2 February 1996

Spray additive can help with water snags

A NEW spray additive to counter the adverse effects of some waters on agrochemical performance has been launched by Derbyshire-based Techsol.

Under the "quirky" names of AcidipHier pHor2pHive, it aims to overcome problems of pesticide breakdown and "lock-up" caused by alkaline and hard water.

According to general manager Bob Drew most pesticides and trace elements work better at pH4/5. But UK water sources are generally much less acidic, ranging from say pH6 in Wales to as high as 8.5 in parts of the east. "In places like Burton on Trent high levels of gypsum make for very hard water," he says.

Formulation can help offset some problems. "But manufacturers can only do so much," he says.

Sprays broken down

Many spray chemicals are quickly broken down by alkaline hydrolysis at high pH levels, he explains. The insecticide dimethoate, for example, loses half its activity within 20mins at pH8. At pH5 that takes three days.

Other chemicals such as glyphosate are partially inactivated by calcium and magnesium in hard water.

By lowering the pH and reducing the metal ions in the water, the new additive allows pesticides to work at maximum efficiency.

The firm plans to make hardness and pH kits available to distributors to allow them to test farm water sources. A chart then advises correct application rate.

At £12.50/litre, a typical 0.1% solution needed to bring water with 300ppm of calcium carbonate to a pH of 4-5 costs "about £1/acre" at a conventional spraying volume of 200litres/ha (18gal/acre).