Operational planning of irrigation regimes for crops taking into account weather conditions

(N 00 О г-Н

О сд (N S (N СО

Winter cereals 0.5 0.55 0.65 0.75 0.8 _ -

Spring cereals 0.35 0.4 0.55 0.7 0.75 0.8 _ - -

Grain legumes 0.35 0.45 0.6 0.7 _ -

Potato late 0.3 0.35 0.45 0.55 0.6 0.65 _ - -

Early potato 0.3 0.4 0.5 0.6 0.65 _ -

_ - - - 0.9

Corn (grain) 0.4 0.5 0.65 0.85 0.9

- - - 0.8

Corn (silage) 0.35 0.4 0.55 0.7 0.75 0.8 _

Sugar beet 0.4 0.45 0.6 0.7 0.8 _ -

Fodder beet 0.3 0.35 0.45 0.55 0.65 0.7 _ -

Table beet 0.3 0.35 0.4 0.5 0.6 0.65 _ -

Alfalfa under sown _ - 0.8 flat 0.5 0.55 0.65 0.75 0.8

Alfalfa of previous _ - 0.9 years 0.5 0.55 0.6 0.65 0.75 0.8 0.85 0.9

Irrigated pasture 0.6 0.4 0.45 0.55 0.6

Continuation of table 20

Cumulative sum of average daily air temperatures from the beginning of the growing season, ° C

Crop 8 о о

Annual grasses 0.3 0.35 0.5 0.65 0.75 0.75

Perennial grass mixtures 0.45 0.5 0.6 0.7 0.75 0.75

Cabbage late 0.3 0.35 0.4 0.5 0.55 0.6 0.6

Early cabbage 0.3 0.35 0.45 0.55 0.6 0.6

Vegetables (tomatoes, cucumbers) 0.3 0.35 0.45 0.55 0.6 0.6

Vegetables (onion) 0.3 0.35 0.4 0.45 0.5 0.5

OPERATIONAL IRRIGATION PLANNING

To obtain high and stable yields on irrigated lands, irrigation regimes must take into account the biological characteristics of the crops being cultivated, local climatic, soil-reclamation, weather, and other conditions, as well as methods, technical means, and irrigation technology. In this case, all changes that inevitably arise in irrigation systems during operation must be considered. In conditions of irrigation water shortage, operational irrigation regimes should provide for the supply of economically viable irrigation rates, taking into account available water resources and the priority of irrigated crops.

The ratio between water intake and water consumption changes over the years with varying signs. At the same time, it should be noted that there is relative stability in the actual water intake for irrigation and the area of actually irrigated land compared to the year-to-year variability in normative irrigation water demand.

On the one hand, the water use accounting system in irrigated agriculture is based on unreliable primary data on water consumption. Frequently, values for water intake volumes similar to the previous year are adopted. On the other hand, water demand standards (group, weighted average by crop and by area) are insufficiently presented, as they are determined based on one or two reference weather stations for a very large and heterogeneous territory of an administrative region.

In addition, the areas of actually irrigated land and the structure of irrigated crops for each calculation year require clarification, which currently presents a difficulty.

In the current situation, the main reserve for increasing irrigation efficiency should be the rational and economical use of available water resources through the improvement of irrigation planning technologies.

In achieving this goal, the primary role should be assigned to water use standardization.

Thus, besides the development of scientifically grounded, territorially and annually differentiated irrigation regimes, it is necessary to create a specialized service for the implementation of these regimes. Without resolving these issues and introducing them into production, further increases in the productivity of irrigated agriculture seem problematic.

For irrigated lands, one of the priorities is operational planning and management of irrigation with the optimization of the timing and rates of their execution.

Operational planning of operational irrigation regimes using mathematical models and computer technology increases the accuracy of standardizing water supply volumes for irrigation, ensuring the efficiency of hydro-reclamation in various natural-landscape territories, the adequate selection of anthropogenic impacts, ecological balance of the natural environment, and resource conservation.

To achieve the greatest effect from irrigation, especially in conditions of a continuous increase in the deficit of water resources, the control of soil moisture of the agricultural field and irrigation management must be carried out systematically with the following frequency:

• during normal periods: at least once every five days;
• during periods of critical plant development phases: daily.

Such frequency of situation assessment and development of management decisions for the upcoming (forecast) period allows for high reliability in optimizing the timing and rates of irrigation for each irrigated plot.

For the operational adjustment of irrigation operational regimes and the calculation of application rates of mineral fertilizers with irrigation water, the FSBSI VNIIRaduga has developed and continues to improve computer programs. In 2008, the computer program "Calculation of the Dynamics of Agroclimatic Resources and Their Regulation" was created and tested. The calculation method is based on the assessment of the water balance equation applied to the soil layer of active moisture exchange.

The income and expenditure items of the balance are determined as follows:

The foundation of operational irrigation management is the daily tracking of soil moisture reserves within the active moisture exchange layer. These indicators change constantly depending on the crop species and its developmental phase. If groundwater levels are high in the area, the water consumption deficit is additionally adjusted based on capillary inflow according to calculated and empirical data.

Principles and Data for Operational Irrigation Planning

To accurately regulate irrigation regimes, information-advisory systems (IAS) are used. They integrate modern technical equipment, satellite monitoring data, and ground-based instruments to account for the variability of hydrometeorological conditions in space and time. The system assesses the potential of heat and moisture resources, calculates the volume required to replenish natural resource deficits, and helps to promptly make adjustments to the operational irrigation regime.

All information entering the system is systematized according to key field, soil, and plant indicators. This allows for the creation of computer programs for calculating substantiated, ecologically balanced irrigation rates that ensure the sustainability of agrolandscapes.

Structure and Algorithm of the Information-Advisory System

Operational irrigation management is built on automated data collection and constant recalculation of the water balance. To achieve this, the IAS is divided into four functional blocks, each responsible for its own stage of information processing.

• Soil moisture monitoring period — per week (mm)
• Meteorological parameters — temperature (°C), air humidity (%), wind speed (m/s), precipitation (mm)
• Schedule issuance period — for 3–5 days

1. Analysis of the current state of agrocenoses: the block monitors soil moisture in the active layer over a week in millimeters.
2. Collection and processing of meteorological information: actual and forecast temperature (°C), air humidity (%), wind speed (m/s), and precipitation amount (mm) are measured.
3. Calculation of operational planning: based on a bioclimatic model using biological and microclimatic coefficients as well as soil-meliorative constants, the system calculates evaporation, soil moisture reserves, capillary inflow from groundwater, natural moisture coefficients, and water consumption deficit.
4. Issuance of recommendations: the system generates and provides updated irrigation schedules for the next 3–5 days in hard copy.

Computer models calculate rational water consumption rates while differentiating coefficients and constants. This allows for an accurate reflection of the dynamics of intra-annual distribution of hydrometeorological factors and the probabilistic nature of processes in agrobiocenoses.

Procedure for Operational Control and Adjustment of Irrigation Regimes

The optimization of operational irrigation regimes is based on operational management: the schedules and volumes of supplied water are adjusted according to the "demand" of specific irrigation plots served by sprinkler machines. This approach allows for precise maintenance of the soil water regime, relying on regular field measurements and water balance calculations.

1. Fixation of starting moisture reserves. At the beginning of the growing season, soil moisture measurements are performed on irrigation plots to determine the initial moisture reserves for further calculations.
2. Calculated monitoring and data collection. The dynamics of soil moisture reserves during the growing season are controlled using a calculation method at intervals of five days, a decade, or a month. To do this, current and forecast meteorological information, data on the condition of crops, the progress of agrotechnical work, as well as the readiness of irrigation equipment, irrigation networks, and pumping stations are systematically collected. Based on all obtained information, water balance calculations are performed for the current period, as well as for five-day and ten-day forecasts.
3. Field control of application. On each crop rotation plot, control measurements of actually implemented irrigation rates are regularly conducted, checking the uniformity of moisture distribution across the field area and soil depth.
4. Decision-making on irrigation. By comparing the calculated water balance and actual measurements, the agronomist evaluates the current situation and makes a decision regarding the feasibility, timing, and volumes of adjusting the crop irrigation regime.