Soil aggregate stability after management with crop rotation and chiseling

The objective of this study was to compare, in compacted soil condition, the aggregate stability after different crops rotations under no-tillage system and chiseling. The following crop rotations were repeated for three consecutive years under no-tillage: triticale (X Triticosecale Wittmack) and sunflower (Helianthus annus) as autumn-winter crops, together with pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor) and sunn hemp (Crotalaria juncea) in spring, preceeding soybean (summer crop). In the chiseling treatment the area was kept bare between the autumn-winter and the summer crops. The study was carried out in three growing seasons (200312004,200412005 and 200512006), in Botucatu, state of Sao Paulo, Brazil. The experiment had a complete randomized block design with split-plot and four replications. The samples for aggregate stability analysis were collected in the layers 0-5 and 5-10 cm after cover crop desiccation, in the first and third year of the experiment. In the first year of the experiment, triticale resulted in a higher percentage of aggregates larger than 2 mm, higher Mean Geometric Diameter and Mean Weight Diameter (MWD) of aggregates at the depth of 0-5 cm, and higher MWD at 5-10 cm. Chiseling and absence of cover crops reduced the percentage of aggregates larger than 2 mm and MWD values at 5-10 cm. Aggregate stability is influenced by crop rotation, and was highest in the layers 0-5 and 5-10 cm when triticale was used as autumn-winter species.