I retired last fall and decided to apply more time to gardening for the table and to my lifelong avocations, botany and natural sciences. In March I went to Trammel Crow Park off Sylvan Ave. in the river floodplain and loaded 1/2 yard of new laid silt from the March rains in my truck for testing. I prepared a mixture of 50% silt, 20% vermicompost 20 % screened compost and 10% clean concrete grade sand for seed beds. In those beds I planted Buckeye, Passionflower, Campsis X (A tree that I am developing), carrots, spinach, okra, mustard, Mediterranean Oregano, lavender, Mullein, Catnip, Sweet Banana Pepper and Roma Tomato. Germination rate was only about .05%. I went back to the river at various locations since and saw that the only prominent germinating species in the new silt is the common Ballon Vine. Based on my observations of pollution sources over the past 50 years, I think that the soil needs to be tested for metals such as aluminum, barium, and thorium, and I think that the primary culprit is aluminum because it is showing up in increasing quanties around the globe and it is notorious for stunting root growth.
Monsanto and Conagra are developing GMO crops that resist the stunting effect of aluminum. For us who DIY, I suggest heavily diluting native soil with organic amendments per Dirt Doctor and company protocols. To learn more about what BIG AGRIBUSINESS is doing put "Arabidopsis" in your search engine.