Controle estatístico da fertirrigação por gotejamento na declividade da linha lateral

Abstract

The consistency of an irrigation system's operation is closely related to its performance. Drip irrigation is the most appropriate system for saving water and energy, as well as the possibility of automation and fertigation, so the system must be evaluated on a regular basis. To achieve the best performance, some evaluation parameters, such as Christiansen's Uniformity Coefficient (CUC) and the Distribution Uniformity Coefficient (CUD), which express the variability of irrigation depth application, must be considered. Several factors influence the uniformity of water and fertilizer application, including the topography of the land, variations in fertilizer concentration, pH, and electrical conductivity of the solution to be applied. The use of statistical process control (SPQ) tools such as Shewhart Control Charts and Process Capability Index (PCI) allows for a more in-depth evaluation of these parameters. Thus, the aim of this work was to evaluate an irrigation system in a protected environment, in which the application of clean water (control treatment) and water with nitrogen solution (urea) in three concentrations (2 g L-1; 4 g) was evaluated L-1; 6 g L-1) at different slopes level (0%), acclivity (2%) and declivity (-2%), with a total of 25 trials for each treatment. Flow, pH, and electrical conductivity were the variables measured in the test. Christiansen Uniformity Coefficients (CUC) and Distribution Uniformity Coefficients (CUD) were calculated and compared using the collected samples, with the CUD being more sensitive to identifying the drop in uniformity with the increase in fertilizer concentration, demonstrating greater severity in the data analysis when verifying that the increase of the urea concentration in 6 g L-¹ affected the uniform distribution of the level system, with values for CUD<70%, observed in the Shewhart Control Chart. The increase in urea concentration in 6 g L-¹ influenced the increase in pH by presenting 7.75 above the predicted limits for irrigation, so the system could apply concentrations up to 2 g L-¹ in level when presenting Cpl = 2.86 for the Process Capability Index analysis.