Artículos y presentaciones en Congresos
- ArtículoAcceso AbiertoSoil survey reveals a positive relationship between aggregate stability and anaerobically mineralizable nitrogen(2020)Soil health status should be monitored to allow planning sustainable management, but indicators available do not encourage frequent soil health evaluation because of the complexity, time-consumption, and expensiveness of the methodologies. Aggregate stability (AS) is a good soil physical health indicator associated with soil (SOC) and particulate (POC) organic carbon but is difficult to monitor. Anaerobically mineralizable nitrogen (AN) has been proposed as soil health indicator because is cheap, simple, and safe to measure, is sensitive to soil-use changes, is also related to soil (SOC) and particulate (POC) organic carbon, and is frequently determined by farmers in Mollisols of the Southeastern Argentinean Pampas to support soil fertility diagnosis. We hypothesize that AN is positively related to and can be used as indicator of AS. Soil samples were taken at 0–5 and 5–20 cm depths from 46 sites throughout the southeastern Buenos Aires province, Argentinean Pampas. In each site, we sampled Mollisols under continuous cropping (CC) and others that had not been disturbed for many years (pseudo-pristine, PRIS). We determined texture, SOC, mineral-associated organic C, POC, AS and AN. We also calculated variable values for 0–20 cm. Soil organic carbon, POC, AN and AS were reduced by continuous cropping. Anaerobically mineralizable N was positively related to SOC (R2 = 0.74, 0.46, and 0.62 at 0–5, 5–20, and 0–20 cm) and POC (R2 = 0.73, 0.33, and 0.60, respectively). An important proportion of the total variability in AS was explained by SOC (R2 = 0.77, 0.65, and 0.73 at 0–5, 5–20, and 0–20 cm, respectively), POC (R2 = 0.75, 0.63, and 0.73, respectively), and AN (R2 = 0.78, 0.69, and 0.81, respectively). The AS increased with the increase of SOC, POC, and AN at all three depths, with slopes that did not differ between CC and PRIS, but with intercepts that differed. Neither sand nor clay contents significantly contributed to explain the variations in AS as a function of SOC, POC, and AN. An independent validation of the regression model relating AS and AN at 0–20 cm was done and the output was very good (RPIQ (ratio of performance to interquartile distance) = 2.20). Results support our hypothesis because AN was positively related to AS. Consequently, AN would be a good indicator of AS, SOC, and POC. Based on our results, we consider that a simple and cheap soil analysis as AN can not only be used to diagnose soil fertility, but to monitor soil physical and biochemical health status.
- ArtículoAcceso AbiertoAnaerobically mineralized nitrogen within macroaggregates as a soil health indicator(2021)Anaerobically mineralized nitrogen (AN) in bulk soil (ANBS) has been described as a soil health indicator. Considering that large macroaggregates (2000–8000 μm, MA) are more sensitive to management practices than the bulk soil (i.e. whole soil), AN within MA (ANMA) would be a better soil health indicator than ANBS. The aim of this study was to evaluate if ANMA is a better indicator of: i) soil organic carbon (SOC) and particulate organic carbon (POC) in bulk soil (SOCBS and POCBS, respectively) and ii) aggregate stability (AS) than ANBS. Soil samples were taken at 0–5 and 5–20 cm from 46 continuously cultivated plots (CC) and a reference plot for each CC (pseudo-pristine, PRIS). These soils, located in the Argentinean Pampas, were classified as Mollisols with contrasting surface textural classes. The AS, SOCBS, POCBS, ANBS, SOC (SOCMA), and POC (POCMA) within MA and ANMA were determined separately at 0–5 and 5–20 cm soil depths and estimated at the 0–20 cm layer. The ANMA was a good indicator of SOCBS (R2 0.75, 0.48, and 0.61 at 0–5, 5–20 and 0–20 cm depths, respectively), POCBS (R2 0.66, 0.31, and 0.49, respectively), and AS (R2 0.80, 0.68, and 0.76, respectively). The ANMA performed similarly to predict SOCBS, POCBS, and AS as compared to ANBS, because ANMA was closely correlated to ANBS (r 0.90 at 0–20 cm). Since ANMA determination is more time-consuming than ANBS determination, its use as a soil health indicator would not be convenient. Therefore, the use of ANBS would be recommended over ANMA as a variable to monitor soil health.
- ArtículoAcceso AbiertoSimplifying the Determination of Aggregate Stability Indicators of Mollisols(2020)Aggregate stability (AS) is a very sensitive soil physical health indicator. The complexity of its determination discourages frequent monitoring. We hypothesized that a reduction of steps to determine AS would yield good AS indicators. We evaluated 196 samples from a range of Mollisols from sandy- to clay-loam surface texture from the southeastern Buenos Aires province, Argentina. Six AS indicators were evaluated: aggregate mean weight diameter (MWD) after capillary wetting (CW) (MWDCW), MWD after sudden immersion in water (VW) (MWDVW), change of MWD (ΔMWD), remnant mass of macroaggregates (MAm) after CW (MAmCW), MAm after VW (MAmVW), and change of MAm between VW and CW (ΔMAmVW-CW). Determining ΔMWD requires six sievings, MWD requires three, ΔMAmVW-CW requires two, and MAm requires only one. Indicators after CW (MWDCW and MAmCW) were not good AS indicators. Likewise, those determined as a difference between CW and VW (ΔMWD and ΔMAmVW-CW) failed to distinguish contrasting AS situations making them unfeasible as universal AS indicators. However, MAmVW explained 99% of MWDVW variability and adequately distinguished among AS situations. With only one sieving, a good indicator of AS could be obtained, and this would encourage the adoption by soil testing laboratories and frequent soil physical health monitoring by farmers.
- ArtículoRestringidoNitrogen mineralized in anaerobiosis as indicator of soil aggregate stability(2020)Monitoring soil health status is imperative to pursue sustainable agriculture. Aggregate stability (AS) is fundamental to define several soil functions and, therefore, physical soil health. The objectives of thisworkwere to (i) evaluate the effect of contrasting cropping systems on AS, soil (SOC) and particulate (POC) organic carbon, and anaerobic nitrogen (AN) both in bulk soil and in macroaggregates (MA), and (ii) assess the relationship between AS and AN both in bulk soil and in MA to facilitate soil physical health monitoring. Aggregate stability, AN, SOC and POC were evaluated at three depths (0–5, 5–20, and 0–20 cm) in a Mollisol of the Southeastern Argentinean Pampas under a long-term experiment of cropping systems (crop-pasture rotations under conventional tillage [CT] and no-tillage [NT]). Bulk-soil SOC and POC contents and AN showed the effect of cropping systems, especially the effect of crop-pasture rotation and at 0–5 cm depth. However, NT did not lead to SOC sequestration except at 0–5 cm depth. In turn, pastures in the rotation and NT improved AS. Bulk-soil AN explained 75, 41, and 71% of AS at 0–5, 5–20, and 0–20 cm depths, respectively, and provides an indication of AS status. Instead, AN in MA did not explain bulk-soil AS changes as much as bulk-soil AN, except at 0–5 cm depth. Therefore, it is not worth determining AN in MA. However, routine bulk-soil AN determination at 0–20 cm depth by producers to diagnose nitrogen soil fertility would also provide an additional valuable indication of AS status.
- ArtículoAcceso AbiertoCarbono extraíble en agua caliente como indicador de salud de molisoles del sudeste bonaerense(2020)Una agricultura sustentable requiere indicadores tempranos del estado de salud edáfica (ISE). Se necesitan variables fácilmente medibles como el carbono extraíble en agua caliente (CAC) para favorecer su uso. El objetivo fue evaluar el CAC como ISE analizando: i) la magnitud de los cambios en CAC producidos por el uso agrícola, en comparación con los producidos en el COT y en el COP, y ii) la relación entre CAC, COP, COT, nitrógeno de amonio producido durante incubaciones anaeróbicas cortas (NAN) con estabilidad de los agregados. Se analizaron muestras de suelo (0-5 y 5-20 cm) de 32 lotes de producción (LP) y situaciones seudoprístinas (SP) localizados en el sudeste bonaerense. Se determinó: densidad aparente (DA), cambio en el diámetro medio ponderado de los agregados (CDMP), COT, COP, NAN y CAC. En 0-20 cm, el CAC varió entre 0,69 y 1,41 g kg-1 para los LP y entre 0,75 y 2,36 g kg-1 para las SP, representando, en promedio, 3,23% y 3,57% del COT, respectivamente. Se relacionó negativamente con la DA y el CDMP, y positivamente con COT y COP expresados como stock referidos a una masa equivalente (COTME y COPME, respectivamente) y con NAN. Además, el CAC en los LP cayó 35%, respecto a las SP, y COPME y COTME cayeron 62% y 25%, respectivamente. El CAC podría utilizarse como ISE, ya que fue sensible a los cambios por el uso agrícola del suelo y se relacionó con otras propiedades edáficas utilizadas como ISE. Su determinación es sencilla, rápida y económica, favoreciendo su adopción por los laboratorios de análisis.