Impact of tillage and sowing systems on the physical properties of a compacted soil from central Spain.

A two-years field experiment was carried out to determine the extent and duration of the combined effect of four tillage systems: no tillage (NT), minimum tillage with chisel plow (MT), conventional tillage with mouldboard plow (CT), and zone-tillage subsoiling with a paraplow (ZT) and two types of direct drill furrow openers: hoe-type and disc-type, on the physical properties of a semi-arid soil (Calcic Haploxeralf) from Central Spain. In the first year, the four tillage treatments were applied. In the second year, the ZT plots were returned to NT to follow the residual effects of ZT. The crop rotation was grey pea (Pisum sativum L.) - barley (Hordeum vulgare L.). In the two years of study, no significant differences between sowing methods in any of the physical parameters studied were observed. When comparing NT and ZT, the immediate effects of sub-soiling on soil physical properties were significant. Zone tillage reduced bulk density compared with NT at the 0-200 mm depth. No tillage and ZT improved soil aggregation and increased soil moisture over MT and CT. In the second year, when the paraplow was not applied, the positive effects on bulk density and moisture content dissipated significantly. On the contrary, the beneficial effect of NT and ZT on soil aggregation clearly remained in the year following sub-soiling.