Effects of Tillage and Crop Rotation On Soil-Borne Pathogen Population.

Traditional cropping systems in Central Montana have been continuous cereals and cereal-summer fallow systems. Continuous mono-cropping often builds up population of certain plant pathogens. Introduction of alternative crops, such as pea, lentil and oilseed crops, into the rotation system may reduce disease impact and increase farmer’s profit. Our objective was to determine the effect of different crop rotations and tillage practices on soil-borne pathogen population. Soil samples were collected from three fields at Moccasin, MT in September, 2010. These three fields had been under wheat (or barley)-wheat, wheat-fallow, wheat-legumes (lentil, spring pea, and winter pea), and wheat-oilseeds (canola and camelina) rotations with conventional or no-till. Five soil cores were taken from 0- 15 cm soil depth of each plot and composited into one sample. Each sample was plated out by soil dilution onto potato-dextrose agar with antibiotics to morphologically identify the isolated fungi into genus level and determine the population by CFU (unit/ml). Fusarium was the only genus we could identify with confidence. Conventional tillage generally had lower Fusarium population than no-till. Pea had apparently less impact on Fusarium population in the soil than other crops, while lentil was more effective in suppressing the population than pea. The population level in the fallow period was inconsistent but reduced. Fusarium population was reduced with oilseed rotations, especially with camelina. Further screening and identification into species level are required to draw more precise conclusion.