Joaquim Odilon Pereira

Resistência do solo à penetração em função do sistema de cultivo e teor de água do solo

The effect of tillage systems (minimum-tillage and no-tillage) and water contents (33, 37 and 39%) on the soil strength was evaluated on the Oxisol, with the corn yield. The resistance of the soil to penetration was determined before the tillage and immediately after the tillage and after the harvest. The results obtained permit to conclude that the water contents of the soil, as well as the tillage systems affected significantly the resistance of the soil to the penetration after the tillage. The water content of 33% caused a reduction of the soil penetration resistance, in both systems, with larger reduction in the system of the minimum-tillage. The water content of 37 and 39% caused an increase of the soil penetration resistance in both the systems with larger increment in the no-tillage system.

Comportamento compressivo de um nitossolo: efeito do tamanho de agregados, do teor de água e da pressão aplicada

Soil compaction has been the subject of intensive researches in the last ten years, but the mechanisms involved in the soil compaction process remain a little known. The contribution of aggregate size of the soil as well as the effect of water content and normal pressure applied on soil compaction and pressure of pre-compaction were investigated in a Clay soil during this trial. Disturbed soil samples constituted by aggregates less than 2.5 mm and 9.3 to 19.4 mm were submitted to a drained compression uniaxial test. The void ratio and the pre-compaction pressure were also evaluated. The results obtained show that the size of the aggregates had effect on the process of soil compaction. The change of soil compaction can be predicted according to the initial state of soil, the applied pressure and the water content of the soil.

Yield of soybean crop in function of soil compaction affected by tillage system on Oxisol of subtropical region

The increase in conservation tillage offers possibles benefits of decreasing soil compaction risk by wheeling. The objective this work was to evaluate the effect of the minimum tillage and direct drilling system after four and eight yars of continuous no-tillaging, on the soybean yield in function of the soil density and organic matter content. This trial was carried out on Oxisol, at Parana, subtropical region from Brazil. The relationship between yield of soybean and tillage system was analyzed as function of the soil density and organic carbon using linear regression model. No-tillage system four years (NT4) and minimum cultivation system in eight years of no tillage (MT8) showed greater decrease in soil density on the surface layer as a function of time, respectively, 0.22g cm-3 (1.318 1.098) and 0.24 g cm-3 (1.248 1.010). Adjust of response curves of soybean yield as function of soil density and organic matter describes strong positive contribution of organic carbon in soybean productivite on the NT4 system and describes no interference of soil density on this system. In both systems (NT8 and MT8), the soybean yield decreases with increasing soil density. Soil sub-surface management after continuous periods of no-tillage should be investigated.

Determination of the soil compaction in real time on field with plate penetrometer and data filtering system

Soil compaction due to traffic is the process whereby soil bulk density is increased. The compaction level depends on the weight of the vehicle, and the soil susceptibility to compaction, which is characterized by its mechanical properties (that is, the stress-strain relationships). The plate penetrometer can be used to quantify the levels of soil compaction in-situ and supply a larger number of information on the control of this phenomenon, in real time. This paper evaluates the use of this tool with data filtering system assistance on semi confined compression assay, for predicting soil compaction in-situ, through parameters pre-compaction stress (spc) and soil compression Index (Cc). The tests were carried out on Experimental Agricultural Engineering Nucleus (NEEA in Portuguese) at West Parana State University - UNIOESTE - Brazil. The sample collection was carried at points along the tire track, 24 h after soil compaction induced by the rear tractor wheel with one, five and ten passages, on the same track. The information system is able to read all data derived from the compression test and carry out a filtering on the data by means of pre-selected parameters, plotting the compression curves and regression equations. The analysis, carried out “in situ”, avoids laboratorial procedures and gives the farmer more agility in the decision process on the management of the agricultural machinery system.