Fe) - Zinc (Zn) - Manganese (Mn) - Copper (Cu) - Boron (B) - Molybdenum (Mo) - Chloride (Cl). In addition to these elements, the plant needs to obtain the elements that make up organic matter, the most important of which are carbon, hydrogen and oxygen, which are obtained through air, water and soil. These three elements together constitute more than 92% of the plant cell’s protoplasm. Nitrogen is absorbed more than any other element, as it constitutes 1-2% of the living protoplasm, as well as phosphorus and potassium. As for calcium, magnesium and sulfur, they are absorbed in smaller quantities. Iron, zinc, manganese, copper, boron and molybdenum are absorbed in very small quantities, and therefore they are considered essential minor elements. The major essential elements such as nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur are found in plant tissues in relatively high concentrations and are usually expressed as a percentage (%). This is due to the plant's need for them in large quantities, and therefore they have a positive effect on growth and yield when added in relatively high balanced quantities. The need and quantity of an element in the plant does not indicate its importance and necessity for plant growth, as some elements may be needed by the plant in very small quantities, but they are very important and necessary for its growth and life, such as micronutrients.

Many nutrients play an indirect role in increasing or reducing the spread of many fungal and bacterial diseases and insect pests. Therefore, it is necessary to be familiar with these effects to benefit from them in fertilization and control programs and include them in integrated disease and pest control programs.

First, the major elements:

1- Nitrogen fertilization.

It was noted that increasing interest in nitrogen fertilization makes plants more tender and thus increases their sensitivity to insect infections. It was found that some insects prefer tomato seedlings in the nursery when the concentration of nitrogen in the leaves increases, but the effect of phosphorus and potassium did not have any effects. In addition, increasing nitrogen fertilization in plants increases tissue tenderness, which facilitates their infection with fungal and bacterial diseases. The same applies to reducing the hardness of the fruits and making them more susceptible to fruit rot diseases. It was also noted that the type of nitrogen fertilizer has an effect on some diseases, as the incidence of rusts and powdery mildew increases with increasing nitrate fertilization and decreases with increasing ammonia fertilization.

2- Phosphate fertilization:

It was noted that increasing phosphate fertilization leads to a decrease in infection rates with some root rots. Potato infection with the Verticillium dahliae fungus, which causes wilt disease, decreases with increasing phosphate fertilization rates to 120 kg per acre. It has been observed that it has an effect on inhibiting and preventing the spread of powdery mildew diseases in many studies. It was found that monopotassium phosphate (MKP) can be used to affect powdery mildew fungi in grapes by direct spraying with the compound or mixing it with fungicides, as well as in peach, apple, mango and cucurbit trees. It was also found that phosphite salts have an important role, as potassium phosphite salt (K3 PO3 Potassium Phosphite) is a product of the reaction of potassium with phosphoric acid H3 PO4 and has a major role in preventing some fungal diseases.

3- Potassium fertilization:

Many scientific studies and research have proven that potassium fertilization plays an important role in increasing lignification in woody and transporting vessels, which reduces the occurrence of dormancy in herbaceous and grassy plants such as wheat and barley. Potassium also plays an important role in regulating osmotic pressure inside cells and the accumulation of sugars and carbohydrates, which reduces fungal infections.

It is believed that the incidence of wilt diseases decreases with increasing rates of potassium fertilization, as is the case with Fusarium wilt in tomatoes. However, potassium fertilization had no effects on either: Verticillium wilt caused by the fungus Verticillium alboatrum, and bacterial wilt caused by the bacteria Ralstonia solanacearum.

4- Calcium fertilization:

Calcium plays an important role in increasing the hardness and cohesion of plant tissues, which makes plants resistant to many field diseases such as Verticillium wilt in tomatoes. It also plays a major role in the hardness of fruits, which improves their quality and tolerance to handling and storage, and reduces the occurrence of rot in fruits, especially after harvest. In addition to its use in treating fruits after harvest in the form of solutions in which fruits are soaked with calcium chloride or sprayed to reduce the rates of fungal infection and reduce the appearance of storage diseases by paying attention to fertilization with calcium compounds (calcium nitrate) and spraying with chelated calcium.

Secondly, trace elements

Trace elements play several important physiological roles in plant life in terms of activating important enzymes to stimulate growth, flowering and fruit set. In addition, it has several other roles in protecting plants and preventing them from some fungal and bacterial diseases, such as copper (copper sulphate). It can be added to irrigation water to prevent the growth of harmful fungi in the soil, such as some root rot diseases and seedling death, taking into account the use of the optimal concentration so as not to cause toxicity to the plants treated with it. It is used from (5-10 kg/acre) with irrigation water or spraying.