Grey water footprint related to nitrogen of steer manure from intensive and extensive production systems in Buenos Aires, Argentina

MARÍA MACARENA ARRIEN; MAITE M. ALDAYA; CORINA IRIS RODRIGUEZ

Simposio; Water-Energy-Food Nexus Symposium; 2023

Water Footprint Nework

The livestock sector is the fastest growing sector globally compared to other agricultural sectors, and for this reason it is the subject of attention and study, as it can contribute to the degradation of natural resources such as water and soil, emissions of methane, nitrogen and phosphorus, and the impacts of water scarcity. This study is a part of a biggest objective from my PhD thesis, which is calculate the water footprint (WF) of meat produced in different systems. The grey WF related to nitrogen (N) of steer manure was estimated in two case studies located in the province of Buenos Aires, Argentina, applying different methodologies depending on whether the production system was intensive or extensive. In the extensive livestock farming, a soil N balance of the forage where the animal grazing was carried out, considering the kilograms of N per animal per day contributed by excreta, following the methodology proposed by MAPAMA (2021). Some data were taken from literature and adjusted with local data. In the case of the manure pits in an intensive farming system, the manure once on the ground, drains into an unsealed pit, where it remains untreated. First the N leaching fraction (α) was determined according to Franke et al. (2013), adjusting the equation with local data. The IPCC (2006) method was used to calculate the applied pollutant load. Finally, in both cases, extensive and intensive productions systems, the grey WF was estimated using the equation proposed by Hoekstra et al. (2011). The soil N balance of extensive rearing was negative because more nitrogen is extracted than is incorporated, resulting in a grey WF equal to 0. In the case of the intensive system where the grey WF of manure reached 65.16 m3 water/animal.The grey WF of the intensive production system represents a significant contribution to the grey WF of the entire steer production chain from the cradle to the farm gate. Earlier studies on the grey WF of livestock focus on manure application in agricultural fields. To our knowledge there are not previous WF studies focusing on the grey WF related to N leaching from manure pits in intensive farming systems, which could represent an underestimation of the grey WF.