Principles and significance of desiccation in modern crop production

Desiccation is the pre-harvest drying of standing crops. This practice accelerates crop maturation and facilitates harvesting with combine harvesters. Under the influence of chemical desiccants, protoplasmic colloids in the cells are destroyed, causing the plants to rapidly lose moisture and dry out. At the same time, seeds, tubers, and root crops are not damaged: they are protected by their outer layers, and the flow of nutrients from the drying leaves is redirected toward the fruit.

This practice is especially necessary during an unfavorable, prolonged autumn with frequent rains, as well as on irrigated plots and with high application rates of fertilizer, which extend the growing season. Beyond direct drying, desiccation acts as a phytosanitary measure. The products possess insecticidal and acaricidal properties, which help to reduce the population of overwintering pests in the fields by the following spring.

In modern crop production, desiccation is used on many crops:

• sunflower and rice;
• potato (for pre-harvest haulm removal);
• seed crops of perennial grasses;
• sugar beet seed plantings;
• lupin, castor bean, and hemp;
• cotton (in combination with defoliation).

On cotton, this practice changes the microclimate of the bush — it improves light penetration, reduces air and soil humidity, and increases the temperature in the ground layer. As a result, the bolls open faster, which allows for a prompt harvest, clearing of plant residues, and timely autumn ploughing for the next year’s crop.

Choice of preparation and mechanism of action

Desiccants work as contact, locally acting products: they burn the tissues at the point of contact with the working solution. By penetrating the leaves and stems, they destroy cell membranes, denature proteins, and stop respiration and transpiration. Because of this, the above-ground part of the plant dries out rapidly, stimulating the outflow of plastic substances into the fruit and the dehydration of the seeds.

In crop production practice, the following products are most often used:

• magnesium chlorate;
• calcium chlorate-chloride;
• bufitox;
• reglone.

The most universal and least toxic desiccant is magnesium chlorate. Since the product does not have systemic action, it is critically important to strictly follow the dosages and ensure uniform coverage of the crop. The aqueous solution of the product is prepared on the day of treatment in wooden or iron containers.

Dynamics of magnesium chlorate action on treated crops:

• Start of intensive moisture loss — first 6 hours
• Complete leaf drying — after 48 hours
• Maximum sunflower seed moisture for treatment — no more than 35–40 %
• Optimal application timing on sunflower — end of August – first half of September

The use of desiccants allows for the optimization of the harvesting process and directly affects the farm's economics. For example, treating rice with magnesium chlorate dries the standing crop, allowing a shift to direct combining. Field trials show that this reduces grain losses during harvesting to a minimum and provides a yield increase. Such an agricultural practice allows for planning the harvesting campaign with minimal risks.

On sugar beet seed crops, desiccation with magnesium chlorate solves two tasks at once: it increases the physical seed yield and raises the sugar content of the resulting root crops. Below are the results of field experiments evaluating the effectiveness of this technology on rice and sugar beet. These data confirm the economic feasibility of pre-harvest drying.

For the correct application of desiccants, it is important to strictly observe the regulated dosages and the developmental stages of the plants. An insufficient dose will not provide the required drying effect, while an excessive one may negatively affect the product quality. The main parameters for working with magnesium chlorate on various crops are presented in the table.

In addition to magnesium chlorate, other preparations are used on cotton. Calcium chlorate-chloride is applied 6–12 days before the start of harvesting with an application rate of 45–50 kg/ha. The preparation Bufitox is used on the same crop 10 days before harvesting, with an application rate of 3–6 kg/ha.

Application of Reglone on industrial and seed crops

Reglone shows high efficiency in the desiccation of a wide range of crops. When treating castor beans at a rate of 2 kg/ha, the preparation significantly increases combine productivity, shortens harvesting time, and reduces field losses. It also reduces farm costs for subsequent forced drying of seed. In potato planting, the use of Reglone solves an additional phytosanitary task — it curbs the spread of viral infections and accelerates tuber ripening.

Desiccation with Reglone is of particular importance for sunflower. The preparation is applied at a rate of 3 kg/ha based on the active ingredient. Spraying is scheduled 40–45 days after mass flowering, focusing on the beginning of head browning and seed moisture.

• Reduction of sunflower seed moisture — by 1.5–2 times
• Advance in sunflower harvesting time — by 10–14 days
• Timing of sunflower desiccation — 40–45 days after mass flowering
• Maximum sunflower seed moisture — no more than 40 %

On sugar beet seed crops, it is effective to use Reglone at a rate of 5–10 kg/ha when 30–40 % of the seed balls have already turned brown. On alfalfa seed crops under irrigation, desiccation is carried out with an application rate of 2–4 kg/ha. Compliance with these regulations guarantees the preservation of the quality of the seed material and facilitates mechanized harvesting.