Remote Sensing for Irrigation of Horticultural Crops

2017 Horticulturae  
This paper reviews the literature on applications of remote sensing for monitoring soil-and crop-water status for irrigation purposes. The review is organized into two main sections: (1) sensors and platforms applied to irrigation studies and (2) remote sensing approaches for precision irrigation to estimate crop water status, evapotranspiration, infrared thermography, soil and crop characteristics methods. Recent literature reports several remote sensing (RS) approaches to monitor crop water
more » ... atus in the cultivated environment. Establishing the right amount of water to supply for different irrigation strategies (maximization of yield or water use efficiency (WUE)) for a large number of crops is a problem that remains unresolved. For each crop, it will be necessary to create a stronger connection between crop-water status and crop yield. Horticulturae 2017, 3, 40 2 of 36 productivity will require an enabling policy and an institutional environment that aligns the incentives of producers, resource managers and society, and provides a mechanism for dealing with trade-offs". Irrigation water management is sustainable if it realizes the objectives of preserving the natural environment and sustaining irrigated agriculture for food security. Appropriate irrigation practices are aimed at improving WUE in order to save water and maintain satisfactory yields [14] . Painter and Carren [15] emphasized the importance of reducing water losses below the root zone, improving yield and crop quality, conserving the resource base, and lowering the risk of salinization of groundwater to enhance sustainability. The authors also pointed out that "these gains can only be achieved when all elements of precision operate synergistically within a given environment". For improving WUE at the regional level, Batchelor [16] suggested four methods of agronomic improvements: (1) rely on improved crop husbandry; (2) introduce varieties with higher productivity; (3) maximize cropped area during periods of low potential evapotranspiration and (4) when rainfall is highest, promote water recycling. Wallace and Batchelor [17] reported four categories (agronomic, technical, managerial, and institutional) for improving the efficiency of irrigation. Technical solutions may improve irrigation uniformity, reduce leaching, and lead to adoption of irrigation practices that increase rainfall effectiveness. Among managerial improvements, the authors highlighted the implementation of irrigation scheduling systems based on crop demand. The institutional improvements "rely on the user involvement in scheme operation and maintenance; introduction of water pricing and legal frameworks to provide incentives for efficient water use and disincentives for inefficient use; introduction of integrated catchment management; improved training and extension". In 2005, Johansson [6] emphasized the importance at the farm level of the extension services for improving information or of cheap credit for adjusting to the changing environments associated with water policy reforms (water-pricing reforms, particularly). Because more efficient irrigation practices can optimize WUE [18] , and drip irrigation reduced crop evapotranspiration losses and runoff [19] [20] [21] , the technology was appropriate for applying water to orchards and vegetables [22] . Proper irrigation (timing and amount) increased the crop WUE and crop yield [23] . In contrast, improper irrigation can lead to the onset of crop water deficits causing water and nutrient deficiencies that reduce yield [23, 24] . Nevertheless, regardless of the strategy engaged, the benefits of irrigation scheduling can be reached only by applying the exact amount of water required [25] . Raine et al. [26] define precision irrigation as "the accurate and precise application of water to meet the specific requirements of individual plants or management units and minimize adverse environmental impact". Monitoring water use and crop water status in the field is important for developing effective precautions, and for this purpose, some indicators are required [27] . A very large body of research, spanning almost four decades, has demonstrated that much of the required agricultural information can be derived from remotely sensed data [28] starting from crop water status detection. IN order to develop effective irrigation strategies, it is necessary to identify the appropriate indicators for monitoring crop water status at the farm level [27] . For these purposes, the required agricultural information may be derived from remotely sensed data [28] .
doi:10.3390/horticulturae3020040 fatcat:4axxl4k5yfagbdca6sojbu2baq