Search Results (24)

This study evaluates the effectiveness of agroecological practices—organic fertilization and biofertilization—in enhancing ecosystem services in agroforestry and pasture systems. A field experiment was conducted over three years, comparing these practices to a control treatment and a natural ecosystem as a reference. Soil chemical, physical, and biological parameters were assessed, including soil organic carbon (SOC), microbial respiration, root density, and gene abundances of key microbial groups (Archaea, Bacteria, and Fungi). Organic fertilization resulted in a significant increase in SOC, phosphorus, microbial biomass, and root density, indicating improved soil structure and fertility. Biofertilization showed selective effects, promoting archaeal abundance but reducing bacterial and fungal diversity. Seasonal variation influenced nutrient cycling, with organic fertilization buffering against dry-season declines in microbial activity and nutrient availability. Aboveground dry biomass and litter deposition were highest in the natural ecosystem, followed by organic fertilization treatments in agroforestry and pasture systems. Despite improvements under agroecological management, the natural ecosystem consistently maintained superior soil quality and biological resilience. The findings highlight that organic inputs and diversified cropping systems enhance soil health but do not fully replicate the ecological benefits of undisturbed forests. In conclusion, agroecological practices provide viable alternatives to mitigate soil degradation and sustain ecosystem services in tropical Oxisols. Organic fertilization emerges as the most effective strategy, fostering long-term improvements in soil fertility and microbial dynamics. However, continued research is needed to optimize these practices for greater resilience and sustainability in Amazonian agroecosystems. Full article

Effective nitrogen (N) management and the development of novel N fertilizers are essential for enhancing maize growth in tropical soils. One strategy to increase N use efficiency is the use of organic matrices as a source of N or their combination with the application of mineral N sources. Among these organic matrices, biochar emerges as a highly promising option for optimizing N use efficiency. Thus, the aim of this study was to evaluate the effects of different feedstocks, their respective biochars, and their combination with N on the dynamics and uptake of N by maize plants in two contrasting Oxisols. A 30-day greenhouse experiment was conducted using maize grown under treatments with four feedstocks (bamboo, sunflower cake, chicken manure, and shrimp carcass) and their respective biochars. The biochars were applied with or without ammonium nitrate (AN), alongside negative (no N) and positive (AN-only) controls. Ammonium and nitrate levels were analyzed in the soil solution at 1 and 15 days and in the whole soil before and after cultivation. Maize biomass production and shoot N accumulation were also evaluated at the end of the experiment. Among the main results, it was observed that soil type played a key role in available N, maize nutrition, and growth. In the medium-textured Oxisol studied, native soil organic matter partially met maize N requirements due to high content of available N observed. Biochars influenced N availability by increasing nitrate-N prevalence in the soil solution. Although whole-soil N levels were sufficient for robust maize growth, post-cultivation residual N remained low (<75 mg kg⁻¹), indicating the need for supplemental N fertilization for plants grown in pots. In the medium-textured Oxisol, bamboo or sunflower cake biochar combined with AN increased biomass production by ~12% compared with AN alone. Similarly, in the clayey Oxisol, maize fertilized with sunflower cake or shrimp carcass biochar—regardless of AN addition—outperformed AN-fertilized plants by 19–30%. Thus, this study highlights the potential of integrating biochar with N fertilization to improve soil and solution N availability and increase N use efficiency by maize plants. Full article

Copper (Cu) is a critical micronutrient for wheat (Triticum aestivum L.), essential for growth and grain baking quality, yet its availability is limited because Cu is specifically adsorbed on colloids of highly weathered tropical soils like Oxisols. This study hypothesizes that Cu-doped biochar composites can outperform traditional Cu fertilizers in improving wheat growth and Cu use efficiency. Composites were synthesized from chicken manure (FCM), shrimp shells (FSC), and sewage sludge (FSS), doped with copper sulfate (CuSO₄5H₂O) or copper oxide (CuO), and pyrolyzed at 300 °C or 550 °C. The experimental design involved greenhouse trials in two Oxisols (RYL and DRL), assessing Cu release kinetics, plant Cu uptake, and dry matter production. Fourier Transform Infrared Spectroscopy (FTIR) confirmed successful Cu integration. Results revealed that CSS/CS-5 (FSS + CuSO₄5H₂O at 550 °C) improved Cu uptake and shoot biomass in DRL soil, while CSC/CS-3 (FSC + CuSO₄5H₂O at 300 °C) enhanced wheat CuSO₄5H₂O growth in RYL soil. Peak Cu availability varied by CuSO₄5H₂O soil and composite type, with residual Cu highest CuSO₄5H₂O in CuSO₄5H₂O-treated soils. These findings demonstrate that Cu–biochar composites, tailored to soil conditions, offer a sustainable alternative to mineral Cu fertilizers by enhancing the nutrient availability and wheat grain yield. Full article

This research analyzed the effects of inoculation with Rhizobium tropici, combined with beneficial microorganisms, on the reduction of NPK fertilization and its impacts on common beans. Conducted in two types of soil (clayey Oxisol and sandy Ultisol), the experimental design was a randomized block design under a factorial scheme 4 × 4, with different combinations of inoculation (Rhizobium tropici alone or in combination with Azospirillum brasilense, Bacillus subtilis, and Trichoderma harzianum) and fertilization doses (0%, 33%, 66%, and 100% of the recommended dose). The results showed that inoculation with R. tropici, especially in combination with Trichoderma harzianum, increased nodule formation and improved agronomic parameters such as leaf chlorophyll, dry matter of the plant, number of pods, and grains. Co-inoculation with Azospirillum brasilense resulted in a significant increase in grain yield, particularly in clayey soil with 33% NPK. Inoculation with lower doses of NPK was sufficient for good yield, suggesting the feasibility of reducing the use of mineral fertilizers. This study indicates that soils with corrected fertility, in a no-tillage system, can contribute to the reduction of fertilizer use due to the cycling of organic matter and improvement of soil health. Additionally, the use of microorganisms is an effective ally for the sustainability of agroecosystems. Full article

The diversification of cropping sequences has a positive impact on soil organic carbon, while improving nutrient cycling and crop yields. The objective of this research was to assess amylase, cellulase, C and N dynamics, and maize yield on a low fertility oxisol in the Brazilian Cerrado. The experiment was conducted under field conditions during three maize crop succession cycles. The treatments consisted of cultivating maize during the summer, after sorghum and lablab cropped as green manure and fallow during the winter. Higher maize yields were achieved by sorghum–maize succession compared to monocropping, due to higher N fertilizer and biomass inputs to topsoil. Sorghum–maize succession also provided a higher proportion of stable C and N compared to other successions. Maize yields declined as tropical soil fertility intrinsically decreased along three crops succession cycles. Cellulase activity decreased over time, whereas amylase activity increased as the plant residues were already in advanced stages of decomposition. The sorghum–maize crop succession stood out compared to lablab and fallow as it provided the highest maize yields, while maintaining higher C and N levels, and amylase activity. This better performance was likely due to larger amounts of incorporated biomass and better mineral N fertilizer management. Full article

Integrated crop–livestock systems (ICLS) have sustainably intensified modern agricultural practices worldwide. This research assessed how production systems and crop types impact the chemical properties of an Oxisol in the Brazilian Cerrado, the grain yield of corn intercropped with palisade grass (Urochloa) in the off-season in an ICLS, and the grain yield (GY) of soybean in succession. Intercropped and monocropped systems were assessed in a three-year field experiment: corn + Urochloa ruziziensis–soybean; corn + U. brizantha cv. Piatã–soybean; corn + U. brizantha cv. Paiaguás–soybean (ICL–Paiaguás); corn–soybean under a no-tillage system (NTS); corn–soybean under a conventional tillage system (CTS); Piatã grass–continuous grazing (Perennial Piatã); and Paiaguás grass–continuous grazing (Perennial Paiaguás). The residual impact of phosphate fertilization was more pronounced in the ICLS treatments. In the soil layer from 0.0 to 0.2 m depth, ICLS–Paiaguás and Perennial Piatã had the most positive effects on soil chemical quality. In the last year, grain yield was highest in corn monoculture under the NTS and soybean in succession under the ICLS. ICL–Paiaguás improved soil chemical properties for soybean in succession. These results confirm that an intermittent pasture system for legume crops in sequence is an alternative that can maintain or improve soil chemical composition, and that CTS should be avoided in tropical sandy soils. Full article

The soil solution is the compartment where plants uptake nutrients and this phase is in equilibrium with the soil solid phase. Changes in nutrient content and availability in the soil solution can vary among soil types in response to humic acid concentrations, thereby affecting Brachiaria growth. However, there are no studies demonstrating these effects of humic acid application on different soil types and how they affect Brachiaria growth. Thus, the aim of this study was to evaluate the effects of humic acid concentrations (0, 5, 10, 25, and 60 mg kg⁻¹ carbon-humic acid) on Brachiaria brizantha growth and soil solution properties of contrasting tropical soils. Plants were grown for 35 days in greenhouse conditions in pots containing Sandy Entisol, Clayey (Red Oxisol), and Medium Texture (Red-Yellow Oxisol). Soil solution was assessed for pH, electrical conductivity (EC), carbon, and nutrient content. Shoot and root dry matter, as well as macro and micronutrients accumulation in the shoot, were determined. In a soil type-dependent effect, pH, EC, and concentrations of nutrients in solutions changed in response to carbon-humic acid concentration. In the less-buffered soils, Sandy Entisol and Red-Yellow Oxisol, the addition of 30–40 mg kg⁻¹ carbon-humic acid increased root proliferation by 76–89%, while Brachiaria biomass produced in all soils increased by approximately 30%. Levels of carbon in solution were high (>580 mg L⁻¹) and varied depending on the investigated soil type. Though solution carbon contents did not appear to be a driving factor controlling the positive effects of humic acid concentrations on Brachiaria dry matter, there was a direct relationship between other properties and nutrient content in the soil solution, and Brachiaria dry matter production. Full article

This study aims to investigate the effects of parent rock and minerals on lateritic weathering. The study presents X-ray diffraction (XRD), whole-rock geochemistry, and Nd-Sr isotopic data for examining two profiles, 10 and 12 m thick, respectively, that illustrate the regional tropical weathering status in the Midwest of Brazil. The profiles, developed from metasedimentary and sedimentary rocks, are constituted by saprolite, mottled horizon, lateritic duricrust, and oxisol. Across the profiles, the minerals controlling the weathering geochemistry are muscovite, microcline, quartz, kaolinite, hematite, goethite, and gibbsite. Red and yellow zones in the saprolite and mottled horizon as well as the lateritic duricrust with breccia/fragmental, pisolitic, and oolitic textures make profile 1 more complex. In contrast, profile 2 has an oxisol that mantles the homogeneous vermiform lateritic duricrust. Fe₂O₃, accumulated during surface weathering, is a potent element in the geochemical profile control since it forms the harder goethite to hematite lateritic duricrust, bearing most of the trace elements (As, Cu, Cs, Pb, Sc, Sr, Th, U, V, and Zn) with similar ionic radii and electrovalence. The LREE have affinity for the elements of the Fe₂O₃ group of the lateritic duricrust. On the other hand, the K₂O group together with Zr and TiO₂ e in the phyllite, saprolite, and mottled horizon of profile 1, are associated with the HREE. Additionally, in profile 2, the HREE are mostly associated with the Al₂O₃ group and the residual minerals in the oxisol. The indication that REE is associated with phosphates, zircon, rutile/anatase, cereanite, and muscovite/illite, which have variable weathering behavior, caused the REE fractionation to occur across and between the profiles. Despite the REE fractionation, the Ɛ_Nd(0) values along the profiles consistently maintain the signature of the parent rock. Muscovite and microcline weathering, in profiles 1 and 2, respectively, control the decrease in ⁸⁷Sr/⁸⁶Sr signatures of both profiles and the distinct radiogenic ratios. The development of lateritic duricrust in both profiles indicates a similar weathering intensity, although the gibbsite–kaolinite predominance in the oxisol of profile 2 highlights a geochemical reorganization under humid conditions, as well as near-intense soluble silica leaching. Full article

Understanding economic scenarios is crucial in all production chains. Tropical pastures are Brazil’s primary food source for beef cattle production, and current pasture management is not ideal due to land degradation. An economic evaluation assists farmers with improving pasture management using novel techniques, such as nitrogen (N) fertilization, which is straightforward and practical. The economic effects of different N fertilizer levels in beef cattle production were evaluated. This study was conducted over three years (2014/2015, 2015/2016, and 2016/2017) using four concentrations of urea fertilizer (0, 90, 180, and 270 kg N/ha). A principal component analysis and sensitivity analysis were performed using financial data. A financial pattern was observed, with increases in some variables, such as cost-effective operating and cost-total operating from those measuring costs and gross revenue, operating profit, and net income from those estimating revenues. Treatment with 180 kg N/ha fertilizer resulted in increased profitability, payback, internal rate of return, and net present value (at 6% and 12% tax) of 17.76%, 2.79 years, 35.79%, and USD 5926.03 and USD 1854.35, respectively. For this study, the main costs associated with profitability were supplementation, animal purchases, and sale prices. The best treatment to achieve excellent grazing pressure in tropical areas with oxisol is 180 kg/ha per year. Full article

Soil structure controls soil hydraulic properties and is linked to soil aggregation processes. The aggregation processes of Oxisols are controlled mainly by clay mineralogy and biological activity. Computed microtomography (µCT) may be a tool for improving the knowledge of the hydraulic properties of these soils. Thus, this study brings an advance in the use of 3D image analysis to better comprehend the water behavior in tropical soils. In this work, three Oxisols were studied with the objective to (i) characterize the soil water retention curve (SWRC), the corresponding pore size frequency, and the saturated hydraulic conductivity (K_sat); (ii) use µCT to obtain, based on 3D images of soil structure and pore size distribution; and (iii) correlating parameters from SWRCs, K_sat, and µCT with other physical-hydric, chemical, and mineralogical attributes. Rhodic Haplustox—P1, Anionic Acrustox—P2, and Typic Hapludox—P3 were the three studied Oxisols. The differences among the SWRCs were related to the microgranular and block type’s structure morphology, which modified the soil pore space. The pore size frequency was calculated from SWRCs for pores with diameters of 87 ± 2 μm in P1, 134 ± 11μm in P2, and 175 ± 18 μm in P3. Pore size distribution from µCT was determined for the range of 20–100 µm, mainly with the highest percentages: 12 ± 1.09% for P1 and 12 ± 1.4% for P2. Pore connectivity was assessed from images by calculating Euler Numbers (EN), with the differences related to the biggest pore (EN_bigpore): P1 (−44,223 ± 10,096) and P2 (−44,621 ± 12,573) showed more connected pores (EN_bigpore) in comparison to P3 (−11,597 ± 6935). The parameter EN_bigpore was decisive in understanding the water retention and conduction processes of the studied soils. The better-connected pore space increased K_sat in P1 (220 ± 0.05 mm h⁻¹) and P2 (189 ± 0.1 mm h⁻¹) in comparison to P3 (20 ± 0.3 mm h⁻¹) and modified the shape of SWRCs. Full article

Maintaining soil fertility and obtaining good crop yields in highly weathered tropical soils through organic practices–without chemical/synthetic inputs—requires a scientific approach and skillful managements, especially for phosphorus (P) nutrient. Our objective was to find a combination of lime and rock phosphate additions that made soil pH low enough so that rock phosphate would be adequately soluble, yet high enough so soil acidity is not harmful to most crops. Thus, a controlled (greenhouse) experiment was conducted to quantify soil properties, and soybean (Glycine max cv. Kahala) growth when rock phosphate, coral lime, and cowpea (Vigna unguiculata) green manure were applied as organic amendments to an acid, nutrient poor Oxisol of Hawaii. The treatments were a factorial combination of 3 application rates (0, 1, 2 g/kg) of coral lime (86% CaCO₃ equivalent) from Western Samoa, 3 rates (0, 75, 150 mg/kg total P) of rock phosphate (10.6% total P, and 3.7% citrate extractable P) from central Florida, and 3 rates (0, 5, 10 g/kg) of a local cowpea green manure (2.7% N, 2.8% K). Each treatment was replicated 3 times, yielding a total of 81 pots of 2 kg soil each. Soybean seedlings were grown as a test crop. Our results showed that a combination of 1 g/kg (2 tons/ha) of lime and 75 mg/kg (150 kg P/ha) of rock phosphate provided enough P for soybean growth and simultaneously alleviated soil acidity problems (the green manure was to supply adequate N and K to the crop). Corresponding soil parameters were: soil pH = 5.2, exchangeable (KCl-extractable) Al = 3.6 mg/kg, Olsen (NaHCO₃- extractable) P = 11 mg/kg, and soil-solution P of 0.05 mg/L. Our results lent support to the sustainable potential of organic farming. Full article

Despite the increasing adoption of proximal sensors worldwide, rare works have coupled proximal with remotely sensed data to spatially predict soil properties. This study evaluated the contribution of proximal and remotely sensed data to predict soil texture and available contents of micronutrients using portable X-ray fluorescence (pXRF) spectrometry, magnetic susceptibility (MS), and terrain attributes (TA) via random forest algorithm. Samples were collected in Brazil from soils with high, moderate, and low weathering degrees (Oxisols, Ultisols, Inceptisols, respectively), and analyzed by pXRF and MS and for texture and available micronutrients. Seventeen TA were generated from a digital elevation model of 12.5 m spatial resolution. Predictions were made via: (i) TA; (ii) TA + pXRF; (iii) TA + MS; (iv) TA + MS + pXRF; (v) MS + pXRF; and (vi) pXRF; and validated via root mean square error (RMSE) and coefficient of determination (R²). The best predictions were achieved by: pXRF dataset alone for available Cu (R² = 0.80) and clay (R² = 0.67) content; MS + pXRF dataset for available Fe (R² = 0.68) and sand (R² = 0.69) content; TA + pXRF + MS dataset for available Mn (R² = 0.87) content. PXRF data were key to the best predictions. Soil property maps created from these predictions supported the adoption of sustainable soil management practices. Full article

Black oat (Avena strigosa) is a cover crop with great potential for weed suppression and erosion control while conserving soil moisture. Little is known about the potential of black oat for enhancing the soil food web structure and the ecosystem services in tropical Oxisols. Two-year field trials were conducted in Hawaii to compare three pre-plant treatments: (1) black oat (BO) as a pre-plant cover crop followed by no-till practice (previously managed by cover crop and cash crop rotation and conservation tillage for 7 years); (2) bare ground (BG) followed by conventional tillage (previously managed by conventional tillage and cash crop planting for 7 years); (3) conventional tilling of bare ground followed by soil solarization (SOL) (previously fallow with weeds for 5 years then summer solarization and cash crop planting for 2 years). Various soil properties and the soil food web structure using nematodes as soil health indicators were monitored throughout the subsequent corn (Zea mays) crops. SOL served as a negative control pre-plant treatment known to manage plant-parasitic nematodes but be destructive to the soil food web. No-till cropping with BO resulted in higher levels of volumetric soil moisture, field capacity, and soil organic matter, and supported a fungal-dominated decomposition pathway in trial I and more structured nematode communities than BG and SOL in trial II. This study provides evidence that no-till cover cropping with black oat improves the soil water conservation and soil food web structure following a continuous conservation tillage system in tropical Oxisols if the black oat biomass is high (36 tons/ha). However, no-till cropping with BO in Oxisol decreased the soil macroporosity and increased the soil bulk density, which were not favorable outcomes for water infiltration. On the other hand, SOL following conventional tillage was successful in generating lethal temperatures to suppress plant-parasitic nematodes and increased water infiltration in both years but was destructive to the soil food web and reduced the soil organic matter and soil moisture in both years, even when solarization failed to generate lethal temperatures in the second year. Full article

Effective and efficient nutrient management is central to best-practice agriculture, facilitating sustainable intensification while reducing negative externalities. The application of biochar-based fertilizers (BBF) in tropical agronomy has the potential to improve nutrient management by enhancing nutrient availability and uptake. Here, we performed pot-trials with Theobroma cacao L. seedlings planted in an Oxisol with critically low phosphorus levels. Four fertilizer levels were deployed, including BBFs using micro-dosed biochar (16 g plant⁻¹ i.e., 0.3% soil amendment w/w) charged with mineral fertilizer. Three different fertilizer-placement levels (topsoil, root-zone hotspot and root-zone layer) were evaluated. The results from the topsoil application of mineral fertilizer (farmer practice) served as the reference data. The root-zone layer application of BBF increased the aboveground biomass, total leaf area and chlorophyll content index by 56%, 222%, and 140% respectively. Foliar phosphorus levels were also significantly elevated by 53%. The N:P ratio of the foliar tissue was improved, indicating the potential of BBF to ameliorate P limitations. Thus, low dosages of biochar, which is upgraded to BBF, can considerably improve plant nutrition. Small scale technology to produce biochar can be easily adopted and integrated in T. cacao systems. We suggest that BBF production and application within tropical, perennial systems can contribute to achieving a range of sustainable development goals (SDGs), including climate action. Full article

Efficient use of co-composted organic manure with biochar is one of the sustainable management practices in an agriculture system to increase soil fertility and crop yield. The objectives of this research are to evaluate the use of co-composted biochar, biochar in formulation with poultry litter (PL), and PL compost on soil properties and maize growth. Organic amendments were applied at 10 Mg ha⁻¹, and synthetic fertilizer was applied at the recommended rate of maize (N: P₂O₅: K₂O at 60:60:40 kg ha⁻¹). The results showed that addition of organic amendment significantly increased the total biomass parameter compared to the control, which ranged from 23.2% to 988.5%. The pure biochar treatment yielded lower biomass than the control by 27.1%, which was attributed to its low nutrient content. Consequently, the application of the co-composted biochar achieved higher plant height and aerial portion, which ranged from 46.86% to 25.74% and 7.8% to 108.2%, respectively, in comparison to the recommended fertilizer rate. In addition, the soil amended with co-composted biochar had a significant increase in soil organic matter and had significantly higher chlorophyll and nutrient concentrations in plants, which increased with an increase in the biochar ratio of the co-composts. This was probably attributed to the release of the nutrients retained during composting, thereby possibly making the co-composted biochar act as a slow-release fertilizer. In conclusion, the addition of organic manure with biochar enhanced the nutrient supply by gradual release in comparison to the mineral fertilizer. Full article