Impact of Different Agricultural Waste Biochars on Maize Biomass and Soil Water Content in a Brazilian Cerrado Arenosol

Soil Fertilization With Medicinal Plant Processing Wastes Suppresses Tuta absoluta (Lepidoptera: Gelechiidae) and Aphis gossypii (Hemiptera: Aphididae) Populations

Organic soil amendments can influence insect pest populations and the damage to plants they cause. In this study, the effects of medicinal plant processing wastes (MPPWs) applied as organic fertilizers on the host preference and performance of Tuta absoluta and Aphis gossypii were investigated on tomato and cucumber plants, respectively. Processing wastes of cumin, rosemary, thyme, artichoke, chamomile, fenugreek, and nettle were applied in four levels of 0, 20, 40, and 80 g dry matter/1kg culture media in pot experiments. Results showed the application of MPPWs, especially 80 g of nettle, reduced the number of T. absoluta eggs (from 0.8 to 0.4 egg/leaf) and their hatching percentage (from 90 to 76%). The highest and lowest number of aphids were observed in control (36 aphids/plant) and treated cucumbers with 80 g of cumin (18 aphids/plant). Also, the lowest intrinsic rate of increase (0.08 d-1) and net reproductive rate (20 offspring) of T. absoluta were observed in tomatoes fertilized with nettle. The highest and lowest net reproductive rate of A. gossypii were obtained on control and treated plants with 80 g of nettle, respectively. Results of damage assessment showed that the percentage of dry weight loss in the aphid-infested plants was reduced by the use of MPPWs, so that lowest weight loss was observed in the treatment with 80 g of nettle. In conclusion, soil amendment using MPPWs could result in lower pest populations and may improve plant tolerance to insect pest stress, thus these by-products could be considered a valuable tool in pest management.

Tailoring the phosphorus release from biochar-based fertilizers: role of magnesium or calcium addition during co-pyrolysis

The presence of magnesium (Mg) and calcium (Ca) in biochar-based fertilizers is linked to the slow release of phosphorus (P), but these alkali metals have not been systematically compared under identical conditions. In this study, sugarcane filter cake was treated with H₃PO₄ and MgO or CaO followed by pyrolysis at 600 °C to produce a Mg/P-rich biochar (MgPA-BC) and a Ca/P-rich biochar (CaPA-BC), respectively. The P-loaded biochars were studied by extraction and kinetic release in water over 240 hours to assess the potential P availability. X-ray diffraction and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the pristine and post-kinetics biochars to identify the responsible phases for phosphate release. Additionally, the dissolved P concentrations in the kinetic release experiment were compared to thermodynamic solubility calculations of common Mg and Ca phosphates. Both MgPA-BC and CaPA-BC had P loadings of 73–74 g kg⁻¹ but showed distinctly different release behaviors. Phosphate dissolution from MgPA-BC was gradual and reached 10 g P per kg biochar after 240 hours, with rate-determining phases being Mg₂P₂O₇ (Mg pyrophosphate), MgNH₄PO₄·6H₂O (struvite), and Mg₃(PO₄)₂·22H₂O (cattiite). In contrast, CaPA-BC only released 1.2 g P per kg biochar. Phosphate release from CaPA-BC was limited by the low solubility of Ca₂P₂O₇ (Ca pyrophosphate) and (Ca,Mg)₃(PO₄)₂ (whitlockite). Co-pyrolysis with MgO retained P in a more soluble and available form than CaO, making MgO a preferential additive over CaO to immobilize phytoavailable P in biochar-based fertilizers with higher fertilizer effectiveness.

The addition of MgO in the co-pyrolysis of sugarcane filter cake with H₃PO₄ resulted in a biochar-based fertilizer with gradual P release over time. In contrast, the P release from the biochar modified with CaO and H₃PO₄ was poor.

A meta-analysis on biochar's effects on soil water properties - New insights and future research challenges

Biochar can significantly alter water relations in soil and therefore, can play an important part in increasing the resilience of agricultural systems to drought conditions. To enable matching of biochar to soil constraints and application needs, a thorough understanding of the impact of biochar properties on relevant soil parameters is necessary. This meta-analysis of the available literature for the first time quantitatively assess the effect of not just biochar application, but different biochar properties on the full sets of key soil hydraulic parameters, i.e., the available water content (AWC), saturated hydraulic conductivity (K_sat), field capacity (FC), permanent wilting point (PWP) and total porosity (TP). The review shows that biochar increased soil water retention and decreased K_sat in sandy soils and increased K_sat and hence decreased runoff in clayey soils. On average, regardless of soil type, biochar application increased AWC (28.5%), FC (20.4%), PWP (16.7%) and TP (9.1%), while it reduced K_sat (38.7%) and BD (0.8%). Biochar was most effective in improving soil water properties in coarse-textured soils with application rates between 30 and 70 t/ha. The key factors influencing biochar performance were particle size, specific surface area and porosity indicating that both soil-biochar inter-particle and biochar intra-particle pores are important factors. To achieve optimum water relations in sandy soils (>60% sand and <20% clay), biochar with a small particle size (<2 mm) and high specific surface area and porosity should be applied. In clayey soil (>50% clay), <30 t/ha of a high surface area biochar is ideal.

Marginal Agricultural Land Low-Input Systems for Biomass Production

This study deals with approaches for a social-ecological friendly European bioeconomy based on biomass from industrial crops cultivated on marginal agricultural land. The selected crops to be investigated are: Biomass sorghum, camelina, cardoon, castor, crambe, Ethiopian mustard, giant reed, hemp, lupin, miscanthus, pennycress, poplar, reed canary grass, safflower, Siberian elm, switchgrass, tall wheatgrass, wild sugarcane, and willow. The research question focused on the overall crop growth suitability under low-input management. The study assessed: (i) How the growth suitability of industrial crops can be defined under the given natural constraints of European marginal agricultural lands; and (ii) which agricultural practices are required for marginal agricultural land low-input systems (MALLIS). For the growth-suitability analysis, available thresholds and growth requirements of the selected industrial crops were defined. The marginal agricultural land was categorized according to the agro-ecological zone (AEZ) concept in combination with the marginality constraints, so-called ‘marginal agro-ecological zones’ (M-AEZ). It was found that both large marginal agricultural areas and numerous agricultural practices are available for industrial crop cultivation on European marginal agricultural lands. These results help to further describe the suitability of industrial crops for the development of social-ecologically friendly MALLIS in Europe.

Use of Carbonized Fallen Leaves of Jatropha Curcas L. as a Soil Conditioner for Acidic and Undernourished Soil

Jatropha (Jatropha curcas L.) represents a renewable bioenergy source in arid regions, where it is used to produce not only biodiesel from the seed oil, but also various non-oil biomass products, such as fertilizer, from the seed cake following oil extraction from the seeds. Jatropha plants also generate large amounts of fallen leaves during the cold or drought season, but few studies have examined the utilization of this litter biomass. Therefore, in this study, we produced biochar from the fallen leaves of jatropha using a simple and economical carbonizer that was constructed from a standard 200 L oil drum, which would be suitable for use in rural communities, and evaluated the use of the generated biochar as a soil conditioner for the cultivation of Swiss chard (Beta vulgaris subsp. cicla “Fordhook Giant”) as a model vegetable in an acidic and undernourished soil in Botswana. Biochar application improved several growth parameters of Swiss chard, such as the total leaf area. In addition, the dry weights of the harvested shoots were 1.57, 1.88, and 2.32 fold higher in plants grown in soils containing 3%, 5%, and 10% biochar, respectively, compared with non-applied soil, suggesting that the amount of biochar applied to the soil was positively correlated with yield. Together, these observations suggest that jatropha fallen leaf biochar could function as a soil conditioner to enhance crop productivity.

Impacts of land-use and land-cover change on stream hydrochemistry in the Cerrado and Amazon biomes

Studies on the impacts of land-use and land-cover change on stream hydrochemistry in active deforestation zones of the Amazon agricultural frontier are limited and have often used low-temporal-resolution datasets. Moreover, these impacts are not concurrently assessed in well-established agricultural areas and new deforestations hotspots. We aimed to identify these impacts using an experimental setup to collect high-temporal-resolution hydrological and hydrochemical data in two pairs of low-order streams in catchments under contrasting land use and land cover (native vegetation vs. pasture) in the Amazon and Cerrado biomes. Our results indicate that the conversion of natural landscapes to pastures increases carbon and nutrient fluxes via streamflow in both biomes. These changes were the greatest in total inorganic carbon in the Amazon and in potassium in the Cerrado, representing a 5.0- and 5.5-fold increase in the fluxes of each biome, respectively. We found that stormflow, which is often neglected in studies on stream hydrochemistry in the tropics, plays a substantial role in the carbon and nutrient fluxes, especially in the Amazon biome, as its contributions to hydrochemical fluxes are mostly greater than the volumetric contribution to the total streamflow. These findings demonstrate that assessments of the impacts of deforestation in the Amazon and Cerrado biomes should also take into account rapid hydrological pathways; however, this can only be achieved through collection of high-temporal-resolution data.

Biochar feedstock and pyrolysis temperature effects on leachate: DOC characteristics and nitrate losses from a Brazilian Cerrado Arenosol mixed with agricultural waste biochars

Dissolved organic carbon (DOC) leached from Brazilian Cerrado Arenosols can lead to carbon (C) losses and lower soil fertility, while excessive nutrient, e.g. nitrate (NO₃^-), leaching can potentially cause water contamination. As biochar has been shown to stabilize C and retain soil nutrients, a greenhouse experiment was conducted to test different biochars' contributions to DOC and NO₃^- leaching from a sandy soil. Biochars were made from four local agricultural waste feedstocks (cotton residue, swine manure, eucalyptus sawmill residue, sugarcane filtercake) pyrolysed at 400, 500 and 600 °C. Biochar was mixed with soil at 5% weight in pots and maize seeds planted. Leachate was collected weekly for six weeks and analyzed for DOC and NO₃^- concentrations, while fluorescence spectroscopy with parallel factor analysis (PARAFAC) was used to interpret DOC characteristics. Cotton and swine manure biochar treatments had higher DOC and NO₃^- losses than eucalyptus biochar, filtercake biochar, and control treatments. Cotton and swine manure biochar treatments at high temperatures lost mostly terrestrial, humified DOC, while swine manure, filtercake, and eucalyptus biochars at low temperatures lost mostly labile, microbially-derived DOC. Through the practical use of fluorescence spectroscopy, our study identified filtercake and eucalyptus biochars as most promising for retaining DOC and NO₃^- in a Cerrado Arenosol, potentially reducing stable C and nutrient losses.