Urea

Urea CO(NH₂)₂ is the most concentrated of solid nitrogen fertilizers, containing 46% nitrogen. All nitrogen is in the amide form, a water-soluble, slow-acting, nitrate-free fertilizer with an almost neutral reaction.

It is used in fertilizer systems in all soil and climatic zones as the main application and for top dressing.

In the fertilizer system of spring grain crops, it is applied for pre-sowing cultivation.

Urea should be used more effectively for crops with a long growing season. In the soil, the amide form is transformed into ammonia, and later into nitrate. The processes of ammonification and nitrification occur slowly, at temperatures of + 20°C and above, so nitrogen from urea is more evenly absorbed by plants during the growing season – prolonged action of fertilizers. Amide nitrogen is not washed out of the soil, its losses are very minimal.

Top dressing with urea solution is recommended to be carried out at an air temperature of no more than + 20°C and no less than + 10…12°C, in the evening or (in cloudy weather) during the day, which ensures an increase in the coefficient of nitrogen utilization from fertilizer. Foliar top dressing is especially effective on healthy plants that are well supplied with other nutrients.

Foliar top dressing is a complex technological process, the positive effect of which is manifested only under certain conditions. Thus, for different crops, permissible concentrations of urea solution that do not inhibit plant development are established, %: corn, beans, tomatoes, cucumbers, grapes – 0.5; apple, cherry, plum, tobacco – 1.0; potatoes, cabbage – 1.6; beets, peach – 2.0; onions – 2.5; carrots – 3.0; cereals – 5–30. Foliar feeding of grain crops in the earing period – the beginning of the milky state of grain with a 10–15% urea solution helps to increase its yield by 2.5–3 c/ha and protein content by 1–3%..

Foliar feeding with urea is recommended to be combined in one working solution with pesticides and micronutrients, which improves the effect of chemicals and reduces the impact of stress factors caused by them. The volume of the working solution should be at least 200–250 liters per 1 hectare.

At high concentrations, an aqueous solution of urea can cause burns. Young plants are more resistant to them, and also use nitrogen better. The permissible concentration of urea solution for foliar feeding is 5-15%, depending on the crop and development phase. For grain crops – up to 15 kg/ha (in physical weight).