ABSTRACT Understanding soil organic matter (SOM) dynamics in production systems on tropical soils is necessary to guide strategies to increase SOM formation. This study aimed to evaluate soil carbon (C) dynamics by combining applications of different plant residues used on tropical soils. An incubation study was carried out with and without adding millet (Pennisetum americanum) residues combined with six crop residues (legumes and non-legumes); and one additional treatment with only millet residue. Higher C-CO2 fluxes recorded in jack bean, sunflower and velvet bean residues were correlated with high soluble compound contents (49.5, 49.6 and 32.1 %, respectively). Adding millet residues resulted in positive PE for all residue combinations. Soils without millet, except jack bean, had a negative PE. Residues application promoted four times increase in C-POM content (from 1.04 to 4.2 g kg-1 soil). The C-MAOM content had 2.4 times increase, being more expressive due to its high initial content (from 15.3 to 37.3 g kg-1 soil). The comparison between the final C contents in the SOM fractions showed a significant increase of 8.8 times for MAOM in relation to POM, demonstrating the larger dimension of this C reservoir in the soil. Both combinations of legumes + non-legumes and non-legume + non-legume contributed significantly to the conversion of C to MAOM. The results give insight into possible management strategies for significant C increments in the more stable SOM fractions, depending on the residue type (quality) and residue combination.

Abstract Background: SARS-CoV-2 virus changed society’s behaviour. Population was advised to reduce unnecessary heath care use to accommodate urgent cases and daily increase of COVID-19 patients. Health care facilities faced huge challenges, having to readjust their response to preserve good quality of care. In Portugal, a significant reduction in the number of admissions to the Emergency Department (ED) was reported all over the country, however the impact on the dynamics of undeferrable surgery remains to be reported. This study compares the volume and characteristics of urgent/emergency surgery during the 2020 COVID-19 pandemic with the homologous period in 2019, chronologically illustrating the national evolution of new COVID-19 cases and the social and hospital containment response. Methods: A retrospective observational study was conducted in a tertiary hospital center located in the most affected region by COVID-19 in Portugal. Medical records of patients who underwent urgent/emergency surgery between March 1st and May 2nd of both 2020 and 2019 were examined and the volume of surgeries were compared. Also, daily national updates from Portuguese Directorate-General for Health were analysed. Results: During the COVID-19 pandemic approximately 30% less patients underwent urgent/emergency surgery (99%CI = 0.18–0.61, p< 0.001). Waiting time for surgery showed no difference between both years (p= 0.068), but patients who did surgery during the 2020 pandemic had higher mortality rates than the ones who did it in 2019 (11.4% in 2020 and 5.9% in 2019, p= 0.001). Reduction in surgery volume was correlated with the increasing number of infected cases nationally. Conclusion: This study demonstrates decreasing numbers of urgent/emergency procedures during the COVID-19 pandemic that may be justified by the national growth number of infected cases. Preoperative mass screening strategy was implemented without compromising the efficiency of surgical service, but patients’ mortality was higher. The importance of visiting the ED during COVID-19 pandemic for serious cases that cannot be managed in other settings should be highlighted.

ABSTRACT: Accidents related to the rupture of iron ore tailings dams have dramatically impacted on the Brazilian natural ecosystem. So, the development of strategies to recover soil organic matter levels and build-up Technosols are required. This study aimed to evaluate the effect of N-mineral and -organic fertilization and the rhizospheric effect on soil organic matter mineralization from Technosols built under iron ore tailings. The experiment was carried out in a greenhouse; we used a factorial scheme 2 × 2 × 3: without and with the plant Crotalaria juncea ; without and with mineral fertilization; and three different organic fertilization (without organic fertilization, sewage sludge, and household waste composting), with four randomized blocks. The experimental units were PVC columns installed with a top layer of iron ore tailing from a dam, where gases were sampled to determine the CO2-C, CH4-C concentrations, and CO2-δ13C. The organic fertilization promoted a positive priming effect of 184 %. However, with mineral fertilization, no effect was observed in soil derived-CO2-C accumulated and priming effect. Similarly to non-planted soil, the planted soils with mineral and organic fertilization promoted a steady reduction in soil derived-CO2-C accumulated and rhizosphere priming effect. The soil with mineral fertilization improved in 5.52 and 0.45 g per column the shoot and root dry matter of Crotalaria when compared to the soil without mineral fertilization. In summary, the organic fertilization in Technosols built over iron ore tailings dams during revegetation was not enough to ensure the plant development and preservation of soil organic matter. However, the combination of mineral and organic fertilization promoted negative rhizosphere priming effect and a significant increase in plant biomass.

ABSTRACT This study aimed: i) to evaluate the influence of fertilization and irrigation management on eucalyptus plantations for soil carbon (C) dynamics; ii) to evaluate the impact of fertilization and irrigation management on eucalyptus plantations in the C allocation in depth compared to the Cerrado biome. This study was carried out in an eucalyptus plantation at the end of the third rotation (7 years), which received different fertilizations and irrigations, and a Cerrado area was used as reference. Soil samples were collected in trenches and the gases (CO2 and CH4) on the surface. The total organic carbon (TOC) is more influenced by the availability of water than nutrients. Soils under eucalyptus stands are more efficient at C stocks in depth than the Cerrado and act as a liquid drain of CO2 and CH4 from the atmosphere.

ABSTRACT Harvesting and reform in eucalyptus can lead to changes in soil organic matter (SOM). The objective of this work was to evaluate the changes in total organic C (TOC) and N (NT), C and N in humic acid (HA), fulvic acid (FH), light organic matter (LOM) and microbial biomass (MB), in Ultisol of eucalypt stands over one, two and four years of renovated areas in Rio Grande do Sul state. After the first year of eucalyptus reform, there were 78% of increases in TOC (0.0-1.0-m soil layer). After two years, there was an increase in TN and an average reduction of 52% in LOM-C (0.0-0.1-m soil layer). FA-C, HA-C, and HU-C presented mean reductions of 43 Mg ha–1 (0.0-1.0-m soil layer) after four years of reform. The litter contribution of previous crop and the crop residues from the harvest resulted in increments of the SOM fractions. However, there is a negative effect in later years.

ABSTRACT The amount of harvest residues retained in Eucalyptus plantations strongly influences soil organic matter (SOM), but the efficiency of conversion to SOM may vary according to the type of residue. This study evaluated the recovery of C from Eucalyptus residue components - leaves, bark, branches, roots, and a mix of all residues - in different SOM fractions with or without mineral-N supplementation (200 mg kg-1 of N). Variation in natural 13C abundance was used to trace the destination of residue-derived C in the soil. The C content of the light fraction (LF) and heavy fraction (HF) of SOM increased over a 240-days decomposition period in response to incorporation of Eucalyptus residues in the soil. Bark and leaf residues showed the best results. Bark residues increased the C content of the HF by 45 % over the initial condition. Leaf residues made the largest contribution to LF-C, increasing it by 8.6 times. Leaf residues also led to the highest N contents in the LF and HF, whereas branches, roots, and the mixture of residues caused significant net transfers of N from the HF. Mineral-N supplementation had no effect on stabilization of organic C in the HF of SOM, in which the C could be maintained for longer periods due to physical/colloidal protection against microbial decomposition. These results highlight the importance of keeping Eucalyptus harvest residues in the planted area, especially the bark, which is the most abundant harvest residue component under field conditions, for maintenance of SOM.

In this paper, we report the results of studies on the solubility (water solubility trial) and the response by plants (greenhouse pot experiment using Zea mays) for four types of monoammonium phosphate fertilizers (Conventional MAP - MAP1, MAP coated with a natural organic acid - MAP2, MAP coated with a synthetic organic acid - MAP3, and MAP coated with a peat humic organic acid - MAP4) applied at five increasing doses (0, 100, 300, 600 and 1200 mg P dm-3) and pre-incubated with the soil for five lengths of time before planting (0, 15, 30 and 60 d). The coating with organic acids reduced the water solubility of the P fertilizers - MAP4 provided a more gradual release of P over time. In the soil pot experiment, it was found that MAP1 required the highest dose to reach 90% of dry matter accumulation by the maize plant, followed by the Coated-Slow-Release Fertilizers (CSRF). The agronomic efficiency (AE) of P applied as the CSRF was 3 to 13% greater than that of MAP1. In addition, MAP4 led to higher values of AE (+11%) and apparent P recovery by maize (+41%) in comparison to MAP1. The physicochemical properties imposed by the chemical composition of the organic acid coatings generated fertilizers with distinct release rates and improved agronomic efficiencies.