Sprinkler Irrigation Pressure and Spacing Effect for Cold Protection of Strawberries

Abstract

Irrigation for cold protection in strawberries has been used for many years to protect plants from cold damage; however, large volumes of high-quality water are needed for this purpose. Based on computer modeling for citrus, an application rate (AR) of 6.35 mm h−1 with impact sprinklers providing full coverage has been recommended and successfully used for this practice in other crops. Nevertheless, lower rates have not been field verified. Thus, the objective for this study was to assess the effect of varying irrigation system pressure and sprinkler spacing on AR and strawberry yield. The treatments evaluated consisted of grower’s practices (GROW), representing grower cold protection practices using 345-kPa irrigation pressure at 14.6-m sprinkler spacing; automated control (AC), with the same setup as GROW but testing an automated control system based on real-time dew point; low-pressure system (LOW), evaluating irrigation at 207 kPa and 14.6-m spacing; shorter spacing (SPC), assessing an irrigation system at 345 kPa and 12.2-m spacing; and nonirrigated (NI) or control. A thermostat and resistive thermodevices (RTDs) controlled irrigation for GROW, LOW, and SPC treatments in 2011–2012 and 2012–2013, respectively, whereas wireless temperature and relative humidity (RH) sensors computed dew point (DP) and activated the AC irrigation on the basis of plant specific thresholds. Significant yield differences between the irrigated treatments and NI were observed in both seasons. After a cold event, only irrigated treatments showed a comparable linear recovery of yield; however, this recovery was not found in the NI treatment. Water savings of 5% and up to 23% were achieved during the 2011–2012 and 2012–2013 seasons, respectively, using an automated irrigation system for cold protection (AC treatment). No yield differences were obtained when the irrigation system pressure was reduced from 345 to 207 kPa, but 22% water savings was achieved. Thus, a lower pressure can reduce irrigation use without affecting yield in years with mild freezes.