Effect of soil chiseling on soil structure and root growth for a clayey soil under no-tillage

Soil chiseling under no-tillage (NT) promotes root growth in depth. This practice, however, might affect soil aggregation. This study evaluated the chiseling effects on the aggregation of a Ferralic Nitisol (Rhodic), under NT, in humid subtropical climate region. The treatments carried out consisted of the time that soil was kept under NT after chiseling: continuous NT for 24 months after chiseling in September 2009; continuous NT for 18 months after chiseling in March 2010; continuous NT for 12 months after chiseling in September 2010; continuous NT for 6 months after chiseling in March 2011; NT in newly chiseling soil in September 2011; continuous NT without chiseling (control). The species cultivated in the area were: corn in 2009/2010 growing season; wheat in 2010; soybean in 2010/2011 growing season; rye in 2011; and corn in 2011/2012 growing season. Treatment effects were evaluated through the following determinations: soil organic carbon, aggregates stability, mean weight diameter, aggregates larger than 2 mm, and soil macroaggregates and microaggregates. The corn root density was correlated to the soil aggregation parameters. The effect of soil chiseling, in a clayey humid subtropical soil under NT, reduced the size of soil aggregates, in the layer 0.07 to 0.17 m, in the first six months after this practice. However, 12 months after the soil chiseling, the aggregates returned to the original size. Root growth was favored in the layer between 0.07 and 0.20 m, due to the chisel action, and did not influence soil aggregation in relation to the control treatment. The soil chiseling practice, therefore, did not promote persistent improvement in the structure of a clayey soil under NT, in humid subtropical climate region.