Analysis of allelopathic effects and resource competition of weed suppression ability of wheat (Triticum aestivum) under low nitrogen stress condition

Allelopathic effects and resource competition are critical factors of weed suppression ability of crops. To separate the allelopathic effects from resource competition of weed suppression ability of wheat under low nitrogen stress condition, two strong allelopathic wheat accessions ('115/Q' and '92L89') and one weak allelopathic wheat accession ('K10103') were used in two sets of separate experiments (co-cultivated Alopecurus aequalis with wheat and treating Alopecurus aequalis with hydroponic solutions of co-cultured wheat root exudates) to evaluate bio-interference, allelopathy and resource competition effects. The experiments were conducted in gradient N concentration hydroponic solutions with N levels of 25 mg·L^-1, 50 mg·L^-1, 100 mg·L^-1 and 200 mg·L^-1. The results showed significantly differences in the abilities of inhibition to the growth of Alopecurus aequalis in the three wheat accessions in both experiments. Weed suppression ability (inhibitory rate, IR) increased with decreasing N level in all the wheat accessions. The rank order of IR for different wheat accessions was '115/Q' (55.1%?73.9%) > '92L89' (48.9%?65.9%) > 'K10103' (15.4%?45.5%). Generally, IR increased with decreasing N level in hydroponic solutions. Both allelopathic effects and resources competition were critical for wheat weed suppression. Different ecological strategies were noted in different allelopathic potential wheat accessions under low N stress condition. Weed suppression ability improved by increasing allelopathic effects of strong allelopathic wheat accessions. This was triggered by enhanced resources competition of weak allelopathic wheat accessions. Allelopathic effects increased with decreasing N level and the changes in inhibitory rate with N level well fitted quadratic equations.