Sprinkler irrigation changes maize canopy microclimate and crop water status, transpiration, and temperature
During a sprinkler irrigation event some water is lost due to wind drift and evaporation (WDEL). After the irrigation event, plant-intercepted water is lost due to evaporation. The water lost causes microclimatic changes which could result in positive or negative plant physiological changes. We studied the microclimatic and physiological changes on two fields grown with maize (Zea mays L.) irrigated with a solid-set sprinkler system. The temperature and vapor pressure deficit (VPD) of the air were measured at the crop canopy level and above and below the canopy. Changes in maize canopy temperature, transpiration, and leaf water potential (LWP) were determined. Sprinkler irrigation during daytime strongly modified the microclimate where plants grow during the irrigation time and for a short period after the irrigation event finished. Daytime irrigation decreased air temperature by 3.3 to 4.4°C and VPD by 1.0 to 1.2 kPa at 0.5 m below the crop canopy height. The decrease was lower as the measurement height increased. Microclimatic changes during nighttime irrigation were minimal. Daytime irrigation reduced maize canopy temperature by 4 to 6°C and plant transpiration by 58%, and increased LWP from –1.2 and –1.4 MPa to –0.54 MPa. Transpiration reduction must be considered positive because it supposes a reduction of WDEL. The decrease in maize canopy temperature could be positive or negative, but the increase in LWP is a positive effect.