Might be a godsend for chlorotic trees.Greensand is a naturally occuring, mined, long-accepted and organic source of minerals: composition 1%P, 5-7%K; 50% silica, 18-23% iron oxide; 22 trace minerals. Its effects last for up to 10 years, applied at a rate of 10 lb. per 100 sq. ft. It loosens clay soils and is slowly available to the roots.