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Context. Sustainable management of the soil is one of the pillars of conservation agriculture (CA). Aims. The objective of this study was to evaluate the long-term effects of soil management systems (SMS) on liming efficiency, soil chemical properties and wheat yield. Methods. This study was part of a long-term experiment established in 1986 in Passo Fundo, Rio Grande do Sul, Brazil, but using data from 2008 to 2015 to explore the effects of agricultural lime applied in 2008. The experiment was laid out in a split-plot design where the main plot (SMS) were arranged in randomised blocks and the cropping systems (sub-plot treatments) were randomised within the main plots. This study assessed the effects of the SMS; i.e. two CA systems [no-tillage (NT) and reduced tillage] and two conventional tillage (CT) systems (disk ploughing + disk harrowing annually, and mouldboard ploughing + disk harrowing annually). Key results. The NT system was the most sustainable due to improvements in soil organic carbon concentration. After liming, CT systems were more effective than CA systems in decreasing [Al.sup.3+] toxicity and increasing soil pH and [Ca.sup.2+] and [Mg.sup.2+] concentrations at deeper soil layers. The NT system had a considerable advantage over other SMS, due to a greater average wheat yield (18%). Conclusions. The SMS evaluated in this study modified chemical properties when compared with the native forest area. The NT system was the least detrimental to soil organic carbon, an important indicator of soil quality. Implications. The NT system provided greater average wheat yield (18%), and thus was the most viable SMS for subtropical spring wheat production. Keywords: aluminium toxicity, conservation agriculture, exchangeable calcium, exchangeable magnesium, no-till, Rhodic Ferralsol, soil management, soil organic carbon, subsoil acidity., Introduction Soil degradation [i.e. decreases in soil organic carbon (SOC), increases in soil compaction, acidification and erosion] is one of the consequences of transitioning forests and grasslands into agricultural production [...]

Quantification of the impact of long-term agricultural land use on soil organic C (SOC) is important to farmers and policymakers, but few studies have characterized land use and management effects on SOC across physiographic regions. We measured the distribution and total stock of SOC to a depth of 20 cm under conventional tillage (CvT), conservation tillage (CsT), and pasture in 87 production fields from the Southern Piedmont and Coastal Plain Major Land Resource Areas. Across locations, SOC at a depth of 0 to 20 cm was: pasture (38.9 Mg [ha.sup.-1]) > CsT (27.9 Mg [ha.sup.-1]) > CvT (22.2 Mg [ha.sup.-1]) (P [less than or equal to] 0.02). Variation in SOC was explained by management (41.6%), surface horizon clay content (5.2%), and mean annual temperature (1.0%). Higher day content and cooler temperature contributed to higher SOC. Management affected SOC primarily at the soil surface (0-5 cm). All SOC fractions (i.e., total SOC, particulate organic C, soil microbial biomass C, and potential C mineralization) were strongly correlated across a diversity of soils and management systems (r = 0.85-0.96). The stratification ratio (concentration at the soil surface/concentration at a lower depth) of SOC fractions differed among management systems (P < 0.0001), and was 4.2 to 6.1 under pastures, 2.6 to 4.7 under CsT, and 1.4 to 2.4 under CvT; these results agree with a threshold value of 2 to distinguish historically degraded soils with improved soil conditions from degraded soils. This on-farm survey of SOC complements experimental data and shows that pastures and conservation tillage will lead to significant SOC sequestration throughout the region, resulting in improved soil quality and potential to mitigate C[O.sub.2] emissions. Abbreviations: CMIN, potential C mineralization; CsT, conservation tillage row cropping; CvT, conventional tillage row cropping; MLRA, Major Land Resource Area; MWD, mean-weight diameter; POC, particulate organic carbon; SMBC, soil microbial biomass carbon; SOC, soil organic C; SOM, soil organic matter.

Particulate organic matter (POM), an established soil quality indicator, is too costly for routine testing by analytical labs. Chemical oxidation of labile soil organic matter is less costly and may prove to be an equally effective indicator. The objectives of this study were to test the relationship between POM and chemically labile organic matter (CLOM) and to evaluate the effects of soil management on POM and CLOM. The study was conducted within a long-term crop rotation x fertility treatment study in central Pennsylvania. Crop rotation sequences were continuous corn (Zea mays L.), corn-soybean [Glycine max (L.) Merr.], 4 yr of corn followed by 4 yr of alfalfa hay (Medicago sativa L.), and corn-oat (Avena sativa L.)winter wheat (Triticum aestivum L.)-2 yr of red clover hay (Trifolium pratense L.). Fertilizer treatments were mineral fertilizer, N-based liquid dairy manure, and P-based liquid dairy manure. A significant linear relationship between POM-C and CLOM-C treatment means was observed (re = 0.74). Both POM-C and CLOM-C concentrations were greatest for manure-based fertility treatments and for crop rotations receiving the most frequent applications of manure. Only CLOM-C, however, distinguished between the N-based and P-based manure treatments. Further development of CLOM-C as a soil quality indicator may yield a reliable, cost-effective soil quality management tool. Abbreviations: CA, 4 yr of corn followed by 4 yr of alfalfa; CC, continuous corn; CLOM, chemically labile organic matter; COWH, corn-oat-wheat-2 yr of red clover hay; CS, corn-soybean; HRE, Hunter Rotation Experiment; MF, mineral fertilizer; POM, particulate organic matter; SOM, soil organic matter.

Losses of soil organic carbon (SOC) have contributed to C[O.sub.2] emissions from soils to the atmosphere and to global climate change. We hypothesized that in semiarid agroecosystems of the Mediterranean region, a shift from the traditional management system (including conventional tillage [CT] and a cereal-fallow rotation) to a more conservative system, including no-till (NT) and continuous cropping, could reduce C[O.sub.2] emissions during the cropping season. Thus, in this study, we studied the effects of tillage and cropping systems on C inputs and soil C[O.sub.2] fluxes during three cropping seasons at three different sites in the Ebro River valley (northeast Spain). Carbon inputs ranged from 650 to 6000 kg [ha.sup.-1] and seasonal average C[O.sub.2] flux ranged from 0.10 to 1.76 g C[O.sub.2] m-2 h-1. Differences in rainfall led to marked differences in C inputs and soil fluxes among growing seasons. Although differences among tillage treatments were weak, C[O.sub.2] fluxes under NT were always lower. Intensification of cropping systems led to an increase in C input. A move from CT to NT together with cropping intensification is suitable to increase C inputs and to reduce soil C[O.sub.2] fluxes in semiarid Mediterranean agroecosystems. Abbreviations: AG, Agramunt site; CF, cereal-fallow rotation; CT, conventional tillage; NT, no-till; PN, Penaflor site; PN-CC, continuous cropping system at the Penaflor site; PN-CF, cereal-fallow rotation at the Penaflor site; SV, Selvanera site.

The Soil Conservation Service curve number methodology (SCS-CN) has been used in hydrological and crop models to evaluate the effects of soil management in olive (Olea eurapaea L. subsp, europaea) orchards on runoff, erosion, and water balance. To our knowledge, it has never been calibrated or validated for olive orchards. A physically based runoffmodel for olive orchards at a hillslope scale was used to generate rainfall-runoff relationships for different scenarios of soil type (four), tree size (two), tree spacing (two), antecedent soil moisture (three), and soil management (11) for a 140-m-long and 5% steep hillslope. The resulting relationships were used to derive the values of the curve number parameter, [CN.sub.d], for the SCS-CN methodology. The resulting [CN.sub.d] values were validated using rainfall-runoff data for three different locations and different soil management. Predictions of daily runoff using [CN.sub.d] were compared with those made using CN values extracted from the standard SCS-CN tables, [CN.sub.SCS]. The derived [CN.sub.d] values presented a root mean square error in runoff predictions between 0.5 and 7.3 mm, and a model efficiency between 82 and 97%. The extracted [CN.sub.SCS] values presented a root mean square error in runoff predictions between 1.4 and 10.4 mm, and a model efficiency between -81 and 89%. Our analysis identified some issues in the hydrology of olive orchards where our understanding remains limited. Among them are the need for further validation of the derived CN values given the limited rainfall-runoff data, and the effect of soil management on soil properties and their temporal evolution. Abbreviations: CN, curve number; [CN.sub.bf], curve number values developed through fitting to the observed runoff data; [CN.sub.d], curve number values derived for olive orchards from the physically based model; [CN.sub.SCS], curve number values extracted for olive orchards from the Soil Conservation Service curve number tables; [CN.sub.I], curve number for dry antecedent soil moisture content; [CN.sub.II], curve number for average antecedent soil moisture content; [CN.sub.III], curve number for wet antecedent soil moisture content; CC, cover crop soil management; CT, conventional tillage soil management; NT, no-till; RR, random roughness; SCS-CN, Soil Conservation Service curve number methodology.

Moist-soil management of playas enhanced the production of seeds in aboveground willow smartweed, pink smartweed and barnyard grass. However, it did not influence the production of seeds and standing crop of curly dock, and reduced production of seeds and standing crop of spikerushes. Seed and standing crop production increased in 1990 as compared to 1989 figures as a result of effective moist-soil management.