14 Effects of crop management on microbial diversity and biochemical properties of agroecosystems under semi-arid conditions

Thursday, August 6, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Rina Kumari , Biological Sciences, Texas Tech University, Lubbock, TX
Cheryl Murzello , Biological Sciences, Texas Tech University, Lubbock, TX
Randall M. Jeter , Biological Sciences, Texas Tech University, Lubbock, TX
V. Acosta-Martinez , Cropping Systems Research Laboratory, USDA-ARS, Lubbock, TX
Michael J. San Francisco , Biological Sciences, Texas Tech University, Lubbock, TX
John C. Zak , Biological Sciences, Texas Tech University, Lubbock, TX
Background/Question/Methods

A complex community of microorganisms inhabits the soil in association with plant roots. These microbes are nourished by root exudates and in exchange, they provide a variety of benefits to the plants. The interactions among rhizosphere microbes and plant roots are complex and appear to be controlled by multiple abiotic constraints and biotic activities. Crop management practices designed to increase plant productivity can alter the biotic and abiotic actions within the rhizosphere. This study focused on understanding the effect of different crop management methods on the biodiversity and biochemical properties of peanut and cotton rhizosphere in semi-arid climate of west Texas. In this study, we analyzed the effect of tillage practice, fertilizer applications and irrigation schedule on microbial diversity and soil nutrient status for agroecosystem in semi-arid west Texas. The crops involved were continuous peanut and continuous cotton. The treatment consisted of minimal and conventional tillage, added nitrogen and early vs. late irrigation. Soil samples were collected monthly from March to October over a period of two years and evaluated for microbial biomass carbon (MBC), Fatty Acid Methyl Esters (FAME), selected microbial enzymes and nutrient analysis.

Results/Conclusions

There are statistically significant effects of crop management on MBC, extractable levels of NH4-N, NO3-N, soil organic matter and available P. Nitrogen application decreased microbial biomass carbon, soil organic matter, and available P in the peanut cropping system. The highest levels of enzyme activities were found in the peanut compared to cotton rhizospheres. FAME data also indicated that there was more microbial diversity associated with peanut rhizosphere in comparison to the cotton. Depending upon season, irrigation did not influence microbial activity. The choice of a cropping system can have a major impact on subsequent microbial activity and may increase the need for additional inputs to maintain crop productivity.

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