This study evaluates the chemical processes responsible for the nitrous oxide (N₂O) and methane (CH₄) fluxes in the managed pasture (PM) and unmanaged pasture (PNM). In addition, the impact of nitrogen fertilization on the N₂O and CH₄ fluxes was assessed. The experiments were conducted on three farms in Alta Floresta city in the state of Mato Grosso. Both regular and intensive samples were collected from PM, PNM, and forest areas for each of the properties. The gases were sampled using static chambers in the morning. Higher N₂O fluxes were recorded in the PMs, whereas the CH₄ fluxes showed no influence of nitrogen fertilization in both regular and intensive samples. Low fertilizer levels resulted in low N₂O emissions.

Soil amendment with biochar has been claimed as an option for carbon (C) sequestration in agricultural soils. Most studies on biochar/soil organic carbon (SOC) interactions were executed under laboratory conditions. Here we tested the stability of biochar produced in a traditional kiln and its effects on the stocks of native SOC under field conditions. The biochar was characterized using pyrolysis–gas chromatography–mass spectrometry, and then added to an Oxisol under savannah climate. This soil was amended with 0, 5, 10, 20 and 40 Mg ha−1 of biochar in a randomized complete block design with four replications and cultivated with soybean over four cropping seasons (CSs; 120 days each). Soil samples from the 0–10 cm top layer were collected at the end of the first and fourth CSs and analyzed for CO2 emissions, isotopic C abundance (13C/12C ratio) and enzymatic activity (fluorescein diacetate and dehydrogenase). The biochar showed a low degree of thermal modification. Its relative decomposition rate was higher (k = 0.32–1.00 year−1) than generally claimed (k = 0.005–0.0005 year−1), and higher than the decomposition of native SOC (k = 0.22 year−1). Addition of biochar didnot affect the stocks of native SOC. Our findings highlight the need for critically reviewing the potential of locally produced biochar to sequester C.

In this paper, soil carbon, nitrogen and phosphorus concentrations and stocks were investigated in agricultural and natural areas in 17 plot-level paired sites and in a regional survey encompassing more than 100 pasture soils In the paired sites, elemental soil concentrations and stocks were determined in native vegetation (forests and savannas), pastures and crop-livestock systems (CPSs). Nutrient stocks were calculated for the soil depth intervals 0-10, 0-30, and 0-60 cm for the paired sites and 0-10, and 0-30 cm for the pasture regional survey by sum stocks obtained in each sampling intervals (0-5, 5-10, 10-20, 20-30, 30-40, 40-60 cm). Overall, there were significant differences in soil element concentrations and ratios between different land uses, especially in the surface soil layers. Carbon and nitrogen contents were lower, while phosphorus contents were higher in the pasture and CPS soils than in native vegetation soils. Additionally, soil stoichiometry has changed with changes in land use. The soil C :N ratio was lower in the native vegetation than in the pasture and CPS soils, and the carbon and nitrogen to available phosphorus ratio (PME/ decreased from the native vegetation to the pasture to the CPS soils. In the plotlevel paired sites, the soil nitrogen stocks were lower in all depth intervals in pasture and in the CPS soils when compared with the native vegetation soils. On the other hand, the soil phosphorus stocks were higher in all depth intervals in agricultural soils when compared with the native vegetation soils. For the regional pasture survey, soil nitrogen and phosphorus stocks were lower in all soil intervals in pasture soils than in native vegetation soils. The nitrogen loss with cultivation observed here is in line with other studies and it seems to be a combination of decreasing organic matter inputs, in cases where crops replaced native forests, with an increase in soil organic matter decomposition that leads to a decrease in the long run. The main cause of the increase in soil phosphorus stocks in the CPS and pastures of the plot-level paired site seems to be linked to phosphorus fertilization by mineral and organics fertilizers. The findings of this paper illustrate that land-use changes that are currently common in Brazil alter soil concentrations, stocks and elemental ratios of carbon, nitrogen and phosphorus. These changes could have an impact on the subsequent vegetation, decreasing soil carbon and increasing nitrogen limitation but alleviating soil phosphorus deficiency.

Feed intake and average daily gain (ADG) in Nellore cattle were determined to calculate residual feed intake in two performance tests: first during the growth phase (RFI_growth) and then during a measurement of the methane emission phase (RFI_met). During the RFI_growth test, 62 males and 56 females were classified as low-, medium-, and high-RFI. Enteric methane emission was measured in 46 animals; 23 males used for RFI_met measurement plus 23 females (22 low-RFI_growth and 24 high-RFI_growth). Diet consisted of Brachiaria brizantha cv. Marandu hay (445 g/kg DM) and concentrate (555 g/kg DM). During the RFI_growth and RFI_met phases, DMI was lower in the animals with low RFI, with no difference in ADG. Residual feed intake was -0.359 and 0.367 kg DM/d for low- and high-RFI animals. Enteric methane emission (g/d, g/kg BW^0.75 and g/kg ADG) did not differ between RFI_growth classes. Enteric methane emission (g/d) was higher in high RFI_met and lower in low RFI_met males. Spearman correlations among traits obtained during both tests, which were high between metabolic BW (r = 0.959) and between DMI (r = 0.718), and zero between ADG (r = -0.062), resulted in moderate correlation between RFI_growth and RFI_met (r = 0.412). However, it is not possible to confirm that high-efficiency animals release less enteric methane, since different results were obtained when enteric methane was compared between the RFI_growth and RFI_met classes.

While a number of papers have shown that subway systems have an impact on the air quality through the release of particulate matters, no information about the impact of such particles on tree attributes is available. Tree leaves from three different species from the exit side of a subway station in Rio de Janeiro, Brazil, were more asymmetrical than leaves from the entrance side. This leaves also presenting changes in leaves cuticle and chlorophyll content.

A REGIÃO Metropolitana de São Paulo tem passado por uma séria crise hídrica. A ameaça de racionamento despertou o interesse da sociedade em compreender como se chegou a essa situação e, principalmente, quais são as possíveis soluções para superar esse problema. Entre os diversos fatores que levaram à crise hídrica, este artigo analisa a perda da cobertura vegetal do entorno da região da Cantareira e sugere uma estratégia de médio prazo para a revegetação destas áreas e para a reativação das nascentes ali localizadas.

Oilseed-derived biochar, a by-product of pyrolysis for biodiesel production, is richer in aliphatic compounds than the commonly studied wood-derived biochar, affecting both its mineralization in soil and its interaction with native soil organic carbon (nSOC). Here, we investigated the soil C sequestration potential of three different oilseed biochars derived from C₃ plant material: soyabean, castor bean and jatropha cake. The chemical composition of these biochars was determined by elemental analysis (CHN) and ¹³C NMR spectroscopy. The cumulative CO₂ efflux from 30-day laboratory incubations of biochar mixed with a sandy soil containing nSOC from C₄ plants was measured as a proxy for mineralization rate. The relative contribution of each source to CO₂production was calculated based on the ¹³C-signatures of total CO₂ efflux and the source materials (soil and biochars). Our results showed that: (i) castor bean biochar contained relatively large amounts of aliphatic compounds, resulting in a greater mineralization rate than soyabean and jatropha biochars; (ii) CO₂ efflux from the soil-biochar mixtures originated mostly from the biochars, suggesting that these biochars contain rapidly decomposable compounds; and (iii) all three oilseed biochars decelerated nSOC mineralization. This negative priming effect appeared to be caused by different factors. We conclude that oilseed biochars have the potential to increase soil C stocks directly and increase soil C sequestration indirectly in the short term through negative priming of nSOC mineralization.