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Methods for planning and operational management of crop irrigation regimes

For agronomists

6 min read

Methods for planning and operational management of crop irrigation regimes

How to calculate water requirements: designing an irrigation regime

Designing an irrigation regime helps to pre-calculate how much water the crops will need for the entire season and whether the irrigation network can handle such a load. The water usage plan is based on multi-year data. It is important to correlate the specific needs of a crop at different growth stages with the natural moisture reserves in the root-inhabiting soil layer.

In zones with an unstable climate, it is necessary to take into account significant fluctuations in weather, both within a single season and between years. Because of this, the plants' need for moisture is constantly fluctuating. To create an accurate irrigation schedule, an agronomist needs to solve three main tasks:

  • Determine the multi-year dynamics of the crop's water consumption.
  • Establish the potential moisture deficit by season and calculate the irrigation regime for different levels of natural soil moisture.
  • Calculate the irrigation module and water application rates for the irrigated area.

The irrigation regime and irrigation technique are closely linked. Choosing the wrong method of water delivery can render all calculations of irrigation rates void. When planning, it is important to strive for the maximum use of natural precipitation.

Irrational irrigation leads to water losses. If artificial irrigation is not balanced with natural precipitation, moisture moves into deep soil layers or runs off the surface. This causes erosion and compaction of the topsoil, leaching of nutrients from the root zone, and a rise in groundwater levels.

Operational management: what data an agronomist needs

The water requirements of plants change constantly and depend on a multitude of random factors. Therefore, managing water distribution in hydro-reclamation systems is complex. The accuracy of irrigation depends on the timeliness of data acquisition and the extent to which calculation models reflect real-world processes in a specific field.

In operational irrigation management, an enterprise must solve several key tasks. Specialists need to optimize water distribution between fields throughout the season. Additionally, the collected data allows for the preparation of feasibility studies to secure additional water sources.

Operational irrigation planning requires constant data collection. All necessary information is divided into reference data, operational data, and object-specific data.

Type of information Content
Normative reference information
  • Sum of active air temperatures
  • Calculated soil layer by crop and development stage
  • Bioclimatic water consumption coefficients
  • Parameters for calculating total evaporation and moisture reserve dynamics
  • Parameters for calculating moisture exchange in the aeration zone
  • Permissible mineralization of groundwater
  • Parameters for calculating water losses, assessing the state of the network and irrigation equipment
Object-specific information
  • Initial moisture reserves in the calculated soil layer
  • Moisture reserves at field capacity
  • Critical moisture reserves depending on field capacity
  • Cultivated crop
  • Water-physical and agrochemical properties of the soil at the start of the growing season
  • Characteristics of the irrigation equipment and drainage network used
Seasonal and operational information
  • Start date of the calculated irrigation period (sowing or resumption of the growing season)

- current meteorological indicators - temperature, air humidity deficit, wind speed; Operational information - evaporation from a water surface evaporator;

- daily precipitation total;

- groundwater depth;

Continuation of Table 12 Type of information Content

- groundwater mineralization;

- indicators of variability of bioclimatic coefficients;

- development stages of plants;

- indicators of meteorological factor variability

Nomenclature of parameters used in calculations

Name of indicators (calculation) Influence of parameter changes Surface air layer Decadal precipitation, mm 0 -8 0 ±1 Decadal air temperatures, t °C 0-50 ±1

Average long-term daily evaporability, mm/day 0.1-9.9 ±0.1

Average wind speed, m/s 0-9.9 ±0.3

Average long-term decadal evaporability module, mm/°C 0.1-0.5 ±0.005
Plant (Name and number of the crop, ha) 1-90
Biological coefficients of crops, fractions of a unit 0.50-1.20 ±0.01
Soil (Bulk density, t/m3) 0.50-1.70 ±0.01
Humidity corresponding to field capacity (FC), % by mass or volume 5.0-35.0 ±0.1
Pre-irrigation humidity, % of FC 60.0-90.0 ±5
Groundwater depth, m 0.5-20 ±0.1
Technical irrigation means (Number and model of the sprinkler machine) 0-98

Methodological foundations for operational irrigation management include:

  • daily assessment of soil moisture reserves in the active moisture exchange layer;
  • accounting for the dynamic connection with the type and development stage of the agricultural crop.

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