Date of Completion

4-26-2019

Embargo Period

4-25-2022

Keywords

biofilm PVC polyethylene polymer water quality irrigation

Major Advisor

Rosa Raudales

Associate Advisor

Richard McAvoy

Associate Advisor

John Inguagiato

Associate Advisor

Leslie Shor

Field of Study

Plant Science

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Clogging of irrigation systems affects irrigation uniformity, water use, crop yields, and production costs. The objectives of this research were to: 1) Evaluate if published classification guidelines could predict and identify the causes of clogging in greenhouses; 2) Determine if pipe materials and flow frequency affect biofilm accumulation; 4) Determine if biofilms inside pipes affect plant health; and 5) Determine total suspended solids (TSS) thresholds that affect the performance of pressure–compensated drippers with anti–drain mechanism. The first study revealed that the current classification guidelines serve as an indicator of relative risk of clogging, but not as predictors. The assumptions of the classification guidelines outweigh the presence of nutrients in fertigation as a cause of clogging, disregard interactions among water quality parameters, and do not consider the qualitative characteristics of microbial communities. In the second study, biofilm accumulated more on polyvinyl chloride pipes (PVC) than polyethylene (PE) pipes with continuous or intermittent flow. Biofilms changed the initial hydrophobicity and topography of PVC pipes. In the third study, plants were bigger and Pythium spp. was isolated at lower percentage when using pipes with a six-month biofilm compared to clean pipes. In the final study, TSS (0, 30, 60, and 120 mg·L-1) did not clog the emitters. On the contrary, discharge increased by 10 to 30% when the solution had 60–120 mg·L-1 TSS. These results suggest that clogging depends on interactions between factors rather than single parameters and that plastic pipes may be a substrate for beneficial biofilms.

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