Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/11/2007
Publication Date: 5/1/2008
Citation: Acosta Martinez, V., Rowland, D., Sorensen, R.B., Yeater, K.M. 2008. Microbial community structure and functionality under peanut-based cropping systems in a sandy soil. Biology and Fertility of Soils. 44(5): 681-692. Interpretive Summary: Although peanut is an important food supply in the United States, there is no information of the impacts of cotton (Ct) and peanut (Pt) cropping systems on soil properties to evaluate soil functioning and environmental impacts. Our study found consistent trends of higher organic C, microbial biomass, enzyme activities, and potentially mineralizable N under continuous peanut compared to a cotton and peanut rotation in a sandy soil after 5 years. However, it is known that monoculture continuous practices are not a long-term sustainable system. Thus, this study indicated that changes or increases in the soil properties investigated under continuous peanut, although important in soil function, are not always an indication of plant productivity and/or better sustainability of the soil-cropping system. However, our results also indicated that the order or frequency of the cotton and peanut rotation may play an important role in these soil properties as well. For example, there were higher soil microbial biomass, potentially mineralizable N, and phosphatases and arylsulfatase activities under a peanut and cotton rotation with two consecutive years of peanut (PtPtCt) compared to that with only year of peanut (CtCtPt). In addition, some of the microbial properties investigated were not different between continuous peanut (PtPtPt) and the rotation with two consecutive years of peanut (PtPtCt) in this sandy soil. These findings can provide indications of positive impacts on soil functioning as well as better cropping system sustainability under some cotton and peanut cropping systems.
Technical Abstract: Summary Little is known about the long-term impacts of cropping systems of cotton (Gossypium hirsutum L.; =Ct) and peanut (Arachis hypogaea L.; =Pt) on the soil chemical, microbial, and biochemical properties in order to understand their impacts on the soil functioning and the crop-soil system sustainability. Soil samples (0-20 cm) were taken in April, June, and September of 2002 from plots under PtPtPt, PtPtCt, and CtCtPt in Georgia, United States. The soil was a Tifton sandy loam (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) with an average pH of 6.3 and with 80% sand, 13% clay, and 8% silt. Soil organic C was higher under PtPtPt (avg: 8.7 g C kg-1 soil) and PtPtCt (avg: 7.7 g C kg-1 soil) compared with CtCtPt (avg: 4.7 g C kg-1 soil). A similar trend was found for soil total N content. Enzyme activities involved in nutrient cycling such as '-glucosidase, '-glucosaminidase, arylsulfatase, acid phosphatase, alkaline phosphatase, and phosphodiesterase activities were higher in soils under PtPtPt than under PtPtCt and CtCtPt in all sampling dates. In June and September, the activities of the phosphatases and arylsulfatase showed this significant (P<0.05) trend: PtPtPt> PtPtCt>CtCtPt. Soil microbial biomass C and N were generally higher in PtPtPt and PtPtCt compared to CtCtPt. Same trend was found for potentially mineralizable N and it was correlated to Nmic (r >0.47*) in April. The higher microbial biomass and enzyme activities in soils under continuous peanut are not in agreement with the sustainability problems of continuous monoculture systems (i.e., higher plant pathogens, lower yields). However, there was also an enhancement of the soil chemical, microbial, and biochemical properties investigated under the rotation with two consecutive years of peanut (PtPtCt) compared to the rotation with only one year of peanut (CtCtPt).