Fertilizer system for crops in the agro-climatic zones of the North Caucasus

Agroclimatic Zones of the North Caucasus

The diversity of soil and climatic conditions in the North Caucasus requires a flexible approach to designing a plant nutrition system. About 100 crop varieties are cultivated in the region, and each of them requires its own fertilizer regime. The entire commercial farming territory is divided into five agroclimatic macrozones.

• First zone (steppe, arid): annual precipitation is 200–300 mm, the sum of effective temperatures reaches 3200–3700 °C. Light chestnut solonetzic soil prevails. This zone includes the northeast of Stavropol Krai, the east of Rostov Oblast, and the northern part of Dagestan.
• Second zone (steppe, insufficient moisture): annual precipitation is 300–400 mm, the sum of effective temperatures is 3100–3400 °C. The main soils are dark chestnut and common chernozems (medium- and low-humus). It covers Rostov Oblast, the northeastern and southeastern districts of Stavropol, the northern part of Kabardino-Balkaria, North Ossetia, Ingushetia, Chechnya, and central Dagestan.
• Third zone (steppe and forest-steppe, unstable moisture): annual precipitation is 400–600 mm, the sum of effective temperatures is 2800–3500 °C. The soil cover consists of common low-humus, deep, super-deep, typical, and leached (including fused) chernozems, as well as meadow and meadow-chernozem soil. The zone includes the southwest of Rostov Oblast, Adygea, Krasnodar Krai (excluding the foothills), the west and center of Stavropol, and the middle part of the North Caucasian republics.
• Fourth zone (mountain, humid): annual precipitation exceeds 600 mm, the sum of effective temperatures ranges from 1200 to 3600 °C. Sod-podzolic and gley soil, leached fused chernozems, as well as gray and dark gray forest-steppe soil prevail. It includes the foothill regions of Krasnodar and Stavropol Krais, as well as the North Caucasian republics.
• Fifth zone (mountain and high-mountain): practically not used for agricultural production.

Nutrition system: humus conservation and fertilizer application

The decline in soil fertility is a critical challenge for the region's farmers. Due to a deficit of organic matter, the rate of humus depletion in the topsoil is reaching dangerous levels. Restoring balance requires a mandatory set of measures: manure application, ploughing of green manure crops, grass sowing, and maximum use of crop residues in the field.

• Annual humus loss — 0.05%
• Application rate of pure manure — 8–10 t/ha
• Manure with mineral fertilizers — 6–8 t/ha
• Number of crops cultivated — about 100

The specific dose of organic fertilizers is adjusted taking into account the soil type, crop rotation structure, and planned volumes of mineral nutrition.

The demand for nitrogen and phosphorus directly depends on the moisture zone. Nitrogen fertilizers are most in demand in zones of sufficient and unstable moisture, especially as early spring top dressing for winter wheat. Phosphate fertilizers show maximum returns in the zone of insufficient moisture on common chernozems and chestnut soil. The need for potassium in all soil types is moderate: it is applied only as part of a complete mineral fertilizer (NPK), and with low doses of nitrogen and phosphorus, potassium may not be used.

In addition to the main nutrients, the region requires chemical amelioration. Liming must be planned on acidic soil, and gypsum application on solonetzic areas. Particular attention is paid to perennial plantations (orchards, vineyards, berry fields), which require increased doses of fertilizer, as well as to subtropical crops on the Black Sea coast.

When scheduling fertilizer applications, observe the optimal work sequence:

1. Apply the main fertilizer during winter ploughing — this ensures deep incorporation and maximum nutrient uptake. Application during pre-sowing tillage provides a significantly lower effect.
2. Apply starter fertilizer during sowing for all field crop rotation crops for a quick start of the root system.

The efficiency of the nutrition system in the North Caucasus depends on the precise matching of fertilizers to the needs of a specific crop. When designing a nutrition scheme, it is important to consider the biological characteristics of the plants and the planned yield. This allows for optimizing costs and obtaining maximum returns from each hectare.

Each group of crops requires its own starter and main set of nutrients:

• Cereals — phosphorus fertilizers;
• Sugar beet — complete nitrogen-phosphorus-potassium fertilizer;
• Corn, potatoes, and vegetables — nitrogen-phosphorus fertilizers.

To create an effective plan for fertilizer application, follow this algorithm:

1. Conduct an agrochemical soil survey to determine the supply of available nutrients.
2. Compare the obtained results with data from long-term field trials for your zone.
3. Adjust for the farm's technical capabilities and the characteristics of the cultivated cultivars.
4. Determine the need of winter wheat for top dressing based on comprehensive soil, stem, and leaf diagnostics.

Choice of technology and adjustment of fertilizer rates

The use of fertilizers — their rates, timing, and methods of application — must be strictly differentiated. The choice of a specific nutritional scheme depends on the basic technology followed by the farm. In practice, there are three main technological levels:

• Normal (low-input) technologies. Used on soils with low effective soil fertility. In this case, they are limited to applying starter fertilizer rates directly during sowing.
• Intensive technologies. Involve the use of increased mineral nutrition rates. They are applied fractionally, distributing them across key plant development phases.
• High-intensity technologies. Aimed at high-precision management of yield formation. They require strict adherence to all scientific and technical developments and high qualifications of the agronomic service.

Approximate fertilization systems in reference books are usually designed for intensive technologies and contain fairly high rates. You can reduce these rates by 1.5–2 times, taking into account yield plans and the actual capabilities of the farm. At the same time, it is crucial to maintain the original ratio of fertilizer types.

• Organic matter application frequency — every 3–5 years
• Reduction of approximate rates — by 1.5–2 times
• Cereal starter fertilizer — P10–20
• Early spring top dressing of wheat — N30
• Threshold for excluding application — less than 20–30 kg/ha of active ingredient

If the calculated rate of the main fertilizer or top dressing falls below the minimum threshold of active ingredient, this practice is completely excluded. In this case, the balance of elements in the remaining nutrition scheme must remain unchanged. For example, as an mandatory minimum for cereals, keep the at-sowing application of phosphorus at a rate of P10–20 and early spring nitrogen N30 for winter wheat.