Just How Efficient Can We Get? the Potential and Limits of Decreased Flow Rates and/or Increased Frequencies in Drip Irrigation.

Water and nutrient use efficiencies are increased under drip irrigation as zones of relatively high water content and high concentrations of minerals in solution are maintained and availability for root uptake is maximized.  Potentially, due to this relative high availability, water and nutrient application rates under drip can be reduced without negatively affecting growth and yield of crops. Indeed, studies show benefits in water and/or nutrient savings as drip irrigation frequency increases, from intervals of weeks or days between irrigation events, as practiced under other application methods, to daily or multiple applications per day made possible with pressurized drip systems.

Today, technology allows even further extending of high availability and unchanging root zone conditions through ultra high frequency with non-leaking drippers reaching potentially dozens of applications per day or through irrigation events lasting for long periods of the day by way of very low rate emitters.

We asked if high availability can be infinitely beneficial or if there is a limit to potential uptake efficiency by roots in agricultural systems?  We also addressed the question of low water quality. When salt leaching is required, just how do ultra high frequencies or ultra low flow rates stand up? We investigated the literature and experimented on crops including grapevines, bell peppers, radish, melons, and corn.  

The results indicate that, with good quality water and most soils, great benefit occurs as applications increase to daily and even 4-8 times per day but that little if any additional benefit is found as irrigation regimes reach more than several applications per day or start lasting throughout most of the day. With water containing problematic concentrations of dissolved salts, the highest frequencies and lowest flow rates subtly but consistently indicate lower capability for leaching.