The composite effects of two irrigation frequencies (one irrigation at crown root initiation stage and
five irrigations at five critical physiological stages of wheat), eight nutrient treatments consisting of
N, P and K either applied alone or in combinations at the recommended doses (N:P2O5:K2O at
120:60:40 kg/ha) on population and dry weight of weeds and on the growth, nutrient uptake and
yield of wheat were investigated. Observations on the components of the weed population and their
biomass made at 60 DAS did not reveal any significant difference between the high and low frequency
irrigation. Among the nutrient treatments, the N-treated plots (N, NP, NK and NPK) had a higher
population and biomass of grass weeds, whereas sole P and K application or their combination
produced the greater growth of broad-leaved weeds. However, the overall weed competition was
significantly higher in the P- and K-treated plots than in the N-treated plots. The NP, NPK, NK and
N treatments produced significantly higher values for dry weight, crop growth rate, leaf area, number
of tillers, nutrient uptake, number of ear-bearing tillers, protein content and grain yield than the other
treatments. Weeds in unweeded control plots did not significantly affect wheat growth (CGR, dry
weight, tillers/plant) and uptake of the nutrients except of the P at 60 DAS. However, the number
of ear-bearing tillers, grains per ear and yield were significantly higher in the weed-free plots than in
the unweeded control treatment.