| Zdroj: |
Munkholm, L J & Abdollahi, L 2015, ' Conservation agriculture effects on soil pore characteristics ', Nanjing, China, 14/09/2015-18/09/2015, . |
| Popis: |
Conservation tillage in combination with crop rotation, residue management and cover crops are key components of conservation agriculture. A positive long-term effect of applying all components of conservation agriculture on soil structural quality is expected. However, there is a lack of quantitative knowledge to support this statement. This study examines the long-term effects of crop rotations, residue management and tillage on soil pore characteristics of two sandy loam soils in Denmark. Results are reported from a split plot field experiment rotation as main plot factor and tillage as subplot factor. The crop rotations differed from a cereal based rotation with winter crops to a diverse rotation including a mix of winter and spring crops as well as cover crops. For the latter crop rotation, straw was removed in some plots and retained in others. The tillage systems were: Mouldboard ploughing to a depth of 20 cm (MP), harrowing to a depth of 8-10 cm (H) and direct drilling (D). Minimally disturbed core samples were taken at 4-8, 12-16 and 18-27 cm depths 11 years after experimental start. Water retention characteristics were measured for a range of matric potential ranging from -10 to -1000 cm. Air permeability and gas diffusivity were measured at matric potentials ranging from -30 to -300 cm for 4-8 and 12-16 cm depth (100 cm3 cores). At 18-27 cm depth (250 cm3 cores) air permeability was determined at matric potentials ranging from -10 cm to -100 cm. Tillage systems clearly influenced almost all the investigated parameters at all depths and at all matric potentials studied. The MP resulted in highest air-filled porosity, air permeability, gas diffusivity and the lowest bulk density at 4-8 and 12-16 cm depth. At the 18-27 cm depth, however, direct drilling resulted in a higher air permeability and pore continuity index. Generally, residue input, especially when combined with direct drilling at the Foulum site, decreased bulk density and the volume of blocked air porosity, and increased air-filled porosity, volumetric water content, air permeability and gas diffusivity. Our results suggest that a strategy of leaving residues in the field can alleviate negative effects of reduced tillage on soil structural quality. |
