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Understanding the effects of N application or the introduction of a legume on N cycling is critical for achieving productive and sustainable grassland systems. This 2-year study assessed the N cycling of three pasture treatments: (1) mixed Marandu palisadegrass (Brachiaria brizantha) and forage peanut (Arachis pintoi) without N fertiliser (GRASS + LEGUME); (2) monoculture Marandu palisadegrass fertilised with 150 kg N ha−1 year−1 (GRASS + N); and (3) monoculture Marandu palisadegrass without N fertiliser (GRASS). Continuous stocking was used with a target canopy height of 0.20 to 0.25 m. Litter responses, forage and N intake, N livestock excretion and N cycling were measured. Existing litter and litter deposition rate were greatest in GRASS pasture (3030 and 84.3 vs. 2140 kg ha−1 and 64.8 kg OM ha−1 d−1; average of GRASS + N and GRASS + LEGUME pastures, respectively; P

The 15N natural abundance (δ15N) technique offers good prospects for the quantification of the contribution of biological nitrogen fixation (BNF) to crop nutrition. The objectives of this study were to determine which plant parts best represented the whole plant with respect to δ15N and to quantify the BNF contribution to sugarcane. The experiment was carried out in pots of soil (100 kg pot−1) from the field. The sugarcane varieties used were RB867515 and RB92579 with the reference plants Brachiaria decumbens, millet (Pennisetum americanum) and sorghum (Sorghum bicolor). The experimental design was randomised blocks with four replications. The treatments were inoculation of the sugarcane with or without diazotrophic bacteria and the different parts of the sugarcane plant (root, green leaf, senescent leaf and different stem sections). The δ15N of different cane parts and varieties ranged from + 2.68 to + 5.85‰ after 365 days, while the δ15N of reference plants were from + 7.8 to + 8.3‰. The mean contribution of BNF to the sugarcane crop N supply was estimated to be 47% with no effect of variety or inoculation. The results indicate that the δ15N value of the entire shoot can be considered to represent the entire sugarcane plant, but no single organ could be relied on for this purpose.

Diazotrophic bacteria applied as a seed inoculant can improve the grain yield of several crops including maize. The current study aimed to test the agronomic efficiency and contribution of biological nitrogen fixation (BNF) of the endophytic diazotroph Herbaspirillum seropedicae strain ZAE94 to maize under field conditions. Eighteen field assays were conducted in four different locations during consecutive years on two hybrids and two varieties of maize in a random block design with four replicates using a peat-based inoculant. The inoculant containing the ZAE94 strain was applied without nitrogen (N) fertilization or with 40 kg N ha–1 and was compared to the application of 40 and 80 kg N ha–1 without inoculation. Crop productivity and N accumulation in the grain were evaluated in addition to 15 N natural abundance (°15 N) to evaluate BNF in the treatments without N fertilization. Fertilization at 40 kg N ha–1 plus bacterial inoculation produced crop yields similar to the treatment with 80 kg N ha–1 and increased grain N content, especially in the off-season with 40 kg N ha–1. The inoculation treatments showed lower °15N values than the non-inoculated treatments, which was most evident in the off-season. The BNF contributed about 30% of N accumulated in plants inoculated with ZAE94. On average, 64% of the N fertilized plots showed an increase of the parameters evaluated in the inoculated treatments, compared with the control. Inoculation also increased root length, root volume, and leaf area, and these parameters were positively correlated with plant weight using a hydroponic assay. This study revealed that the application of H. seropedicae inoculant increased the amount of N in plants owing to BNF, and there is a better chance of yield response to inoculation under low N fertilizer application in the off-season.

In grass-legume pastures, grazing management strategies are an essential factor affecting nitrogen (N) cycling. This study assessed the impact of grazing management on N cycling in rotationally-stocked mixed pastures of ‘Marandu’ palisadegrass (Brachiaria brizantha) and ‘Comum’ calopo (Calopogonium mucunoides). Treatments included three grazing management strategies, defined by interruption of the rest period when the canopy reached 90 (90LI), 95 (95LI) and 100% (100LI) of the interception of photosynthetically active radiation. A 2-yr experimental period was adopted. Plant litter responses, forage intake and livestock excretion were evaluated. No differences between grazing management were obtained for existing (294 g OM m−2) and deposited litter (6.7 g OM m−2 d−1, P > 0.10). Compared to the dry season, the litter decomposition rate increased 24.0%, and the half-life decreased 37.8% in the rainy season (P 0.10). Less frequent defoliation (100LI) resulted in reduced proportion of legume intake (P

Field studies on soil ammonia (NH3) volatilization are restricted in many countries owing to the high costs commonly demanded for accurate quantification. We assessed the accuracy of a simple, open chamber design to capture NH3 under field conditions, as affected by different chamber placement schemes. Urea-15N was surface applied to lysimeters installed in the spaces between maize rows. Open chambers made from plastic bottles were installed on each lysimeter with variations in i) N rates (3, 8, 13, and 18 g m–2), ii) the height of the chamber above the soil surface (0, 5, and 10 mm), and iii) chamber relocation (static vs. dynamic). Reference lysimeters without chambers were used to measure NH3 losses by 15N-balance. Losses of NH3 -N accounted for more than 50% of the applied N. Relocation of the chambers had no impact on their NH3-trapping efficiencies, proving to be an unnecessary procedure. Variation in the height of the chambers above the soil surface affected the capture of NH3, but the results still maintained high linearity with the NH3 losses quantified by the reference method (R2 > 0.98). When the same placement scheme used in the introductory study describing the chamber was utilized (static and touching the soil surface), we found a trapping efficiency of 60%, which was very similar to that (57%) obtained in the previous study. Our results show that this simple, open chamber design can be used with satisfactory accuracy under field conditions, provided that simple, standardized procedures are warranted.

Measuring ammonia (NH3) volatilization from urea-fertilized soils is crucial for evaluation of practices that reduce gaseous nitrogen (N) losses in agriculture. The small area of chambers used for NH3 volatilization measurements compared with the size of field plots may cause significant errors if inadequate sampling strategies are adopted. Our aims were: i) to investigate the effect of using multiple open chambers on the variability in the measurement of NH3 volatilization in urea-amended field plots and ii) to define the critical period of NH3-N losses during which the concentration of sampling effort is capable of reducing uncertainty. The use of only one chamber covering 0.015% of the plot (51.84 m2) generates a value of NH3-N loss within an expected margin of error of 30% around the true mean. To reduce the error margin by half (15%), 3–7 chambers were required with a mean of 5 chambers per plot. Concentrating the sampling efforts in the first two weeks after urea application, which is usually the most critical period of N losses and associated errors, represents an efficient strategy to lessen uncertainty in the measurements of NH3 volatilization. This strategy enhances the power of detection of NH3-N loss abatement in field experiments using chambers.

Made available in DSpace on 2021-06-25T11:49:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-26 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) In warm-climate grasslands, litter deposition and decomposition are one of the main pathway of nutrient cycling. The application of nitrogen (N) fertilizer or the inclusion of a legume in such grasslands modifies litter characteristics and chemical composition. This study evaluated how the N supply of palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] pastures affect litter characteristics two years after seeding. Treatments were palisadegrass fertilized or not with N (150 or 0 kg N ha(-1) year(-1)) or mixed with the legume forage peanut (Arachis pintoi cv. Amarillo). The experimental period covered two consecutive rainy seasons. Nitrogen fertilization increased by 43 and 62% the existing litter mass (organic matter, OM), and by 32 and 23% the litter deposition rate compared to unfertilized palisadegrass or legume-grass mixtures, respectively. Both variables were affected by grazing cycle (GC), with low litter deposition rate (14 kg ha(-1) d(-1) OM) and existing litter mass (1390 kg ha(-1) OM) in the GC4 due to low rainfall. Nitrogen fertilized palisadegrass had greater litter N concentration (7.9 +/- 0.4 g kg(-1) OM-C:N ratio 34 +/- 2) than in monoculture or legume-grass mixtures (C:N ratios 45 and 58 +/- 2, respectively). Our results indicated that N fertilization of palisadegrass increased litter accumulation, however, N fertilization was not a key driver of the litter decomposition rate, even though it increased litter N concentration. After 2 years of establishment, the proportion of forage peanut in the litter was still low, reducing the benefits of legume inclusion to enhance litter nutrient cycling in these pastures. Sao Paulo State Univ, Dept Anim Sci, Via Acesso Prof Paulo Donato Castellane, BR-14884900 Jaboticabal, SP, Brazil Embrapa Agrobiol, Rodovia BR 465,Km 7, BR-23891000 Seropedica, RJ, Brazil Univ Florida, North Florida Res & Educ Ctr, Marianna, FL 32446 USA Sao Paulo State Univ, Dept Anim Sci, Via Acesso Prof Paulo Donato Castellane, BR-14884900 Jaboticabal, SP, Brazil FAPESP: 2016/11086-1 FAPESP: 2017/11274-5 FAPESP: 2015/16631-5 CNPq: 404169/2013-9

The soybean crop in Brazil has been growing in area and productivity in recent years and the analysis of its energy efficiency is very important to guarantee the sustainability of the production system. Assessment of energy efficiency (EE) enables the evaluation of the sustainability of agrosystems, as well as decision-making regarding the reduction in production costs and negative environmental impacts. In this context, the objective of this study was to assess energy efficiency of soybean in different regions of Brazil. For this purpose, 29 areas of soybean across the major producing states were assessed. Energy inputs and outputs of agricultural operations and/or agricultural inputs were calculated by multiplying the amount used by their calorific value or energy coefficient at each stage of production. Energy efficiency was calculated as the ratio between the total output energy and the total input energy during the production process. For every MJ of energy consumed in the production of soybean crop, 6.1; 6.7; 7.1 and 7.2 MJ of energy were produced in the form of grain, respectively in the areas assessed in the Midwest, northeast, southeast and south regions of Brazil. Generally, the main energy expenditure on soybean cultivation in different regions of Brazil was with fertilizers, seeds and herbicides. The adverse weather conditions of the year / harvest evaluated in the south-central region of Brazil resulted in low soybean yields and consequently resulted in lower energy efficiency in these regions. The evaluation of energy efficiency in soybean crops to be representative must be carried out in different regions and edaphoclimatic conditions.

Beef cattle producers seldom use fertilizers for their pastures in tropical regions of Brazil. Slowly, this is changing but because of the need for repeated applications, N fertilizer is rarely applied. The introduction of a forage legume is an appropriate solution for this problem, but until recently adoption has been very low as the legumes generally have not persisted in the sward. We report research on how grazing management can affect the persistence of stoloniferous legumes in pastures of Brachiaria spp. and the problems of establishing and maintaining crown‐forming legumes such as Stylosanthes spp. With suitable management, milk or bovine carcass yields can be equal or greater from mixed than from grass‐alone pastures fertilized with 120 or 150 kg Nha‐¹ year⁻¹. In addition to savings in CO₂ emissions from fossil fuels for the production and distribution of N fertilizers, nitrous oxide emissions from cattle excreta and legume residues are lower than those from N‐fertilized brachiaria grass monocultures. Other studies indicate that enteric methane emissions from cattle may be mitigated when forage legumes are included in their diet. The use of forage legumes in mixed pastures for tropical regions is emerging as a feasible strategy to keep meat and milk production at acceptable levels with reduced greenhouse gas emission rates.

Identification of variability in biological N2 fixation (BNF) contribution among common bean (Phaseolus vulgaris L.) cultivars under field conditions requires a reliable methodology. This study aimed to assess different common bean cultivars for plant growth and grain yield and to quantify the BNF contribution to the crop using the 15N natural abundance technique. Two field experiments were conducted in an Oxisol in Brazil over two consecutive years, with eight common bean cultivars inoculated with rhizobium or fertilized with mineral N. Plants were analysed at mid-pod filling stage (two weeks after full-flowering) and at grain maturity. BNF was estimated by the 15N natural abundance technique. Average grain yields were 1614 or 2942 kg ha−1 in Experiment I, and 3284 or 3919 kg ha−1 in Experiment II, with rhizobium inoculation or mineral N, respectively. The average contributions of N derived from atmosphere were 14 and 26%, and amounts of N2-fixed were 7 and 22 kg N ha−1, in bean plants at mid-pod filling, respectively, in Experiment I and Experiment II. The contributions of BNF increase when common bean crop reached its optimum yield potential even though soil N was the most important source for the plants. There is good relationship between δ15N values of grains and shoots, provided cultivars are of similar growth habit. The 15N natural abundance technique allowed identifying cultivars with relatively high BNF capability for commercial crop and breeding purposes.

The introduction of a forage legume into a tropical pasture should decrease the need for N fertilizer, provided biological N

Millions of hectares (ha) of the Atlantic forest of Brazil have been deforested and replaced by pastures, quite a large proportion of this in the last 60 years. There have been few studies on the impact of this land-use change on stocks of soil organic matter (SOM) only one study reported the state of vigour of the pastures. The aim of this study was to estimate the overall change in SOM stocks 16 years after the removal of forest vegetation in this biome in southern Bahia and the installation of pastures of Brachiaria brizantha fertilized with N and maintained under controlled grazing. Soil samples were taken for evaluation of density and texture and for analyses of C and N total and 13C abundance to a depth of 100 cm at 100 m intervals along four transects of 400 m from the pastures into the forest. Grazing was found not to have any significant effect on soil density (compaction). The live weight gain of the Nellore cattle on both cultivars of B. brizantha, fertilized with 120 kg N ha−1 yr−1 as urea during 12 years, was close to 500 kg ha−1 yr−1. The gain in soil C was similar under the two grass cultivars, being approximately 15 Mg C ha−1 to a depth of 30 cm and 20 Mg C ha−1 to 100 cm. The 13C abundance data showed that the large gain in soil C was due to the slow decomposition of the forest-derived C (total loss 12.6 Mg C ha−1 over 16 years) and the large accumulation of C derived from the Brachiaria (total gain 43.2 Mg C ha−1). These results confirm the potential of productive Brachiaria pastures to accumulate soil C in a tropical climate with year-round rainfall.

Nitrogen (N) management affects herbage production and chemical composition, however, information on the impact of tropical herbage on N and carbohydrate fractions is scarce. A two-year study was conducted to investigate the potential use of pintoi peanut (Arachis pintoi) compared with N fertilization of palisade grass (Brachiaria brizantha cv. Marandu) by evaluating the herbage chemical composition (fractionation of protein and carbohydrate), herbage mass and accumulation rate, herbage disappearance rate, and stocking rate of pastures. The experiment was conducted in a completely randomized design with three treatments, and four replications (paddocks) were used with twenty-one non-lactating crossbred dairy heifers. Treatments consisted of pastures of palisade grass without a N source (control), fertilized with urea (150 kg/ha/year, fertilized), or mixed with pintoi peanut (mixed). Inclusion of the legume increased concentrations of fractions A (p = 0.009), which is the soluble N compound, and B3 (p &lt, 0.001), which is slowly degraded true protein, compared with pastures fertilized with N and non-fertilized pastures. Nitrogen fertilization increased fraction B1 + B2 (p = 0.046), mainly true proteins, and decreased fraction C (p = 0.0007), indigestible protein, and neutral detergent fiber concentrations (p = 0.0003), contributing to increasing the nutritive value of the herbage. Additionally, N fertilization increased herbage mass (p = 0.004) and herbage allowance (p = 0.0001). Both N fertilization and biologically fixed N increased herbage allowance (p = 0.02) and accumulation rate (p = 0.02), as well as the crude protein content of herbage (p &lt, 0.0001) compared with non-fertilized pastures. Nitrogen fertilization increased true protein and decreased indigestible protein of herbage and promoted a greater herbage mass production, while the inclusion of legumes increased soluble protein and decreased the slowly degraded true protein of herbage. Both N management strategies increased herbage allowance and accumulation rate.

Purpose: Soybean is the most important grain crop in Brazil with a mean N accumulation of over 250 kg N ha-1, principally from biological N2 fixation. The residual N benefit depends heavily on the quantity of the belowground N at harvest, much which cannot be directly recovered in roots. The purpose of this study was to investigate different aspects of the 15N leaf-labelling technique to quantify non-recoverable root N (NRRN) derived from senescent roots and nodules (rhizodeposits). Methods: Soybean plants were grown in pots of soil and at 27 days after planting (vegetative stage V4) cut or whole leaves were exposed to highly enriched 15N-labelled urea or glutamine. Seven sequential harvests of the plants and soil were taken until the final grain harvest at 70 days after labelling.Results: After only 48 h, the plants labelled with 15N urea transferred approximately 5% to the soil, while only 1% was found in the roots. Leakage of 15N label was even more pronounced when the leaves were labelled with 15N glutamine. After this initial leakage, the excess 15N deposited in the soil only increased by a further 2.6% of applied label, which suggested that only part of this N represented senescence of roots or nodules.Conclusions At the final harvest, N in roots separated from the soil amounted to 6.4% of total plant N. Discounting the early rapid deposition of 15N-enriched N to the soil, our calculations indicated that at final harvest the total NRRN was 2.8% of total plant N.

Assessment of energy efficiency (EE) enables the evaluation of the sustainability of agrosystems, as well as decision-making regarding reduction in production costs and environmental pollution and even to increase production in a sustainable way. In this context, the objective of this study was to assess energy efficiency in maize in different regions of Brazil. For this purpose, 32 areas of maize crop distributed across the major producing states and regions were assessed. Energy inputs and outputs of agricultural operations and/or agricultural inputs were calculated by multiplying the amount used by their calorific value or energy coefficient at each stage of production. Energy efficiency was calculated as the ratio between the total output energy and the total input energy during the production process. For every megajoule (MJ) of energy consumed in the production of second-crop maize and first-crop maize seasons, 9.9 and 8.7 MJ respectively of renewable energy were produced in the form of grain. In both maize cropping seasons, most of the energy use was attributed to fertilizers, herbicides and fuel. To be representative the evaluation of energy efficiency of the maize crop should be performed in different Brazilian cultivation regions, as it will represent different edaphoclimatic and management conditions spread over the national territory within an agricultural year. A avaliação da eficiência energética (EE) pode evidenciar a sustentabilidade dos agrossistemas e a tomada de decisões relativas à redução dos custos de produção, poluição do ambiente e até mesmo aumento de produção de forma sustentável. Diante deste contexto, o objetivo deste trabalho foi avaliar a eficiência energética na cultura do milho em diferentes regiões brasileiras. Para isso, foram avaliadas 32 áreas de milho distribuídas pelos principais estados das regiões produtoras desta cultura. As entradas e saídas de energia das operações agrícolas e/ou insumos utilizados foram calculadas pela multiplicação da quantidade utilizada pelo seu poder calorífico ou coeficiente energético em cada etapa de produção. A eficiência energética foi obtida pela razão entre a quantidade de energia total de saída e o consumo total de energia durante o processo produtivo. Para cada 1,0 MJ de energia consumida na produção de milho safrinha e safra, produziu-se respectivamente 9,9 e 8,7 MJ de energia renovável, na forma de grãos desta cultura. Os principais gastos energéticos foram com fertilizantes, herbicidas e combustível. A avaliação da eficiência energética na cultura do milho para ser bem representativa deve ser realizada em diferentes regiões brasileiras de cultivo, pois assim representará diferentes condições edafoclimáticas e de manejo espalhadas pelo território nacional dentro de um ano agrícola.

Made available in DSpace on 2021-06-26T02:53:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundacao de Amparo a Pesquisa doEstado de Sao Paulo Cattle excreta and nitrogen (N) fertilizer deposited on tropical grasslands are important sources of ammonia (NH3) emission. We conducted three field trials (wet, intermediate, and dry conditions) to quantify NH3 emissions from urea fertilizer and simulated excretions of heifer urine and dung on warm-climate grasslands in Brazil. Heifer excreta were derived from pastures of palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster 'Marandu'] under three forms of N supply (without or with N fertilization [0 or 150 kg N ha(-1) yr(-1)] or mixed with forage peanut [Arachis pintoi 'Amarillo']). Cumulative NH3-N emissions across rainfall conditions were 7.6-16.6% (mean, 11.7%) for urine, 1.4-2.9% (mean, 2.0%) for dung, and 11.2-20.5% (mean, 14.8%) for urea. Ammonia loss from urine was significantly greater than from dung under all rainfall conditions. Emission from urine and dung differed from those when urea was applied on palisadegrass. There were greater NH3 emissions from urine in the wetter times of the year. Heifer excreta from N-fertilized pasture had greater NH3 emission than excreta from the grass-legume mixture and unfertilized palisadegrass. Urea applied on palisadegrass presented greater NH3 emissions in wet rainfall conditions compared with dry conditions but did not differ from intermediate conditions. Our study showed that N-fertilized systems increase N losses as NH3 emission from excreta, and emissions from urea fertilizer must be included in this system. Heifer excreta and urea fertilizer deposited on warm-climate grasslands increased the NH3 emissions mainly under wet conditions. Sao Paulo State Univ, Dep Anim Sci, Via Acesso Prof Paulo Donato Castellane, BR-14884900 Jaboticabal, SP, Brazil Embrapa Agrobiol, Rodovia BR 465,Km 7, BR-23891000 Seropedica, RJ, Brazil Univ Florida, North Florida Res & Educ Ctr, Marianna, FL 32446 USA Sao Paulo State Univ, Dep Anim Sci, Via Acesso Prof Paulo Donato Castellane, BR-14884900 Jaboticabal, SP, Brazil CNPq: 404169/2013-9 Fundacao de Amparo a Pesquisa doEstado de Sao Paulo: 2015/16631-5

Fil: Villarino, Sebastian Horacio. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias. Laboratorio de Agroecologia; Argentina

The ruderal babassu palm (Attalea speciosa) is expanding on large areas of degraded Amazon landscapes. Decomposition of leaves and roots is in the center of plant:soil interactions. We evaluated decomposition and nutrient concentrations of leaves and fine roots of babassu in comparison with two exotic reference species, Acacia mangium (slow degradability) and Leucaena leucocephala (fast degradability), in a 138-day litterbag assay carried out in secondary forest stands of different age and babassu abundance. We chose 4-mm over 2-mm mesh litterbags based on a pilot study. Babassu leaves degraded slower than leaves of A. mangium and L. leucocephala, and also had lower nitrogen, phosphorus and calcium concentrations in all stages of decomposition. By contrast, potassium concentrations in babassu leaves were higher than in both reference species at 0 and 50 days. Roots of all three species decomposed slower than leaves. Compared to the leaves, both biomass loss and nutrient concentrations differed less between babassu and reference-species roots, except for lower nitrogen concentration in babassu roots. Leaf-litter decomposition of all three species was significantly faster in old than in young secondary forest, suggesting an acceleration of decomposition along succession. Babassu leaves decomposed faster in old babassu-dominated than non-dominated secondary forest, pointing to the existence of specialized decomposer communities in babassu-dominated stands. RESUMO A palmeira ruderal babaçu (Attalea speciosa) se expande em grandes áreas da Amazônia já desmatada e degradada. A decomposição é chave na dinâmica sucessional e nas interações planta:solo. Avaliamos decomposição e concentração de nutrientes de folhas e raízes finas de babaçu e de duas espécies exóticas de referência, Acacia mangium (decomposição lenta) e Leucaena leucocephala (decomposição rápida), em capoeiras de diferente idade e grau de dominância de babaçu usando litterbags durante 138 dias. Usamos litterbags com malha de 4 mm em vez de 2 mm, com base em um estudo-piloto. As folhas de babaçu se decompuseram mais lentamente que as de A. mangium e L. leucocephala, e apresentaram concentrações mais baixas de nitrogênio, fósforo e cálcio em todos os estágios de decomposição. Em contraste, a concentração de potássio em folhas de babaçu foi mais alta que nas espécies de referência aos 0 e 50 dias. Raízes se decompuseram mais lentamente que folhas nas três espécies. Tanto a perda de massa, como a concentração de nutrientes diferiram menos entre as raízes que entre as folhas de babaçu e as espécies de referência, exceto a concentração de nitrogênio nas raízes de babaçu. A decomposição foliar das três espécies foi significantemente mais rápida em capoeira velha que em capoeira jovem, sugerindo uma aceleração da decomposição ao longo dos estágios sucessionais. A decomposição foliar do babaçu foi mais rápida em capoeira velha com alta dominância de babaçu que em capoeira velha com baixa dominância, apontando para a existência de comunidades especializadas de decompositores em áreas dominadas por babaçu.

The objective was to evaluate milk production, N2-fixation and N transfer, forage yield and composition (under two cutting intervals) in a silvopastoral system (SPS) with Leucaena leucocephala-Megathyrsus maximus and M. maximus-monoculture (MMM) with crossbred cows in a completely randomized design. Forage yield in the SPS was 6490 and 6907 kg DM ha&minus, 1 for cutting intervals (CI) of 35 and 50 days. Forage yield for the MMM was 7284 and 10,843 kg DM ha&minus, 1, and forage crude protein (CP) was 29.0% and 26.1% for L. leucocephala, harvested at 35 and 50 days, respectively. CP for the associated M. maximus was 9.9% and 7.8% for CI 35 and 50 days, respectively, and for MMM was 7.4% and 8.4%, harvested at 35 and 50 days. Milk production was 4.7 kg cow&minus, 1 day&minus, 1 for cows grazing MMM and 7.4 kg cow&minus, 1 under SPS. Nitrogen fixation in L. leucocephala (%Ndfa) was estimated to be 89% and 95%, at 35 and 50 days, with an N2 transfer to the associated grass of 34.3% and 52.9%. SPS has the potential to fix and transfer important amounts of N2 to the associated grass, and increase forage CP content and milk production.

The existence of large population of ineffective native rhizobia and inconsistent performance of exotic strains in Ghanaian soils necessitate the need to identify effective and locally adapted elite strains for enhanced legume-rhizobium symbiosis. This study was designed to test the suitability of two previously selected potential elite Bradyrhizobium strains for use as inoculants on cowpea (Vigna unguiculata L. Walp) and groundnut (Arachis hypogaea L.) in multi-location experiments. Field experiments were set up at 26 locations (12 planted with cowpea and 14 planted with groundnut) in the Northern region of Ghana. Four treatments were applied at each location: inoculation with Bradyrhizobium strains KNUST 1002 and KNUST 1006, a positive nitrogen (+N) control and a negative control (without nitrogen or inoculation) arranged in randomized complete blocks with four replications. The results showed that inoculation with strains KNUST 1002 and KNUST 1006 promoted significant increases in grain yields of both cowpea and groundnut. On average, inoculating cowpea with strains KNUST 1002 and KNUST 1006 resulted in 63 and 52% increases in grain yield when compared to the negative control. Pod yields of groundnut on the other hand, were significantly (p< 0.05) increased at 57% of the study location with one or both test strains. Responses to inoculation were, however, highly variable across the different study locations (i.e. significant Treatment ⸼ Location Interaction, TLI). A detailed analysis of this significant TLI based on the genotype main effect (G) plus genotype-by-environment (GE) interaction (GGE) biplot analysis revealed that location contributed 71 and 88% of the variation observed in cowpea and groundnut, respectively, and grouped the locations into mega-environments. These results demonstrate that native elite Bradyrhizobium strains KNUST 1002 and KNUST 1006 have potential for use as inoculants to increase cowpea and groundnut production in Northern Ghana.

The evaluation of 15N abundance of N derived from biological N2 fixation (BNF) in legume shoots (‘B S ’ value) is essential for quantifying BNF inputs to field-grown legumes. The aim of this study was to investigate the impact of shading, development stage of soybean (Glycine max) and rhizobium strain on the ‘B S ’ value. Soybean plants were grown in pots of autoclaved sand/perlite mixture in the open field. Plants were harvested at weekly intervals from 46 days after planting (DAP) to 75 DAP. All material was analysed for N and 15N abundance. ‘B S ’ was calculated assuming 50% of seed N was translocated to the shoots. ‘B S ’ was stable until 60 DAP but subsequently increased for the three strains tested. Nodule efficiency (N2 fixed g DM nodule−1) was greatly increased by shading and was significantly different between Bradyrhizobium species. ‘B S ’ was greatly increased by shading. We recommend that ‘B S ’ should be evaluated on plants of the same development stage and light intensity as those where BNF is quantified in the field. Different Bradyrhizobium strains make a large impact on ‘B S ’ and may lead to considerable errors in estimation of BNF inputs to plants with high %N derived from BNF.

The ‘B’ value, the 15N abundance of plants depending completely on biological nitrogen fixation (BNF) for growth, is required for quantifying BNF using the 15N natural abundance technique. This study aimed to investigate how common bean (Phaseolus vulgaris L.) cultivars with different growth patterns could affect the ‘B’ value calculated for the plant shoot. Two experiments were conducted in N-free solution. Experiment I had a factorial design with three cultivars and two rhizobium inoculants. Plants were harvested at pre-flowering stage. Experiment II was also factorial with two cultivars and two times of sampling: full flowering and mid-pod filling. Total N and δ15N analyses of different plant parts were carried out to estimate the ‘B’ value. There were differences between cultivars for N accumulation and 15N abundance, but no difference between rhizobium inoculants. Results revealed differences in ‘B’ value between cultivars of small and large seeds, the growth stage being also relevant. The ‘B’ values of −2.08 and −1.34‰ could be used for BNF estimates in small-seeded cultivars at full flowering and mid-pod filling stages, respectively, while such values should change, respectively, to −1.73 and −1.03‰ for large-seed cultivars. The mean ‘B’ value in shoots was −1.90 and −1.20‰ at full flowering and mid-pod filling stages, respectively. There are variations in ‘B’ value between cultivars of different cycle length and seed sizes, which are associated with plant architecture, thus a ‘B’ for each growth stage of common bean plants is required.

Successful inoculation of legume crops with rhizobia depends on dominating nodule occupancy with highly efficient strains. The aim of this study was to develop a rapid and reliable conventional PCR methodology to specifically detect an elite Bradyrhizobium strain in root nodule extracts from soil-grown cowpea plants. The draft genome sequence of Bradyrhizobium pachyrhizi BR 3262 was compared to the closely related strain PAC 48T. BR 3262-specific regions were selected to design specific primer pairs, which were tested with respect to PCR amplification specificity and efficiency on extracted DNA, bacterial cells and root nodules from cowpea plants grown under gnotobiotic conditions and in soil. Eleven designed primer pairs were specific for BR 3262 amplification and two of them (pairs 2645 and 2736) were highly sensitive and selected for further analyses. Experiments with gnotobiotic and soil-grown plants showed that both primer pairs were suitable to reliably determine nodule occupancy and confirmed the competitiveness of strain BR 3262 in natural soil. Primer pairs 2645 and 2736 are novel tools to accompany the fate of strain BR 3262 in inoculation experiments of cowpea in soil. This strategy should be applicable to other rhizobium/legume symbioses in the field.

The inoculation of cereal crops with plant growth-promoting bacteria (PGPB) is a potential strategy to improve fertilizer-N acquisition by crops in soils with low capacity to supply N. A study was conducted to assess the impact of three inoculants on grain yield, protein content, and urea-15 N recovery in maize (Zea mays L.) under Cerrado soil and climate conditions. The main treatments included inoculants containing (i) Azospirillum brasilense strain Sp245, (ii) A. brasilense strains AbV5 + AbV6, (iii) Herbaspirillum seropedicae strain ZAE94, and (iv) a non-inoculated control. The subtreatments were (i) urea-N fertilization (100 kg N ha−1) at 30 days after sowing and (ii) no N addition at the stage. To determine fertilizer-N recovery, 15N–labelled urea was applied in microplots. Inoculants carrying A. brasilense improved urea-15 N acquisition efficiency in maize and also improved grain yield compared to the non-inoculated control, while urea-N fertilization enhanced grain quality by providing higher protein content. Our results suggest that the inoculation of maize grains with PGPB represents a strategy to improve fertilizer-N recovery and maize yield in Cerrado soil with a low capacity to supply N.

The objectives of this study were to determine the rates of plant litter deposition and decomposition in Marandu pastures (Urochloa brizantha cv. Marandu) under a) three forms of nitrogen (N) supply, b) at different stages of rotational grazing and c) to compare the single-exponential decay constant (‘k’) derived from litterbags with values derived from estimates of deposited and existing litter (DEL technique). The three N supply treatments were: without or with N fertilization (zero or 150 kg N ha-1 yr-1) or with the legume Desmodium ovalifolium. There were no significant differences (p

This study evaluated soil parameters involved in ammonia (NH3) fluxes from livestock excreta and urea fertilizer. Treatments were distributed in a randomized block design, with five replicates. Treatments included application of 1) urine; 2) dung; or 3) urea fertilizer (50 kg N ha-1) on palisadegrass pasture (Brachiaria brizantha cv. Marandu). Excreta was collected from crossbred heifers grazing palisadegrass pastures. One soil background treatment without excreta or urea was included for the measurement of NH3 fluxes. Treatments were applied in May/2017, April/2018, and Jul/2018. One liter of urine, 1.6 kg of dung, and 2.67 g of urea fertilizer were added inside the chamber according to treatment. Ammonia flux was evaluated using a semi-opened free static chamber and N determination by steam distillation. The extracted solution of fresh soil was analyzed in spectrophotometer. Pearson’s correlation and linear regression analyses were run to identify which soil parameters explained NH3 fluxes. Soil parameters were ammonium (NH4+), nitrate (NO3-), pH, and water filled pore space (%WFPS). For urine, a negative correlation (r = -0.68; P = 0.005) was found between NH3 flux and NO3-. Soil NO3- and pH affected NH3 fluxes as determined by multivariate regressions analysis. For urea fertilizer, a positive correlation was found between NH3 flux and NH4+ (r=0.62; P = 0.03), NH3 flux and NO3- (r = 0.57; P = 0.03), and NH3 flux and %WFPS (r = 0.59; P = 0.02). The %WFPS affected NH3 fluxes as determined by single regressions analysis. There was no significant correlation between NH3 fluxes and the soil parameters (P > 0.05) when dung was applied. Greatest N loss by NH3 emission when urine was applied decreased soil NO3-. Dung formed a superficial crust that might have acted as a physical barrier, reducing losses. Greater soil moisture increased urea hydrolysis resulting in soil ammonification and nitrification. Nitrates for urine and %WFPS for urea were the major drivers affecting NH3 fluxes.

To quantify the BNF contribution to legumes using the 15N natural abundance technique, it is important to know the abundance of 15N of the plants grown entirely dependent on BNF (value ‘B’). The aim of the study was to determine the 15N natural abundance of N2 fixed by different Bradyrhizobium strains in symbiosis with one soybean cultivar. Treatments consisted of soybean plants cultivated with and without inoculation with ten Bradyrhizobium strains, in five replicates planted in Leonard jars in a sand/vermiculite mixture. Plants were harvested after 46 days. The ‘B’ values of the aerial tissue (‘Bs’) ranged from -2.6 to -3.9 ‰. There was a tendency for the ‘Bs’ values of plants inoculated with strains of B. elkanii to be more negative than plants inoculated with other strains. All ‘B’ values of the whole plant were less than 1 unit of δ15N (‰) different from zero, suggesting that the symbioses have little tendency to show significant isotopic fractionation during N2 fixation, but there is considerable depletion in 15N of the N translocated to the shoot tissue. RESUMO: Para quantificar a FBN em leguminosas, através da técnica de abundância natural de 15N, é importante conhecer a abundância de 15N da planta leguminosa crescida inteiramente dependente da FBN (valor ‘B’). O objetivo deste estudo foi determinar a abundância natural de 15N do N2 fixado por diferentes estirpes de Bradyrhizobium em simbiose com uma cultivar de soja. Os tratamentos consistiram de plantas cultivadas sem e com inoculação com dez estirpes de Bradyrhizobium, em cinco repetições. Foram utilizados vasos de Leonard, substrato de areia e vermiculita. As plantas foram colhidas após 46 dias. Os valores de ‘B’ parte aérea (‘Bpa’) variaram entre -2.6 to -3.9 ‰. Houve tendência para a abundância de 15N dos valores de ‘Bpa’ das plantas inoculadas com estirpes de B. elkanii a serem mais negativos que as plantas inoculadas com as outras estirpes. Todos os valores de ‘B’ da planta inteira foram menos de 1 unidade de δ 15N (‰) diferente de zero, sugerindo que as simbioses têm pouca tendência de mostrar fracionamento isotópico significativo, mas houve considerável empobrecimento do isótopo 15N no N translocado a parte aérea.

Made available in DSpace on 2020-12-11T03:11:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Livestock production systems are an essential agribusiness activity in Brazil, but a critical challenge of Brazilian farmers is to maintain the equilibrium of the ecosystem, using herbage resources efficiently with a minimum impact on the environment. Nitrogen (N) fertilization and the inclusion of forage legumes into tropical grass pastures are management strategies which increase the productivity and nutritive value of pastures and may also affect methane (CH 4) production by ruminants. The objective of this study was to examine the effects of either fertilizing palisade grass pastures with N or including the forage peanut (Arachis pintoi) into grass pastures on enteric CH4 emission, microbial protein production in the rumen via purine derivatives in the urine, and N balance. Twenty-one nonlactating crossbred dairy heifers were used in a completely randomized design with 3 treatments. The treatments consisted of pastures of palisade grass without N fertilization (control), fertilized with urea (fertilized), and palisade grass mixed with forage peanut (mixed). Seven animals (replications) were used to evaluate dry matter intake, digestibility, CH4 emission, urea, purine derivatives, and volume of urine, and N ingestion and excretion. Four paddocks (replications) were used to measure herbage mass; morphological, botanical, and chemical composition of herbage; and herbage allowance. The CH4 emissions were determined using the sulfur hexafluoride (SF6) tracer gas technique. The efficiency of N utilization (ENU) was calculated using the N balance data. Crude protein (CP) concentration of herbage increased with fertilization or legumes inclusion (P < 0.0001) while neutral detergent fiber (NDF) concentration decreased (P = 0.0355). The leaf allowance was higher in the fertilized treatment (P = 0.0294). Only uric acid excretion increased with N fertilization (P = 0.0204). The ENU was not affected by fertilized or mixed compared to control and averaged 55% (P = 0.8945). The enteric CH4 production was similar between treatments and averaged 129 g/d (P = 0.3989). We concluded that the changes in chemical composition of herbage provided by N fertilization or the inclusion of the legume showed no reduction in enteric CH4 emissions, but the ENU was more significant than previous studies with palisade grass, suggesting that different management strategies might alter the ENU under grazing conditions. Sao Paulo State Univ, Dept Anim Sci, BR-14884900 Jaboticabal, SP, Brazil Texas A&M Univ, Dept Anim Sci, College Stn, TX 77843 USA Embrapa Agrobiol, BR-23891000 Seropedica, RJ, Brazil Embrapa Pecuaria Sudeste, BR-13560970 Sao Carlos, SP, Brazil Sao Paulo State Univ, Dept Anim Sci, BR-14884900 Jaboticabal, SP, Brazil FAPESP: 2015/16631-5 FAPESP: 2016/110861 FAPESP: 2017/11274-5 CNPq: 404169/2013-9

Conventional livestock are monoculture systems where the major species are native grasses or African grasses, with biomass production being limited by seasonality of rainfall and low soil fertility. In animal production systems, the pasture degradation is associated with the nitrogen (N) cycle. Therefore, if farmer applied no subsequent fertilizer, milk production or live weight gains have been gradually reduced. As animals slowly gain weight, they produce more methane (CH4) and nitrous oxide (N20). This has led to the search for strategies to help minimize the impacts of livestock, and the excessive application of fertilizers, on the environment and natural resources. One strategy with promising results that has been developed in Latin America is the conversion of traditional livestock systems to silvopastoral systems (SPS), which include the establishment of shrub legumes at high densities and forage grasses aimed at increasing livestock profitability. With the association of legumes and forage grasses, forage quality can increase, more than 100%, compared to monoculture-based pastures and, consequently, production costs related to the purchase of imported cereal grains and nitrogen fertilizers are reduced. On the other hand, changes in climate and grazing pressure to increase stocking rate have resulted in extensive degradation of existing vulnerable pastures, which favour poorly palatable, perennial species, affecting directly livestock production and enhancing greenhouse gas (GHG) emissions and the loss of soil carbon and nitrogen stock severely affecting soil fertility. The importance of the association of species of legumes with grasses and Leucaena (Leucaena leucocephala L., (Lam.) de Wit) is an environmentally friendly proposal of positive interactions to improve soil fertility and animal productivity. Overall, improving forage quality and N efficiency of dietary nutrients is an effective way of decreasing GHG. Silvopastoral systems (SPS) are used successfully in many regions around the world, and there is considerable evidence that SPS can increase production efficiency, increase carbon sequestration and improve N cycling on land used for livestock production.

Made available in DSpace on 2021-06-25T11:54:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-03 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster cv. Marandu] is widely used in Brazil and is typically managed with little or no N fertilizer, which often leads to pasture decline in the long-term. The current relationship between beef price and fertilizer cost in Brazil does not favor fertilizer use in pastures. Legume inclusion is an alternative to adding fertilizer N, but often legumes do not reach a significant proportion (> 30%) in pasture botanical composition. This study evaluated herbage responses to N inputs and pasture species composition, under intermittent stocking. Treatments included palisadegrass-forage peanut (Arachis pintoi Krapov. & W.C. Greg. cv. Amarillo) mixture (mixed), unfertilized palisadegrass (control), and palisadegrass fertilized with 150 kg N ha(-1) yr(-1) (fertilized). Treatments were applied over two rainy seasons with five growth cycle (GC) evaluations each season. Response variables included herbage biomass, herbage accumulation, morphological components, total aboveground N of forage peanut (TAGN(FP)), and contribution of biological N-2 fixation (BNF). Herbage biomass was greater for fertilized palisadegrass [5850 kg dry matter (DM) ha(-1)] than for the palisadegrass-forage peanut mixture (3940 kg DM ha(-1)), while the unfertilized palisadegrass (4400 kg DM ha(-1)) did not differ from the mixed pasture. Nitrogen fertilizer increased leaf mass of palisadegrass (2490 kg DM ha(-1)) compared with the control and mixed treatments (1700 and 1310 kg DM ha(-1), respectively). The contribution of BNF to the forage peanut ranged from 79 to 85% and 0.5 to 5.5 kg N ha(-1) cycle(-1). Overall, benefits from forage peanut were minimal because legume percentage was less than 10%, while N input in the system by N-fertilizer increased palisadegrass herbage biomass. Sao Paulo State Univ, Dept Anim Sci, Jaboticabal, SP, Brazil Embrapa Agrobiol, Antiga Rodovia Rio Sao Paulo, Seropedica, RJ, Brazil Univ Florida, North Florida Res & Educ Ctr, Marianna, FL USA Sao Paulo State Univ, Dept Anim Sci, Jaboticabal, SP, Brazil FAPESP: 2016/11086-1 FAPESP: 2017/11274-5 FAPESP: 2015/16631-5 CNPq: 404169/2013-9

In Brazil’s central savanna region, government policy is to encourage the conversion of conventional plough tillage (PT) agriculture to no-till (NT) and raise the productivity of under-utilized pastures, including their conversion to integrated crop-livestock (ICL) systems, with the objective of increasing soil organic carbon (SOC) at the expense of atmospheric carbon dioxide. An experiment was established in 1991 by liming and fertilizing at two levels an area of native vegetation (NV). The treatments, replicated in randomized plots, included pastures, continuous cropping and ICL systems under PT or NT. The aim of this study was to quantify the SOC accumulation to 100 cm depth under these treatments over time. The high C:N ratios suggested that there was a high proportion of charcoal present in the soil. Increasing fertilizer inputs had no overall significant effect on SOC stocks. Stocks of SOC changed little under pastures. Analyses of 13C abundance showed that higher fertilizer inputs increased the decomposition rate of C derived from NV under pure grass pastures. Continuous cropping under NT preserved SOC and under PT there were significant losses. The highest SOC stocks were found under ILP treatments, but not all ILP treatments accumulated SOC even under NT. These results indicate that government initiatives to substitute PT with NT and to intensify beef cattle production will have only modest short-term gains in SOC accumulation.

SUMMARYCowpea (Vigna unguiculata L. Walp) is the most important food grain legume in Africa. Cowpea is nodulated by rhizobium bacteria in almost all soils of the tropics, but studies performed in the 1970s and 1980s in Nigeria suggested only modest responses of grain yield in the field to inoculation of selected rhizobium strains. More recently, experiments performed in Brazil have shown that cowpea responded to inoculation of rhizobium selected locally and grain yields increased by up to 30%. We tested some of the Brazilian strains on cowpea at a site in northern Mozambique and at several sites in Northern Ghana. At all sites phosphorus fertilizer (26 kg P ha−1) was added to all plots. At the site in Mozambique despite considerable damage to the crop by the parasitic yellow witchweed (Alectra vogelii), grain yields were more than doubled by inoculation of one of the Brazilian strains and reached 1.4 Mg ha−1. In on-station experiments conducted in 2012 in June and August in northern Ghana using the local cowpea variety Padi-Tuya as the test crop, nodule weight at 35 days after planting (dap) tripled with rhizobium strain BR 3299 (530 mg plant−1) in August with the other inoculants (BR 3267 and a mixture of BR 3267 and BR 3299) also increased nodule weight to over 300 mg plant−1. In the first on-station experiment, grain yields were doubled by the inoculation of any of the three rhizobium strains, and in the second experiment, significant increases in grain yield ranged from 39% to 57% and reached over 2.0 Mg ha−1. Similar increases in nodulation and grain yield due to inoculation were observed in 22 on-farm trials. Nitrogen fertilizer application promoted vegetative growth but did not increase grain yield and nodulation. Inoculating cowpea with highly effective rhizobium strains can therefore enhance grain yield of smallholder farmers in Africa.

Rice is the second-most produced cereal worldwide and actively contributes to greenhouse gas (GHG) emissions, particularly methane, especially under deepwater production. Assessments of energy efficiency (EE) and GHG emissions can indicate the sustainability level of agrosystems and support decisions related to the reduction of production costs and environmental pollution. This study aimed to assess both EE and GHG emissions in organic and conventional rice production in the Southern region of Brazil. For this study, eight rice fields were evaluated. Energy inputs and outputs were calculated by multiplying the production input amounts by their respective calorific values or energy coefficients at each stage of production. EE was determined using the ratio between the total energy output and the total energy consumed during the production process. GHG emissions were estimated using the principles of the lifecycle assessment methodology in addition to the Intergovernmental Panel on Climate Change (IPCC) recommendations. Each 1.0 MJ consumed during the production of organic and conventional rice produced renewable energy averages of 10.5 MJ and 7.90 MJ, respectively, as grains. The primary energy expenses for organic rice were represented by seeds, fuel, tractors, and agricultural machinery and implements, and those for conventional rice were seeds, fuel, and fertilizers. Each kilogram of organic and conventional rice produced accounted for the emission of 0.21 and 0.32 kg of CO2eq, respectively, during the production cycles and delivery to the warehouse, with seeds, fuel, and fertilizers being the main sources of CO2eq emissions to the atmosphere.

A cultura do feijao-caupi normalmente cultivada nas regioes Norte e Nordeste do Brasil vem ganhando espaco na regiao Centro-Oeste, com essa expansao tem exigido o avanco em novas tecnologias de producao. Com isso o objetivo deste estudo foi avaliar o efeito da pre-inoculacao de sementes de feijao-caupi com inoculante polimerico em comparacao com inoculante turfoso. Desta forma o ensaio foi realizado em Sinop-MT na safra 2010/2011, na area experimental da Embrapa Agrossilvipastoril, comparando sementes pre-inoculadas com inoculante turfoso e polimerico com 0, 7, 14 e 35 dias, mais o controle positivo com 70 kg N ha -1 e controle absoluto. Nao houve diferenca signi cativa na nodulacao entre os tratamentos pre-inoculados com polimero ou turfa ate 14 dias, mas com 35 dias, a nodulacao usando o veiculo polimerico e superior a turfa proporcionando, tambem, a maior massa seca de nodulos e a segunda maior produtividade em valores absolutos 1549,8 kg ha -1 .

This study aimed to quantify nitrous oxide (N2O) and methane (CH4) emission/sink response from sugar cane soil treated with fertilizer nitrogen (N) and vinasse applied separately or in sequence, the latter being investigated with regard to the time interval between applications for a possible effect on emissions. The study was carried out in a traditional area of unburned sugar cane in São Paulo state, Brazil. Two levels of N fertilization (0 and 100 kg N ha(-1)) with no added vinasse and combined with vinasse additions at different times (100 m(-3) ha(-1) at 3 and 15 days after N fertilization) were evaluated. Methane and N2O fluxes were monitored for 211 days. On average, the soil was a sink for CH4, which was not affected by the treatments. Emissions of N2O were induced by N fertilizer and vinasse applications. For ammonium sulfate, 0.6% of the added N was emitted as N2O, while for vinasse, this ranged from 1.0 to 2.2%. Changes in N2O fluxes were detected the day after application of vinasse on the N fertilized areas, but although the emission factor (EF) was 34% greater, the EF was not significantly different from fertilizer N alone. Nevertheless, we recommend to not apply vinasse after N fertilization to avoid boosting N2O emissions.

Made available in DSpace on 2018-11-26T16:01:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Embrapa Federal Rural University of Rio de Janeiro We aimed to quantify nitrous oxide (N2O) and methane (CH4) emissions as a function of the addition of different quantities of bovine faeces and urine on soil under pasture. Two experiments were performed in randomised complete blocks with five replicates. In the first experiment, the emissions of CH4 and N2O were evaluated for 14 days after the addition of four amounts of faeces (0.0, 1.2, 1.8 and 2.4 kg of fresh faeces per plot), and in a second experiment, N2O emissions were evaluated for 43 days after addition of four volumes of urine (0.0, 1.0, 1.5 and 2.0 L). Urine and faeces came from crossbred (Fresian x Gir) dairy cows fed on pasture and concentrates. N2O emissions from faeces did not alter the emission factor (EF) according to the faeces weight (P = 0.73). N2O-N EF from faeces-N averaged 0.18% (+/- 0.05) of total applied N. The volume of urine applied influenced N2O losses. The EF decreased linearly (P = 0.015) with increasing volumes of urine, being 4.9% (+/- 0.75), 3.36% (+/- 0.7) and 2.43% (+/- 0.46) of N applied emitted as N2O for the 1.0, 1.5 and 2.0 L volumes of urine respectively. The EF from urine was significantly (P < 0.0001) higher than the EF from faeces. There was no change to the CH4 emissions per kilogram of excreta when the amount of faeces added was varied (P = 0.87). However, the CH4 emitted increased linearly with the amount of faeces (P = 0.02). The CH4 EF was estimated to be 0.95 (+/- 0.38) kg/head.year. Sao Paulo State Univ, Dept Anim Sci, Via Acesso Prof Paulo Donato Castellane, BR-14884900 Jaboticabal, SP, Brazil Embrapa Agrobiol, Antiga Rodovia Rio Sao Paulo,Km 47, BR-23891000 Seropedica, RJ, Brazil Sao Paulo State Univ, Dept Anim Sci, Via Acesso Prof Paulo Donato Castellane, BR-14884900 Jaboticabal, SP, Brazil

Cattle ranching is one of the most important agricultural activities in Brazil. The impact of livestock on soil N 2 O emissions in Brazil has only been assessed using a Tier 1 approach of the IPCC guidelines, as there are no data available from field studies. Apart from the need for accumulating data for the development of proper direct N 2 O emission factors, we tested for possible differences between urine and dung as N 2 O sources and the difference in emissions between the dry and wet season. An area of Brachiaria brizantha at the Embrapa Rice and Bean Centre in the Cerrado (central savannah) region (Goias state) was subdivided into plots where fresh cattle urine and dung were monitored for three consecutive periods (two in the rainy and one in the dry season) for N losses, principally N 2 O emissions and NH 3 volatilization. 15 N-labelled urine N was used in the first monitoring period for an N balance study which indicated that denitrification and NH 3 volatilization were the most important processes for N loss. Percentages of N lost as N 2 O and as volatilized NH 3 were greater for urine than for dung. In addition, N losses as N 2 O in the rainy season were much greater than during the dry season. Representing the Cerrado region and the extensive pasture systems common in this region, direct emission 0.007 g N 2 O–N g −1 (0.7%) excreta N, well below the EF 3PRP of 0.020 g N g −1 (2%) used by IPCC for cattle N in excreta. The fraction of excreta N lost as NH 3 of ∼15% was in line with the IPCC guidelines. Disaggregation of emission factors for excreta type is recommended.

Methodologies based on 15N-enrichment for estimating the transfer of nitrogen (N) between legumes and companion non-legume species in agro-ecosystems are critically reviewed and classified according to whether they (i) are direct or indirect (ii) are dependent or independent of the measurement of yield and (iii) are estimating transfer of legume N, biologically-fixed legume N, or non-legume N. The two most commonly used methods are the indirect 15N isotope dilution method and the direct 15N shoot-labelling method. Published estimates both within and between agro-ecosystems are very variable, ranging from 0 to >50% of the N present in a companion species estimated to have been derived from a companion legume. The transfer of N also occurs from companion species to legumes, but is generally much less than the opposite flux. Factors conducive to N transfer include inter alia species proximity (i.e. intimacy of root contact), legume pruning, defoliation or death and the length of the transfer period. It was concluded that two methodologies (15N2 exposure and the split-root technique) lack field applicability. New insights into the various mechanisms of N transfer in agro-ecosystems may assist in the selection or development of more appropriate methodologies for estimating N transfer by both above- and below-ground pathways.

In the south-eastern region of Brazil there are millions of hectares of deforested, almost-treeless hillsides with sparse ground-cover of grasses of African origin. For the establishment of more productive pastures in these areas, silvopastoral systems (SPSs) have been recommended, and the objective of this study was to quantify the N fluxes in the soil/plant/animal systems as a means compare the sustainability of a SPS planted with legume trees (Acacia mangium and Mimosa artemisiana) and eucalyptus, compared to that of a grass-alone Brachiaria decumbens (BDH) pasture. The annual live weight gain of Zebu × Friesian heifers, assessed 5 years after pasture establishment, was significantly higher on the SPS than on the grass-alone pasture, at 205 and 177 kg head−1 year−1 respectively. The N deposited as animal excreta (38–49 kg ha−1 for BDH and SPS, respectively), especially urine, is considered to be much more susceptible to loss than N derived from decomposing plant litter, and was found to be much less than the N recycled though the grass litter (107 and 114 kg ha−1, respectively) in both systems. The extra N recycled in tree-leaf and grass litter increased this by 34 kg N ha−1 in the SPS and we conclude that this would contribute to sustain forage productivity. The added advantage of trees in the provision of shade for the animals and protection from soil erosion should further contribute to the long term sustainable productivity of this SPS.