Due to the growing population and consequent pressure of use, agricultural soils must maintain adequate levels of quantity and quality to produce food, fiber, and energy, without falling victim to a negative impact on their balance of nutrients, health, or their ability to function

The correct use of closed field chambers to determine N2O emissions requires defining the time of day that best represents the daily mean N2O flux. A short-term field experiment was carried out on a Mollisol soil, on which annual crops were grown under no-till management in the Pampa Ondulada of Argentina. The N2O emission rates were measured every 3 h for three consecutive days. Fluxes ranged from 62.58 to 145.99 ∝g N-N2O m-2 h-1 (average of five field chambers) and were negatively related (R² = 0.34, p < 0.01) to topsoil temperature (14 - 20 ºC). N2O emission rates measured between 9:00 and 12:00 am presented a high relationship to daily mean N2O flux (R² = 0.87, p < 0.01), showing that, in the study region, sampling in the mornings is preferable for GHG.

Information about abiotic regeneration of air-filled porosity in silty soils is scarce. It could be a key mechanism to explain their low physical resilience. In the present work, we aim at evaluating whether changes in intrinsic soil properties (e.g., soil organic carbon, clay content, and clay mineralogy) caused by degradation affected soil volume response to wetting-drying cycles. Volume and size distribution of cracks and clod shrinkage curves were determined in silty loamy soils (Typic Argiudoll) of Argentina under nearby conventionally tilled (CT), eroded CT, and Pasture management. Crack volume increased from 1000 cm³ in CT and Pasture soils to 6000 cm³ in the more clayey and swelling eroded CT soil. Crack size distribution was similar in all studied soils with large cracks (first and second size order) prevailing over small ones (fourth and fifth size order). Clod shrinkage curves had no S-shape, thus showing the lack of structural shrinkage in all studied soil management regimens. Air content in structural pores was as low as 0.03 to 0.10 cm³ g⁻¹ at the air entry point. This little air entry during drying agreed with the lack of small cracks and can be related to the prevalence of plasma (i.e., silt and clay) over sand. Results showed that key intrinsic properties did not drive soil volume changes in the studied silty loamy soils. They change their volume during drying, but the creation of air-filled structural pores is little or null. ABBREVIATIONS: A_Cr: area of the crack calculated from its width and length; AE: air entry; Airp: air content of the plasma; Airstr (AE): air content of structural porosity at the air entry transition point; Air_str (SAT): air content of structural porosity at saturation; CT: conventionally tilled; Cter: eroded conventionally tilled; D_Cr: depth of the crack; Id: density of cracks; K_Bs: slope of the basic shrinkage; K_R: slope of the residual shrinkage; K_Str: slope of the structural shrinkage; L_Cr: length of the crack; ML: macroporosity limit; MS: aximum swelling; PD: particle density; S: surface of the pot; SC: swelling capacity of the soil from saturation to the shrinkage limit transition point; ShC: shrinkage curve of the soil; SL: shrinkage limit; Subang Bk: subangular blocks; V: bulk specific volume; V_AE: specific volume at the air entry transition point; V_Cr: specific volume of the crack calculated from its area and depth; V_ML: specific volume at the macropore limit transition point; V_MS: specific volume at the maximum swelling transition point; V_P(AE): plasma porosity at the air entry transition point; V_p(ML): plasma porosity at the macropore limit transition point; V_p(MS): plasma porosity at the maximum swelling transition point; V_p(SL): plasma porosity at the shrinkage limit transition point; V_SL: specific volume at the shrinkage limit transition point; V_str(AE): structural porosity at the air entry transition point; V_str(ML): structural porosity at the macropore limit transition point; V_str(MS): structural porosity at the maximum swelling transition point; V_str(SL): structural porosity at the shrinkage limit transition point; W: gravimetric water content; W_AE: gravimetric water content at the air entry transition point; W_Cr: width of the crack; W/D cycles: soil wetting and drying cycles; W_ML: gravimetric water content at the macropore limit transition point; W_MS: gravimetric water content at the maximum swelling transition point; W_p: water content in the plasma porosity; W range (SAT-SL): gravimetric water content range from saturation to the shrinkage limit transition point; W_SL: gravimetric water content at the shrinkage limit transition point; W_Str: water content in the structural porosity; φ_ML: bulk density at the macropore limit transition point; φ_MS: bulk density at the maximum swelling transition point; φ_SAT: bulk density at saturation; φ_SL: bulk density at the shrinkage limit transition point.

South America covers a vast area with diverse climates and landscapes, with high participation in the global production of food and fibers. It is crucial to understand the risks, vulnerabilities, and opportunities that climate change brings to this region. We analyzed the increasing tension between agribusiness models and smallholder models, the risks, opportunities, and main adaptation measures that can be adopted in the agricultural sector of the South American countries facing climate change. This study is a review of [...] ABSTRACT South America covers a vast area with diverse climates and landscapes, with high participation in the global production of food and fibers. It is crucial to understand the risks, vulnerabilities, and opportunities that climate change brings to this region. We analyzed the increasing tension between agribusiness models and smallholder models, the risks, opportunities, and main adaptation measures that can be adopted in the agricultural sector of the South American countries facing climate change. This study is a review of

Maize root growth is negatively affected by compacted layers in the surface (e.g. agricultural traffic) and subsoil layers (e.g. claypans). Both kinds of soil mechanical impedances often coexist in maize fields, but the combined effects on root growth have seldom been studied. Soil physical properties and maize root abundance were determined in three different soils of the Rolling Pampa of Argentina, in conventionally-tilled (CT) and zero-tilled (ZT) fields cultivated with maize. In the soil with a light Bt horizon (loamy Typic Argiudoll, Chivilcoy site), induced plough pans were detected in CT plots at a depth of 0-0.12 m through significant increases in bulk density (1.15 to 1.27 Mg m-3) and cone (tip angle of 60 º) penetrometer resistance (7.18 to 9.37 MPa in summer from ZT to CT, respectively). This caused a reduction in maize root abundance of 40-80 % in CT compared to ZT plots below the induced pans. Two of the studied soils had hard-structured Bt horizons (clay pans), but in only one of them (silty clay loam Abruptic Argiudoll, Villa Lía site) the expected penetrometer resistance increases (up to 9 MPa) were observed with depth. In the other clay pan soil (silty clay loam Vertic Argiudoll, Pérez Millán site), penetrometer resistance did not increase with depth but reached 14.5 MPa at 0.075 and 0.2 m depth in CT and ZT plots, respectively. However, maize root abundance was stratified in the first 0.2 m at the Villa Lía and Pérez Millán sites. There, the hard Bt horizons did not represent an absolute but a relative mechanical impedance to maize roots, by the observed root clumping through desiccation cracks.