SUMMARY
The area devoted to growing tobacco (Nicotiana tabacum L.) in the province of Granma, Cuba, accounted for nearly 2600 ha in the year 1997, which represented the 4% of the total tobacco plantation area on the island in that year. Tobacco is tillage-intensive since traditional production systems entail seven or eight cultivation operations before transplanting. The objective of this study was to evaluate two alternative tillage systems in comparison with conventional tillage for tobacco production with the aim to improve soil conditions, reduce the number of tillage operations for soil preparation for transplanting, and increase yields. The treatments studied were: (T1) conventional or traditional tillage, (T2) reduced tillage with a multi-tiller plough, and (T3) reduced tillage with a chisel plough. T1 consisted in disc ploughing twice and disc harrowing twice for primary tillage, while before transplanting plots were ploughed twice with a horse-drawn mouldboard plough and harrowed twice with a horse-drawn spike-tooth harrow. In T2 primary tillage was accomplished with two passes with the multi-tiller followed by disc harrowing twice before transplanting. In T3 chisel ploughing was substituted for multi-tiller ploughing. The two reduced tillage systems improved the physical conditions of the soil, which resulted in: lower bulk density, with average values across the 0-30 cm soil profile of 1.48, 1.34 and 1.30 Mg m-3 in T1, T2 and T3, respectively, at the end of the growing season; higher soil water content in the soil profile in all four sampling dates per season; greater porosity; and lower resistance to penetration with values of 2.48, 2.15 and 1.71 MPa in T1, T2 and T3, respectively, before crop harvesting. Tillage system T3 provided the highest crop yields (2.26 Mg ha-1) compared with T2 (2.14 Mg ha-1) and T1 (1.95 Mg ha-1), for the plants grown on T3 plots had the largest number of leaves. The size of the leaves was similar in all three systems, however.