Go. Kegode et al., THE INFLUENCE OF JOHNSONGRASS INFESTATION AND NITROGEN RATES ON GRAIN-SORGHUM, Journal of agronomy and crop science, 172(4), 1994, pp. 242-246
Grain sorghum [Sorghum bicolor (L.) Moench] is grown on marginal land
and johnsongrass [Sorghum halepense (L.) Pers] is the most common and
hard to control weed in this crop. The agronomic performance of grain
sorghum at different nitrogen (N) and johnsongrass infestation levels
in the field has not been adequately investigated. Therefore, research
was conducted on a Decatur silty clay loam soil (Rhodic Paleudult) to
determine the influence of N rates (0, 40, 80 and 120 kg ha-1) and jo
hnsongrass infestation levels (0, 2, 4, 6 and 8 plants per 5 m crop ro
w) on the growth and yield of grain sorghum (cv. GK522G) and johnsongr
ass. Increase in N rates increased seed weight, seed yield and percent
protein in grain sorghum as well as dry matter and percent protein of
johnsongrass. The increase in johnsongrass infestation (from 0 to 8 p
lants per 5 m crop row) significantly decreased the performance of gra
in sorghum and johnsongrass at all the N rates. The results suggest th
at 40 kg N ha-1 with up to 2 johnsongrass plants per 5 m crop row or 8
0 kg N ha-1 with up to 4 johnsongrass plants per 5 m crop row produced
grain sorghum yields equivalent to absence of johnsongrass in the cro
p.