Biochar & low fertility soils - meta-analysis

Biochar application to low fertility soils: A review of current status, and future prospects

Highlights

• Biochar has potential to be the best management practice for low fertility soils.

• Biochar coating with organic materials can result in enhanced crop nutrient supply.

• Biochar may accelerate the composting process and improve the end-product quality.

• The influence of biochar varies strongly according to the types of feedstock/soil.

Abstract

Rapid industrial development and human activities have caused a degradation of soil quality and fertility. There is increasing interest in rehabilitating low fertility soils to improve crop yield and sustainability. Biochar, a carbonaceous material intentionally produced from biomass, is widely used as an amendment to improve soil fertility by retaining nutrients and, potentially, enhancing nutrient bioavailability. But, biochar is not a simple carbon material with uniform properties, so appropriate biochar selection must consider soil type and target crop. In this respect, many recent studies have evaluated several modification methods to maximize the effectiveness of biochar such as optimizing the pyrolysis process, mixing with other soil amendments, composting with other additives, activating by physicochemical processes, and coating with other organic materials. However, the economic feasibility of biochar application cannot be neglected. Strategies for reducing biochar losses and its application costs, and increasing its use efficiency need to be developed. This review synthesized current understanding and introduces holistic and practical approaches for biochar application to low fertility soils, with consideration of economic aspects.

Biochar Effects on Rice Paddy: Meta-analysis

Author links open overlay panelYasser M.Awad^*†JinyangWang^‡Avanthi D.Igalavithana^*Daniel C.W.Tsang^§Ki-HyunKim^¶Sang S.Lee^||Yong SikOk^*

https://doi.org/10.1016/bs.agron.2017.11.005Get rights and content

Abstract

Rice is staple for nearly half of the world population. Biochar (BC) improves crop yields, reduces greenhouse gas (GHG) emissions, and immobilizes heavy metals in the soil. This study was aimed to meta-analyze the data from the published articles focused on the various BCs’ effects on rice yield, soil acidity, GHG emissions, and bioavailability of Cd and Pb. The data of pyrolysis temperature, application rate, and feedstock of BCs were categorized by using the MetaWin software for calculating the mean effect sizes (E) with 95% confidence intervals (CI). Compared to the control, the BCs increased soil pH and rice yield by 11.8% (medium E +: 0.436 to 0.439) and 16% (large E +: 0.790 to 0.883), respectively. Applying BCs derived from different feedstocks and pyrolysis temperatures reduced N₂O emissions from rice paddies (large E −: − 0.692 to − 0.863). The BCs produced at 550–600°C reduced the GHG emission with medium to large negative effects (E −: − 1.571 to − 0.413). Applications of BCs at a range of 41–50 t ha^− 1 were the best for rice productivity. Applications of all types and rates of BCs showed the significant decrease of available Cd by 35.4%–38.0% in a soil and led to the Cd reduction by an average of 43.6% in rice grains compared to the untreated soils. Applying BC is a promising approach to meet the challenges of sustainable global rice production, and the properties of BCs should be fully characterized and designed depending on its needs prior to its application.

Effects of biochar application on root traits: a meta-analysis

Effects of biochar application on root traits: a meta-analysis - Xiang - 2017 - GCB Bioenergy - Wiley Online Library

"Overall, biochar application increased root biomass (+32%), root volume (+29%) and surface area (39%). The biochar-induced increases in root length (+52%) and number of root tips (+17%) were much larger than the increase in root diameter (+9.9%); this result suggests that biochar application benefits root morphological development to alleviate plant nutrient and water deficiency rather than to maximize biomass accumulation. "

Read the full report from the link above.

Biochar characteristics and application in the agriculture

Biochar characteristics and application in the agriculture [

Martyna Glodowska, Malgorzata Lyszcz
Institute of Soil Science and Plant Cultivation – State Research Institute, Pulawy, Poland

Abstract 

Recently biochar gained importance as a way to deal with global climate change, by sequestering C into soils, but also as a soil amendment and bioremediation tool. Many studies have demonstrated the positive influence of biochar on soil quality and subsequently, plant growth, although the results are not consistent and climate seems to be the main reason for this inconsistency. Number of studies has been conducted to find out how biochar affect soil characteristic, fertilizers efficiency as well as soil microbiota. The main focus of this review is to discuss biochar features and it application in agricultural practices that could improve soil productivity and in consequence plant growth and development.

1. Introduction 

Biochar, although not in the form we know today, has been used since centuries. The incorporation of charcoal into the soil to enhance soil quality has been an agricultural practice for thousands of years (Xu et al. 2012). Pre-Columbian people were combining charred residues of organic and inorganic wastes with the soils that are known today as Terra Preta - rich in organic matter and nutrients Amazonian soil. The oldest description of charcoal use in agriculture may be from the 17th century Encyclopedia of Agriculture by Yasusada Miyazaki, where he cited an even older textbook from China. We know from there that rice husk charcoal has been used as a soil amendment probably since the beginning of rice cultivation in Asia (Ogava and Okimori, 2010). Nowadays, the term “biochar” refers to a product of biomass pyrolysis, wherein plant-based materials are heated under anaerobic conditions to capture combustible gases. Originally, biochar production was associated with slow pyrolysis, characterized by a long time (more than 10 h) under relatively low temperature, typically around 400°C. More recently, there has been growing interest in biochar production through fast pyrolysis, where the organic materials are rapidly heated to 450-600°C (Xu et al. 2012). The reason why biochar gained public interest is mainly associated with its carbon sequestration ability. Biochar is a promising tool to reduce the atmospheric CO2 concentration because it slows the return of photosynthetically fixed carbon to the atmosphere (Xu et al., 2012). The half-life of biochar in the soil is estimated to range from hundreds to thousands of years (Zimmerman 2010). Therefore, supplying the soil with biochar is a strategy for long-term carbon sequestration. Moreover, there is increasing interest in biochar as a soil amendment. Number of studies has demonstrated that biochar application can significantly improve crop productivity (Chan et al. 2007), improve soil conditions (Xu et al., 2012), and increase the efficiency of fertilizers (Asai et al., 2009), it can also be used in remediation processes (Chan et al., 2012). The main goal of this paper is to review the effect of biochar on soil properties and discuss it use in the agricultural practices.

6. Conclusion 

Biochar became [could become?] an important tool to mitigate the climate changes caused by anthropogenic activities. But as it is presented above biochar can also be successfully used in agricultural sector. The literature review presented above suggests that biochar is a material that significantly affects soil quality by changing its structure as well as chemical composition. It can be used in the water stress management and in the bioremediation processes, particularly in recovery of the soils contaminated with PAHs and heave metals. There are a growing number of evidences showing positive effect of biochar on plant growth and development; however this effect is strongly related to the climate and soil type. Also, biochar when applied together with mineral or organic fertilizers seems to significantly improve fertilizer efficiency and use by the plant. Finally, biochar was found to cause important changes in soil microbiota structure and function and it is believe to create favorable conditions for microorganisms.

Biochar average crop boost of 25% in tropics

This research supports potential biochar crop benefits for SEA region. It will be interesting to see how temperate biochar world responds to findings. There are plenty of reasons to use biochar other than crop production enhancement... and there are plenty of temperate soils with deficiencies that biochar can help with and thus boost crop yields. I think that a 'meta-analysis' flattens out all the data, hiding success and failure. The researchers have provided a link to their data spreadsheet. Maybe the results can be refined based on soil deficiency? This would be more useful?

new research on effect of biochar in open field crops:

"Biochar boosts tropical but not temperate crop yields''

"For years it has been promoted as a soil additive to increase crop yields. A new study casts doubt on that view, finding that biochar only improves crop growth in the tropics, with no yield benefit at all in the temperate zone.

The team of researchers gathered data from more than 1,000 empirical observations conducted around the world, each measuring the effect of biochar on crop yield. Then, they used meta-analysis, an advanced statistical technique that analyses many studies at the same time, to test whether the beneficial effect of biochar addition depends on geography.

That’s when the surprising result emerged: “Location, location, location: it really matters for biochar”, said Dr. Jeffery, lead author of the study and senior lecturer at Harper Adams University. “Biochar had a huge benefit in the tropics, a 25 per cent increase in yield. But in the temperate zone, there was just no effect at all. We were really surprised.”

The surprise came because past work has assumed that the beneficial yield effects of biochar are universal, applying to soils no matter where they occur. The new study was the first to test rigorously whether geography matters, and the researchers were able to do this because of the very large dataset they assembled.

The idea of biochar was inspired by a rare type of soil that occurs in the tropics, ‘terra preta’ – Portuguese for ‘black earth’, so named because the soil is rich in black carbon, the partially burned remains of old plants, much like charcoal. ‘Terra preta’ is fertile, with favourable pH, unlike typical tropical soils which are low in fertility and acidic. Initial experiments showed that adding biochar to typical tropical soils increased crop yields, making it possible for farmers to cultivate a plot of land in these soils for more than a few years.

The new study supports that view: “Our findings confirm that biochar can benefit farms in low-nutrient, acidic soils such as in the tropics”, explained Dr. Jeffery. “But in more fertile soils, such as those in the temperate zone, obtaining yield increases through biochar application is much less certain.” While it is possible that, biochar may maintain yields in some soils, while cutting costs on the purchase and application of fertilisers and agricultural lime, more research is needed to identify soils where such applications are relevant.

Many other benefits have been claimed for biochar, including managing waste, sequestering carbon in the soil, soil greenhouse gas flux mitigation, crop disease suppression, and being more environmentally friendly than adding synthetic chemicals to the soil. The new study did not evaluate these other potential benefits, and the authors note that some of these may still hold in both temperate and tropical regions, and that biochar research needs to focus on trade-offs between biochar’s interaction with these ecosystem services.

“While there may be other benefits to using biochar in the temperate zone, like increasing soil carbon to slow climate change”, said Dr. Jeffery, “our analysis, summarising over 1,000 observations, shows that the yield benefits just aren’t there. So if the goal for biochar application is boosting crop yield, stick to the tropics.”

The report has been published, open access, in Environmental Research Letters."