Greenhouse Gas Emissions and Crossbred Cow Milk Production in a Silvopastoral System in Tropical Mexico

Abstract

In Mexico, pasture degradation is associated with extensive pastures; additionally, under these conditions, livestock activities contribute considerably to greenhouse gas (GHG) emissions. Among the options to improve grazing systems and reduce GHG emissions, silvopastoral systems (SPS) have been recommended. The objectives of this work were to quantify the N outflow in a soil–plant–animal interface, as well as the CH4 emissions and milk production in an SPS with woody legumes (Leucaena leucocephala) that is associated with stargrass (Cynodon nlemfuensis). This was then compared with stargrass in a monoculture system (MS) in the seasons (dry and rainy period) over a two-year period. Dung was collected from the animals of each of the grazing systems and applied fresh to the land plots. Fresh dung and urine were collected from the cows of each grazing system and were applied to the experimental plots. In addition, the soil CH4 and N2O contents were measured to quantify the emissions. Average milk yield by seasons was similar: MS (7.1 kg per animal unit (AU)/day−1) and SPS (6.31 kg per AU/day−1). Cows in the MS had a mean N intake of 171.9 g/UA day−1 without seasonal variation, while the SPS animals’ mean N intake was 215.7 g/UA day−1 for both seasons. For the urine applied to soil, the N2O outflow was higher in the MS (peak value = 1623.9 μg N-N2O m−2 h−1). The peak value for the SPS was 755.9 μg of N-N2O m−2 h−1. The N2O emissions were higher in the rainy season (which promotes denitrification). The values for the feces treatment were 0.05% (MS) and 0.01% (SPS). The urine treatment values were 0.52% (MS) and 0.17% (SPS). The emissions of CH4 showed that the feces of the SPS systems resulted in a higher accumulation of gas in the rainy season (29.8 g C ha−1), followed by the feces of the MS system in the dry season (26.0 g C ha−1). Legumes in the SPS helped to maintain milk production, and the N2O emissions were lower than those produced by the MS (where the pastures were fertilized with N).

Keywords

• nutrient cycling
• tropical grassland
• urine
• N balance
• milk production