Short-lived effects of walnut shell biochar on soils and crop yields in a long-term field experiment

Abstract

Many field studies exploring biochars' effects on plant productivity and soil quality have been limited to just one or two seasons, particularly in temperate agroecosystems, and have not shown how such impacts change as biochars age in the soil. Therefore, we investigated the lasting effects of a walnut shell (WS) biochar on crop yields and soil nutrient cycling and availability over four years in a field experiment. Long-term plots of a tomato-corn rotation were established in a 2x2 factorial design of treatments i) with or without WS biochar amendment and ii) fertilized with mineral fertilizer (MF) or composted poultry manure (CP). Biochar was applied once in 2012 (Year 1) at a rate of 10 t ha −1. Crop yields were measured over four seasons, and soil samples were analyzed for ammonium (NH 4 +-N) and nitrate (NO 3 −-N) concentrations and for other nutrient parameters, including exchangeable K + , Ca 2+ , PO 4-P, SO 4-S, each year. WS Walnut shell biochar had an effect only in Year 2 2013, one year after biochar application, when it increased corn yields by ~8% in both MF and CP fertilizer systems and increased

Impact of biochar and compost amendment on soil quality, growth and yield of a replanted apple orchard in a 4‐year field study

“…19 However, in neutral soils, where nutrient retention is relatively high, 20,21 the positive effects of biochar on nutrient availability might be low during the first 3 years after soil amendment, as observed in this experiment. 16,21 Nevertheless, the increase in TN during the first year of this study was inconsistent with other studies. This could be partially due to the addition of decomposed cow manure with high amounts of organic N in winter (December 2014), allowing soil microbes to degrade organic compounds in the presence of appropriate amounts of precipitation.…”

“…Higher soil nutrient content could be initially due to direct addition of biochar and compost through the immediate increase of nutrient supply, followed by higher nutrient adsorption on the surface of biochar/compost particles in the upper soil profile and slower desorption of adsorbed nutrients during following years . However, in neutral soils, where nutrient retention is relatively high, the positive effects of biochar on nutrient availability might be low during the first 3 years after soil amendment, as observed in this experiment . Nevertheless, the increase in TN during the first year of this study was inconsistent with other studies.…”

Eucalyptus biochar application enhances Ca uptake of upland rice, soil available P, exchangeable K, yield, and N use efficiency of sugarcane in a crop rotation system

“…At the start of our experiment, exchangeable soil Ca was very low (70 mg kg -1 ) but increased significantly with the addition of 35 kg Ca ha -1 under the 6.2 Mg ha -1 biochar treatment at rice harvest. Increasing soil exchangeable Ca by biochar application was found in several studies (Griffin et al, 2017;Mehmood et al, 2017;Zong et al, 2018). In our study, a direct influence of eucalyptus biochar on soil exchangeable Ca was supported by a positive correlation with the amount of Ca applied.…”

Three‐Year Field Observation of Biochar‐Mediated Changes in Soil Organic Carbon and Microbial Activity

“…A similar tendency was found in soil CEC contents, where no significant change with biochar addition was found under long‐term field condition (Novak et al, 2009). These results were dissimilar to laboratory experiments (Van Zwieten et al, 2010; Yuan et al, 2011), but consistent with the long‐term field experiments (Griffin et al, 2017) Biochar amendment was unlikely to significantly alter the nutrient retention capacity of the soil under long‐term uncontrolled climate and moisture conditions. The effects of organic amendment on soil nutrient and SOC contents depended on type and rate (Table 2).…”