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The effects of different tillage systems on the properties and microbial diversity of an agricultural soil was investigated. In doing so, soil physical, chemical and biological properties were analysed in 2013-2015, on a long-term field experiment on a loamy sand at the IUNG-PIB Experimental Station in Grabów, Poland. Winter wheat was grown under two tillage treatments: conventional tillage using a mouldboard plough and traditional soil tillage equipment, and reduced tillage based on soil crushing-loosening equipment and a rigid-tine cultivator. Chopped wheat straw was used as a mulch on both treatments. Reduced tillage resulted in increased water content throughout the whole soil profile, in comparison with conventional tillage. Under reduced tillage, the content of readily dispersible clay was also reduced, and, therefore, soil stability was increased in the toplayers, compared with conventional tillage. In addition, the beneficial effects of reduced tillage were reflected in higher soil microbial activity as measured with dehydrogenases and hydrolysis of fluorescein diacetate, compared with conventional tillage. Moreover, the polimerase chain reaction - denaturing gradient gel electrophoresis analysis showed that soil under reduced tillage had greater diversity of microbial communities, compared with conventionally-tilled soil. Finally, reduced tillage increased organic matter content, stability in water and microbial diversity in the top layer of the soil. [ABSTRACT FROM AUTHOR]

Abstract: Tillage experiments were carried out in order to study the effect of water content on the aggregate size distribution produced by tillage, and to investigate the relationship between the soil structures produced by tillage and Dexter''s index of soil physical quality, S. Tillage with a mouldboard plough was done on four different soils over a range of naturally occurring water contents. The aggregate size distribution and the specific surface area produced by tillage were obtained by sieving. We define the optimum water content for tillage, θ OPT, as the water content at which the specific surface area of the aggregates produced is maximum. This is consistent with the water content at which the amount of small aggregates produced is greatest and the proportion of clods produced is smallest. For the four investigated soils, θ OPT was found to be close to the water content at the inflection point of the water retention curve, and in the vicinity of 0.8θ PL (where θ PL is the lower plastic limit). At water contents either lower or higher than θ OPT, the specific surface area produced was smaller. The specific surface area produced at θ OPT was found to be strongly correlated with the index of soil physical quality, S. The specific surface area produced is larger the greater S, i.e. the better the soil physical quality. Consistently, the proportion of small aggregates produced at θ OPT is larger and the proportion of clods produced at θ OPT smaller, the greater S. No clods (>50mm) are produced on soils with good physical quality. [Copyright &y& Elsevier]

Abstract: Compaction of tilled layers under the single effect of rainfall or irrigation was called slumping. Slumping affects strongly root development and plant biomass production. It has been observed in different soil types, but sandy soils appear particularly prone to this physical degradation. Our objectives in this study were (i) to measure in the field the changes in soil structure and water status simultaneously, (ii) to study the effects of rainfall and management practices on slumping, and (iii) to propose a conceptual model for sandy soil slumping. An experimental site was selected in Northeast Thailand and we studied the effect of tillage depth and initial water content on slumping dynamic. Plots (9m×15m each) were tilled at (i) two depths (20 and 40cm, called S and D respectively) in dry conditions, (ii) at 20cm depth in dry or wet conditions (called Y and W respectively). These plots were submitted to natural rainfall for 20 or 61 days to get different total rainfall amounts (114 and 212mm respectively). In addition, smaller plots (0.24m2 each) were used for experimental flooding irrigation (similar to measured rainfalls, i.e. 100 and 200mm). Soil bulk density, soil surface elevation, soil water content and matric potential were measured. A decrease in soil elevation was observed in all treatments. In the absence of erosion it was interpreted as a loss of porosity which resulted from slumping. Bulk density increased in all layers of the tilled profile (from 1.38 to 1.57gcm−3). In the surface layer (0–5cm) this increase was systematically higher compared to deeper layer. No significant difference in final bulk density was found between the S and W treatments, and between the Y and W treatments. Bulk density increased more rapidly in the Y and W treatments than in the S and D treatments, even though the cumulative rainfall was lower. After the flooding experiments, bulk density was higher than after natural rainfall despite similar amounts of water added to the soil. [Copyright &y& Elsevier]

Abstract: No-tillage has been adopted worldwide as a strategy to reduce the negative effects of soil erosion in conventional tillage. However, no-tillage can lead to over-compaction of the soil, which can have detrimental effects on soil structure and on crop yield. The objective of this study was to evaluate the soil physical functionality of a Rhodic Ferrasol under long-term no-tillage. The following physical properties were measured: dry bulk density (Db), total porosity (Pt) and macroporosity as well as saturated hydraulic conductivity (K sat) and intrinsic air permeability (K a). Physical quality of the soil was also evaluated by the S index at each depth increment. The study was carried out in a Rhodic Ferrasol under a 14-year old, no-tillage system in Ponta Grossa, Paraná, Brazil. Undisturbed soil samples were collected at depths of 0–0.10, 0.20–0.30, 0.40–0.50, and 0.60–0.70m. The soil properties such as dry bulk density, total porosity and macroporosity showed the presence of a denser layer at a depth of 0.20–0.30m. The Db and Pt values in this layer were significantly different from the other layers. However, the values of 1.23Mgm−3 for Db, 0.52m3 m−3 for Pt, and 0.17m3 m−3 for macroporosity were all still adequate for the growth and development of roots at this layer. The values of K sat and K a were higher at the surface layer than deeper layers. The lowest values were around 80 and 70% in comparison with surface, respectively to the depths of 0.40–0.50, and 0.60–0.70m K sat and K a values were 7.79×10−5, 2.76×10−5, 1.58×10−5, and 1.91×10−5 ms−1, and K a values were 3.70×10−11, 2.04×10−11, 7.69×10−12, and 1.10×10−11 m2 for the depths of 0–0.10, 0.20–0.30, 0.40–0.50, and 0.60–0.70m, respectively. This demonstrated that better conditions for the exchange of gases and water existed in the layers above 0.30m. The S index indicated that the soil had good structure in all layers studied, with values above 0.035, but that a small increase in Db in the 0.20–0.30m layer could lead to deterioration of the soil structural quality. The long-term use of no-tillage resulted in increases of organic carbon and pore connectivity in the surface layer, providing functionality in the soil. [Copyright &y& Elsevier]