|Porter, Dana - TAMU COLLEGE STATION|
Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 8, 2002
Publication Date: August 28, 2003
Citation: Acosta Martinez, V., Upchurch, D.R., Porter, D. 2002. Impacts of cotton and peanut rotations on a sandy soil: organic matter, aggregate stability, microbial biomass, microbial community composition, and enzyme activities. Technical Abstract: The impacts of different cotton (Gossypium hirsutum L.) (=Ct) and peanut (Arachis hypogaea L.) (=Pt) rotations on a Brownfield fine sand soil (Loamy, mixed, superactive, thermic Arenic Aridic Paleustalfs) from West Texas, USA were investigated. Soil surface samples (0-12.5 cm) were taken in March and June 2002 from PtPt at 75% (evapotranspiration ) ET irrigation, and from CtCt and PtCt at 50, 75 and 100% ET irrigation. The samples were taken again in September 2002 when the rotations became PtPtPt, CtCtPt, and PtCtCt. The soil contains 91% sand, 7% clay, and 2% silt. The soil properties investigated were not affected by irrigation. The soil total N and aggregate stability were not affected by crop rotations. The soil pH was generally >8.0, however continuous peanut showed lowest soil pH values in comparison to the rotations. In all the samplings, the soil organic C, the activities of beta-glucosidase, beta-glucosaminidase, acid phosphatase, alkaline phosphatase and phosphodiesterase, and the intracellular and total arylsulfatase activity were higher in continuous peanut than in the peanut-cotton rotations. The soil enzyme activities in the peanut-cotton rotations were generally similar during March, June and September but there was a decrease in the soil enzyme activities from March to June in soils under PtPt. Therefore, it appears that this change was not due to seasonal effects but to differences in enzyme stabilization in soil under different cropping systems. The soil microbial biomass C (Cmic) was significantly higher under PtPt than under CtCt in March and under PtPt than under PtCt in June. In September, there were no significant differences in soil Cmic among the systems, but it was increased in comparison to June sampling due to the rhizosphere effect on the soil microorganisms. Fatty acids methyl ester (FAME) analyses, which provide a characterization of the soil microbial community structure, revealed higher concentrations of the fungi indicator fatty acids 18:2w6c and 18:1wc in the continuous peanut than in the peanut and cotton rotations in March and June. For this sandy soil, in contrast to soils with higher contents of clay and organic matter, the continuous peanut tended to promote soil microbiological properties compared to crop rotations. However, it is known that this is not a long-term sustainable system.