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Soil biological activity (i.e. mineralized carbon (C) (Cmin)) is a crucial property to evaluate soil health and its changes due to soil use. In the southeastern Buenos Aires province (SEB) there is scarce information about how agriculture ecological intensification (IEA) affects soil global biological activity and the potentially mineralized C (C0) to improve the comprehension of the mechanisms that regulate soil C dynamics. It would be relevant to determine the adequate incubation time at which the determination of Cmin can predict C0 in soils from the SEB. Moreover, the Cmin determined in early incubation days has been proposed as a quick alternative to estimate C0. It has been hypothesized that it is necessary to run longer incubations to correctly evaluate C0 of soils of the SEB and that the CO2 emitted during short incubation periods is a good estimator of C0. Soil samples were taken (0-5 and 5-20 cm) from a long-term experiment on crop-pasture rotations on Mollisols at Balcarce with different levels of IEA under conventional tillage and no-tillage (SD). Total (COT), particulate (COP) and associated organic C were determined, as it was the Cmin from aerobic incubations under controlled conditions at 2, 4, 6, 10, 16, 22, 28, and 63 days. The C0 was estimated from the Cmin at 22, 28, and 63 days. The Cmin and C0 showed similar patterns among cropping systems. The estimations of C0 from the Cmin at 63 days were the most trustable (mean of C0 466,9 and 517,8 mg C kg-1 from Cmin(28) and Cmin(63), respectively). Furthermore, the Cmin at a few days of incubation showed high correlation coefficients with C0 (r between 0.68 and 0.92 at 0-20 cm for 2 to 10 incubation days) and therefore short incubations would be promising to estimate C0. [ABSTRACT FROM AUTHOR]

Soil health is related to aggregate stability (EA) and, therefore, it is important to monitor its status frequently. The methods to do this should simulate the disruption forces that occur in the soil, ought to be sensitive and fast, and would have to be usable for different soil conditions. There is not agreement about the best methodology for the loam and high-organic-matter soils of the Southeastern Buenos Aires province (SEB). The objective of this work was to evaluate three laboratory methods to determine EA. Four soil use and management situations of a Typic Argiudoll soil were selected: a) park, b) continuous cropping under no-tillage, c) continuous cropping under conventional tillage, and d) degraded soil. Soil samples were taken at 0-5 and 5-20 cm and their EA was determined through: M1: Six et al. (1998); M2: De Leenher & De Boodt (1958) modified by Suero & Garay (1978), y M3: Le Bissonnais (1996). Soil total (COT), particulate (COP), and mineral-associated (COA) organic carbon were also determined. Results are shown for 0-5, 5-20, and 0-20 cm layers. The EA determined through all three methods showed a highly significant correlation with COT and COP for all three depths (r 0.91-0.98). All the methods required approximately the same time to obtain the final result of each sample. Besides, their results highly correlated with the results of each other (r 0.86-0.98). However, methods M1 and M2 allowed distinguishing soil use and management situations more sensitively than M3. Therefore, it is recommended to use either M1 or M2 for specific studies of EA on soils of the SEB with loam surface texture. Nevertheless, it is necessary to evaluate the performance of these methods for a broader range of textural classes and management situation to be able to confirm this. [ABSTRACT FROM AUTHOR]

Tillage systems (SL) are a fundamental tool in agriculture since they allow manipulating the soil to achieve the necessary conditions for crop growth and development. The objective of this work was to evaluate the effect of different SL on bulk density (DA), mechanical penetration resistance (RMP), infiltration rate (VI) and aggregate stability (EA) of a Mollisol in the southeastern Buenos Aires province. Soil samples and determinations were taken in a long-term SL experiment carried out at Balcarce, Southeastern Buenos Aires Province. Five SL were evaluated: conventional tillage (LC), no-tillage (SD), combined tillage (Lcom), vertical tillage (LV) and disk tillage (LD). Bulk density was the lowest under Lcom and the highest under LD at 5-20 cm depth, but there were no differences between SL in the upper 5 cm. Infiltration rate was not affected by SL. Mechanical penetration resistance was higher under SD from 2.5 cm up to 10 cm depth, being higher under LD beyond that depth. Conventional tillage and Lcom did not show significant differences in RMP at any of the analyzed depths. Both LC and Lcom showed lower RMP than SD from 2.5 cm to 20 cm depth. At the 0-5 cm depth, LC presented lower EA than the other SL (which did not differ among them). Although the decrease in EA was not as marked as the increase in the degree of disturbance, less aggressive SL such as SD, Lcom and LD showed higher EA as compared to LC. [ABSTRACT FROM AUTHOR]

Green bridge crops (CPV) effect on soil and succeeding cash crops depends on the type of CPV and on how their residues decompose. We hypothesized that 1) decomposition rate of grass CPV is lower than that of legume CPV; 2) decomposition dynamics of CPV legume will lead to a higher and faster availability of nitrogen (N); and 3) residue decomposition will lead to a higher but delayed increase of labile soil organic matter fractions with grass CPV and when located on soil surface. We carried out an experiment on a Typic Argiudoll with CPV with oats (Avena sativa L.), vetch (Vicia villosa Roth.) and a control without CPV (TE). Equal amounts of chopped residues of both CPV were placed on surface and mixed with soil (buried). We took soil samples at 0-20 cm in 7 moments along 133 days to determine remnant residue (CR), carbon (C), total (COT), and particulate organic C (COP), ammonium N freed in anaerobiosis (NAN), and nitrate N (N-NO3 -). Remnant C of both CPV decreased over time, but at a higher rate when buried with differences between vetch and oats. On surface, vetch residues decomposed faster than oats residues, at the end of the experiment, 60 and 79% of the residues, respectively, had decomposed. Neither COT, COP, nor NAN changed along the experiment. After oats, COT and COP (75.1 y 18.6 Mg ha-1, respectively) were higher than after vetch and TE (70.4 y 16.8 Mg ha-1, respectively). Besides, these were lower when residues were buried (69.7 y 15.,9 Mg ha-1, respectively) than when residues were left on surface (73.3 y 18.9 Mg ha-1, respectively). The position of residues did not affect NAN, but it was higher after oats and vetch (63.1 mg kg-1) than after TE (50.2 mg kg-1). Up to 49 days from the start of the experiment there was an increase of N-NO3 - (45 up to 108 kg ha-1). N-NO3 - was higher when CPV was vetch and there was no difference between oats and TE. We did no collect enough evidence to reject the first and the second hypothesis, but evidences were enough to reject the third one. [ABSTRACT FROM AUTHOR]

An alternative to pursue a soil physical property improvement is including cover/green manure crops (CP) between two cash crops in a crop sequence. The objective of this work was to evaluate the effect of using contrasting tillage systems (SL) and a CP on some soil physical properties of a Mollisol in the SEB. Soil samples and determinations were taken in a longterm SL experiment carried out in Balcarce. The factor CP was assigned to sub-sub-plots with two levels: with (Con V) and without (Sin V) vetch (V) (Vicia villosa Roth) preceded by corn (Zea mays L.) since 2008. Bulk density, EA, INF and RMP were determined after corn harvest. Aggregate stability decreased with the increase of tillage aggressiveness. No-tillage led to higher EA at the upper 5 cm with respect to LD and LC. On the other hand, at 5-20 cm, SD showed higher EA than LC but without difference with LD. Under SD, RMP in the first 10 cm of the soil layer it was higher than under LD and LC, but between 10 and 20 cm depth a sharp increase under LD was observed. Contrary to what was expected, DAP was higher under LC than under LD and SD in the upper 5 cm of soil, but there were no differences among SL at 5-20 cm depth. Infiltration rate was not significantly affected by SL. The inclusion of V as CP increased INF under all SL and decreased RMP under SD. However, the CP did not affect DAP nor EA. The soil loosening degree with tillage did not diminish DAP and did not increase INF. The V as CP improved INF. [ABSTRACT FROM AUTHOR]