Telmo Palancar

Comportamento mecânico do solo sob tráfego em dois sistemas de preparo do solo

A former concern related to agricultural soil, under no tillage systems, might be the state of compaction due to farm machinary traffic. Two treatments corresponding to two different tillage systems (disk plowed, LC, and no tillage, SD) included four traffic subtreatmets (0; 80; 160, and 240 Mg km ha-1) on a Typic Hapludert. Cone index (IC) and dry bulk density (DA) were the experimental dependent variables asessed. Soil reology under traffic had a different behaviour in both treatments. In both treatments for the higher traffic intensities (160 and 240 Mg km ha-1) statistical significant difference (P < 0,05) were measured when compared with the control plots, when the IC was considered. Considering LC treatment and the higher traffic intensities, the dry bulk densities values measured arised to 1.83 Mg m-3, the disk plowed, and no tillage under traffic soils reologies are different. If the depth of the maximum response in terms of IC measurements is considered, a direct relationship between traffic intensities and depth, could be stablished.

Deep loosening for direct drilled soil recovery

Maintaining a sustainable soil management system with annual double cropping is a considerable challenge, even when a conservation technique such as direct drilling is used. No tillage means less vehicular traffic, but not necessarily a reduction in traffic intensity because of the excessively high axles loads associated with some agricultural machines. Direct drilled soils appear to have a better recovery following agricultural traffic, but evidence has suggested that problems related to compacted layers occur in these profiles with time. Subsoiling, as a well known technique to alleviate soil compaction, has been widely quoted for tilled soils, but rather little is known about how no tilled soils respond to this technique. The task is to loosen compacted subsoil layers, with minimal disturbance of the topsoil to avoid subsequent problems during drilling. Research was performed on a fine Typic Argiudol soil managed with no tillage, annual double cropping and with and without deep loosening. Both soil treatments received the standard traffic demanded by the cropping system. Soil penetration resistance and dry bulk density were the dependant variables assessed. Results showed that although there was a major compaction tendency after traffic on loosened soil, there was also evidence that the effects of loosening persisted for almost nine months. Interestingly, it was also evident that layers below the mechanically loosened horizon exhibited a reduction in penetration resistance and bulk density. It was concluded that periodic subsoiling can alleviate the soil compaction caused by agricultural traffic in deep soil layers and will allow direct drilling to continue sustainably. Subsoiling not only alleviates compaction in the mechanically disturbed layers, but also in the horizon immediately below.