Wheat and maize-derived water-washed and unwashed biochar improved the nutrients phytoavailability and the grain and straw yield of rice and wheat: A field trial for sustainable management of paddy soils.

A field experiment was carried out to evaluate the effects of different biochars on grain yield and phytoavailability and uptake of macro- and micro-nutrients by rice and wheat grown in a paddy soil in a rotation. Soil was treated with i) maize raw (un-washed) biochar (MRB), ii) maize water-washed biochar (MWB), iii) wheat raw biochar (WRB) or iv) wheat water-washed biochar (WWB) and untreated soil was used as control (CF). Inorganic fertilizers were applied to all soils while biochar treated soils received 20 ton ha-1 of designated biochar before rice cultivation in rice-wheat rotation. The WRB significantly (P < 0.05) increased rice grain yield and straw by up to 49%, compared to the CF. Biochar addition, particularly WRB, significantly increased the availability of N, P, K and their content in the grain (26-37%) and straw (22-37%) of rice and wheat. Also, the availability and grain content of Fe, Mn, Zn, and Cu increased significantly after biochar addition, particularly after the WRB, due to WRB water dissolved C acting as a carrier for micronutrients in soil and plant. However, the water-washing process altered biochar properties, particularly the water extractable C, which decreased its efficiency. Both wheat- and maize-derived biochars, particularly the WRB, are recommended to improve nutrients availability and to improve grain yield in the rice-wheat rotation agro-ecosystem. These results shed light on the importance of crop straw transformation into an important source for soil C and nutrients necessary for sustainable management of wheat-rice agro-ecosystem. However, with the current and future alternative energy demands, the decision on using crop biomass for soil conservation or for bioenergy becomes a challenge reliant on regulatory and policy frameworks.

Animal carcass- and wood-derived biochars improved nutrient bioavailability, enzyme activity, and plant growth in metal-phthalic acid ester co-contaminated soils: A trial for reclamation and improvement of degraded soils.

Reclamation of degraded soils such as those with low organic carbon content and soils co-contaminated with toxic elements and phthalic acid esters (PAEs) is of great concern. Little is known about the efficiency of plant- and animal-derived biochars for improving plant growth and physicochemical and biological properties of co-contaminated soils, particularly under low content of organic matter. Hence, a pot trial was carried out by growing pak choi (Brassica chinensis L.) to assess the influence of different doses (0, 0.5, 1, 2, and 4%) of animal (pig carcass) and wood (Platanus orientalis) derived biochars on soil properties, nutrient availabilities, plant growth, and soil enzyme activities in two soils containing low (LOC) and high (HOC) organic carbon contents and co-contaminated with di-(2-ethylhexyl) phthalic acid (DEHP) and cadmium (Cd). Biochar applications improved pH, salinity, carbon content, and cation exchange capacity of both soils. Addition of biochars significantly increased the bioavailability and uptake of phosphorus and potassium in the plants in both soils with greater effects from pig biochar than wood biochar. Biochar additions also significantly enhanced urease, sucrase, and catalase activities, but suppressed acid phosphatase activity in both soils. The impact of pig biochar was stronger on urease and acid phosphatase, while the wood biochar was more effective with sucrase and catalase activities. The biomass yield of pak choi was significantly increased after biochar addition to both soils, especially in 2% pig biochar treatment in the LOC soil. The positive response of soil enzymes activities and plant growth for biochar addition to the Cd and DEHP co-contaminated soils indicate that both biochars, particularly the pig biochar can mitigate the risk of these pollutants and prove to be eco-friendly and low-cost amendments for reclaiming these degraded soils.

Biochar composition-dependent impacts on soil nutrient release, carbon mineralization, and potential environmental risk: A review.

Biochar application has multiple benefits for soil fertility improvement and climate change mitigation. Biochar can act as a source of nutrients and sequester carbon (C) in the soil. The nutrient release capacity of biochar once applied to the soil varies with the composition of the biochar, which is a function of the feedstock type and pyrolysis condition used for biochar production. Biochar has a crucial influence on soil C mineralization, including its positive or negative priming of microorganisms involved in soil C cycling. However, in various cases, biochar application to the soil may cause negative effects in the soil and the wider environment. For instance, biochar may suppress soil nutrient availability and crop productivity due to the reduction in plant nutrient uptake or reduction in soil C mineralization. Biochar application may also negatively affect environmental quality and human health because of harmful compounds such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins, and dibenzofurans (PCDD/DF). In this review, we discuss the linkage between biochar composition and function, evaluate the role biochar plays in soil fertility improvement and C sequestration, and discuss regulations and concerns regarding biochar's negative environmental impact. We also summarize advancements in biochar production technologies and discuss future challenges and priorities in biochar research.

Soil nutrients status affected by simple and enriched biochar application under salinity conditions.

In order to study the effect of biochar application as simple and enriched, on the soil nutrients status in the salinity conditions, a research was conducted as a factorial arrangement based on completely randomized design (CRD) with three replicates. The biochar (grape pruning residues) was applied in three levels (0, 2% biochar, and 2% enriched biochar by rock phosphate and cow manure). Also, the salinity treatment was considered in three levels (2, 4.5, and 9 dSm-1). After treating the soil, it was incubated in polyethylene containers for a 70-day period at 25 °C and 70% field capacity moisture regime. The results showed that salinity significantly affected the soil pH, electrical conductivity (EC), calcium, magnesium, sodium, basal respiration, and nitrifying bacteria frequency (P < 0.001) and chloride concentration (P < 0.01). Also, the biochar significantly affected the pH, organic carbon, concentration of total nitrogen, phosphorous, solution potassium, sodium, iron, zinc, copper, basal respiration, and nitrifying bacteria frequency (P < 0.001) of the soil. The interaction effect of biochar and salinity levels was significant on soil sodium concentration (P < 0.01) and pH (P < 0.05). In comparison with the control treatment, the enriched biochar, decreased soil pH (about 1.4%) and increased the phosphorous, iron, and zinc up to 36%, 29%, and 36%, respectively and simple biochar increased the Nitrogen and Potassium up to 46% and 48%, respectively. In general, it was concluded that both types of the biochars lowered the sodium concentration of the soil in different salinity levels due to high potential of biochar for sodium absorption which this ability may be considered in saline soils remediation.

Selenium nanomaterials improve the quality of lettuce (Lactuca sativa L.) by modulating root growth, nutrient availability, and photosynthesis.

Macro- or micro-nutrients are essential for crop yield and nutritional quality. In this work, selenium engineering nanomaterials (Se ENMs, 0.5 mg‧kg-1) significantly increased the yield and nutritional quality of lettuce, which was better than that of selenite (Na2SeO3). Under the treatment of Se ENMs, macro-nutrients including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were increased by 15.8%, 98.5%, 42.8%, 146.9%, and 62.5%, respectively, and micro-nutrients including manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) were also increased by 87.4%, 78.0%, 61.1%, and 56.1%, respectively. As a result, the improved nutritional status of lettuce leaves increased photosynthesis (59.2%) and yield (37.6%). Root diameters and root tips of lettuce were increased by 23.9% and 18.6%, respectively, upon exposure to Se ENMs, which may be responsible for facilitating the absorption of macro and micro nutrients from the soil. These effects were significantly better than SeO32- treated group. Metabolome results indicated that Se ENMs could improve the shikimic acid, phenylalanine, and tyrosine pathway, resulting in an enhancement of the beneficial compounds, including quercetin, rutin, and coumarin, by 2.9, 2.7, and 2.4-fold, respectively. Besides, pyruvic acid and TCA cycle were also improved by Se ENMs. These results provide new insight into the positive effect of Se ENMs on crop yield and nutritional quality, which demonstrate that the Se ENMs-enabled agriculture practices have a promising prospect as a sustainable crop strategy.

Biochar is superior to lime in improving acidic soil properties and fruit quality of Satsuma mandarin.

A better understanding is required for using biochar as an alternative option to lime materials for sustainable amelioration of soil acidity and improvement of fruit quality in acidic soils. In this study, a pot experiment was conducted to investigate the comparative effects of biochar (three different dosages of biochar, 1%, 2% and 4%, were denoted by BC-1, BC-2 and BC-3, respectively) and lime (three different dosages of lime, 1.2, 2.4 and 3.6 g kg-1, were denoted by L-1, L-2 and L-3, respectively) on soil properties and fruit acidity of Satsuma mandarin. The decreased rates of fruit titratable acid (TA) by BC-1, BC-2 and BC-3 were 16.18%, 25.00% and 14.71%, which were higher than those by L-1, L-2 and L-3 were 11.76%, 16.18% and 5.88%. Moreover, the increased rates of fruit total soluble solid (TSS)/TA were 14.94%, 31.73%, 28.04% by BC-1, BC-2 and BC-3, but were 11.42%, 21.77%, 10.15% by L-1, L-2 and L-3, suggesting that biochar had better effects on improving fruit quality. Acidic soil properties were improved by biochar and lime, but biochar had better amelioration effects, as evidenced by soil-treated with BC-2 and BC-3 had greater increases of soil pH, soil respiration (SR) and microbial metabolic quotient, activities of soil urease (SU), invertase (SI), catalase (CAT) and cellulose (SC), and concentrations of soil phosphorus (P), potassium (K) and magnesium (Mg). Principal component analysis showed that soil pH, SR, SU, SI and CAT were main contributors to the differences of improvement effects of biochar and lime. Correlation analysis showed that fruit TA had negative relationships with soil pH, SU, SI, CAT, SC and soil P, K, Mg. This study indicates that the better effects of biochar on improving fruit quality of Satsuma mandarin were associated with the greater effects of it on improving acidic soil properties.

Colony formation in two Microcystis morphotypes: Effects of temperature and nutrient availability.

The ability of Microcystis to form large colonies is a key trait that contributes to competition ability over other phytoplankton and facilitates the formation of surface scums in many freshwater systems. The effect of temperature and nutrients on this trait, however, is far from clear and needs further investigation, especially under a warmer climate and nutrient overloading in aquatic systems globally. In this study, two colonial strains of Microcystis (M. wesenbergii and M. ichthyoblabe) originally isolated from Lake Taihu in China, were used to investigate cyanobacterial aggregation under a range of temperatures (15-30 °C), phosphorus availability (0.004-8 mg P L-1), and nitrogen availability (0.04-40 mg N L-1). The mechanism of colony formation in Microcystis was determined based on growth rates and extracellular polysaccharide (EPS) contents. The colony size of both strains increased significantly when the temperature rose from 15 to 25 °C. A further increase in temperature from 25 to 30 °C, however, reduced the colony size of M. ichthyoblabe significantly, and, in contrast, increased the colony size of M. wesenbergii. Higher phosphorus availability promoted the formation of larger colonies in both strains. In comparison, nitrogen had no significant effect on the colony size. Furthermore, although EPS was a significant contributor to the formation of large colonies in colonial Microcystis, growth rate was a dominant driving factor in this process. The findings of this study highlight that warmer temperatures and phosphorus enrichment might enhance surface Microcystis scums directly through increasing the colony size. This study also provides new insights into the mechanism of colony formation in Microcystis.

Low-temperature hydrothermal pretreatment followed by dry anaerobic digestion: A sustainable strategy for manure waste management regarding energy recovery and nutrients availability.

This study evaluated the feasibility of low-temperature hydrothermal (HT) pretreatment for improving dry anaerobic digestion (AD) of swine manure (SM) and nutrient elements reclamation, with specific goals to minimize the drawbacks of conventional HT process including high energy consumption, inhibitory compounds formation and unfavorable pH/alkalinity decrease. Pretreatment at 110-130°C for holding 30min increased the soluble organic carbon (SOC) concentration in SM by 13-26%. After being mixed with inocula, the pretreated SM was applied for dry AD tests successfully without initial pH adjustment, achieving a CH4 yield of 280.18-328.93ml/g-VSfed (14-34% increase compared to that from raw SM). Energy assessment indicated a positive net gain of 0.95kJ/g-VS by adopting HT pretreatment at 130°C. Except for increment in CH4 yield, low-temperature HT pretreatment also promoted organic-N mineralization, increasing N fractions in the digestate available for plants. After 70days' dry AD, a high ammonia-N to total nitrogen (TN) ratio of 71% was obtained for the SM sample pretreated at 130°C, in sharp contrast to that of 38% in raw SM. P bioavailability in the final digestate was not greatly affected by the HT pretreatment since the labile organics were mostly degraded after AD, in which P existing forms were influenced by the multivalent metals content in SM. Overall, 23-27% of the total P was potentially bioavailable in all digestates.

Dinámica del ciclo del nitrógeno y fósforo en suelos / Nitrogen and phosphorus cycles dynamics in Soils

Los ciclos biogeoquímicos del fósforo (P) y del nitrógeno (N) son sistemas dinámicos que suceden a través de la biosfera, de cuyos mecanismos de transformación depende la disponibilidad de estos elementos para diferentes formas de vida. Se acepta que la diversidad y actividad de las poblaciones microbianas posee un papel crucial en la dinámica de los nutrientes y por tanto el desafío está en comprender, como responden a las condiciones ambientales. La actividad microbiana en los suelos depende tanto de la condición del recurso y como de sus propiedades químicas, físicas y biológicas. En este documento se describen conceptos que se han empleado para entender la dinámica del nitrógeno y el fósforo, con el propósito de discutir cómo las características de las diferentes fracciones orgánicas y minerales seleccionan el potencial biológico encargado del recambio de dichos elementos, panorama que actualmente se aborda a través de técnicas independientes del cultivo para estudiar las poblaciones microbianas in situ.

Biogeochemical cycle’s phosphorus (P) and nitrogen (N) are dynamic systems taking place through the biosphere, whose mechanisms of transformation depends on the availability of these elements for different forms of life. It is accepted that the diversity and activity of microbial populations plays a crucial role in nutrient dynamics and therefore the challenge is to understand how they respond to environmental conditions. Microbial activity in soils depends on both the resource condition and its chemical, physical and biological properties. Concepts described herein have been used to understand the nitrogen and phosphorus dynamics, with the aim to discuss how the characteristics of the different organic and mineral fractions select the biological potential responsible for the turnover of these elements, scenario currently addressed through cultivation-independent techniques to study microbial populations in situ.