Monitoring the uniformity of soil permeability for orchard precision irrigation

Irrigation accounts for 46% of world food production using systems designed to apply water uniformly. However, non-uniform field combinations of soil parameters give justification to apply water variably across a field (VRI). Therefore, a sensor-based irrigation scheduling is necessary to determine the optimal timing and amount of irrigation to apply in orchards and agriculture in general. A grid of 21 acquisition nodes was prepared, according to an equidistant and regular layout. The acquisition nodes consisted of an Arduino board, to which the air and soil temperature and humidity sensors were connected, recording values with a frequency of 10 min and storing data. An experiment plot on a bare soil, positioning the sensors where the drip irrigation pipes of the orchard would be positioned, was set up to evaluate the grid on the ground and assess it in irrigated condition. Acquisition series of 3 days each were developed following an irrigation event. Based on the geoelectric resistivity and the soil map of the study site, the main soil parameters (soil texture, organic carbon and rock fragment content) were estimated at the grid's points. Various hydrological parameters were calculated using pedotransfer functions (PTFs). Data processing focused on verifying the uniformity of the data collected on the observed surface. The difference between the soil moisture values at two different depths and the relative clustering allowed the implementation of maps of water infiltration at known times. The maps obtained with the acquisition grid showed a distribution of both the water infiltration capacity in the soil and the georesistivity. The proposed methodology to investigate the variability of the soil, in terms of reaction to water, will contribute to improve the design of irrigation systems for precision water management of orchards and vineyards.