Wednesday, November 7, 2007
292-8
Long-Term Impacts of Different Cropping Systems on Soil Microbial Communities.
Terry J. Gentry1, John E. Matocha2, Heidi J. Mjelde1, and E.C. Martin1. (1) Soil & Crop Sciences, Texas A&M University, 2474 TAMU, College Station, TX 77843, (2) Soil & Crop Sciences, Texas AgriLife Research and Extension Center at Corpus Christi, 10345 State Hwy 44, Corpus Christi, TX 78406
Soil microbial diversity and activity were evaluated for field plots under different long-term (>20 yrs) crop rotations. Cropping systems included continuous corn, cotton, and sorghum along with two different cotton/sorghum rotations. Soil samples were collected from both 0-3 and 3-6 inch depths in triplicate plots for each treatment. Microbial diversity was determined using fatty acid methyl ester (FAME) analysis. Microbial activity was estimated by measuring the enzymatic activity of acid and alkaline phosphatases, arylsulfatase, and β-glucosidase. FAME results indicated that the different cropping systems selected for different microbial populations, and these effects were most pronounced in the 0-3 inch samples. The continuous sorghum generally produced the highest soil enzyme levels followed by the cotton/sorghum rotations and continuous corn and cotton treatments, depending on the particular enzyme. Enzyme activities were higher in the 0-3 inch soil samples than the 3-6 inch samples, and the treatment impacts were greatest in the 0-3 inch samples. These results indicate the ability of different long-term cropping systems to impact soil microbial diversity and activity.