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Intensive agricultural practices have resulted in progressive soil degradation, with consequences on soil ecosystem services. The inclusion of service crops is a promising alternative to support the sustainability of the agricultural system. The aim of this study was to analyze in a six-year field experiment the effect of Brachiaria brizantha (perennial tropical grass) and Zea mays as service crops in a degraded common bean monoculture system in northwest Argentina. After six years, service crop treatments revealed a significant increase in most physical, chemical and biological properties of the soil (enzyme activities, microbial biomass, respiration and glomalin-related soil protein), compared with common bean monoculture. Also, a lower disease incidence was observed under B. brizantha treatments, associated with increased populations of Trichoderma spp. and Gliocladium spp. The phospholipid fatty acid profiles detected higher values of total microbial biomass under service crops. Our results suggest that the inclusion of several cycles of B. brizantha constitutes a promising soil management for recovering degraded agroecosystems. [ABSTRACT FROM AUTHOR]

Three sites were selected for the present study: native forest (FR), an agricultural land subjected to minimum water erosion by terracing farming (ARMN), and an agricultural land subjected to moderate water erosion without terracing farming (ARMD). Conversion of forest to agricultural land significantly affected soil physicochemical properties. The lowest contents of both humic and fulvic acids were registered in the ARMD site, while the highest was observed in FR. The site with moderate water erosion showed a decrease of total microbial activity as estimated by fluorescein diacetate activity (FDA), but an increase of dehydrogenase activity. Both C-related enzyme activities glucuronidase and glucosidase as estimated by fluorogenic methylumbelliferil (MUF)-substrates were also reduced in ARMD, with moderate values in ARMN site, and high values in FR. Our study revealed that ARMD had the mean microbial biomass estimated by phospholipid fatty acid (PLFA) profiles. Furthermore, the ARMD site showed the highest Gram-positive to Gram-negative ratio, suggesting that moderate water erosion may also affect soil microbial community structure. The results of the present research have important implications for the study of deforestation under sites subjected to water erosion, which is one of the most significant ecological changes facing in central Argentina and the world. [ABSTRACT FROM AUTHOR]

Abstract: Argentina is the world’s third most important soybean producer; hence, there is an urgent need to preserve soil health by applying appropriate agricultural practices to maintain sustainable production in the upcoming years. Because productivity of agricultural systems largely depends on soil microbial processes, the influence of different management strategies on soil microbial community structure was analyzed in a long-term field trial started in 1992. The experimental design was a split-plot arrangement of treatments, consisting in two tillage treatments: zero tillage (ZT) and reduced tillage (RT), in combination with two crop rotation treatments: soybean monoculture (SS) and corn-soybean (CS). Phospholipid fatty acid (PLFA) profiles were used to assess total microbial community structure. Denaturing gradient gel electrophoresis (DGGE) profiles of 18S rRNA were generated to describe the influence of crop practices on fungal communities. Total PLFA content was lowest in soil under reduced tillage and soybean monoculture; therefore the use of reduced tillage-soybean monoculture in agroecosystems might produce important reductions in total microbial biomass. The structure of total microbial communities, as estimated by PLFA, was affected by crop rotation. Moreover, the fungal communities, as estimated by DGGE analysis, were influenced by combined effects of crop rotation and tillage system. [ABSTRACT FROM AUTHOR]

The expansion of the common bean monoculture system along with intensive agricultural practices focused on productivity has generated a misuse of natural resources, accompanied by a significant decline of the soil ecosystem services. The aim of this study was to analyze the short-term effect (3 years) of the inclusion of different cover crops (legumes, non-legumes and mixtures) on the physicochemical, biological properties and crop yield in a degraded common bean monoculture system in the north region of Argentina. The inclusion of legumes (vetch and melilotus) and non-legumes (oat and wheat) as sole cover crops over three consecutive years significantly increased the abundance of the main microbial groups, microbial biomass C and N (MBC and MBN) and the activity of the common bean rhizosphere microbial community, which resulted into a fast improvement of soil quality and rhizosphere microbiota compared with bean monoculture. However, mixed cover crops (oat + vetch) had a positive but lower impact on rhizosphere microbial community abundance compared to legume or non-legume cover crops when used as sole cover crops. The information generated in this study will contribute to the evaluation of the inclusion of specific cover crops as a conservation strategy to recover soil health and minimize soil degradation, while maintaining crop yields. • Three-years of cover crops improved soil quality and crop yields of a common bean monoculture. • The inclusion of cover crops increased C and N soil stocks by more than 50% of a common bean monoculture. • Microbial biomass and soil enzyme activities were enhanced by cover crops inclusion. • Mixed cover crops had lower benefits on soil quality compared to legume and non-legume cover crops used as sole crops. [ABSTRACT FROM AUTHOR]