@Ct Farmer : Thanks for your answer and information. There is no doubt that keeping the land totally free of weed without use of chemicals (or bushfire from time to time ;-) ) will be impossible; but this is not necessary. At this moment I´m removing the weed/brushes that have grown over the last ten to twenty years; once donde this I will try to keep the weed more controlled, using the brushcutter three of four times the year. What I want to do, once removed manually all the big brushes/weed, is pass the cleaning bucket with my backhoe to leave a smooth surfuce without at least bigger stones and, if possible, even without gravel on the surface, what will makes a lot more easier the recollection of the cutted weed with a rake. I´ve tested my "pond-method" in a smaller scale, but I´m not satisfied with the result: Most part of organic material flows out with water, but in the remaining sump there are still a lot of almonds (the land was a former almond plantation) and other organic material not swimming up. And it needs _very_ much water. I found a air-curtain-type solution, mixed with high-performance electronics: The mixed material is beeing scanned with cameras while falling from a conveyor belt, each particle classified for size, color, material and then, before landing on a lower conveyor belt, blown out by discrete air streams from high-speed nozzels controlled by the computer. With this method they achieve to clean 20 tons of topsoil per hour, removing any stones, plastic and other debris. Or, in larger scale, sorting different stone types in quarries, up to 200 tons/hour. Impressive but maybe some overkill for my task. I will do some test with separation by mass and density, first accelerating the material mix and "throw" it of the belt´s end and then see if it is possible to separate by "flight path/distance". And if this one will not work, it will try with a cyclonic separator. At this moment the material is all very dry, due to lack of rain in the last 4 months.