Potential risk of weed outbreak by increasing biochar's application rates in slow‐growth legume, lentil (Lens culinaris Medik.)

BACKGROUND Biochar amendment is a promising tool to improve the soil quality and, consequently, higher crop yield has received more attention during last decades. The positive effects of biochar have been attracting more attention especially in the areas with low precipitation rates, such as the Middle East, due to low soil organic carbon content, higher drought intensity, and increasing demands for food production. However, biochar can lead to lower herbicide efficacy, resulting in higher consumption of herbicides. In this study, the impact of two biochars on soil properties, plant growth, and fomesafen efficacy under rain‐fed condition was investigated. RESULTS Biochar amendment at the rate of 5 t ha−1 improved soil quality and plant growth by 40–200% and 46–57%, respectively, compared to the control. The increase of biochar application rate from 5 t ha−1 to 15 t ha−1 showed small additional positive effects on soil and lentil as the tested crop plant, whereas the growth of weeds elevated by 200% in this case. CONCLUSION Albeit biochar application could be an effective way to improve the soil fertility, the potential risk of weed outbreak in the long term should be evaluated carefully before the use of biochar amendment at field scale. © 2017 Society of Chemical Industry