Strategic grazing management and nitrous oxide fluxes from pasture soils in tropical dairy systems

Guilhermo F S Congio; Marília B Chiavegato; Camila D A Batalha; Patrícia P A Oliveira; Thomas M R Maxwell; Pablo Gregorini; Sila C Da Silva

doi:10.1016/j.scitotenv.2019.04.186

Strategic grazing management and nitrous oxide fluxes from pasture soils in tropical dairy systems

Sci Total Environ. 2019 Aug 1:676:493-500. doi: 10.1016/j.scitotenv.2019.04.186. Epub 2019 Apr 13.

Authors

Guilhermo F S Congio¹, Marília B Chiavegato², Camila D A Batalha³, Patrícia P A Oliveira⁴, Thomas M R Maxwell⁵, Pablo Gregorini⁶, Sila C Da Silva⁷

Affiliations

¹ Animal Science Department, University of São Paulo, "Luiz de Queiroz" College of Agriculture (USP/ESALQ), Piracicaba, São Paulo, Brazil. Electronic address: guilhermo.congio@usp.br.
² Animal Science Department, University of São Paulo, "Luiz de Queiroz" College of Agriculture (USP/ESALQ), Piracicaba, São Paulo, Brazil. Electronic address: marilia.chiavegato@usp.br.
³ Animal Science Department, University of São Paulo, "Luiz de Queiroz" College of Agriculture (USP/ESALQ), Piracicaba, São Paulo, Brazil. Electronic address: camila.delveaux@usp.br.
⁴ Embrapa Pecuária Sudeste, São Carlos, São Paulo, Brazil. Electronic address: patricia.anchao-oliveira@embrapa.br.
⁵ Faculty of Agriculture and Life Sciences, Lincoln University, Christchurch, New Zealand. Electronic address: tom.maxwell@lincoln.ac.nz.
⁶ Faculty of Agriculture and Life Sciences, Lincoln University, Christchurch, New Zealand. Electronic address: pablo.gregorini@lincoln.ac.nz.
⁷ Animal Science Department, University of São Paulo, "Luiz de Queiroz" College of Agriculture (USP/ESALQ), Piracicaba, São Paulo, Brazil. Electronic address: siladasilva@usp.br.

PMID: 31055205
DOI: 10.1016/j.scitotenv.2019.04.186

Abstract

Greenhouse gases emissions are considered one of the most important environmental issues of dairy farming systems. Nitrous oxide (N₂O) has particular importance owing to its global warming potential and stratospheric ozone depletion. The objective of this study was to investigate the influence of two rotational grazing strategies characterized by two pre-grazing targets (95% and maximum canopy light interception; LI_95% and LI_Max, respectively) on milk production efficiency and N₂O fluxes from soil in a tropical dairy farming system based on elephant grass (Pennisetum purpureum Schum. cv. Cameroon). Results indicated that LI_95% pre-grazing target provided more frequent defoliations than LI_Max. Water-filled pore space, soil and chamber temperatures were affected by sampling periods (P₁ and P₂). There was a significant pre-grazing target treatment × sampling period interaction effect on soil NH₄⁺ concentration, which was most likely associated with urinary-N discharge. During P₁, there was a greater urinary-N discharge for LI_95% than LI_Max (26.3 vs. 20.9 kg of urinary-N/paddock) caused by higher stocking rate, which resulted in greater N₂O fluxes for LI_95%. Inversely, during P₂, the soil NH₄⁺ and N₂O fluxes were greater for LI_Max than LI_95%. During this period, the greater urinary-N discharge (46.8 vs. 44.8 kg of urinary-N/paddock) was likely associated with longer stocking period for LI_Max relative to LI_95%, since both treatments had similar stocking rate. Converting hourly N₂O fluxes to daily basis and relating to milk production efficiency, LI_95% was 40% more efficient than LI_Max (0.34 vs. 0.57 g N-N₂O/kg milk·ha). In addition, LI_95% pre-grazing target decreased urea-N loading per milk production by 34%. Strategic grazing management represented by the LI_95% pre-grazing target allows for intensification of tropical pasture-based dairy systems, enhanced milk production efficiency and decreased N-N₂O emission intensity.

Keywords: Canopy light interception; Elephant grass; Grazed soils; Nitrous oxide fluxes; Soil nitrogen; Sustainable intensification.

MeSH terms

Air Pollutants / analysis*
Animal Husbandry / methods*
Cameroon
Dairying*
Global Warming
Herbivory*
Nitrous Oxide / analysis*
Temperature
Tropical Climate

Substances

Air Pollutants
Nitrous Oxide