Nitrogen fertilizers are mineral and organic substances used as a source of nitrogen nutrition of plants, which are subdivided into:
• organic fertilizers (manure, peat, compost) containing other plant nutrients in addition to nitrogen;
• mineral fertilizers produced by industry;
• green fertilizers (lupine, seradella, etc.).
Ammonium fertilizers include: ammonium sulfate, ammonium chloride, ammonium bicarbonate, liquid nitrogen fertilizers. Ammonium sulphate and ammonium chloride are most effective on soils saturated with bases (chernozems, carbonate soils, gray soils, chestnut soils), which have the ability to neutralize the acidifying effect of these fertilizers. Systematic fertilization with ammonium sulfate and ammonium chloride of acid soils causes an increase in acidity. This deficiency can be eliminated by liming.
Ammonium nitrogen is less prone to leaching than nitrate, so ammonia fertilizers can be introduced before sowing, in the fall. They are less suitable for superficial (with top-dressing of winter crops) and local (in rows, holes and nests) insertion. Excess chlorine in ammonium chloride adversely affects the size and quality of the yield of many crops (potatoes, flax, oilseeds, tobacco, grapes, etc.). Ammonium forms have a great importance for liquid fertilizers – liquid anhydrous ammonia, aqueous ammonia, ammonia.
Ammonium nitrate fertilizers include: ammonium nitrate (ammonium nitrate, nitric acid ammonium), ammonium sulfonitrate (lane-nitrate, montane-nitrate, ammonium nitrosulphate). Ammonium nitrate is produced mainly in granular form. It weakly acidifies the soil especially ammonium sulfonitrate, which have relatively high acidifying ability.
Nitrate fertilizers: sodium nitrate (sodium nitrate, nitric acid nitrate, chilean nitrate), calcium nitrate (calcium nitrate, nitric acid nitrate, calcareous nitrate, Norwegian nitrate), potassium nitrate (potassium nitrate, nitric acid potassium nitrate). Sodium nitrate is a physiologically alkaline fertilizer, so it’s better to use it on acidic soils, especially sugar beet, wheat, barley and other soils, which are sensitive to soil acidity. Calcium nitrate is released in granular form usually with an admixture of ammonium nitrate. It also makes the soil alkaline. Potassium nitrate, in addition to nitrogen, contains potassium and is a source of nitrogen potassium-nutrition of plants. They bring it under sensitive to chlorine crops. All nitrate forms of nitrogen are not absorbed by the soil. In areas of excessive moistening on light soils with a weak water-retaining capacity, nitrate fertilizers are washed out, therefore, it’s advisable to use ammonia as the main fertilizer.
Amide fertilizers – urea (carbamide), calcium cyanamide, urea-formaldehyde fertilizers. The most valuable urea. It easily passes into ammonium carbonate in the soil. Firstly, it slightly alkalized and then weakly acidifies the soil. It’s recommended to insert in advance. It’s also used as a protein supplement for ruminant animals. Cyanamide calcium has the property of reducing the acidity of the soil. It effective on loose, organic-rich neutral soils if fertilized in the fall. It not suitable for local application. Calcium cyanamide is also used as a defoliant for the pre-harvest removal of leaves from cotton. Urea-formaldehyde fertilizers are not washed out of the soil. They are particularly effective in areas of excessive moisture and irrigated agriculture. You can apply high doses of these fertilizers, providing plants with nitrogen for several years.
Nitrogen fertilizers are an effective means of agricultural crops yield increasing, especially in the non-chernozem zone, in humid regions of the forest-steppe and in the zone of irrigated agriculture where soils contain insufficient nitrogen. The norms of mineral fertilizers depend on soil conditions, biological characteristics of crops, availability of manure or other organic fertilizers.
Approximate rates of nitrogen fertilizers (in kg per 1 hectare in terms of nitrogen):
• for winter cereals sown in a busy pair – 40-60, for a clean pair – 30-40;
• for spring cereals – 40-60;
• for corn for silage and grain in the non-chernozem zone and northern part of the forest-steppe zone – 60-120, in rich chernozem forest-steppe – 45-60, in irrigated areas – 120-150;
• under the sugar beet on chernozem forest-steppe – 45-60, on gray forest soils, podzolic chernozems of the forest-steppe and in the non-chernozem zone – 80-120, in irrigated areas – 100-150;
• for cotton – 120-140;
• for linen – 40-60;
• for cannabis – 45-90;
• for potatoes – 45-90;
• for cabbage – 90-120;
• for tomatoes, cucumbers – 60-90;
• for fruit and berry crops – 60-100.
Smaller doses are applied to soils more rich in natural nitrogen, and also with simultaneous use of manure or other nitrogen-containing organic fertilizers. Nitrogen fertilizers are used as the main fertilizer and in top-dressing. Under winter crops sown on a clean pair, they are introduced only in early spring fertilizing (30-40 kg of nitrogen per 1 ha) along the frozen-thawed soil (along the “shard”). Under spring crops, nitrogen fertilizers can be used in full norm before sowing, and in irrigation – in several ways before irrigation.