Abstract

In sugar cane crop fertigation management systems, about 500 m³ ha^-1 of diluted vinasse is applied annually by cycle, promoting nutrient recycling and supply to the soil, especially that of potassium (K). With the increase of sugar cane areas with subsurface drip irrigation, hydraulic characterization related to vinasse intermittent application is important, in order to verify uniformity flow in drippers. The aim of this study was to hydraulically characterize performance and orifice position of different dripline models subjected to intermittent vinasse application, in order to verify flow disorders. The experiment conducted was in a test bench in the Biosystem Engineering Department - ESALQ/USP. The experimental design was completely randomized, with 10 repetitions. Four dripline models (Hydrolite HY 0.65, Hydrolite HY 1.0, Drip Net PC DN 0.6 and Drip Net PC DN 1.6) and 13 consecutive weekly assessment periods were used as treatments. At the same time, dripline orifice position influence (upward and downward) was assessed in two (Hydrolite HY 0.65 and Drip Net PC DN 0.6) of the four dripline models in the respective periods (2x2x13 factorial = Two models, two orifice positions and 13 periods/weeks). Ten drippers from each model were randomly selected, in order to monitor flow. Vinasse application was conducted daily during four hours, with dripline product rest for 20 h, and flow reading at every 168 test h (weekly). HY models (0.65 L h^-1) with drippers positioned upwards and downwards, and upwards HY (1.0 L h^-1) and DN (1.6 L h^-1) showed flow variation coefficient (VC) lower than 5%, which is rated as excellent. The other models showed VC lower than 10%, which was classified as good, enabling vinasse use in the 2:1 concentration in driplines.

Key words: Flow variation coefficient. clogging. fertigation. dripping. potassium. vinasse.