Nutrient Leaching of Root Zones
University of Central Lancashire
Comparative leaching studies of the use of two inorganic soil amendments and a sand based control was performed in a laboratory in the United Kingdom during 1997-98. The two inorganic soil amendments tested were ZeoPro and a calcined diatomaceous earth (DE) product (Isolite).
Testing involved nutrient leaching studies in laboratory lysimeters. All tests were conducted with replicate treatments to allow statistical evaluation of the data.
Plastic columns were filled with 300 mm of root zone mixes. The bottom 180 mm was sand. The top 120 mm were the root zone mixes described above (10%v ZeoPro:90% sand and 10%v DE:90% sand and 100% sand). Five replicates were made for each of the three treatments. Fertilizer (granular) was applied to each column, 2.8 grams per column mixed into the top 3 mm ( a mixture of urea, ammonium nitrate and potash). Every day for five consecutive days each column was leached with 100 ml of distilled water. The total leachate was collected from each leaching episode and analyzed for ammonium-N and potassium. No grass was growing in these lysimeters.
The figures below present the mean leachate losses for ammonium-N and potassium for each treatment. For both ammonium-N and potassium the greatest leach losses occurred for sand-only columns, intermediate was the calcined DE amended root zone and the lowest leach losses were with the ZeoPro amended column root zone mix. Cumulative loss of ammonium-N by the sand only lysimeter was approximately 6.7 mg, compared to 4.0 mg for the calcined DE amended sand and only 2.7 mg for the ZeoPro amended sand (for the five day leaching period). For potassium, the sand lysimeter lost 18% of the applied K in five days, compared to 6% by the DE amended sand and only 2% with the ZeoPro amended sand. The differences are largely attributed to the significantly higher cation exchange capacity of ZeoPro compared to the calcined DE and sand.
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