Greenhouse gases emissions from tropical grasslands affected by nitrogen fertilizer management

Abstract

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 (N 2 O), methane (CH 4), and carbon dioxide (CO 2) 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 N 2 O, CH 4, and CO 2 emissions were significantly affected by increasing N fertilizer levels. The seasons also affected GHGs emissions. Nitrogen fertilizer favored CH 4 consumption relative to the control plot without N, with mean emission of 23.7 μg CH 4 −C m −2 h −1 in the fertilized plots compared to 61.6 μg CH 4 −C m −2 h −1 in the control. The N-fertilized areas presented higher CO 2 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 N 2 O emission. Soil temperature drove CO 2 emissions. Increasing N fertilization in grazed marandu grass increases N 2 O and CO 2 emissions during the growing season, while reducing CH 4. 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.

Grazing Intensity Impacts on Herbage Mass, Sward Structure, Greenhouse Gas Emissions, and Animal Performance: Analysis of Brachiaria Pastureland

“…Beef cattle production is an important source of protein, minerals, and vitamins for human nutrition. However, it requires significant quantities of natural resources and may negatively impact the environment through greenhouse gas (GHG) emissions [1][2][3]. Beef cattle production is pasture-based in tropical regions, but tropical grasses usually have low crude protein (CP), and high neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations, which lead to lower animal performance and greater enteric methane (CH 4 ) emissions [2,4].…”

“…Nitrous oxide (N 2 O) is also emitted when excreta and forage residues decompose. Greenhouse gases from the soil are affected by soil structure, particularly compaction, which affects soil moisture, oxygen (O 2 ) availability, and animal emissions [3,12,13]. Grazing Marandu to a 15 cm sward height implies a greater stocking rate, and hence more excretal returns and soil trampling by the animals.…”

Land Use, Temperature, and Nitrogen Affect Nitrous Oxide Emissions in Amazonian Soils

“…These changes tend to increase up to 2.8 times the emitted N 2 O and pasture soils with more than 10 years of use [32]. In addition to the age of the pasture, the low availability of nutrients in the soil explains the lower emission of N 2 O since the last fertilization was applied in 2016 with reactive natural phosphate and in the absence of nitrogen [12,33].…”

“…The amount of mineral N present in the soil determines the magnitude of N 2 O production in the atmosphere [12]. The response of soil to the addition of N depends on the type of management or condition of the soil and its intending purpose.…”

“…Native forests usually undergo burning processes to form pastures or agricultural areas, and at first, the availability of N in the soil increases due to mineralization caused by fire [13]. In the pasture areas, nitrogen fertilization and excreta from grazing animals increase the supply of ammonium (NH 4 + -N) and nitrate (NO 3 − -N) for denitrifying organisms [12]. Agricultural areas with annual crops have high levels of nitrogen fertilization, applied annually, resulting in characteristics similar to those observed in pasture areas.…”