Learn to protect the soils

29 Jul, 1999 02:12 AM
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LEARNING from past mistakes may hold the key if WA's fragile soils are to be preserved for the future, according to University of WA soil scientist Professor Bob Gilkes. "We have made mistakes here the same as were made in biblical times," Professor Gilkes said. "We need to learn from these mistakes. "Soils form very slowly and it takes a very long time to form the new soils needed to replace those damaged and destroyed. We ignored history and our record is poor." According to Professor Gilkes, records show ploughs were used 6000 years ago, and the results of that can be seen in the Mediterranean countries. As long as 20,000 years ago, much of WA was a windy barren desert, he said. In Lower Egypt and the Nile Valley, the alluvial soils have become damaged by erosion, salinity, alkalinity and waterlogging. "Our poorly structured, exposed soils have a wind erosion problem," Professor Gilkes said. "The answer to this is reduced tillage, stubble retention, banks and limited stocking rates. The same applies to water erosion. Poor soil structure inhibits root development. "Unfortunately, we do not look at our subsoils or look at the effects from constant tillage and subsequent low organic material levels." Regarding soil salinity, he said there should be more use of water efficient crops, more salt tolerant species and leaching of the salts back deep into the subsoil. The natural infertility of much of WA soils was due to their great age. Professor Gilkes said landowners must act because of the growing magnesium deficiency in local soils. "There is a creeping deficiency in many soil nutrients because we are mining them," he said. Tree planting must be beneficial, with the increase in root development important to soil structure and drainage. Similarly with the potential increase in soil cadmium. Professor Gilkes said there was no way to rid the soil of cadmium, therefore it was vital farmers did not contaminate the soil. "North American soils can handle a certain level of animal wastes and contaminates, but in WA we must be careful we know what animal wastes may contain," he said. ÿ

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