Nitrogen dynamics during ecosystem development in tropical forest restoration

We considered whether ecological restoration using high diversity of native tree species serves to restore nitrogen dynamics in the Brazilian Atlantic Forest. We measured delta(15)N and N content in green foliage and soil; vegetation N:P ratio; and soil N mineralization in a preserved natural forest and restored forests of ages 21 and 52 years. Green foliage delta(15)N values, N content, N:P ratio, inorganic N and net mineralization and nitrification rates were all higher, the older the forest. Our findings indicate that the recuperation of N cycling has not been achieved yet in the restored forests even after 52 years, but show that they are following a trajectory of development that is characterized by their N cycling intensity becoming similar to a natural mature forest of the same original forest formation. This study demonstrated that some young restored forests are more limited by N compared to mature natural forests. We document that the recuperation of N cycling in tropical forests can be achieved through ecological restoration actions. (C) 2011 Elsevier B.V. All rights reserved.CNPq[135532/2007-8

Carbon, nitrogen and biomass activity under different managements system in Rio Verde – Goias State (Brazil)

The aim of this study was verify alterations in soil biologic attributes under different management systems at Cerrado. Soil samples were taken at dry (july 2006) and wet (february 2007) season at Red distrofic Oxisol (50 – 70 % clay) in Rio Verde, Brazil (17o39’07’’S - 51o06’49’’O) under: native Cerrado (CE), 20 years old pasture (PA), 29 years old conventional tillage (CT), and 10 and 15 years old no-tillage (NT - 10 and NT - 15). Were analysed: soil and microbial carbon and nitrogen levels (C, N, Cmic and Nmic), Cmic:C and Nmic:N ratios, basal respiration (BR) and metabolic quotient (qCO2). Higher soil moisture at wet season led 100 % higher Cmic and Nmic and lower qCO2 level than dry season. Among the management systems, the grass cultivation, animal wastes and area reform were possibly majors factors with which led to higher Cmic e Nmic values in PA, indeed under degradation, than any other one. NT adoption was important to increase Cmic and Nmic, and at least after 10 years pointed out higher values than CT.C and N microbial were more sensitive than total C and N, while other biological parameters also did not show differences

Methane emission from soil under long-term no-till cropping systems

Methane (CH4) emission from agricultural soils increases dramatically as a result of deleterious effect of soil disturbance and nitrogen fertilization on methanotrophic organisms; however, few studies have attempted to evaluate the potential of long-term conservation management systems to mitigate CH4 emissions in tropical and subtropical soils. This study aimed to evaluate the long-term effect (>19 years) of no-till grass- and legume-based cropping systems on annual soil CH4 fluxes in a formerly degraded Acrisol in Southern Brazil. Air sampling was carried out using static chambers and CH4 analysis by gas chromatography. Analysis of historical data set of the experiment evidenced a remarkable effect of high C- and N-input cropping systems on the improvement of biological, chemical, and physical characteristics of this no-tilled soil. Soil CH4 fluxes, which represent a net balance between consumption (-) and production (+) of CH4 in soil, varied from -40 +/- 2 to +62 +/- 78 mu g C m(-2) h(-1). Mean weighted contents of ammonium (NH4+-N) and dissolved organic carbon (DOC) in soil had a positive relationship with accumulated soil CH4 fluxes in the post-management period (r(2) = 0.95, p = 0.05), suggesting an additive effect of these nutrients in suppressing CH4 oxidation and stimulating methanogenesis, respectively, in legume-based cropping systems with high biomass input. Annual CH4 fluxes ranged from -50 +/- 610 to +994 +/- 105 g C ha(-1), which were inversely related to annual biomass-C input (r(2) = 0.99, p = 0.003), with the exception of the cropping system containing pigeon pea, a summer legume that had the highest biologically fixed N input (>300 kg ha(-1) yr(-1)). Our results evidenced a small effect of conservation management systems on decreasing CH4 emissions from soil, despite their significant effect restoring soil quality. We hypothesized that soil CH4 uptake strength has been off-set by an injurious effect of biologically fixed N in legume-based cropping systems on soil methanotrophic microbiota, and by the methanogenesis increase as a result of the O-2 depletion in niches of high biological activity in the surface layer of the no-tillage soil. (C) 2012 Elsevier B.V. All rights reserved.Brazilian Council for Scientific and Technologic Development (CNPq)Brazilian Council for Scientific and Technologic Development (CNPq)Foundation of Research Support of Rio Grande do Sul State (Fapergs)Foundation of Research Support of Rio Grande do Sul State (Fapergs

Soil organic carbon and fertility interactions affected by a tillage chronosequence in a Brazilian Oxisol

No-till (NT) adoption is an essential tool for development of sustainable agricultural systems, and how NT affects the soil organic C (SOC) dynamics is a key component of these systems. The effect of a plow tillage (PT) and NT age chronosequence on SOC concentration and interactions with soil fertility were assessed in a variable charge Oxisol, located in the South Center quadrant of Parana State, Brazil (50 degrees 23`W and 24 degrees 36`S). The chronosequence consisted of the following six sites: (i) native field (NF); (ii) PT of the native field (PNF-1) involving conversion of natural vegetation to cropland; (iii) NT for 10 years (NT-10); (iv) NT for 20 years (NT-20); (v) NT for 22 years (NT-22); and (vi) conventional tillage for 22 years (CT-22) involving PT with one disking after summer harvest and one after winter harvest to 20 cm depth plus two harrow disking. Soil samples were collected from five depths (0-2.5; 2.5-5; 5-10; 10-20; and 20-40 cm) and SOC, pH (in H(2)O and KCl), Delta pH, potential acidity, exchangeable bases, and cation exchangeable capacity (CEC) were measured. An increase in SOC concentration positively affected the pH, the negative charge and the CEC and negatively impacted potential acidity. Regression analyses indicated a close relationship between the SOC concentration and other parameters measured in this study. The regression fitted between SOC concentration and CEC showed a close relationship. There was an increase in negative charge and CEC with increase in SOC concentration: CEC increased by 0.37 cmol(c) kg(-1) for every g of C kg(-1) soil. The ratio of ECEC:SOC was 0.23 cmol(c) kg(-1) for NF and increased to 0.49 cmol(c) kg(-1) for NT-22. The rates of P and K for 0-10 cm depth increased by 9.66 kg ha(-1) yr(-1) and 17.93 kg ha(-1) yr(-1), respectively, with NF as a base line. The data presented support the conclusion that long-term NT is a useful strategy for improving fertility of soils with variable charge. (C) 2008 Elsevier B.V. All rights reserved.FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior

Influence of fertilizer inputs on soil solution chemistry in eucalypt plantations established on Brazilian sandy soils

International audienceThe present paper is part of a comprehensive approach currently developed in Brazil to study biogeochemical cycles at the ecosystem level in Eucalyptus grandis plantations. It aims at assessing changes occurring in water chemical composition throughout their transfer in the soil, during the first year after planting. A lysimetry was installed in a 5-year-old E. saligna stand. Lysimeters were strategically positioned within a compartment of E. saligna prior to the clear felling of the stand that would allow the assessment of a fertilization experiment planned on the same site for the next rotation. About 180 zero-tension lysimeters were installed in the upper soil layers and 136 ceramic cups were setup horizontally down to a 3 m depth and connected to an automatic vacuum pump. After the harvest of the E. saligna stand, a fertilization experiment of E. grandis improved seedlings was initiated using a complete randomized block design, with 6 blocks and 5 treatments. The objective was to compare the influence of different amounts of ammonium sulphate and sewage sludge fertilizations on biogeochemical cycling. At the end of the rotation, nutrient concentrations in soil solutions were low whatever the depth and the lysimeter type. After clear felling, soil solution ionic balances were dominated by NO3- and Al3+, whose concentrations increased substantially. No obvious change in concentrations was observed for all other elements. A proton unbalance, resulting from the interruption of NO3- uptake by plants after harvesting, might be responsible for the aluminium accumulation in soil solutions. After planting, fertilizer inputs were responsible for increasing concentrations of all elements applied until 1 m deep. Twelve months after planting E. grandis, the chemistry of soil solutions at 3 m deep had not developed. The monitoring of soil solution chemistry is going on in order to quantify the effects of these different fertilizations on deep drainage nutrient losses

Influence of mineral and organic fertilizer inputs on nitrogen cycling in Eucalypts plantations

International audienc

Soil nitrous oxide emissions in long-term cover crops-based rotations under subtropical climate

It has been shown that cover crops can enhance soil nitrous oxide (N(2)O) emissions, but the magnitude of increase depends on the quantity and quality of the crop residues. Therefore, this study aimed to evaluate the effect of long-term (19 and 21 years) no-till maize crop rotations including grass [black oat (Avena strigosa Schreb)] and legume cover crops [vetch (Vigna sativa L), cowpea (Vigna unguiculata L. Walp), pigeon pea (Cajanus cajan L. Millsp.) and lablab (Dolichos lablab)] on annual soil N(2)O emissions in a subtropical Acrisol in Southern Brazil. Greater soil N(2)O emissions were observed in the first 45 days after the cover crop residue management in all crop rotations, varying from -20.2 +/- 1.9 to 163.9 +/- 24.3 mu g N m(-2) h(-1). Legume-based crop rotations had the largest cumulative emissions in this period, which were directly related to the quantity of N (r(2) = 0.60, p = 0.13)and inversely related to the lignin:N ratio(r(2) = 0.89,p = 0.01) of the cover crop residues. After this period, the mean fluxes were smaller and were closely related to the total soil N stocks (r(2) = 0.96, p = 0.002). The annual soil N(2)O emission represented 0.39-0.75% of the total N added by the legume cover crops. Management-control led soil variables such as mineral N (NO(3)(-) and NH(4)(+)) and dissolved organic C influenced more the N(2)O fluxes than environmental-related variables as water-filled pore space and air and soil temperature. Consequently, the synchronization between N mineralization and N uptake by plants seems to be the main challenge to reduce N(2)O emissions while maintaining the environmental and agronomic services provided by legume cover crops in agricultural systems. (C) 2009 Elsevier B.V. All rights reserved