Biochar has been shown to improve soil properties and plant productivity in soils with inherently low fertility. However, little has been reported for upland corns under dry and wet precipitation regimes. This study investigates the effect of biochar addition on a range of soil physicochemical, biological, and hydrological properties, and corn growth and productivity under agrometeorological drought and wet conditions. Here, experiments were laid out in a randomized complete block design with three replications at two sites during 2017 and 2018 in South Korea. Treatments included (i) CN: control (ii) IF: inorganic fertilizer (N–P–K) at 145–30–60 kg ha⁻¹; (iii) BS: barley straw at 5 t ha⁻¹; (iv) CWBC: corn waste biochar at 5 t ha⁻¹; (v) CWBC + IF: corn waste biochar + inorganic fertilizer; (vi) CWBC + BS: corn waste biochar + barley straw. The year 2017 was relatively dry, whereas the year 2018 was wet. Despite drought conditions in the year 2017, biochar facilitated soil water conservation. However, higher precipitation in 2018 increased the quantity and distribution of soil water and nutrients in the top 15 cm. Biochar reduced soil bulk density, and increased porosity, cation exchange capacity and total organic carbon in both years but increased total bacterial counts during the dry year only. Bacterial population was generally higher under wet conditions. Similarly, more soil CO₂ was emitted in the wet year than in the dry year. Results further indicated that biochar can enhance corn biomass and grain yield regardless of precipitation conditions. The grain index was, however, affected by rainfall and was significantly different across treatments in the year 2018 only. All biomass, grain yield, and grain index were highest in CWBC + IF treatment and lowest under CN treatment. Indeed, biochar addition appeared to improve soil quality and soil conditioning effects in the drought and wet years, ameliorating soil and plant properties. Overall, biochar can improve water and nutrients storage, availability, and uptake, and therefore corn productivity during hydrological extremes. Graphical abstract

Applying soil amendments such as biochar has been proposed as a means to improve soil properties and reduce greenhouse gas emission from agricultural soils. The objective of this study was to evaluate and compare the effects of biochar and straw application on rice yield, select soil properties, global warming potential (GWP), and greenhouse gas intensity (GHGI) over the 3-year period. The study treatments included control (CN), barley straw biochar (BC, 2,000 kg ha⁻¹), barley straw (BS, 2,000 kg ha⁻¹), and BC+BS (each 1,000 kg ha⁻¹). During the rice-growing season, significant interactive effects of BC and BS treatment were observed in major soil properties. The average rice yields in BC, BS, and BC+BS treatments increased by 4.6%, 4.7%, and 18.7%, compared with CN treatment, respectively. Also, BC+BS treatment produced relatively stable yield during the 3-year study. Both BC and BS applications, either alone or in combination, lowered soil bulk density values compared to the CN treatment. Further, BC application produced a low total CH₄ flux than other treatments. The total produced GWP over the 3 years occurred in the order: BS ≧ CN > BC+BS > BC treatment. These results clearly demonstrate the advantages of biochar and straw applications in improving rice yield and soil fertility while reducing GWP and GHGI.

Biochar, widely recognized for its capacity to counteract climate change impacts, has demonstrated substantial benefits in agricultural ecosystems. Nevertheless, empirical studies exploring its efficacy during climatic aberrations such as heavy rainfall are limited. This study investigated the effects of compost and biochar addition on corn growth attributes, yield, and soil CO₂ and N₂O fluxes under heavy rain (exceeding 5-yr average) and waterlogging conditions. Here, treatments included compost (CP, 7.6 t ha⁻¹); rice husk biochar (RB, 7.6 t ha⁻¹); wood biochar (WB, 7.6 t ha⁻¹); and control (Cn). Under high rainfall and waterlogging, the CP treatment manifested a pronounced enhancement in corn biomass and productivity, exceeding biomass and productivity of Cn treatment by 12.6 and 32.2%, RB treatment by 120 and 195%, and WB treatment by 86.1 and 111%, respectively. Corn yield increased in the order: CP > Cn > WB > RB. Intriguingly, negligible disparity occurred between the RB and WB treatments in straw yield, grain yield, grain index, and corn productivity but both treatments recorded distinctively lower values than CP treatment. Also, the CO₂ and N₂O fluxes remained largely similar for two biochar treatments but lower than CP treatment. Overall, CP increased corn yield, straw, and grain yield whereas biochars reduced N₂O flux during waterlogging. Although derived from a short-term experimental window, these pivotal findings furnish invaluable insights for devising soil amendments for yield and environmental benefits in contexts of extreme climatic perturbations. Our findings offer a robust foundation for refining nutrient management strategies confronted with waterlogging challenges, but long-term studies are necessary for definitive conclusions.

A field experiment was carried out to investigate crop productivity, emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O), and soil quality of an upland field treated with compost and varying rates of biochar (BC) derived from soybean stalks during crop growing periods in a corn and Chinese cabbage rotation system. Compost was supplemented with BC derived from soybean stalks at varying rates of 5, 10, 15, and 20 t ha⁻¹ (BC5, BC10, BC15, and BC20, respectively); the control (BC0) area was untreated. Our results reveal that crop productivity and emissions of CO₂ and N₂O varied significantly with the biochar application rate. Moreover, irrespective of the biochar application rate, crop productivity was improved after BC application as compared to the control treatment area, by 11.2–29.3% (average 17.0 ± 8.3%) for corn cultivation and 10.3–39.7% (average 27.8 ± 12.7%) for Chinese cabbage cultivation. Peak emissions of CO₂ and N₂O were mainly observed in the early period of crop cultivation, whereas low CO₂ and N₂O emissions were determined during the fallow period. Compared to the control area, significant differences were obtained for CO₂ emissions produced by the different biochar application rates for both crops. During the two cropping periods, the overall N₂O emission was significantly decreased with BC5, BC10, BC15, and BC20 applications as compared to the control, ranging from 11.1 to 13.6%, 8.7 to 15.4%, 23.1 to 26.0%, and 15.0 to 19.6%, respectively (average 16.9% decrease in the corn crop period and 16.3% in the Chinese cabbage crop period). Soil quality results after the final crop harvest show that bulk density, soil organic carbon (SOC), pH, and cation exchange capacity (CEC) were significantly improved by biochar application, as compared to the control. Taken together, our results indicate that compost application supplemented with biochar is potentially an appropriate strategy for achieving high crop productivity and improving soil quality in upland field conditions. In conclusion, appropriate application of biochar with compost has the concomitant advantages of enriching soil quality for long-term sustainable agriculture and reducing the use of inorganic fertilizers.

This study aimed to produce livestock manure biochar to decrease environmental problems from livestock manure and evaluate its effectiveness as an organic fertilizer by examining the growth and nutrient use efficiency of crops. A plot experiment was conducted to investigate the characteristics of lettuce growth and nitrogen use efficiency in upland soils treated with cow manure biochar. The cow manure biochar was applied at rates of 0, 3, 5, 7, and 10 t ha⁻¹ (referred to as CMB0, CMB3, CMB5, CMB7, and CMB10, respectively), along with inorganic fertilizer (IF, NPK—200-59-12 kg ha⁻¹). The lettuce cultivation test was carried out for 42 days, during which the fresh weight, dry weight, length, and number of lettuce leaves were measured. Nitrogen use efficiency was evaluated by determining the agronomic efficiency of N and the apparent recovery fraction of N. Overall, as the cow manure biochar application rate increased, crop growth and nitrogen uptake improved. Soils treated with CMB5 and CMB7 showed higher lettuce growth, nitrogen content, and nitrogen uptake compared to soils under other treatments. Nitrogen use efficiency followed a pattern similar to that of crop productivity, with cow manure biochar application levels playing a significant role. In particular, the agronomic efficiency of N and the apparent recovery fraction of N, which are both related to crop nutrient utilization, were significantly higher in the CMB5 treatment compared to the IF treatment. These results indicate that nitrogen use efficiency can be enhanced through biochar application when growing crops on agricultural land. Therefore, it is suggested that the appropriate application of cow manure biochar can reduce inorganic fertilizer use and increase crop productivity, thereby enabling sustainable and eco-friendly agriculture.

The global focus continues with respect to increasing agricultural productivity, such as in paddy soils using inorganic fertilizers. Such practices could adversely affect the agricultural environment by deteriorating soils and increasing greenhouse gas emissions. The aim of this study was to assess the effect of biochar pellet blended with condensed molasses soluble (CMS) on rice productivity, soil quality, and methane (CH₄) emissions in a paddy condition for healthy agricultural ecosystem. This study used a commercial scale pyrolysis system to produce biochar at 600 °C from bamboo. The experiment consisted of three different treatments: control, inorganic fertilizer (IF, N-P-K = 90-45-57 kg ha⁻¹), and biochar pellet (BC_PT, 1000 kg ha⁻¹). Compared to other treatments, the biochar pellet decreased annual CH₄ flux by 15.8–18.8%. The rice grain yield under inorganic fertilizer as conventional rice management was slightly more than applied biochar pellets, despite lower soil chemical properties. However, for long-term paddy management, including environmental protection and rice production, biochar pellets are better suited for maintaining a healthy agricultural ecosystem than conventional practices. Indeed, the application of biochar pellets appears to potentially reduce CH₄ emissions and maintain stable rice productivity through the slow release of nutrients.