January 30, 2019

Good pastureland could mitigate climate impact of cattle urine, study says

 

Cow urine releases the greenhouse gas, nitrous oxide, into the atmosphere when it falls on degraded land, and landscape restoration and conservation could help to mitigate such an effect,  the International Center for Tropical Agriculture (CIAT) said.

Described as "a lesser-known climate offender", cattle urine emits nitrous oxide (N2O), "which has warming power far greater than that of carbon dioxide (CO2), the main driver of global warming," the organisation added. It had conducted a study with partner, revealing the advantage of good cattle pasture that could keep N2O emissions in check.

As part of the study, urine samples were obtained from cattle from research sites in five countries across Latin America and the Caribbean.

"(Researchers) spilled these 500 mL samples on paired cattle fields classified as degraded or healthy, which was determined by vegetation coverage. In six of the seven test sites, degraded pastures emitted significantly more N2O - sometimes up to three times as much," CIAT explained.

 

"Degraded pastures are bad in so many ways. This study adds to the case for land restoration. Degraded pastures not only affect food security and the livelihood of farmers today, but affects the livelihood of future farmers because they emit more gases that cause global warming," said Ngonidzashe Chirinda, a CIAT researcher and the study's lead author.

 

The research's outcome highlights the importance for "global land restoration agreements, including Initiative 20x20, which aims to bring into restoration 20 million hectares of land in Latin America by 2020 as a first major step toward even more ambitious restoration targets," CIAT said.

 

Currently, there are about 150 million hectares of degraded lands in Latin America, based on estimates provided by Chirinda. About 80 million hectares of degraded pastureland are found in Brazil.

 

"Degraded livestock land is generally characterised by overgrazing, soil compaction, loss of organic material and low levels of nutrients and soil carbon," CIAT commented.

 

Curbing the effects of greenhouse gas emissions would mean implementing on a large scale land restoration measures that entail better forage grasses, rotational grazing and the addition of shrubs and trees.

 

"In addition to reducing N2O emissions, restored landscapes generally contain more carbon, have healthier soils and more robust and productive livestock," CIAT pointed out.

 

"This study highlights the importance of avoiding land degradation in the first place. Maintaining healthy pastures appears to reinforce goals of both the United Nations' Framework Convention on Climate Change and the UN Convention to Combat Desertification simultaneously," Todd Rosenstock, the study's co-author based at the World Agroforestry Centre (ICRAF), said.

 

However, CIAT also noted that results from a single test sit did not match those obtained in Taluma, Colombia, and could be due to several factors that require more research.

 

"N2O emissions there were by far the lowest at any test site and were the same on both degraded and healthy pastures. The cattle urine used in the experiment had the lowest nitrogen content compared to the other research sites, which likely contributed to the results. The forage grass used there, Brachiaria humidicola, also has an especially high nitrification inhibition capacity, meaning that it prevents nitrogen from becoming N2O," CIAT elaborated.

- The International Center for Tropical Agriculture