# Remote Sensing for Irrigation of Horticultural Crops
## 1 Introduction  
Food is the basic and compulsory human requirement. It is expected that limited land and inadequate water resources will negatively impact the expected increase in demand for food crops during the next fifty years [1; 2; 3]. Subject to scenarios used, and assumptions and models employed, different forecasts have been made for food and agricultural production and related irrigation water needs. Food and Agriculture Organization (FAO) projections indicated a growth rate of world consumption of agricultural products of 1.1% per year for the period from 2005 to 2050. In order to meet this projected global demand, agricultural production would have to increase by 60% from 2005 to 2050 [4; 5]. Production of food requires water. Since water resources are a limiting factor for human actions, Water Use Efficiency (WUE) will be a crucial factor [6]. For these reasons, the European Parliament, in agreement with the Horizon 2020 program, has coined the phrase _\"produce more with less\"_[7]. Agriculture is the main user of water worldwide, accounting for about 70% of total water withdrawals, including the water used in livestock and aquaculture production [8]. Furthermore, it is expected that this sector will witness increased water consumption of about 20% by the year 2025 [9]. Thus, it is widely expected that the competition for water resources in many regions will increase. To meet the increasing population's demands for food and for water, it is critical to improve agricultural water productivity, or economic yield per volume of water used [1; 10]. Forty percent of total agricultural production comes from the 20% of the land that is irrigated [11]. Farmers in developing countries have to improve agronomic and water management practices in order to increase WUE in all agroecosystems (from fully-rainfed to fully-irrigated farming systems). [PERSON] et al., [12] reported that the above goal is chiefly important where water is a scarce commodity (arid and semiarid regions). In these regions, it will be crucial to increase water productivity rather than maximizing crop yield. [PERSON] et al. [13] suggested, _\"The adoptions of techniques to improve waterproductivity 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]. [PERSON] and [PERSON] [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, [PERSON] [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. [PERSON] and [PERSON] [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.