The weed and weedy rice impact on direct seeded rice production in North Macedonia

Abstract

A study from 2017 to 2019 in 10 vilages in the rice producing region of North Macedonia was undertaken to estimate the effect of weed flora on some productive rice properties. The common production technology was implemented. Rice was direct seeded in wet conditons. The weed managent included water bed regulation in combination with herbicide application. The following properties were investigated in three replications: density and infestation of the total weeds, weedy rice and other weed species, crop density, biological, straw and paddy rice yield, harvest index and head rice yield. The results were pooled in 5 groups depending on the weed infestation level. A correlation analysis revaled significant negative effect of the total weeds and the weedy rice component on the crop density, biological yield, harvest index and paddy rice yield. The weeds controled with herbicides were not significanlty correlated and affected the productive properties indirectly as a contributing factor in the total weed density. Low infestation (0.01% to 1.00%) caused drop in paddy rice yield of 6.73%. The most severe cases of weed infestation (15.01% to 25.00%) averaged 100.08 weed tillers/m2 and caused paddy yield drop of 35.30%. These field parcels were located in a region with extensive monoculture, where weedy rice populations constituted 90.68% of the total weed flora, or 90.75 panicles/m2 against 9.33 tillers/m2 from other weed species. Some weedy rice morphotypes were easily distinguished against cultivated rice in field conditions as early as anthesis, while others were more difficult to recognize. This study confirms weedy rice as a serious threat for the direct seeded rice production in the region, and addresses the need to investigate its biology and the most suitable management practices.