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The introduction of biochar has been extensively tested under short-term greenhouse or field studies mainly in sandy or acidic soils, while its effects on soil properties, crop plants, and weed species especially in neutral or alkaline soils are still not well understood. Therefore, this study focused on relatively long effects of two walnut shell biochars (5 t ha−1) on soil nutrient dynamics, two crop plants (wheat and lentil) growth and developments, and weed growth dynamics over 4 years (2014–2017). Applied biochar added once at the beginning of the experiment while planted crops were supplied with macro-nutrients and sprayed with pesticides according to conventional requirements of the region. Biochars improved soil properties by 10–23% during the first and second years while positive effects of biochars on weed growth were drastically higher (60–78% higher weed density) during the whole period of this study most likely due to increase in bioavailability of nutrient shortly after biochar amendment and indirect positive effects of biochars on soil physical properties as well. Consequently, biochar macro- and micro-nutrient will be utilized by weed plants with higher efficacy compared with crop plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Numerous studies have addressed the positive effects of organic amendments on soil and plant productivity under short‐term field studies. However, to date, few studies have been conducted on the effects of organic amendment on the orchards where high nutrient bioavailability is required. This study deals with the effects of biochar and compost on soil quality, growth and yield of a replanted apple orchard in the northeast of Iran. RESULTS: Biochar+compost application resulted in 37% and 300% higher soil total organic carbon and available phosphorus content, respectively, during the first 3 years of experimentation compared to control. Similarly, trunk diameter and shoot number of apple trees increased 23–26% by the end of the first year. Nevertheless, there were no significant changes in fruitfulness, fruit weight or starch pattern index as productivity indices. CONCLUSION: Biochar and compost were beneficial in improving soil quality, mainly by increasing soil nutrient content and decreasing soil bulk density, and in increasing plant growth at early growth stages of apple orchards. However, they failed to enhance overall yield and fruit quality, most likely due to their limited ability to suppress apple replant disease. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: 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 [ABSTRACT FROM AUTHOR]