Fertigation quality with drip irrigation system in grape orchard by using the processcapability index

摘要

The capability of the process is used to produce acceptable products or processes. Process-capability studies have large impact on many management decision problems that occur over the product cycle, including decisions and process improvements that reduce process variability. In order to study the quality of fertigation in grapes, a field experiment with drip irrigation system was conducted in a farm in the state of Parana, Brazil. The experiment was factorial 2 x 4, with two fertilizer concentrations, 200 and 400 mg L-1 of NPK (nitrogen, phosphorus and potassium) and four head pressures, 150, 200, 250 and 300 kPa. Analysis of variance was performed for the coefficients CUC (Christiansen's uniformity coefficient) and CVt (coefficient of total variation). The PC (process capability index) was calculated for all combinations of head pressure with fertilizer concentration. The head pressures of 150 and 200 kPa resulted in more water distribution uniformity. The relationships of CUC and CVt with CP resulted in R2 equal to 91.84% and 93.76%, respectively. The process capability index showed that the head pressure of 300 kPa is inadequate since this index was less than 1. The process capability index showed to be able to diagnose whether the fertigation process maintains acceptable levels of water distribution uniformity. In all evaluations, CUC exceeded 90% and CVt was less than 10%, classifying the water distribution uniformity of the drip irrigation system as "Good" and "Excellent", respectively.