After about 60 years of cultivation, our garden substrate is harboring organisms, both micro and macro, that prevent healthy crops. We are especially discouraged about tomatoes. A local (very local) plant pathologist has suggested (stated) that solarization should be introduced to improve the situation. (If ya can't stand the heat, stay outa the gahden !) That process is under way. Further, you might note a level of international activity in the project, in case some germenes patologicos extranjeros have snuck in. We'll see. If this doesn't work, we may convert to topsy-turvy tomatoes and ornamentals.