State of the water in the green industry, part III

By John Majsztrik, Sarah White, Jim Owen and John Lea-Cox

Water availability and efficient application are the most common operational concerns related to water. But water quality, a factor foundational to crop health, is often overlooked. For instance, how often in the last two years have you monitored the pH and/or soluble salt levels in your irrigation water to determine if you are still irrigating, fertilizing or amending your container substrate correctly? Are your pH and electrical conductivity (EC) values in a “safe” range to promote growth and optimize mineral nutrient availability? (See “How to Interpret A Water Quality Report” at http://tinyurl.com/interpret-water-quality) Many of the problems associated with slow plant growth or unsightly foliage are related to the quality of the irrigation water used. When you develop a baseline water quality, you can plan a successful production schedule with regard to plant species, fertilization requirements, irrigation volumes, and time to market. Without monitoring and managing water quality, there is potential for increased “shrinkage” (i.e. product loss during production) and increased production time resulting in decreased profitability. Knowledge is the best tool to improve water quality operational efficiency.

To gain a better understanding of water-related issues, a survey of 388 U.S. nursery and greenhouse growers was conducted in 2012. When asked if they monitored water quality, the majority of respondents did not (45-80 percent), regardless of their source.

Another layer of complexity related to water quality is that of biotic and chemical contaminants. Biotic (e.g. pathogen, algal, bacterial or viral) and chemical (e.g. nutrients, growth regulators, pesticides or suspended solids) contaminants can impact plant health, and reduce productivity if poor quality water is recycled without adequate treatment. Water conservation is becoming more critical as drought cycles increase and urban populations grow, creating a greater demand. Thus, alternative water sources, including recycled (reuse of production area irrigation runoff) and reclaimed (treated municipal wastewater), may be needed to maintain adequate water resources for crop production. Chemical and biological contaminants in alterative water resources could impact plant quality and growth rates.

Of the 23 percent of respondents who monitored water quality in a containment pond, only 48 percent monitored one parameter once a season or less, 23 percent monitored one parameter on a monthly basis, and 29 percent monitored at least one water quality indicator on a weekly basis. The most common parameters that were monitored included: pH (88 percent), EC (63 percent), alkalinity (50 percent), nutrients (44 percent), suspended solids (31 percent), pathogens (19 percent) and pesticides (6 percent).

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