Biochar and crop residue application to soil: effect on soil biochemical properties,nutrient availability and yield of rice (Oryza sativa L.) and wheat (Triticum aestivum L.)

In the recent past, biochar and crop residues have attracted lots of attention as a viable strategy for maintaining soil health. This paper evaluates the comparative effect of two different doses (equivalent to 2 and 5 t C ha^?1) of each of pine needle and Lantana biochar (PBC and LBC), wheat residue and lentil residue (WR and LR) on soil biological properties, nutrient availability and yield of rice and wheat in pot culture. Energy-dispersive X-ray spectroscopy (EDS) revealed higher C content of biochar than crop residues. Evaluation of biochemical quality reflected high recalcitrance indices of C and N for both PBC and LBC. Application of LBC and PBC increased the wheat grain yield significantly by 6.2%–24.2% over control. Both PBC and LBC significantly increased N and P uptakes in grain over the control and crop residues. Both biochars recorded a significant decrease of 33.9 and 71,7% in β-glucosidase activity in comparison to control at termination of study. PBC and LBC also resulted in more soil available N, P and K in soil at different intervals. The geometric mean of enzyme activities (GMea) reflected improved soil quality by PBC and LR and reduction by LBC application.     

Carbon mineralization in subtropical alluvial arable soils amended with sugarcane bagasse and rice husk biochars

Subtropical recent alluvial soils are low in organic carbon (C). Thus, increasing organic C is a major challenge to sustain soil fertility. Biochar amendment could be an option as biochar is a C-rich pyrolyzed material, which is slowly decomposed in soil. We investigated C mineralization (CO₂-C evolution) in two types of soils (recent and old alluvial soils) amended with two feedstocks (sugarcane bagasse and rice husk) (1%, weight/weight), as well as their biochars and aged biochars under a controlled environment (25 ±2 ℃) over 85 d. For the recent alluvial soil (charland soil), the highest absolute cumulative CO₂-C evolution was observed in the sugarcane bagasse treatment (1 140 mg CO₂-C kg^-1 soil) followed by the rice husk treatment (1 090 mg CO₂-C kg^-1 soil); the lowest amount (150 mg CO₂-C kg^-1 soil) was observed in the aged rice husk biochar treatment. Similarly, for the old alluvial soil (farmland soil), the highest absolute cumulative CO₂-C evolution (1 290 mg CO₂-C kg^-1 soil) was observed in the sugarcane bagasse treatment and then in the rice husk treatment (1 270 mg CO₂-C kg^-1 soil); the lowest amount (200 mg CO₂-C kg^-1 soil) was in the aged rice husk biochar treatment. Aged sugarcane bagasse and rice husk biochar treatments reduced absolute cumulative CO₂-C evolution by 10% and 36%, respectively, compared with unamended recent alluvial soil, and by 10% and 18%, respectively, compared with unamended old alluvial soil. Both absolute and normalized C mineralization were similar between the sugarcane bagasse and rice husk treatments, between the biochar treatments, and between the aged biochar treatments. In both soils, the feedstock treatments resulted in the highest cumulative CO₂-C evolution, followed by the biochar treatments and then the aged biochar treatments. The absolute and normalized CO₂-C evolution and the mineralization rate constant of the stable C pool (K_s) were lower in the recent alluvial soil compared with those in the old alluvial soil. The biochars and aged biochars had a negative priming effect in both soils, but the effect was more prominent in the recent alluvial soil. These results would have good implications for improving organic matter content in organic C-poor alluvial soils.     

稻壳基生物炭对生菜Cd吸收及土壤养分的影响

探讨稻壳基生物炭对Cd污染土壤上叶菜吸收Cd和土壤Cd形态的影响作用,明确稻壳基生物炭对土壤Cd污染的调控效应,可为合理利用稻壳基生物炭降低叶菜Cd含量提供参考。采用盆栽试验,研究了稻壳基生物炭在不同用量水平下对2茬生菜地上部Cd含量、土壤养分含量及Cd赋存形态的影响。结果表明,在5~25 g-kg-1用量范围内,稻壳基生物炭显著降低了2茬生菜地上部和根系Cd含量,且在最大用量25 g-kg-1时效果最好,地上部Cd含量分别比未施稻壳基生物炭的对照处理降低了19.6%和45.8%,根系Cd含量分别降低了36.8%和28.0%。在25 g-kg-1用量水平下,稻壳基生物炭对土壤p H、有效磷、速效钾及有机质含量提升效果明显,但显著降低了土壤碱解氮含量。施加稻壳基生物炭对土壤有效态Cd含量及Cd化学形态也有不同影响。随着稻壳基生物炭用量的增加,土壤NH4OAc提取态Cd含量和弱酸提取态Cd含量显著降低,在用量为25 g-kg-1时,分别比对照降低17.9%和10.4%,可还原态Cd含量无显著变化,可氧化态Cd含量呈减低趋势,残渣态Cd含量增加17.6%。因此推测,提升土壤p H、降低土壤有效态Cd含量、增加残渣态Cd含量可能是稻壳基生物炭降低生菜体内Cd含量的主要原因。稻壳基生物炭可以作为土壤改良剂,抑制Cd污染土壤上叶菜对Cd的吸收,改善土壤养分状况。     

Coffee‐husk biochar application increased AMF root colonization,P accumulation,N2 fixation,and yield of soybean grown in a tropical Nitisol,southwest Ethiopia

Low soil fertility and soil acidity are among the major bottlenecks that limit agricultural productivity in the humid tropics. Soil management systems that enhance soil fertility and biological cycling of nutrients are crucial to sustain soil productivity. This study was, therefore, conducted to determine the effects of coffee‐husk biochar (0, 2.7, 5.4, and 16.2 g biochar kg^?1 soil), rhizobium inoculation (with and without), and P fertilizer application (0 and 9 mg P kg^?1 soil) on arbuscular mycorrhyzal fungi (AMF) root colonization, yield, P accumulation, and N₂ fixation of soybean [Glycine max (L.) Merrill cv. Clark 63‐K] grown in a tropical Nitisol in Ethiopia. ANOVA showed that integrated application of biochar and P fertilizer significantly improved soil chemical properties, P accumulation, and seed yield. Compared to the seed yield of the control (without inoculation, P, and biochar), inoculation, together with 9 and 16.2 g biochar kg^?1 soil gave more than two‐fold increment of seed yield and the highest total P accumulation (4.5 g plant^?1). However, the highest AMF root colonization (80%) was obtained at 16.2 g biochar kg^?1 soil without P and declined with application of 9 mg P kg^?1 soil. The highest total N content (4.2 g plant^?1) and N₂ fixed (4.6 g plant^?1) were obtained with inoculation, 9 mg P kg^?1, and 16.2 g biochar kg^?1 soil. However, the highest %N derived from the atmosphere (%Ndfa) (> 98%) did not significantly change between 5.4 and 16.2 g kg^?1 soil biochar treatments at each level of inoculation and P addition. The improved soil chemical properties, seed yield, P accumulation and N₂ fixation through combined use of biochar and P fertilizer suggest the importance of integrated use of biochar with P fertilizer to ensure that soybean crops are adequately supplied with P for nodulation and N₂‐fixation in tropical acid soils for sustainable soybean production in the long term.     

Biochars influence sweet‐potato yield and nutrient uptake in tropical Papua New Guinea

Currently, the biomass of an invasive and obnoxious weed, kunai grass (Imperata cylindrica), is uncontrollably burnt in Papua New Guinea in subsistence farming systems resulting in unwarranted negative environmental consequences. We explored the possibility of sustainable utilization of biochar produced from the weed biomass along with a standard feedstock‐rice husk (Oryza sativa). Biochars were produced with lab‐scale pyrolysis at 550°C, characterized for chemical properties and plant nutrient composition. Further, agronomic efficacy of soil incorporation of biochars (5 t ha^?1) or co‐applied with mineral fertilizers (100, 11, and 62 kg ha^?1 N, P, K, respectively) was tested for sweet potato (Ipomoea batatas L. Lam) in a field experiment. The two biochars differed significantly (P < 5%) with respect to recovery from the feedstocks, chemical characters and nutrient composition. Kunai grass biochar was poorer in nutrients (< 1%) with distinctly alkaline pH and higher electrical conductivity. Biochar amendment to soil showed significant (P < 5%) improvement of soil moisture, while co‐application of biochars along with mineral fertilizers showed soil moisture decrease. Biochar amendment improved the growth parameters and total tuber yield of sweet potato by about 20%, while co‐application with mineral fertilizers augmented total tuber yield by 100% and above‐ground biomass yields by > 75%. Besides, improving agronomic performance of sweet potato crop, co‐application of biochars with mineral fertilizers enhanced uptake of N, P, K, Ca, Mg, and S. Production and utilization of biochar in sweet‐potato production could offer an efficient means of disposing biomass of kunai grass with concomitant productivity improvement in Papua New Guinea.     

Chemical fractions and bioavailability of nickel in a Ni-treated calcareous soil amended with plant residue biochars

ABSTRACT

Recently, the use of biochars for stabilization of soil heavy metals has been expanded due to their adsorption characteristics, low cost and carbon storage potential. A factorial experiment was performed to investigate the effects of two plant residue biochars (licorice root pulp and rice husk biochar each applied at 2.5% (w/w)) produced at two temperatures (350 and 550 °C), and three Ni application rates (0, 150 and 300 mg Ni kg^?1) on bioavailability and chemical fractions of Ni in a calcareous soil after spinach cultivation. Application of all the biochars significantly reduced Ni bioavailability factor (5–15%) and spinach Ni concentration (54–77%) in Ni-treated soil. The biochars produced at 550 °C were more effective at reducing Ni mobility and Ni uptake by spinach than those produced at 350 °C, attributed to higher CaCO₃ and lower acidic functional group content, which resulted in greater enhancement of soil pH. When comparing the biochars produced at the same temperature, the rice husk biochars were the most effective in reducing Ni bioavailability, likely due to their lower acidic functional group content and higher nano-silica content which resulted in higher soil pH values and potentially promoted the formation of Ni-silicates and hydroxides.

Abbreviations : Ni: Nickel; RHB: rice husk biochar; LRB: licorice root pulp biochar; WsEx: water soluble and exchangeable; CARB: carbonate form; RES: residual; MnOx; manganese oxides bound; AFeOx; amorphous iron oxides bound; CFeOx: crystalline iron oxides bound; OM: organic bound.     

Growth,survival, and heavy metal (Cd and Ni) uptake of spinach (Spinacia oleracea) and fenugreek (Trigonella corniculata) in a biochar‐amended sewage‐irrigated contaminated soil

Irrigation of arable land with contaminated sewage waters leads to the accumulation of trace metals in soils with subsequent phyto‐/zootoxic consequences. In this study, biochar derived from cotton sticks was used to amend an agricultural silt‐loam soil that had been previously irrigated with trace metal contaminated sewage waters. Metal accumulation and toxicity to spinach (Spinacia oleracea) and fenugreek (Trigonella corniculata) was investigated by measuring concentrations of Cd and Ni in plant tissues and various photosynthetic and biochemical activities of plants. Positive impacts of biochar on both spinach and fenugreek were observed in terms of biomass production that increased from 29% to 36% in case of spinach, while for fenugreek this increase was 32% to 36%. In the control treatment there was an increase in malondialdihyde, soluble sugar, and ascorbic acid contents, indicating heavy metal stress. Biochar applications increased soluble proteins and amino acids in plants and reduced the uptake of Cd from 5.42 mg kg^?1 at control to 3.45 mg kg^?1 at 5% biochar amended soil and Ni (13.8 mg kg^?1 to 7.3 mg kg^?1 at 5% biochar) by the spinach plants. In fenugreek, the Cd was reduced from 7.72 mg kg^?1 to 3.88 mg kg^?1 and reduction in Ni was from 15.45 mg kg^?1 to 9.46 mg kg^?1 at 5% biochar treated soil, reducing the possibility of transfer up the food chain. This study demonstrates that the use of biochar made from cotton‐sticks, as an amendment to arable soils that have received contaminated irrigation water, could improve plant growth and decrease Cd and Ni uptake to crops, alleviating some of the negative impacts of using sewage waters on arable land.     

复合改良剂对镉砷化学形态及在水稻中累积转运的调控

为治理镉砷污染农田土壤,选取湘南某矿区镉砷复合污染稻田土壤,以水稻盆栽实验研究了复合改良剂HZB(羟基磷灰石+沸石+改性秸秆炭)对土壤中镉(Cd)、砷(As)赋存形态以及水稻累积转运Cd和As的影响。结果表明,施用HZB能提高土壤p H 0.19~0.79个单位,阳离子交换量增加22.1%~60.4%;施用HZB使活性较大的酸提取态Cd含量降低了6.5%~22.9%,促进了Cd向难溶态的转变,可使有机结合态Cd增加2.5%~56.5%;施用HZB促进活性As向难溶型的钙型As转化,钙型As含量增加2.8%~53.3%,也可使交换态As含量降低7.0%~39.5%,但当施用量超过4.0 g kg-1时则会增加交换态As含量。水稻根系对Cd的富集系数在0.65~1.21之间,对As的富集系数在0.033~0.049之间,富集Cd的能力大于As;谷壳对Cd的转运能力最大,而根系对As的转运能力最大;施用HZB有降低水稻根系富集Cd和As的能力。施用0.5~2.0 g kg-1的HZB能降低水稻地上各部位中Cd和As含量;在2 g kg-1施用水平,水稻糙米中Cd和As含量均低于0.2 mg kg-1,达到国家食品污染物限量标准。     

生物黑炭对玉米苗期根际土壤氮素形态及相关微生物的影响

生物黑炭被作为土壤改良剂应用逐渐被认可,但其应用机制特别是生物黑炭对氮素形态和根际微生物的影响机理尚不明确,影响其推广。本文采用盆栽试验,研究了玉米和水稻秸秆烧制的生物黑炭按不同量施入土壤后,对玉米苗期株高、生物量和根际土壤氮素形态及相关微生物的影响。结果表明,施入60 g·kg-1玉米黑炭和40~60 g·kg-1水稻黑炭均对玉米苗期株高有显著(P0.05)降低作用,其中水稻黑炭的降低效果更为明显;分别施入60 g·kg-1玉米黑炭和20~60 g·kg-1水稻黑炭后,玉米植株地上部生物量均显著降低。施入60 g·kg-1玉米黑炭后根际土壤含水量和微生物量氮显著提高。随两种生物黑炭施入量的不断增加,玉米苗期根际土壤全氮、硝态氮含量以及固氮作用强度也显著增加,且均在60 g·kg-1施用量下达最大值。施用40 g·kg-1玉米黑炭可显著提高玉米苗期根际土壤氨态氮含量。同时,施用两种生物黑炭后,均不同程度地抑制了玉米根际土壤中细菌总体数量,促进了固氮菌和纤维素降解菌的生长,其中施入60 g·kg-1玉米黑炭的效果最为明显。综上,玉米和水稻秸秆生物黑炭的适量施用,可以促进玉米根际土壤氮素的循环转化,影响相关微生物的群落结构,且与水稻秸秆相比,玉米秸秆生物黑炭的施用效果更加明显。本文针对作物生长、土壤氮素形态及相关微生物数量3个方面研究生物黑炭施入土壤对氮有效性的影响,能够更全面、更准确地将生物黑炭如何影响土壤氮素转化展现出来,促进生物黑炭的深入开发利用,对黑土肥力保护具有一定意义。     

Decomposition and Carbon Sequestration Potential of Different Rice-Residue-Derived By-products and Farmyard Manure in a Sandy Loam Soil

Large quantities of rice straw are produced annually in India and the majority of it is burnt in the fields, leading to environmental pollution and loss of carbon (C) and essential nutrients. It is imperative to manage rice residues and by-products to derive benefits for soil health and environment conservation. We studied the decomposition of rice straw (RS), rice-straw-derived biochar and compost (RSC), rice husk (RH), rice husk ash (RHA), and farmyard manure (FYM) in laboratory incubation experiments at 30 ºC and field-capacity moisture. The decomposition of organic sources depended on the size of decomposable and recalcitrant C pools. Carbon mineralization was greater from RS and RH compared to FYM, biochar, RSC, and RHA. The initial rate of mineralization was faster for RS and RH, followed by FYM, biochar, and RSC, and the least for RHA. The proportion of antecedent C mineralized from different sources followed the order RS > RH > FYM> RSC = biochar > RHA. The RS and RH showed larger decomposable pools than the other sources. Rice husk ash had decomposable pool and associated rate coefficient similar to the unamended soil. Residence time for recalcitrant pool in FYM, RSC, and biochar applied at 5 g C kg^–1 soil ranged between 1020 and 1149 days as opposed to 180 and 254 days for RS and RH, respectively. Increasing the rate of C application (15 g C kg^?1) markedly increased the residence time for all the sources, except FYM, and these followed the order RHA (2273 d) > RSC (2000 d) > biochar (1961 d) > RH (529 d) > RS (400 d). It was concluded that RS and RH could result in short-term C accrual in soil, whereas RSC, biochar, and FYM may lead to long-term C sequestration. The disposal of RHA to soil, which is characterized by mainly recalcitrant C, could lead to buildup of soil organic C.     

Short-term effects of biochar amendment on soil microbial community in humid tropics

Biochar is known to ameliorate soil fertility and improve crop production but information regarding soil microbiota responses on biochar amendment remains limited. The experiment was conducted to study the effect of biochars from palm kernel (pyrolysed at 400°C) and rice husk (gasified at 800°C) in a sandy loam Acrisol from Peninsular Malaysia. The soil was amended with palm kernel shell biochar (PK), rice husk biochar (RH), palm kernel biochar with fertilizer (FPK), rice husk biochar with fertilizer (FRH), fertilizer and control soil. Soil samples were taken during maize harvesting and were analysed for physico-chemical properties, microbial biomass, microbial abundance and microbial diversity. Increase in pH, moisture content, CEC, organic C, and labile C were recorded in all biochar amended soils. Microbial biomass C was 65% and 36% higher in RH and FRH, respectively, than control. Microbial biomass N was greatest in FPK and FRH with respective increment of 359% and 341% than control. β-glucosidase and xylanase activities were significantly increased in all biochar treated soils than control. A shift in microbial diversity was not detected. The biochar affects the microbial community by altering the soil environment and increasing labile active carbon sources in the short-term amendment.     

Designing relevant biochars as soil amendments using lignocellulosic-based and manure-based feedstocks

Purpose

Biochars are a by-product of the biofuel processing of lignocellulosic and manure feedstocks. Because biochars contain an assemblage of organic and inorganic compounds, they can be used as an amendment for C sequestration and soil quality improvement. However, not all biochars are viable soil amendments; this is because their physical and chemical properties vary due to feedstock elemental composition, biofuel processing, and particle size differences. Biochar could deliver a more effective service as a soil amendment if its chemistry was designed ex ante with characteristics that target specific soil quality issues. In this study, we demonstrate how biochars can be designed with relevant properties as successful soil amendments through feedstock selection, pyrolysis conditions, and particle size choices.

Materials and methods

Biochars were produced by pyrolysis of parent lignocellulosic feedstock sources—peanut hull (PH; Archis hypogaea), pecan shell (PS; Carya illinoensis), switchgrass (SG; Panicum virgatum), pine chips (PC; Pinus taeda), hardwood wastes (wood), and poultry litter manure (PL; Gallus domesticus), as well as blends of these feedstocks at temperatures ranging from 250 to 700 °C. Additionally, blended feedstocks were made into pellets (>2 mm) prior to pyrolysis at 350 °C. Dust-sized (<0.42 mm) biochar was obtained through grinding of pelletized biochars. After chemical characterization, the biochars were evaluated as fertility amendments in a Norfolk soil (fine-loamy, kaolinitic, thermic, Typic Kandiudult) during two different pot incubation experiments.

Results and discussion

PL biochars were alkaline and enriched in N and P, whereas biochar from lignocellulosic feedstocks exhibited mixed pH and nutrient contents. Blending PL with PC resulted in lower biochar pH values and nutrient contents. In pot experiment 1, most biochars significantly (P?<?0.05) raised soil pH, soil organic carbon, cation exchange capacity, and Mehlich 1 extractable P and K. PL biochar added at 20 g?kg^?1 resulted in excessive soil P concentrations (393 to 714 mg?kg^?1) and leachate enriched with dissolved phosphorus (DP, 22 to 70 mg?L^?1). In pot experiment 2, blended and pelletized PL with PC feedstock reduced soil pH and extractable soil P and K concentrations compared to pot experiment 1. Water leachate DP concentrations were significantly (P?<?0.05) reduced by pelletized biochar blends.

Conclusions

Short-term laboratory pot experiments revealed that biochars can have different impacts at modifying soil quality characteristics. Keying on these results allowed for creating designer biochars to address specific soil quality limitations. In the process of manufacturing designer biochars, first, it is important to know what soil quality characteristics are in need of change. Second, choices between feedstocks, blends of these feedstocks, and their accompanying particle sizes can be made prior to pyrolysis to create biochars tailored for addressing specific soil quality improvements. Utilization of these principles should allow for effective service of the designed biochar as a soil amendment while minimizing unwanted ex facto soil quality changes and environmental effects.     

The interactive effects of biochar and cow manure on rice growth and selected properties of salt-affected soil

Salt-affected soil induces detrimental influences on paddy rice (Oryza sativa L.) growth and ameliorating the influences could be done with organic amendments, such as animal manure and biochar. The aims of the current study are: (1) to examine the interactive effects of biochar and cow manure on rice growth and on selected properties of salt-affected soil, and (2) to identify potential mechanisms related to the amendments. Saline-sodic soil was used for a net house experiment with two experimental factors: biochar (no-biochar, rice-husk, and -straw biochar) and cow manure (with and without cow manure). Without the manure, addition of both rice-hush and – straw biochar significantly increased rice growth, whereas a combination of individual biochar with manure did not show a positive synergistic effect. The interactive effect of two factors was not significant on available P and exchangeable K concentrations, but the main effects of the two factors were significant. Biochar addition resulted in higher soil cation exchange capacity (CEC) (28.8 to 29.0 cmol_c kg^?1) than the control (25.6 cmol_c kg^?1), but manure addition did not. Improved nutrient availabilities such as P and K, as well as CEC are among the potential mechanisms accounting for the enhanced rice growth with biochar.     

Soil management for raising crop water productivity in rainfed production systems in Lao PDR

This study investigated the impacts of organic- and clay-based soil amendments, and their combinations on crop water productivity (CWP) using maize as a test crop. On-station field trials were established over two consecutive years at the Naphok and Veunkham sites in Laos. At each site, 10 treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (10 t ha^?1), bentonite clay (10 t ha^?1), compost (4 t ha^?1), clay-manure compost (10 t ha^?1), rice husk biochar compost (10 t ha^?1), bentonite clay + biochar, bentonite-clay + compost, biochar + compost, and bentonite clay + biochar + compost. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in CWP and growing period evapotranspiration were determined. At Naphok, differences between the amended and control plots in CWP varied between 0.1 and 0.6 kg m^?3 in 2011 and from 0.1 to 0.4 kg m^?3 in 2012, whereas differences at Veunkham varied between 0.3 and 1.0 kg m^?3 in 2011 and from 0.05 to 0.29 kg m^?3 in 2012. At both sites, CWP in 2012 was significantly lower than 2011. Our results illustrate that organic- and clay-based soil amendments improve CWP, indicating that soil-based interventions could be suitable options for improving agricultural productivity.     

Sugarcane Bagasse Biochar: Preparation,Characterization, and Its Effects on Soil Properties and Zinc Sorption-desorption

ABSTRACT

Application of alkaline biochar has been proposed as an alternative to lime for remediation of acidic soils. However, questions remain as to how the reactions and fate of metals in acidic soils can be affected by biochar amendment. To find out how biochar addition might affect sorption-desorption behavior of zinc (Zn) in acidic soils, a soil with an initial pH value of 4.67 was treated with different levels [0 (control), 1%, 3%, and 6%] of biochar produced from pyrolysis of sugarcane bagasse at 600°C and incubated for 30 days under 80% of water holding capacity. At the end of the incubation period, important soil chemical properties were measured and batch isotherm experiments were performed to determine soil Zn sorption-desorption parameters. The results showed that the biochar-amended soils had higher pH values (up to 2.5 pH units), electrical conductivity (up to 2.66 times), and cation exchange capacities (up to 42%) relative to the un-amended acidic soil. Biochar addition also led to significant enhancements in soil exchangeable calcium, magnesium, sodium, and potassium cations. Both sorption and desorption isotherm experiments revealed the significantly higher capacity of the biochar-amended soils to retain Zn than that of the control. Moreover, the biochar-amended soils exhibited a higher affinity for Zn sorption than did the un-amended acidic one. It can be concluded that biochar derived from sugarcane bagasse could serve as a good amendment material to reclaim acidic soils and to reduce Zn mobility and toxicity in acidic metal-contaminated soils.     

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

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.     

Ameliorative effect of Lantana camara biochar on coal mine spoil and growth of maize (Zea mays)

The aftermath of surface mining is a wasteland deprived of vegetation, soil structure and biodiversity. The unearthed overburden material is nutrient deprived and can only support the growth of invasive weeds such as Lantana camera which often cause allelopathy. The aim of the study is to prepare biochar from these noxious weeds and use it as an amendment for the mine spoil reclamation. Lantana biochar (LB) was prepared and applied to mine spoil, and Zea mays L. growth on biochar amended mine spoil was monitored for three months. Biochar application in a coal mine spoil using LB is comparatively de novo approach for reclamation practitioners. LB was prepared at varying temperature (250, 350 and 450℃) and residence times (30, 45 and 60 min) and characterized. After characterization, the most recalcitrant biochar at 450℃ for 60 min was chosen for application for the study. A pot trial was conducted to study the effect of LB at 0, 5, 10, 20 and 30 g kg⁻¹ dosage on the yield of Zea mays and mine spoil properties. Significant ameliorative effects were observed with increase in organic carbon content (2.9 times), cation exchange capacity (2 times), water holding capacity (0.13 times) and decrease in bulk density (0.5 times) in the mine spoil. The seedling vigour index and germination also increased significantly (p < .05) at 30 g kg⁻¹ biochar treatment compared to control. The study concluded that LB has the potential to remediate coal mine spoils and promote re-vegetation in degraded land.     

Ryegrass yield and nutrient status after biochar application in two Mediterranean soils

This study was conducted to evaluate whether biochar, produced by pyrolysis at 300°C from rice husk and grape pomace (GP), affects plant growth, P uptake and nutrient status. A 3-month period of ryegrass (Lolium perenne L.) cultivation was studied on two Mediterranean agricultural soils. Treatments comprised control soils amended only with compost or biochar, and combinations of biochar plus compost, with the addition of all nutrients but P (FNoP) or without any fertilization at all (NoF). Application of both types of biochar or/with compost, in the presence of inorganic fertilization except P, significantly increased (P < 0.05) dry matter yield of ryegrass (58.9–77.6%), compared with control, in sandy loam soil, although no statistically significant increase was observed in loam soil. GP biochar and GP biochar plus compost amended loam soil harvests gave higher P uptake than control, in the presence of inorganic fertilization except P, whereas in sandy loam soil, a statistical increase was recorded only in the last harvest. In addition, Mn and Fe uptake increased with the addition of the amendments in both soils, while Ca increased only in the alkaline loam soil. Biochar addition could enhance ryegrass yield and P uptake, although inorganic fertilization along with soil condition should receive special attention.     

Biochar reduced soil extractable Cd but increased its accumulation in rice (Oryza sativa L.) cultivated on contaminated soils

Purpose

This study focused on the effects and mechanisms of biochar amendment to Cd-contaminated soil on the uptake and translocation of Cd by rice under flooding conditions.

Materials and methods

Pot and batch experiments were conducted using Cd-contaminated soil collected from a field near an ore mining area and a cultivar of Oryza sativa ssp. indica. Biochar derived from rice straw under anaerobic conditions at 500 °C for 2 h was mixed with the soil at the rate of 0, 2.5, and 5%.

Results and discussion

The application of 5% biochar reduced CaCl₂-extractable soil Cd by 34% but increased Cd concentration in brown rice by 451%. Biochar amendment decreased water-soluble Fe²⁺ in soils and formation of Fe plaques on roots and weakened the Fe²⁺-Cd²⁺ competition at adsorption sites on the root surface. Biochar increased water-soluble Cd in the soil and consequently Cd uptake by rice roots by releasing water-soluble Cl^?. Biochar application also reduced the proportion of cell wall-bound Cd in the root, which caused easier Cd translocation from the cortex to the stele in the root and up to the shoot.

Conclusions

Rice straw biochar (with high concentration of water-soluble Cl^?) reduced CaCl₂-extractable soil Cd but increased Cd concentration in rice under flooding condition.