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Highlights: [•] SSP application with seed had less detrimental effect on PSA as compared with MAP. [•] PSA was directly related with clay content, and negatively related with silt content when using MAP. [•] Broadcast as well as side-banded application of SSP and MAP had no damaging effects on PSA. [•] Reduction in PSA did not affect seed yield, suggesting a high capacity of soybean to compensate plant loss. [•] Nodule weight and number were severely affected by application of MAP with seed. [ABSTRACT FROM AUTHOR]

Abstract: Sulfur (S) fertilization has increasingly become an important issue in crop management. In Argentina S deficiencies have been reported, but there has been no success in finding soil tests for predicting soybean response to S fertilization. The objectives of this study were to: (i) evaluate seed S and N:S ratio as a tool for identifying S deficient soybean crops in field conditions and (ii) determine shifts in stoichiometric relationships among nitrogen (N), phosphorus (P) and S in soybean seeds which can be used for identifying S responsive sites under field conditions. Seed samples from 20 field experiments designed to explore response to S fertilization in soybean were collected in a large area in the Argentinean Pampas region. Seed yield (SY) and P (%P), S (%S) and N (%N) concentration in seeds were determined. Different data analyses were tested in order to find an S deficiency index. Moderate SY responses to S fertilization were observed in the present study (i.e. relative SY was never below 75%). seed S concentration increased in response to S fertilization in most responsive sites, and N:S ratio was governed by variations in seed S concentration. Stoichiometric relationships were more accurate for identifying S responsive sites than using single variables (e.g. seed S concentration or N:S). The isometric variations among N, P and S suggest that the accumulation of these nutrients is proportional in seed tissue. A significant increase in the intercept of the stoichiometric relationship between N and S in S deficient crops was observed. An S deficient index (SDI) was calculated based on this difference that can be used as a diagnostic tool for identifying S responsive sites in soybean. The present study shows a novel approach for using stoichiometric concepts in fertilizer management in soybean. [Copyright &y& Elsevier]

• Intensification practices (polyculture, cover crop, fertilization) were assessed. • Intensification increased AS in more than 50% as compared with soybean monoculture. • BD was mostly unaffected by intensification practices. • Soil degradation status influenced intensification practices effects on AS. Soybean (Glycine max (L.) Merr.) monoculture contributes to soil degradation. Intensification of soybean-based sequences through polyculture, cover crops (CC), and crop fertilization can enhance soil physical quality and help mitigate its degradation. We assessed the effect of intensification practices in cropping sequences with soybean predominance on soil physical quality indicators in contrasting soils. Treatments included soybean monoculture with and without phosphorus (P) and sulfur (S) fertilization, CC/PS-fertilized soybean, nitrogen (N)-fertilized CC/PS-fertilized soybean and NPS-fertilized crop rotation including wheat, corn, soybean and CC. Four long-term experiments (10 yr) were established in sites with contrasting edaphoclimatic conditions, and initial soil organic carbon (SOC), where we evaluated bulk density (BD) and aggregate stability (AS). The BD was mostly unaffected by treatments, whereas AS responded to intensification practices at all sites, increasing over 50% as compared with soybean monoculture. Differences in BD and AS among sites were mostly explained by soil texture and initial SOC. On the contrary, AS differences among treatments were not driven by texture, but by the soil degradation at the beginning of the experiments (calculated as the ratio between SOC when experiments were established and the SOC of pristine soil). Therefore, regardless of soil texture, more degraded soils responded to a greater extent to intensification practices in soybean-based rotations. [ABSTRACT FROM AUTHOR]

• We assessed cover crops (CC) and fertilization effects on N and S. • CC increased soil organic N and S (N org and S org) as compared with soybean monoculture. • Texture, climate and CC dry matter explained the magnitude of N org and S org increase. • CC inclusion and soybean fertilization increased the potentially mineralizable N. Nitrogen (N) and sulfur (S) define crops productivity, and are currently deficient in most agricultural soils. In agricultural systems, management practices can affect N and S organic pools (N org and S org , respectively). The objective of our study was to assess how intensification practices [use of grasses as cover crops (CC) and/or fertilization] affect N org and S org , anaerobic N (N an), and carbon (C)/N and C/S ratios as compared with soybean [ Glycine max (L.) Merr.] monoculture, in soils under no tillage, with contrasting edaphoclimatic conditions. The experiment was carried out in four long term experiments (> 10 yr), where four treatments were evaluated: control (soybean monoculture (Sb)), soybean monoculture fertilized with phosphorus (P) and S (Sbf), CC / soybean (Sb/CC), and CC / P + S-fertilized soybean (Sbf/CC). The inclusion of CC increased N org and S org as compared to Sb (from 20 % to 30 % for N org , and from 16 % to 18 % for S org) at 0−5 cm.The magnitude of the effect of CC increase on N org was positively associated with temperature, clay + silt and crops dry matter, whereas the increase in S org was positively associated with precipitation, clay + silt, and crops dry matter. The N an improved over 50 % due to the inclusion of CC. Also, at two sites P + S-fertilization improved N an (37 %) as compared with Sb. Our results suggest that intensification practices (CC and PS-fertilization) result in an accumulation of readily available N and S organic fractions, which can have a potential positive impact on the productivity of other crops in the cropping sequence. However, as previously mentioned, the magnitude of that positive effect will depend on the edaphoclimatic characteristics of each site. [ABSTRACT FROM AUTHOR]

• We assessed polyculture, cover crop and fertilization as intensification practices. • Intensification did not prevent SOC loss due to agriculture but reduced its rate. • Intensification effects on SOC were influenced by the soil degradation status. • Carbon input and climate also influenced the SOC depletion caused by agriculture. • The SOC loss was 26–65% lower in intensified crop sequences. In environments where continuous agriculture leads to soil organic carbon (SOC) depletion, intensification practices (i.e. polyculture, cover crops (CC), and crop fertilization) have been suggested as strategies to improve crop residue inputs which, in turn, can increase SOC storage. However, SOC dynamics are regulated by a complex interplay of climatic and soil conditions. The objective of our study was to assess how intensification practices affect SOC, particulate organic carbon (POC) and SOC stratification ratio (SR SOC) as compared to soybean [ Glycine max (L.) Merr.] monoculture, in soils with contrasting soil properties and climate. The experiment was carried out in four long term experiments (>10 yr) located in areas with contrasting environments. The surface soil textures ranged from sandy-loam to silty-clay and clay-loam, initial SOC (0–20 cm) from 34.5 to 67.8 Mg ha−1, mean air temperature: 14.0–18.9 °C, annual precipitation: 719.8–886.1 mm. Five treatments were evaluated: soybean monoculture (SB), soybean monoculture fertilized with phosphorus (P) and sulfur (S) (SB PS), CC/PS-fertilized soybean (SB PS /CC), nitrogen (N)-fertilized CC/PS-fertilized soybean (SB PS /CC N) and NPS-fertilized crop rotation (ROT NPS). Intensification of crop sequences (SB PS /CC, SB PS /CCN and/or ROT NPS) increased SOC and POC at 0–5 cm and in SR SOC in most sites as compared to SB. All treatments showed SOC depletion as compared to the beginning of the experiment. However, the magnitude of SOC lost during 10 years was 26–65% lower when intensified crop sequences were applied as compared with SB. Carbon input and environment characteristics influenced the impact of intensification practices on the analyzed variables. However, this effect was mostly associated with the ratio between SOC at the beginning of the experiment and the SOC of pristine soil (degradation status). The intensification practices evaluated were not sufficient to reverse the tendency of agricultural soils to lose SOC, but they slowed the rate of this degradation process. [ABSTRACT FROM AUTHOR]