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Fertilisation experiments have demonstrated that nutrient availability is a key determinant of biomass production and carbon sequestration in grasslands. However, the influence of nutrients in explaining spatial variation in grassland biomass production has rarely been assessed. Using a global dataset comprising 72 sites on six continents, we investigated which of 16 soil factors that shape nutrient availability associate most strongly with variation in grassland aboveground biomass. Climate and N deposition were also considered. Based on theory-driven structural equation modelling, we found that soil micronutrients (particularly Zn and Fe) were important predictors of biomass and, together with soil physicochemical properties and C:N, they explained more unique variation (32%) than climate and N deposition (24%). However, the association between micronutrients and biomass was absent in grasslands limited by NP. These results highlight soil properties as key predictors of global grassland biomass production and point to serial co-limitation by NP and micronutrients.

Soil nitrogen (N) availability is critical for grassland functioning. However, human activities have increased the supply of biologically limiting nutrients, and changed the density and identity of mammalian herbivores. These anthropogenic changes may alter net soil N mineralization (soil net Nmin), that is, the net balance between N mineralization and immobilization, which could severely impact grassland structure and functioning. Yet, to date, little is known about how fertilization and herbivore removal individually, or jointly, affect soil net Nmin across a wide range of grasslands that vary in soil and climatic properties. Here we collected data from 22 grasslands on five continents, all part of a globally replicated experiment, to assess how fertilization and herbivore removal affected potential (laboratory‐based) and realized (field‐based) soil net Nmin. Herbivore removal in the absence of fertilization did not alter potential and realized soil net Nmin. However, fertilization alone and in combination with herbivore removal consistently increased potential soil net Nmin. Realized soil net Nmin, in contrast, significantly decreased in fertilized plots where herbivores were removed. Treatment effects on potential and realized soil net Nmin were contingent on site‐specific soil and climatic properties. Fertilization effects on potential soil net Nmin were larger at sites with higher mean annual precipitation (MAP) and temperature of the wettest quarter (T.q.wet). Reciprocally, realized soil net Nmin declined most strongly with fertilization and herbivore removal at sites with lower MAP and higher T.q.wet. In summary, our findings show that anthropogenic nutrient enrichment, herbivore exclusion and alterations in future climatic conditions can negatively impact soil net Nmin across global grasslands under realistic field conditions. This is an important context‐dependent knowledge for grassland management worldwide.

Made available in DSpace on 2022-04-28T19:28:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-03-01 ‘Mavuno’ brachiariagrass (Brachiaria spp.) is a warm-season perennial grass cultivar released in Brazil with potential to be used as forage in subtropical regions. The objective of this study was to evaluate herbage accumulation (HA), nutritive value, and the persistence of Mavuno under different harvest frequencies. The experiment was conducted in Ona, FL, from April to November in 2016 and 2017. Treatments were the factorial arrangement of four grasses: Jiggs bermudagrass [Cynodon dactylon (L.) Pers], ‘Tifton 85’ bermudagrass (Cynodon spp.), ‘Mulato II’ brachiariagrass, and Mavuno and two regrowth intervals (3 or 6 wk), distributed in a randomized complete block design with four replicates. Mavuno and Mulato II had similar total annual HA (11.0 Mg ha−1), and in vitro digestible organic matter (IVDOM, 644 g kg−1), but greater total annual HA and IVDOM than Jiggs (7.8 Mg ha−1 and 500 g kg−1) and Tifton 85 (8.4 Mg ha−1 and 550 g kg−1). Mavuno had the least crude protein (CP) among all treatments (111 vs. 124 g kg−1), and CP and IVDOM were greater at the 3-wk regrowth interval than at the 6-wk interval (130 vs. 111 g kg−1 and 610 vs 548 g kg−1, respectively). Root mass was greater at 3 wk than at 6 wk for Tifton 85 (9.4 vs. 5.4 Mg ha−1) but was not affected by regrowth interval for Jiggs, Mavuno, and Mulato II (6.5 Mg ha−1). Mavuno and Mulato II had superior HA and IVDOM, and Mavuno may be a viable forage source in subtropical regions. Range Cattle Research and Education Center Univ. of Florida Dep. of Animal Science Maringa State Univ. Univ. Estadual Paulista Kyusyu Okinawa Agricultural Research Center NARO Univ. Estadual Paulista

Made available in DSpace on 2020-12-12T01:59:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Nitrogen fertilization is an important input for crop yield; however, it can result in detrimental environmental effects due to low use efficiency of regular N sources. This study evaluated the effects of N fertilizers and application strategies (single vs. split application) on bermudagrass (Cynodon spp.) responses and release pattern and rate in controlled and field incubations. The bermudagrass study was arranged in a two-way factorial scheme of 6 N fertilizers, urea, Polymer Coated Urea (PCU), PCU-6 (6 months), PCU-4 (4 months), PCU-2 (2 months) and urea + urease inhibitor (U-NBPT) applied as a single (400 kg N ha-1 yr-1) or two split applications of 200 kg N ha-1 (400 kg N ha-1 yr-1). The controlled experiment was a two-way factorial of PCU-6, PCU-4, PCU-2 and 15, 45 and 90% water hold capacity (WHC), sampling period of 170 days, the field incubation used the same sources sampled up to 220 days. Enhanced-efficiency fertilizers (EEF) increased herbage accumulation (HA) by 1.3 Mg ha-1 compared to untreated urea, on average. Nitrogen use efficiency (NUE) was greater for EEFs (44%) than urea (36%). Results showed that increased soil moisture inferred positive responses in release pattern and a minimum of 45% WHC was necessary for optimum release. Fertilizers at field conditions resulted in an earlier release than expected, ~20 days. São Paulo State University (Unesp) Campus Jaboticabal Department of Soil Science, Via de Acesso Prof. Paulo Donato Castellane s/n University of Florida Range Cattle Research and Education Center São Paulo State University (Unesp) Campus Jaboticabal Department of Soil Science, Via de Acesso Prof. Paulo Donato Castellane s/n

Soil nitrogen mineralisation (Nmin), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net Nmin) varies with soil properties and climate. However, because most global-scale assessments of net Nmin are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net Nmin across 30 grasslands worldwide. We find that realised Nmin is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential Nmin only weakly correlates with realised Nmin, but contributes to explain realised net Nmin when combined with soil and climatic variables. We provide novel insights of global realised soil net Nmin and show that potential soil net Nmin data available in the literature could be parameterised with soil and climate data to better predict realised Nmin., Nitrogen mineralisation (Nmin), an important index of soil fertility, is often determined in the laboratory, with an uncertain relationship to Nmin under field conditions. Here the authors show that combining laboratory measurements with environmental data greatly improves predictions of field Nmin at a global scale.

Grazing lands are a significant sink for long-term carbon sequestration and play an important role in mitigating global climate change. Because of the vast area of grazing lands throughout the world, small changes in the amounts of carbon storage in this ecosystem can have significant consequences to the global carbon cycle and atmospheric CO2 levels. Carbon sequestration is strongly influenced by climate, topography, soil type, and management. Current grazing land management strategies are often aimed at increasing forage production, however, management can also promote carbon storage in the soil. Research has demonstrated that most techniques used to improve forage production promote carbon inputs to the soil and increase soil carbon sequestration. Fertilization, irrigation, grazing management, fire regimen, introduction of legumes, and use of improved grass species are management practices that can increase plant productivity while promoting soil carbon sequestration. However, management practices may also lead to unintended environmental consequences such as elevated greenhouse gas emissions, water quality problems, reduction in biodiversity, and changes in community composition. Opportunities for increasing soil carbon sequestration using land management practices are ecosystem specific and vary in intensity. Careful consideration should be given to site-specific characteristics and potential counter effects on other ecosystem services. Adoption of management practices that favor carbon inputs and minimize decomposition can also have significant positive impacts on the overall soil quality and can potentially contribute to the sustainability of grazing land ecosystems in the USA.

Made available in DSpace on 2018-11-26T17:55:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-01 Rhizoma peanut (Arachis glabrata Benth.) is a widely used warm-season legume in Florida. Ecoturf is a rhizoma peanut germplasm with superior nutritive value; however, there is limited information about the effects of regrowth interval on this characteristic. The objective was to investigate the effects of regrowth interval on in situ crude protein (CP) and dry matter (DM) disappearance of Ecoturf compared with the predominant cultivar 'Florigraze'. The experiment was conducted from July to October of 2014 and 2015. Treatments were a split-plot design of Florigraze and Ecoturf (main plots) harvested at regrowth intervals of 4, 8, and 12 wk (subplots), distributed in a randomized complete block design with four replicates. Samples of each treatment were incubated in two steers (Bos spp.) for 0, 3, 6, 9, 12, 24, 48, and 72 h, and DM and CP disappearance were fit to a nonlinear model. Ecoturf had greater CP concentration than Florigraze (193 vs. 168 g kg(-1)). There was no effect of genotype on in situ effective disappearance of CP (715 g CP kg(-1)); however, there was a quadratic effect of regrowth interval. Ecoturf had greater effective disappearance of DM than Florigraze only at 4 wk of regrowth (597 vs. 563 g kg(-1)). Dry matter and CP disappearance parameters may differ between Ecoturf and Florigraze. Harvesting at a regrowth interval of 8 wk or less may improve rhizoma peanut nutritive value. Minist Educ Brazil, CAPES Fdn, BR-70040020 Brasilia, DF, Brazil Univ Florida, Range Cattle Res & Educ Ctr, Ona, FL 33865 USA Univ Florida, Dept Agron, Gainesville, FL 32611 USA North Florida Res & Educ Ctr, Marianna, FL 32446 USA Sao Paulo State Univ, Dept Anim Breeding & Nutr, Botucatu, SP, Brazil Univ Estadual Maringa, Dept Anim Sci, BR-87020900 Maringa, Parana, Brazil Sao Paulo State Univ, Dept Anim Support Prod & Hlth, BR-16050680 Aracatuba, SP, Brazil Sao Paulo State Univ, Dept Anim Breeding & Nutr, Botucatu, SP, Brazil Sao Paulo State Univ, Dept Anim Support Prod & Hlth, BR-16050680 Aracatuba, SP, Brazil

Made available in DSpace on 2018-12-11T16:49:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Despite scientific evidence suggesting that warm-season grasses can respond favorably to K and P fertilization, the increasing costs of fertilizers limit the extent to which these nutrients are used in pastures and hayfields. Two field studies evaluated ‘Jiggs’ bermudagrass [Cynondon dactylon (L.) Pers.] and ‘Floralta’ limpograss (Hemarthria altissima Stapf. and Hubbard) herbage accumulation (HA), nutritive value, and persistence to reduced fertilization strategies during 2012 to 2014. Treatments were allocated in a split-plot design with N (90 or 180 kg N ha−1, bermudagrass study) or harvest frequency (6 vs. 12 wk, limpograss study) as the main factors and P (0, 8.7, and 17.4 kg P ha−1) and K (0, 33, and 66 kg K ha−1) levels as subplots. Bermudagrass HA increased linearly (up to 377% in Year 3) as K level increased. Similarly, K fertilization increased limpograss HA from 8.4 to 11.6 Mg ha−1 in 2013 and from 5.8 to 15.7 Mg ha−1 in 2014 as K levels increased from 0 to 66 kg K ha−1; however, no effect was observed in 2012. Bermudagrass HA and ground cover decreased from 2012 to 2014 in all K treatments. Conversely, decreases in limpograss HA and ground cover over time were observed only in the control (no K) treatments. Bermudagrass and limpograss crude protein concentrations generally decreased with increased K level. No effects of N or P were observed. Continuous aboveground removal without proper K fertilization is detrimental to bermudagrass and limpograss production and persistence. Univ. of Florida Range Cattle Research and Education Center Faculdade de Ciências Agrárias e Veterinárias UNESP–Univ. Estadual Paulista, Campus Jaboticabal Instituto Agronômico Univ. Federal do Piauí EMBRAPA Southeast Livestock Univ. Federal de Sergipe DeLaval Faculdade de Ciências Agrárias e Veterinárias UNESP–Univ. Estadual Paulista, Campus Jaboticabal

Soil quality has become an important issue in soil science. Considerable attempts have been made to define soil quality, but a general concept has not yet been accepted by the scientific community. The selection of quantitative indices for soil quality is extremely difficult, and a considerable number of chemical, physical, and biochemical properties have been suggested as potential indicators of soil quality. Because soil organic matter (SOM) can be associated with different soil chemical, physical and biological processes, it has been widely considered as one of the best soil quality indicator. Land use can significantly influence dynamics of organic carbon and N, P, and S cycle. However, changes in total soil organic carbon (SOC) contents in response to land use may be difficult to detect because of the natural soil variability. In the short to medium term, biological properties and readily decomposable fractions of SOC, such as dissolved organic carbon (DOC), are much more sensitive to soil management than is SOM as a whole, and can be used as a key indicator of soil natural functions. Despite the fact that labile C accounts for a small portion of the total organic matter in the soils, DOC is the most mobile and important C-source for microorganisms, and can easily reflect the effects of land use on soil quality. Although several methods are used to characterize DOC, the factors influencing mineralization and bioavailability of elements associated with organic matter (N, P, and S) remains unclear. Future research should focus on the processes that govern DOC and nutrient dynamics and how they affect soil quality. Nas últimas décadas, qualidade do solo tem se tornado um tópico importante na ciência do solo. Embora esforços consideráveis tenham sido dedicados com o intuito de definir "qualidade do solo", ainda não há um conceito amplamente aceito pela comunidade cientifica. A seleção de índices qualitativos para definir qualidade do solo é uma tarefa extremamente difícil, e diversas propriedades químicas, físicas e biológicas tem sido sugeridas como potenciais indicadores. A matéria orgânica do solo está associada com processos químicos, físicos e biológicos no solo, e, portanto, é considerada um dos melhores indicadores de qualidade do solo. O manejo do solo pode influenciar significativamente a dinâmica do carbono orgânico e o ciclo de N, P, e S. Entretanto, mudanças na concentração total da matéria organica em resposta ao manejo pode ser dificil de ser detectada devido à variabilidade natural do solo. Quando comparada com a matéria orgânica total do solo, a fração mais prontamente disponível, como o carbono orgânico dissolvido (COD), é mais sensível às mudanças no manejo do solo a curto e médio prazo e, portanto, pode ser utilizada como indicador fundamental de qualidade do solo ou das alterações das condições naturais. Embora a fração dissolvida represente apenas uma pequena porção da matéria orgânica total do solo, o COD é móvel no solo e constitui uma importante fonte de C para os microorganismos, podendo facilmente refletir os efeitos de diferentes sistemas de manejo. Inúmeros métodos são utilizados para caracterizar o COD, mas os processos que influenciam sua mineralização e a disponibilidade dos elementos associado com a matéria orgânica (N, P, e S) ainda não são completamente entendidos. Pesquisas futuras devem buscar entender os processos que governam a dinâmica de nutrientes e do COD e como os mesmos afetam a qualidade do solo.

Estudou-se a energia livre da reação de adsorção de cobre em amostras superficiais (0-0,2 m) e subsuperficiais (na maior expressão do horizonte B) de três solos paulistas : Latossolo Roxo ácrico (LR), Latossolo variação Una ácrico (LU) e Terra Roxa Estruturada (TE), após a adição de 5, 20, 50, 100, 200, 300, 400 e 600 mg L-1 de cobre. A adsorção de cobre pelos solos foi considerada espontânea, pois a energia livre apresentou valores negativos em todas as concentrações estudadas. Os valores de energia livre diminuíram com o aumento da dose de cobre adicionada. A TE apresentou maior energia livre de adsorção em relação aos Latossolos, sobretudo em superfície. Considerando-se o mesmo solo, os horizontes superficiais apresentaram maior energia livre para as reações de adsorção de cobre em relação aos horizontes subsuperficiais, provavelmente devido ao efeito da matéria orgânica, que apresenta alta afinidade pelo elemento.

Phosphorus management in grazingland ecosystems represents a major challenge of agronomic and environmental importance. Because of the extensive acreage occupied by grazinglands, decisions concerning pasture fertilization and nutrient management in forage-based livestock systems are crucial to both farmers and regulatory agencies. The purpose of this paper is to provide an overview of the literature relevant to pasture P fertilization and the potential impacts on water quality. There continue to be uncertainties regarding interrelationships between pasture management and water quality issues. Despite the extensive body of literature on nutrient transport from grazinglands, limited information is available on the relationships between land use, transport potential, water management, and climatic conditions affecting nutrient losses at a watershed scale. As agriculture continues to modernize and intensify, public concerns about the impacts of plant nutrients on environmental quality will likely increase. Managing water quality protection and profitable agriculture will be a major challenge for the next generations.

Warm-season C-4 grasses are capable of removing excess soil nutrients because of their high Yield potential and nutrient uptake efficiency. Bahiagrass (Paspalum notatum Flugge), limpograss [Hemarthria altissima (Poir.) Stapf& Hubb], and stargrass (Cynodon nlemfuensis Vanderyst), three commonly used pasture grasses in South-Central Florida, were grown to examine the effect of increasing N rates on herbage production and soil P removal. Nitrogen was applied at rates of 67,90, and 134 kg N ha(-1) harvest(-1), representing 1, 1.3, and 2 times the recommended N fertilizer application rate for hay production. During 3 yr of evaluation, all three grasses showed a positive P-removal potential that increased with increasing N fertilizer application. Phosphorus removed by forages over the 3-yr period for the highest N application rate was 106, 132, and 147 kg ha(-1) for limpograss, bahiagrass, and stargrass, respectively. Mehlich 1 extractable P from the Ap horizon of all plots decreased by as much as 80% of the initial P load over the study period; only similar to 15 to 17% of which appeared to leach to subsurface horizons. Nitrogen application enhanced P uptake and consequently reduced P transport to deep (>13 cm) soil depths. These data indicate that stargrass, bahiagrass, and limpograss managed intensively for hay production represent effective options in removing excess soil P from P-impacted sites.

Grasslands are being replaced by urbanization and more profitable agricultural activities around the world. Producers may be faced with land constraints and need to consider intensification of the remaining grasslands as a means of maintaining overall production on a decreasing land resource. However, intensification of the grazing system is usually associated with greater nutrient inputs, including those from commercial fertilizers and supplement fed to animals. Excessive loading of nutrients in intensive grazing systems via fertilizer and animal wastes can cause nutrient buildup in the soil and subsequent water quality problems. Surface runoff and leaching of nutrients are the two major process affecting water quality. Nitrogen and P represent major nutrient concerns as related to water quality. Increased nitrate concentrations render groundwater unsuitable for drinking and can cause serious health issues for humans. Excessive N and P concentrations may contribute to eutrophication of streams and lakes. Maximizing efficiency of nutrient recycling through the soil-forage-animal system minimizes off-site nutrient transport and decreases production costs by reducing the quantity of commercial fertilizer needed. Management strategies to reduce soil and water contamination include refining the balance of nutrient inputs from feeds and fertilizers as well as accounting for the nutrients recycled through the decomposition of plant litter and animal wastes. Current interest in the development and adoption of efficient and sustainable agriculture systems has led forage researchers to amplify the scope of grasslands research by increasing multidisciplinary efforts. There is an increased interest in quantifying the impacts of forage-animal management strategies on the environment, with the goal of developing economically viable best management practices that result in optimum forage production and profitability, while protecting the environment. Furthermore, these best management practices will supply reliable information for future environmental policies that may be adopted by governmental agencies.

Grasses in the Brachiaria genus are the most widely grown forages in tropical America, occupying over 80 Mha (Boddey et al. 2004). Mulato II is apomictic and a vigorous, semi-erect cultivar resulting from 3 generations of crosses including original crosses between ruzigrass (B. ruziziensis) and signalgrass (B. decumbens cv. Basilisk, apomictic tetraploid). According to Peters et al. (2003), Mulato produced 25% more herbage mass than palisadegrass (Brachiaria brizantha) and koroniviagrass (B. humidicola) under similar management practices. Although Mulato II shows promise as forage in tropical regions, herbage accumulation and persistence in subtropical areas is unknown. This publication summarizes results of the research with Mulato II conducted in Florida in the last 5 years.

The application of sewage sludge or biosolids on soils has been widespread in agricultural areas. However, depending on their characteristics, they may cause increase in heavy metal concentration of treated soils. In general, domestic biosolids have lower heavy metal contents than industrial ones. Origin and treatment method of biosolids may markedly influence their characteristics. The legislation that controls the levels of heavy metal contents in biosolids and the maximum concentrations in soils is still controversial. In the long-term, heavy metal behavior after the and of biosolid application is still unknown. In soils, heavy metals may be adsorbed via specific or non-specific adsorption reactions. Iron oxides and organic matter are the most important soil constituents retaining heavy metals. The pH, CEC and the presence of competing ions also affect heavy metal adsorption and speciation in soils. In solution, heavy metals can be present either as free-ions or complexed with organic and inorganic ligands. Generally, free-ions are more relevant in environmental pollution studies since they are readily bioavailable. Some computer models can estimate heavy metal activity in solution and their ionic speciation. Thermodynamic data (thermodynamic stability constant), total metal and ligand concentrations are used by the GEOCHEM-PC program. This program allows studying heavy metal behavior in solution and the effect of changes in the conditions, such as pH and ionic strength and the application of organic and inorganic ligands caused by soil fertilization. A aplicação agrícola de lodos de esgoto ou biossólidos tem se tornado prática comum, mas pode causar o acúmulo de metais pesados nos solos, dependendo das características desses resíduos. Em geral, biossólidos de origem doméstica apresentam teores de metais inferiores aos dos oriundos de descarga industrial. A origem e o processo de tratamento influenciam as características desses materiais. A legislação que controla os níveis de metais pesados presentes nos biossólidos e a concentração máxima nos solos é controversa. O comportamento dos metais pesados em longo prazo, após o término da aplicação de biossólidos, não é bem conhecido. Nos solos, os metais pesados podem ser adsorvidos por meio de reações de adsorção específica e/ou não específica. Dentre os componentes que retém metais pesados, destacam-se os óxidos de Fe e a matéria orgânica. O pH, a CTC e a presença de cátions afetam a adsorção e a especiação iônica de metais pesados nos solos. Em solução, os metais encontram-se como íons livres e/ou formam complexos com ligantes orgânicos e inorgânicos. As espécies-livres são mais importantes em estudos de poluição ambiental, pois correspondem às formas prontamente biodisponíveis. Alguns programas computacionais calculam a atividade dos metais em solução e sua especiação iônica. O programa GEOCHEM-PC utiliza uma base de dados termodinâmicos (constante de estabilidade termodinâmica), a concentração total do metal e dos ligantes em solução. Isso permite observar o comportamento dos metais em solução e a resposta dos mesmos às mudanças nas condições do meio, tais como a variação do pH e da força iônica e a adição de ligantes orgânicos e inorgânicos via adubação.