Weed flora and wheat yield comparison in conventional (small grain cereals) and organic (soybean-wheat rotation) systems

Due to different weed-crop competitions, and despite higher weed abundance, similar or greater yield have been observed in organic planting systems than conventional systems. The effects of small grain cereal (conventional, CNV) and soybean-wheat rotation (organic, ORG) on weed flora and wheat yield was investigated in a two-year field experiment (2022–2023), selected from a 10-year research program. In CNV herbicides, mineral fertilizers, and plowing with chisel plows were used while in ORG no herbicide, low urea fertilizer, moldboard plow, and the return of soybean residues to soil after harvest were used. Indicator species analyses demonstrated the weed species were significantly related to winter wheat in CNV including Johnson grass ( Sorghum halepense L.), little seed canary grass ( Phalaris minor L.), wild oats ( Avena fatua L.), and perennial weeds, and in ORG they were wild mustard ( Sinapis arvensis L.) and redroot pigweed ( Amaranthus retroflexus L.). The weed species associated with CNV had more nitrogen index (7.5) than ORG (7.0) species. Among the three important weeds of CNV, two wild oat and little seed canary grass showed resistance to Granstar herbicide. Although wheat weed biomass in ORG (67 g m −2 ) was twice of CNV (34 g m −2 ), there was no significant difference between the mean wheat yield in these two treatments (3.2 and 3.3 t ha −1 in CNV and ORG, respectively). Our results support the hypothesis that the two cropping systems result in different crop yield and weed biomass. The increased diversity of soil input resources may reduce the importance of weed competition. • Small grain cereal and soybean-wheat rotation affecting weed flora and wheat yield. • Indicator species analyses demonstrated the presence of different weed species. • The weed species associated with CNV had more nitrogen index than ORG species. • Wheat weed biomass in ORG (67 g m −2 ) was twice of CNV (34 g m −2 ). • There was no significant difference between the mean wheat yield in the two systems.