Effects of fertilizer on growth and yield of red beans under competition conditions with Amaranthus retroflexus

In order to investigate the effect of organic and chemical fertilizers on the yield and some physiological traits of beans under conditions of competition with Amaranthus retroflexus, an experiment was performed in the form of slip plots as a complete randomized block design (RCBD) with three replications. The experimental treatments included three densities of Amaranthus retroflexus as the main factor and fertilizer at five levels as the sub-factor. The results showed that the amount of weed nitrogen, ranging from the highest to the lowest, under the intense competitive pressure of Amaranthus retroflexus (D3 = 14) was related to nitrogen (85.08%), biochar (65.78%), compost (19.51%) and manure (16.44%) fertilizer, respectively. The results of this experiment indicated that the negative impact of wild Amaranthus retroflexus competition on grain yield depends on the type of fertilization and weed density of Amaranthus retroflexus. Among all fertilization treatments, at high competitive density of Amaranthus retroflexus, the highest rise in grain yield, compared to non-fertilization was related to compost (184.152), manure (119.24%), biochar (55.76%) and nitrogen (43.99%) treatments respectively. At low competitive weed density, the greatest increase in the grain yield was observed in compost (132.33%), manure (104.43%), biochar (55.71%) and nitrogen (22%) treatments compared to no fertilizer. In the absence of Amaranthus retroflexus, the highest to the lowest level of yield was obtained from the treatments of nitrogen, manure, compost, biochar and no fertilizer, while no statistically significant difference was found between nitrogen treatment and manure.