Biochar application does not improve the soil hydrological function of a sandy soil

The addition of biochar (BC) has been suggested to increase the soil fertility and crop productivity of agricultural lands. This study evaluated the effect of different levels of BC on properties of sandy desert soils and its ultimate impact on plant growth. The samples of desert sand were taken from the Kubuqi of Inner Mongolia, China and the Thar Desert, Pakistan. The sands were treated with a BC made from the fast pyrolysis of pine sawdust at 400 °C. Four BC application rates i.e. 0, 15, 22 and 45 t ha − 1 were used in this study. Effects of BC addition on the water consumption and plant growth of sorghum were monitored for eight weeks in a pot experiment. The hydraulic and chemical properties of soil were analyzed to discern the effect of BC on the fertility of sandy desert soils. The results showed that BC amendment significantly improved soil hydraulic and chemical properties. The BC applied at the rate of 22 t ha − 1 provided the best results as compared to all other treatments. Compared with the control group, the soil water-holding capacity (WHC) increased by 11% and 14%, water-retention capacity (WRC) increased by 28% and 32% and hydraulic conductivity decreased by 32% and 7% under the Kubuqi and the Thar Desert soils, respectively when BC was applied at 22 t ha − 1 . Similarly, total C increased by 11% and 7%, total K increased by 37% and 42%, total P increased by 70% and 68% and total Ca increased by 69% and 75% while soil pH significantly reduced by 0.67 and 0.79 units, in the Kubuqi and the Thar Desert soils, respectively. The sorghum dry matter yield (DMY) was also significantly improved by 18% and 22% under the Kubuqi and the Thar Desert soils, respectively. The higher sorghum DMY consequently improved water-use efficiency (WUE) by 40% and 41% under the Kubuqi and the Thar Desert soils, respectively. In contrast, the plant growth and DMY declined at higher application rate (45 t ha − 1 ) of BC. The BC made from fast pyrolysis of pine sawdust at a temperature of 400 °C showed great potential in improving the quality of sandy desert soils. Hence, it can be used for sandy desert soil management.

Effects of biochar application rate on sandy desert soil properties and sorghum growth

Biochar has potential as a valuable tool for the agricultural industry with its unique ability to help build soil health, increase physical properties of soil,
 soil pH, organic carbon content, conserve water and mitigate drought, reduce GHG emission, conserve nutrients, decrease fertilizer requirements, sequester carbon, increase crop productivity and serve as a most preferred habitat for microbes. In this study, three perishable biomass wastes viz. Pea pod (Pisum sativum), cauliflower leaves (Brassica oleracea) and orange peel wastes (Citrus sinensis) were carbonized and characterized for differential application. The biomass was subjected to carbonization at different temperatures from 100 to 600 °C for 1 h. Biomass and biochar samples were characterized for proximate (M, VM, FC, Ash), ultimate (CHNS-O), biochemical properties (Ce, He, Li), thermo gravimetric analysis, pH, EC and bulk density. The biochars were also analyzed through SEM and FTIR for identification of pore size and functional groups. The char yield was high in cauliflower leaf (30.16 %), followed by orange peel (25.54 %) and pea pod (21.154 %) at 300 °C. The total organic carbon (11.61 %), total negative surface anions (4.25 mmol H+ eq/g C) and water holding capacity (200 %) were high in pea pod biochar. The SEM images of biochar samples showed plane cleavage surfaces with broken edges. The surface functional groups of all the three biochar samples were hydroxyl, methyl, carboxylic and alkene groups. The pea pod and cauliflower leaf biochar showed higher values of organic carbon, total surface anions, water holding capacity and mineral content and performed as best soil amendment than orange peel biochar. These biochar can be used as an effective medium for increasing soil carbon, irrigation efficiency and efficient disposal of agricultural waste-biomass.

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Production, characterization and evaluation of biochar from pod (Pisum sativum), leaf (Brassica oleracea) and peel (Citrus sinensis) wastes

The growing need for food, energy and materials demands a resource efficient approach as the world’s population keeps increasing. Biochar is a valuable product that can be produced in combination with bio-energy in a cascading approach to make best use of available resources. In addition, there are resources that have not been used up to now, such as, e.g., many agro-residues that can become available. Most agro-residues are not suitable for high temperature energy conversion processes due to high alkali-content, which results in slagging and fouling in conventional energy generation systems. Using agro-residues in thermal processes, therefore, logically moves to lower temperatures in order to avoid operational problems. This provides an ideal situation for the combined energy and biochar production. In this work a slow pyrolysis process (an auger reactor) at 400 °C and 600 °C is used as well as two fluidized bed systems for low-temperature (600 °C–750 °C) gasification for the combined energy and biochar generation. Comparison of the two different processes focuses here on the biochar quality parameters (physical, chemical and surface properties), although energy generation and biochar quality are not independent parameters. A large number of feedstock were investigated on general char characteristics and in more detail the paper focuses on two main input streams (woody residues, greenhouse waste) in order to deduct relationships between char parameters for the same feedstock. It is clear that the process technology influences the main biochar properties such as elemental- and ash composition, specific surface area, pH, in addition to mass yield quality of the gas produced. Slow pyrolysis biochars have smaller specific surface areas (SA) and higher PAH than the gasification samples (although below international norms) but higher yields. Higher process temperatures and different gaseous conditions in gasification resulted in lower biochar yields but larger TSA, higher pH and ash contents and very low tar content (16-PAH). From the feedstock data looked at in more detail, a few trends could be deducted in the attempt to learn how to steer the biochar characteristics for specific uses.

Biochar for Soil Improvement: Evaluation of Biochar from Gasification and Slow Pyrolysis

The high consumption of water in industries, domestic areas and increasing earth temperature are major hurdles for the optimization of maize yield. Being the third most widely cultivated cereal crop, improvement in maize yield is a big challenge under the limited availability of irrigation. As the water requirement for maize cultivation is high, it is time to introduce technologies that can mitigate drought stress and are environmentally friendly. The inoculation of rhizobacteria with ‘1-aminocyclopropane-1-carboxylate deaminase’ (ACCD) can play an imperative role in that regard by decreasing stress ethylene in plants. Biochar (BC) can also alleviate drought stress. Therefore, a field study was conducted, to examine the single and combined application of drought-tolerant plant-growth-promoting rhizobacteria (PGPRs) Achromobacter xylosoxidans and Enterobacter cloacae, with 15 Mg ha−1 of timber waste biochar (TWBC) at normal irrigation = 16 irrigations, mild drought = 14 irrigations and severe drought = 12 irrigation for maize cultivation. A significant improvement in shoot dry weight (28%), 1000-grains weight (19%), grain yield (27%), concentrations of N (43%), P (92%) and K (71%) in grains, rate of photosynthesis (33%), transpiration rate (55%), stomatal conductance (104%), chlorophyll A (33%), chlorophyll B (62%) and total chlorophyll (45%) of maize was noted under drought stress where E. cloacae + TWBC was applied. Likewise, the application of A. xylosoxidans + TWBC also significantly enhanced the plant height (24%) and cob length (9%) of maize under drought stress. In conclusion, E. cloacae is more effective than A. xylosoxidans, with 15 Mg ha−1 TWBC to increase maize yield under drought stress, due to the potential of higher ‘1-aminocyclopropane-1-carboxylate’ (ACC)-deaminase synthesis, better nutrient solubilization and indole acetic acid (IAA) production.

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Drought Stress Alleviation by ACC Deaminase Producing Achromobacter xylosoxidans and Enterobacter cloacae, with and without Timber Waste Biochar in Maize

With the rise in global population and increased agricultural requirements comes an increasing need for freshwater. Currently, it is estimated that approximately 75% of fresh water consumption is for the growth of agricultural crops, and only 10% to 30% of this water is actually made available to plants. It is widely accepted that farming practices which rely heavily on chemical fertilizers and unsustainable land management practices have led in many regions to infertile sandy soils with reduced water holding capacity and insufficient amounts of organic matter. Combined with increasing global population, the need to better manage fresh water use, particularly agricultural usage, is paramount. The use of biochar as a soil amendment has been suggested as a way to increase water holding capacity, but only limited quantitative studies exist in terms of the effectiveness of biochar in increasing a soil's water holding capacity. The main purpose of this study was to determine the effect of woody biochar amendment (yellow pine from pyrolysis at 400°C) on the water holding capacity of loamy sand soil with different mixture rates. Results show a doubling in water holding capacity by mass using a 9% mixture of biochar (equivalent to 195 metric ton/ha), which is an agriculturally relevant concentration. High percentage mixtures of biochar increase water holding capacity dramatically. These results suggest the use of biochar has potential to mitigate drought and increase crop yields in loamy sand soil.

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Sam Sink

Papers

Impact of biochar on the water holding capacity of loamy sand soil