Tillage and Crop Rotation Affect Bulk Density and Penetration Resistance.
Ivica Kisic, Ferdo Basic, Milan Mesic, Krunoslav Sajko, and Zeljka Zgorelec. Faculty of Agriculture, Svetosimnuska 25, Zagreb, Croatia
Increasing soil compaction has become a global problem due to the use of ever larger and heavier tractors and attachments, i.e. more intensive tillage and also tillage under unfavourable conditions. As a consequence, low or decreasing yields are obtained due to increased bulk density of the soil, which is also reflected in reduced infiltration and transmission of water into/through the soil, lower pipe drainage efficiency and crop root depth, higher incidence of plant diseases and reduced root efficiency. Aimed at determining the optimal tillage system for the region, ten year penetration resistance measurements, among others, were carried out on the Stagnic Luvisol of the trial field "Freivogel's Hill" near Daruvar in central Croatia. The trial included the following treatments: 1. Standard plot - black fallow, ploughed up/down the slope; 2. Plowed (till 25 cm) up/down the slope; 3. No-tillage; 4. Plowed across the slope (till 25 cm); 5. Very deep plowed across the slope (50 cm) and 6. Subsoiling to the depth of 60 cm + plowed across the slope. Crops were sown in the following crop rotation: 1994/95; 1999/00 - maize, 1995/96; 2000/01 - soybean, 1996/97; 2001/02 - winter wheat, 1997/98; 2002/03 – oil seed rape and 1998/99; 20003/04 - spring barley + soybean. Soil resistance is measured in four repetitions on depth of tillage, as the principal parameter of soil compaction, were carried out continuously parallel to the plant cover growth and application of appropriate agricultural practices using the recording penetrometer. Ten year investigations lead to the conclusion that the soil resistance to penetration is predominantly influenced by the effective state of the plant cover development, actual soil moisture and the tillage system applied. The lowest penetration resistance were recorded in all trial treatments in the first measurements, immediately after the application of tilling practices. In treatments involving deep practices (very deep ploughing and subsoiling) penetration resistance values were constant to the measurement depth whereas an increase was recorded in penetration resistance below the ploughing depth in treatments with ploughing to the depth of 25 cm. Soil resistance to penetration recorded in the winter period was expressly low, one might say it was practically non-existent. According to the soil resistance values recorded in treatments with deeper soil tillage, as well as the achieved yields, these treatments rendered the best results in the investigations.