Influence of soil physical factors like soil compaction has been known to affect root growth and tuberous root development of sweetpotato. This physical factor is often left-out in the evaluation of newly released cultivars of sweetpotato. A pot experiment was conducted to evaluate the growth and yield responses of sweetpotato cultivars to various levels of soil compaction and to determine the degree of soil compaction that would result in optimum growth of various sweetpotato cultivars. A 4 x 3 factorial experiment with 4 sweetpotato varieties (PSB SP-16, PSB SP-17, PSB SP-25 and Ciete Flores) as factor A under 3 levels of compaction (1.1, 1.3 and 1.5 g cm-3 bulk density) as factor B was conducted. Results showed that depth of tuberous root formation and number of marketable tuberous roots decreased with the increasing degree of soil compaction. Other growth and yield parameters were not significantly affected by the treatments applied. Interaction effect of sweetpotato cultivars and levels of soil bulk density was significant on depth of tuberous root formation and number of marketable tuberous roots. Observation on the nature of formation, penetration, distribution and direction of tuberous root development showed that those at lower degree of compaction (1.1 g cm-3), tuberous roots were evenly distributed and were able to penetrate vertically and formed at deeper parts of the soil layer. However, the tuberous roots in compacted soils (1.3 to 1.5 g cm-3) were formed at shallower depths andwere not able to penetrate deeply.
Keywords: Compaction, Bulk Density, Sweetpotato cultivars, Tuberous root formation,