Resumen
- Erosion and soil compaction are two important degradation processes of modern agricultural production in Western Europe. One of the principal causes of soil degradation are deep and intensive tillage operations, especially under moist soil conditions. To minimize erosion and soil compaction, the adoption of conservation tillage or reduced tillage (RT) agriculture is widely recognized. However, crop rotations in Western Europe often include root crops that are generally assumed to be less suitable under RT agriculture because they result in a high disturbance of the soil at the formation of the ridges and at harvest. A detailed understanding of the influence of the different types of tillage on the soil properties aggregate stability, penetration resistance (PR) and field-saturated hydraulic conductivity (Kfs) is important for management strategies. The objective of this chapter is comparing the physical properties of silt loam soils under different tillage systems in Belgian fields. The aggregate stability of the 0-10 cm layer was measured in the laboratory. The stability index measured by the ‘dry and wet sieving’ method of De Leenheer and De Boodt (1959) was 40% higher under RT than conventional tillage (CT) agriculture. The mean weight diameter (MWD) measured with the three methods of Le Bissonnais (1996) was significantly higher even after short-term RT compared to CT agriculture. The MWD after a heavy shower, a slow wetting and stirring the soil after prewetting was 19%, 38% and 34% higher for RT than CT fields, respectively. The PR was studied in the field with a hand penetrologger. The PR of fields under RT was higher in the first layers due to less (RT with cultivator or soil loosener [=RTC]) or no disturbance (RT by direct drilling [=RTDD]) of the soil structure. The crop growth of RTC fields seemed not to be affected by this superficial compaction. However, the crop growth of RTDD fields was lower than of CT fields. The PR measurements indicated a plough pan at depth in some field under CT. The measurement of the infiltration rate with a Guelph pressure infiltrometer in the field showed that Kfs tended to be lower under CT than the other types of tillage. We can conclude that RTC is a form of agriculture that is more sustainable than CT agriculture in these silt loam soils. This research indicated that short term RTDD agriculture under crop rotations with root crops often result in a lower crop yield, which is probably correlated with the higher PR in the 10-30 cm depth layer. Therefore, the potential of RTDD agriculture in Western Europe is probably limited.