SOIL DEVELOPMENT AND PLANT NUTRITION

Abstract

Silts and sands were separated from mainly silt loam soils in 7 locations representing increasing degrees of soil development. Utah, N. Dakota and Kansas represented the lesser while increasing soil development was illustrated by samples from Iowa, Missouri, southern Illinois, and Mississippi. The separates were subjected to reaction with electrodialyzed colloidal clay as a weathering agency and were then diluted with quartz sand to serve as a growth medium for soybean plants. Plant analyses together with chemical and mineralogical analyses of the separates served to determine how well these soil fractions delivered plant nutrients via acid colloidal clay. Ga release by the minerals was a requisite for plant growth. Different combinations of nutrients were released according to different sample locations, with fewer kinds and amts. with increasing degrees of soil development represented. The coarser separates varied widely in Ca delivery. Heavy feldspars suggested themselves as important nutrient sources. The study suggests that soil classi-fication for productivity may well give attention to the mineralogical composition of the silts and sands as indications of needs for Ca, Mg, and K as soil treatments.