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Made available in DSpace on 2021-06-25T10:36:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Greenhouse gases (GHGs) emissions from livestock systems are important because of their significant contribution to global warming. Nitrogen fertilization can improve system production; however, it alters soil gas emissions. We evaluated soil nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions to investigate how they are affected by increasing levels of N fertilizer (urea) in a productive Marandu grass [Urochloa brizantha (Hochst ex A. Rich) Stapf] pasture subjected to continuous grazing by young Nellore beef cattle (Bos indicus). The N2O, CH4, and CO2 emissions were significantly affected by increasing N fertilizer levels. The seasons also affected GHGs emissions. Nitrogen fertilizer favored CH4 consumption relative to the control plot without N, with mean emission of 23.7 μg CH4−C m−2 h−1 in the fertilized plots compared to 61.6 μg CH4−C m−2 h−1 in the control. The N-fertilized areas presented higher CO2 emissions compared to the control plot without N. The areas that received N fertilization showed a positive linear association between the water-filled pore space and N2O emission. Soil temperature drove CO2 emissions. Increasing N fertilization in grazed marandu grass increases N2O and CO2 emissions during the growing season, while reducing CH4. The effect of fertilization during the transition season was not apparent, and perhaps other factors could provide a better explanation for the GHG emissions during this period. Department of Animal Science Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista (UNESP), Via de acesso Professor Paulo Donato Castellane Department of Exact Science Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista (UNESP), Via de acesso Professor Paulo Donato Castellane Department of Animal Science Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista (UNESP), Via de acesso Professor Paulo Donato Castellane Department of Exact Science Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista (UNESP), Via de acesso Professor Paulo Donato Castellane CNPq: 118700/2017-0 FAPESP: 2015/15631-3 FAPESP: 2015/16631-5 FAPESP: 2017/11274-5

Nitrogen fertilizer is routinely required to produce maximum corn (Zea mays L.) yield in the mid-South. Two field experiments were established to evaluate the fertilizer-N recovery and partitioning of ¹⁵N-labeled urea applied pre-plant to furrow-irrigated corn at the R6 growth stage. Pre-plant ¹⁵N-labeled fertilizer was applied at rates of 0, 34, 67, and 100 kg N ha–¹ using application methods including an incorporated, surface broadcast, and water-furrow application. Additional non-labeled N was applied in-season at the V6 growth stage so that the season-total N fertilizer rate applied in all treatments receiving N was equal to 270 kg N ha–¹. The mass fertilizer-nitrogen recovery (MFNR) and Δ MFNR increased as pre-plant N rate increased in both years. Pre-plant N rate and application method displayed no significant influence on total-nitrogen (TN) uptake when additional N was applied in-season. Fertilizer-N recovery efficiency (FNRE) of pre-plant N ranged from 14.8 to 39.9%. Of the MFNR of pre-plant N at maturity, 75% was taken up by the corn after the V6 growth stage. The 67 kg N ha–¹ application rate of pre-plant N was the lowest N rate that simultaneously maximized yield and FNRE both years. Pre-plant N fertilizer that was applied broadcast or incorporated resulted in the greatest yield, percent TN in the grain, and percent MFNR in the grain at maturity in both years. Producers are encouraged to incorporate or broadcast 67 kg N ha–¹ or less pre-plant for furrow-irrigated corn when additional N is applied in-season.

Bahiagrass (Paspalum notatum Flugge) is the most utilized forage for beef cattle (Bos spp.) in Florida, but there is concern that bahiagrass pastures are declining due to insufficient K fertilization. Two studies determined the effects of K and N fertilization on bahiagrass herbage mass (HM) and nutritive value in field plots (Exp. 1), and greenhouse (Exp. 2). At two locations from May to December 2014 and 2015, Exp. 1 evaluated the combinations of three N fertilization levels (0, 50 kg N ha–¹ in May, or 50 kg N ha–¹ in May and August) and two levels of K fertilization (0 or 42 kg K ha–¹). Potassium fertilization did not affect HM, crude protein (CP), or in vitro digestible organic matter (IVDOM); however, tissue K concentration increased from 10.6 to 11.2 g kg–¹ with increasing K fertilization. Plots fertilized with N had greater HM than the control, but there was no difference between plots fertilized in May only vs. those fertilized in May and August. Experiment 2 was conducted in a greenhouse in 2014 and 2015 with a factorial combination of three levels of N fertilization (0, 50, and 100 kg N ha–¹) and four levels of K fertilization (0, 16, 33, and 66 kg K ha–¹). There was a quadratic relationship between tissue K concentration and herbage accumulation (HA) and maximum HA occurred with tissue K concentration of 17 g kg–¹. Bahiagrass tissue K concentration and response to K fertilization are variable and can be related to fertilization levels.

This research was supported under the National Development Plan through the Research Stimulus Fund administered by the Department of Agriculture, Food and the Marine (Grants RSF10-/RD/SC/716 and RSF11S138) and from the Department of Agriculture and Rural Development for Northern Ireland and by the Teagasc Walsh Fellowship Scheme. peer reviewed In temperate grasslands, N source influences greenhouse gas emissions. Nitrification and urea hydrolysis inhibitors can reduce these losses. The objective of this study was to evaluate the impact of N source, urease inhibitors, and nitrification inhibitors on temperate grassland yields and N uptake. Experiments were conducted at three locations over 2 years (6 site-years) on the island of Ireland, covering a range of soils and climatic conditions. Results showed that calcium ammonium nitrate (CAN), urea+N-(n-butyl) thiophosphoric triamide (NBPT), urea+NBPT+dicyandiamide (DCD), and urea had equal annual dry matter yield. Urea+DCD had lower dry matter yield than CAN for 3 site-years. Calcium ammonium nitrate and urea+NBPT consistently had the same N uptake, urea+DCD had lower N uptake than CAN in 4 of 6 site-years, urea had lower N uptake than CAN in 2 site-years, and urea+NBPT+DCD had lower N uptake than CAN in 1 site-year. Urea+NBPT is a cost-effective alternative to CAN, which is consistently equal in terms of yield and N uptake in temperate grassland. Teagasc Walsh Fellowship Programme Department of Agriculture and Rural Development for Northern Ireland Department of Agriculture, Food and the Marine