Tillage effects on differently compacted soil and on cotton yield in Nigeria

Abstract

Effects of repeated tractor traffic on soil characteristics and on yield performance of cotton in Nigeria were investigated for a loamy soil. Four tillage treatments were compared after four levels of compaction had been applied: no tillage (NT), disk harrowing (D), mouldboard ploughing followed by disk harrowing (MD) and disk ploughing followed by disk harrowing (DD). The compaction levels comprised 0, 5, 10 and 15 passes (wheel-to-wheel) of a 45-kW agricultural tractor with a rear tyre inflation pressure of 95 kPa. Soil dry bulk density showed an increase with depth and number of tractor passes for NT, but a decrease for all other tillage methods. Soil dry bulk density was higher at 10 than at 2 weeks after sowing for all compaction treatments. Cone penetration resistance increased with increase in soil depth and number of tractor passes for all tillage treatments and all compaction levels at 10 weeks after sowing. this was less so at 2 weeks after sowing. At 2 weeks after sowing, soil moisture content showed an increase with incresing soil depth and with the number of tractor passes for no tillage (NT), but was little influenced by other tillage methods. However, at 10 weeks after sowing, soil moisture, content still showed an increase with the number of tractor passes but a decrease with increasing depth. For each tillage method, with the exception of NT which showed a slight decrease (from 73 to 47%), the germination percentage showed no appreciable difference as the number of tractor passes was increased. The yield of cotton seeds decreased with increasing number of tractor passes, attaining a minimum at 10 passes before showing a increase. With increasing number of tractor passes, field weediness increased, while cotton root length density decreased.