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Why Should I Use a Lysimeter?

excerpt from the Soil Report Newsletter of Soilmoisture Equipment Corp.

In the case of our lead article about the Royal Kunia golf course, the initial effort was to justify that pesticides, nitrates, and pollutants were not being carried into Hawaii's shallow groundwater reserves. The use of lysimeters as a preventative tool is very familiar to those working to protect our groundwater resources. It is easier and less expensive and more logical to use a lysimeter to detect potential contaminants before they reach the resource we want to protect. Expensive monitoring or remediation wells after the ground waters become polluted is certainly no sensible solution. Today, lysimeters are used extensively throughout the United States under landfills, storage tanks, land farms, with municipalities, industry, agriculture, and governmental agencies all working to protect our ground water from pollution. What is perhaps less understood is the part lysimeters can play as a diagnostic tool in the development of "best management practices" that result in premium crops.

Pore water (the water a plant uses) is affected by its water soluble constituents, both natural and man-made. Even slightly soluble elements, like selenium or copper, can have a dramatic effect on plant crop vitality; whether it's a putting green in Hawaii or a carrot patch in California's central valley. Crop health and the ability to produce fruit, seed, or bulk will in large part be determined by the nutritional environment created by the percolating pore liquids surrounding a plant's roots. That carrot you munch as a quick snack will contain and be influenced by its uptake of pore liquids throughout its brief life span. A soil water sampler (also known as a lysimeter) is perhaps the most effective tool to measure and monitor pore liquid contents that will directly affect crop production and vitality.

Water Quality is an important factor for satisfactory crop production. A lysimeter can provide vital information about the difference between the supply water (from either wells or municipality sources) and the pore water after an irrigation cycle. Substantial changes to the source water affecting crop production can be due to soil/mineral exchange capacities, water or soil pH, evaporation patterns and seasonal effects, may take place within the soil. A lysimeter provides an inexpensive way to gather and measure the differences between water supplies used in irrigations and the final wet concoction your crop drinks. Being able to measure and develop those water relationships can provide the knowledge necessary to optimize plant nutritional needs independent of irrigation water quality.

Working amendments are often ballyhooed to the agricultural community as remedies to make your crop grow taller, fatter, faster, with a greater zest for life. A lysimeter is a great equalizer; a way for you to get the information and solid data necessary to corroborate or refute any salesman=s claims. The soil fluids can easily be extracted and measured and the relationship between pore fluid contents and plant growth vitality correlated. Either it=s a close relationship or, in many cases, a nonexisting one.

Proper care and feeding are as necessary to plants as humans. A lysimeter allows for the quantitative determination of what's working well now, giving you the ability to replicate or introduce those same conditions throughout the crop. In the case of a golf course, the trees, roughs, fairways, and greens all have different feeding habits and nutritional needs. The knowledge gained by measuring and monitoring pore liquids associated with each specialty crop segment will be crucial to the understanding and development of best management practices for each of those crop segments.

The stuff we apply like fertilizers, pesticides moves in the soil. You (and most likely some regulatory agency) probably want to know where they're going. For you, the more important facts for consideration are: "Is it too much?" or "Is it being used too often?" A suite of lysimeters at 3-4 depths is an excellent assemblage to quantify pore fluid contents and movements. A multiple lysimeter suite can, for example, help determine fertilizer or herbicide penetration, dilutions due to depth or root uptake, the effectiveness of "timed" release supplements and much more. Potentially harmful crop inclusions such as pesticide residues or leached heavy metals can also be monitored and measured in a similar manner as they move and are modified through the soil profile. With a soil water sampler you are in control, developing and measuring the effects of an application cycle tuning it for optimum performance, minimum loss or runoff at minimum costs.