John Ossa: Make A Wish

John Ossa

The green industry is undergoing a period of rapid change brought on by a confluence of events. Environmental concerns, water shortages and an increasing regulatory environment demand that contractors and groundskeepers act on more science-based information and become more knowledgeable. An area of critical concern for our industry is landscape water management – effective scheduling of irrigation.

The issue boils down to a lack of grounding in the fundamentals of "what happens" when we irrigate. What we are trying to irrigate is roots. If we irrigate in a way that encourages and produces more and deeper roots, we will have healthier and more resilient plants.

It is helpful to understand the limitations of the hardware. For many years, we have used fixed sprays, impact heads, rotors and multi-stream nozzles – spray irrigation hardware of various configurations. They all share some key constraints. There is overspray onto non-landscape or a majority of a given area is over-irrigated to get the least "overlapped" area an adequate minimum of water.

When over spraying and over irrigating most of an area, we are waiting for the "right amount" of water to infiltrate and move down through the root zone. While waiting for water to move down, the saturated surface area excludes oxygen and induces stress. This is an environment ripe for soil pathogens like Pythium or Phytophthora to develop.

When water does move down, it can be called gravitational water. Proper irrigation scheduling hopes to stop that downward percolation at the limit of the root zone. This is difficult to do since spray heads all basically work by a cycle of flood/dry, flood/dry. Gravitational water occurs because the soil cannot "hold" all the water – there is such a concentration (flood) of water that it fills available pore spaces and is pulled by gravity.

For our industry to grow it may need to embrace irrigation without flooding, or creating excess gravitational water. Working with nature is to use the forces at work in nature. Sub surface irrigation delivery hardware supplies a low rate of irrigation output, so the soil through the principle of capillarity will move the water against the force of gravity – upward – and in a manner that matches the output to what a given soil type can hold. These unfailing principles at work in nature, combined with reliable distribution hardware, provide the opportunity for extremely high irrigation efficiencies.

How much water a given soil can hold, and how long to irrigate before water becomes gravitational water is "knowable." With training like the California Landscape Contractors Association's Water Management Certification Program, which teaches science-based concepts, and new high-efficiency irrigation hardware, the green industry will continue to evolve and provide solutions that communities are seeking.
 

John Ossa is the national accounts director at Irrigation Water Technologies America and owns Irrigation Essentials; mail jossa@giemedia.com.