Subsurface Drip Irrigation and ICT for the Innovative Irrigation Water Management: Application to a Citrus Crop (C. reticulata cv. Tardivo di Ciaculli)

Abstract

Subsurface drip irrigation (SDI) is considered one of the most efficient irrigation systems because it allows the optimization of crop water productivity maximizing, at the same time, farmers’ economic benefit. However, to take full advantage of SDI systems it is necessary to prevent emitter obstructions caused by root intrusion, as well as to apply water-saving strategies, such as regulated deficit irrigation (RDI). Regarding the first aspect, manufacturers are claiming different techniques to protect emitters from root intrusion, such as mechanical barriers, addition with different chemical compounds into the emitter itself or chemicals into irrigation water. On the other hand, the application of RDI strategies during specific periods of vegetative growth makes it necessary to control soil/plant water status to identify appropriate irrigation scheduling parameters (timing and doses) and to increase water use efficiency. In this direction, new sensors associated with information and communication technology can allow, in real-time, the remote monitoring of soil and plant water status, avoiding tedious and time-consuming field data collection. Objectives of this ongoing research are: i) to identify precise and automatic irrigation scheduling parameters in a citrus mandarin orchard (C. reticulata cv. Tardivo di Ciaculli) under SDI system, based on the monitoring from remote and in real-time of the soil-plant-atmosphere system and ii) to test different anti-root agents settled in the same emitter model. Moreover, to reduce the total amount of applied water, RDI was applied, in half of the orchard, during phase II of fruit growth. Integrated sensing methodologies, supported by Internet of things and cloud computing technologies, together with a suitable communication infrastructure, were used for the continuous monitoring of soil water status with “drill & drop” sensors (Sentek, Stepney, Australia) and climate variables using a Spectrum weather station. Scholander chamber observations were additionally used to assess the orchard water status through weekly measurements of predawn and midday stem water potentials. Data collected during the first season allowed to identify the threshold of soil water content below which crop water stress occurs, which resulted variable, for the investigated soil, from about 0.20 and 0.25 cm3/cm3.