Planting density effect on growth, dry matter accumulation and weed control efficiency of Indigofera hirsuta Linn. in Ibadan Nigeria

Abstract

A field experiment was conducted at the Crop Garden, Department of Crop Protection and Environmental Biology, University of Ibadan,  Nigeria to investigate the effect of planting density on the performance of Indigofera hirsuta and its ability to suppress weeds. Seeds  sown at 1 cm soil depth were spaced at 20 cm inter-row 2 and varying intra-row spacings: 10, 20, 40, 80 and 160 cm to have densities 50,  25, 12.5, 6.25 and 3.13 plants/m² , which are equivalent to 500,000, 250,000, 125,000, 62,500 and 31,250 plants/ha, respectively. Plots where  I. hirsuta were not planted served as control. The experiment was conducted in two trials in a randomised complete block design  replicated three times with the five densities and control randomly allocated to plots in each block. The plant height (PH) in cm, stem  diameter (SD) in cm, shoot dry weight (SDW) in kg and weed dry weight in kg were measured at 14 weeks after planting and the  treatments compared using one-way ANOVA. The PH of I. hirsuta at density 50 plants/m (105.0 – first trial and 107.0 – second trial) were  significantly higher than the 2 heights recorded in other test densities. The SD and SDW at density 3.13 plants/m (0.97 cm and 0.38 kg –  first trial; 0.93 cm and 0.38 kg – second trial) were significantly higher than the SD and SDW recorded in other test 2 densities. The weed  dry weight on 50 plants/m plot (0.55 kg and 0.59 kg in the first and second trial, respectively) was significantly lower than those on the  other plots. Indigofera hirsuta proved effective in 2 suppressing other weeds, which increased with increasing density (WCE = 23.37 and  22.51% at 3.13 plants/m ; 2 70.11 and 69.11 at 50 plants/m in the first and second trial, respectively). The weed suppressive ability of    Indigofera hirsuta is attributed to competition for light due to its rapid growth and spreading habit.