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Soil organic matter (SOM) and especially its labile fractions such as particulate organic matter (POM) are very sensitive to soil use and strongly influence soil ecosystem services. Particulate organic matter has been proposed as a soil quality/health indicator but its determination is tedious and time consuming (i.e. manhours). Anaerobic mineralizable nitrogen (AN) is closely related to the soil organic fraction and is very easily determined. Therefore, we proposed to evaluate AN as a soil quality/health indicator through the assessment of its relationship with SOM, POM, soil aggregate stability (AS), and maize (<em>Zea mays</em> L.) relative yield (RY) under different long term soil uses for cropping at Balcarce, Argentina (37º 45’ 14’’ S, 58º 17’ 52’’ W). Soil samples had been taken at two depths (0-5 and 5-20 cm) in the fall of 1998, 2000, 2003, 2006, 2009, and 2012 from a long term tillage system (TS, conventional (CT) and no-tillage (NT)) and nitrogen fertilization (NF, with and without nitrogen as fertilizer) experiment on a complex of Typic and Petrocalcic Argiudolls. Carbon contents in SOM (SOC), POM (POC) and AN were determined in all soil samples, whereas AS was determined in other soil samples taken in 2006, 2009 and 2012 from the arable layer (0-20 cm). Regardless of TS and NF, SOC, POC and AN decreased with time under cropping at both 5-20 and 0-20 cm. In the uppermost layer (0-5 cm) decreases of all three variables were observed only under CT. Anaerobically mineralized nitrogen variation related to SOC (R² 0.59 - 0.78, <em>P </em>&lt; 0.05) and especially POC (R² = 0.80-0.85, <em>P </em>&lt; 0.05) variations. Likewise, changes in maize RY related better (R² 0.92 and 0.95 (<em>P </em>&lt; 0.05) for CT and NT, respectively) to variation in AN, than to SOC and POC variations. Besides, changes in the aggregate mean weight diameter (DMWD) related acceptably to AN at 0-20 cm (R²= 0.67, <em>P </em>&lt; 0.05) and much better at 0-5 cm (R²= 0.86, <em>P </em>&lt; 0.05). Both coefficients of determination were higher than those obtained relating DMWD to SOC or POC. Given the easiness of its determination, its sensitivity, and that it relates to the variation of different key soil parameters and crop behavior, AN could be proposed as an effective soil quality/health indicator. However, studies should be carried out taking into account a broader range of soil and management situations in order to validate the trends observed in this work.

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 this work were 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.

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) (MWD CW ), MWD after sudden immersion in water (VW) (MWD VW ), change of MWD (ΔMWD), remnant mass of macroaggregates ( MAm) after CW (MAm CW ), MAm after VW (MAm VW ), and change of MAm between VW and CW (ΔMAm VW-CW ). Determining ΔMWD requires six sievings, MWD requires three, ΔMAm VW-CW requires two, and MAm requires only one. Indicators after CW (MWD CW and MAm CW ) were not good AS indicators. Likewise, those determined as a difference between CW and VW (ΔMWD and ΔMAm VW-CW ) failed to distinguish contrasting AS situations making them unfeasible as universal AS indicators. However, MAm VW explained 99% of MWD VW 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.

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