Paths of influence among components of yield in sorghum (Sorghum bicolor (L) Moench, cv Tegemeo) grown in the semi arid area of Dodoma Region, Tanzania

Abstract

Sorghum is a food security crop in tropical marginal areas. Improvement strategies for yield under such conditions are important. Genetic improvement for yield is done through improvement of its components. Due to yield component compensation, this improvement strategy is made less rewarding. It is therefore important to know compensatory mechanisms existing for better improvement strategies. Studies on the nature of component compensations in sorghum are limited and virtually lacking under Tanzanian conditions. A field experiment was conducted to investigate the nature of interrelationships among components of yield in sorghum at the experimental plots of Hombolo Research Station in the semi-arid zone of Dodoma Region, Tanzania. Six treatment combinations, of rain water harvesting techniques and fertilizer were laid out in a randomized complete block design (ReED) with four replications during the growing season of 1996/97. Number of grains was an important component which was significantly correlated (r = O.982***) with grain yield and had a high positive direct effect (0.979) on yield. Average grain weight was not important in influencing yield of sorghum. Plant biomass had a negative direct effect (-1.2997) on average grain weight but was not important in influencing number of grains. Plant height and percent light intercepted directly influenced number of grains and average grain weight negatively. The negative influence (- 0.8712) of plant height on number of grains was compensated to a low relationship (r= -0.337) mainly by its positive indirect influence (0.3780) through light interception. Improvement strategies should aim at shorter plants with more grains, of lesser canopy development and biomass in these semi arid areas.

Keywords: Biomass, component compensation, grain number, light interception, plant height, semi arid, sorghum

Tanzania J. Agric. Sc. (1998) Vol. I No. 2, 99-108