Irrigation prescription maps Drone Guide

Water management is one of the most important challenges facing modern agriculture. Farmers must provide crops with sufficient water to maintain healthy growth and maximise yield while avoiding unnecessary irrigation, excessive energy consumption, nutrient loss, waterlogging, and pressure on increasingly limited water resources. Traditional irrigation management often applies water uniformly across an entire field. However, agricultural fields are rarely uniform. Soil type, drainage, elevation, crop condition, sunlight exposure, compaction, previous management, and local weather conditions can cause significant differences in water requirements across relatively short distances. **Irrigation prescription maps** provide farmers with a more precise approach. Instead of treating a field as one uniform area, a prescription map divides it into management zones and provides information that can be used to determine where irrigation requirements may differ. Drones can play an important role in producing these maps. Agricultural drones equipped with RGB, multispectral, thermal, hyperspectral, LiDAR, and accurate positioning technologies can collect detailed information about crop and field conditions. When combined with soil moisture sensors, weather information, irrigation records, and agronomic knowledge, these datasets can support highly targeted irrigation decisions. The objective is straightforward: **apply the appropriate amount of water to the appropriate area at the appropriate time.** ## **What Is an Irrigation Prescription Map?** An irrigation prescription map is a geographically referenced digital map used to support variable irrigation decisions across a field. Rather than simply showing an aerial photograph, the map separates areas according to identified differences in crop or field conditions. For example, a field might contain zones representing different irrigation requirements. The prescription information can subsequently be transferred to compatible irrigation equipment or used by farm managers when planning irrigation activities. The exact recommendation should be based on appropriate agronomic analysis rather than drone imagery alone. ## **Why Fields Have Different Water Requirements** Two plants located within the same field can experience very different growing conditions. Soil composition can vary significantly, affecting how quickly water drains or how long moisture remains available. Changes in elevation influence drainage and water accumulation. Compacted soil may restrict infiltration and root development. Different crop growth rates create different water demands, while shade, wind exposure, and sunlight can influence evapotranspiration. Drone mapping helps farmers visualise some of this variability across the entire field. ## **RGB Drone Mapping** High-resolution RGB cameras provide the foundation for many agricultural drone surveys. RGB imagery can document crop coverage, irrigation infrastructure, field boundaries, bare soil, drainage features, standing water, and visible areas of crop stress. Photogrammetry software combines overlapping photographs into an orthomosaic—a geographically accurate aerial image of the field. This provides the base map onto which additional agricultural information can be added. Repeated RGB surveys also create a valuable visual record throughout the growing season. ## **Multispectral Imaging** Multispectral cameras record specific wavelengths of reflected light beyond the information available from conventional photography. These sensors are widely used in precision agriculture because vegetation reflects different wavelengths according to factors including crop structure and condition. Vegetation indices generated from multispectral imagery can help identify variations across a field that warrant further investigation. Areas showing unusual patterns may be experiencing water stress, nutrient deficiencies, disease, pest pressure, soil problems, or other conditions. For this reason, multispectral information should be combined with field observations and additional data before irrigation decisions are made. ## **Thermal Imaging** Thermal imaging is particularly interesting for irrigation management. Plants lose water through transpiration, which influences canopy temperature. Under suitable environmental conditions, vegetation experiencing water stress may exhibit different temperature patterns from adequately watered vegetation. A drone-mounted thermal camera can map these temperature differences across large areas. This can help agronomists identify zones requiring closer investigation. Thermal information can be particularly powerful when combined with multispectral imagery, soil moisture measurements, and weather information. ## **Crop Water Stress** Identifying water stress before severe visible symptoms develop can provide farmers with an opportunity to respond earlier. Drone surveys can help identify spatial patterns that may indicate differences in crop condition. Instead of walking through a large field and inspecting a limited number of locations, agronomists can use drone maps to understand variability across the entire crop. Ground inspections can then concentrate on specific areas identified from the aerial information. This combination of aerial screening and targeted field verification improves efficiency. ## **Soil Moisture Sensors** Drone imagery becomes significantly more valuable when combined with ground-based soil moisture measurements. Sensors positioned at representative locations can measure moisture conditions at different depths. The drone provides broad spatial information, while ground sensors provide direct measurements at specific points. Combining the two helps farmers understand whether observed crop differences are genuinely related to water availability. This reduces the risk of interpreting every vegetation anomaly as an irrigation problem. ## **Weather Data** Irrigation requirements are strongly influenced by weather. Temperature, rainfall, humidity, solar radiation, and wind all affect crop water use. Weather stations and forecasting platforms can therefore provide essential information for irrigation prescription systems. A modern platform might combine: - Drone imagery - Soil moisture measurements - Rainfall - Temperature - Humidity - Wind - Solar radiation - Evapotranspiration estimates - Crop growth stage - Previous irrigation records Combining these datasets provides a much stronger basis for irrigation decisions than relying on a single sensor. ## **Identifying Over-Irrigation** Precision irrigation is not only about finding areas that require more water. Over-irrigation can create significant problems. Excess water can contribute to waterlogging, root problems, nutrient leaching, disease pressure, soil erosion, and unnecessary pumping costs. Drone imagery can help identify unusual vegetation patterns or areas of standing water that may warrant investigation. Digital elevation information can also help determine whether terrain is contributing to water accumulation. Correcting these issues can reduce both water consumption and crop damage. ## **Detecting Irrigation System Problems** Sometimes crop water stress is caused not by irrigation scheduling but by malfunctioning equipment. Blocked sprinklers, damaged pipes, incorrect pressure, leaking irrigation lines, malfunctioning valves, and uneven application can create distinctive patterns across fields. Drone imagery provides an efficient way to identify spatial patterns that may correspond with irrigation infrastructure. Once identified, maintenance teams can inspect the relevant equipment. This can reduce the time required to locate faults across large irrigation systems. ## **Centre Pivot Irrigation** Centre pivot systems are particularly suitable for prescription-based irrigation. These systems move around a central point and can cover large agricultural areas. Variable Rate Irrigation technology can