Intercropping pigeon peas with pastures reduces methane emissions by up to 70%

Intercropped plantations increase productivity and reduce GHG emissions
calendar icon 16 November 2023
clock icon 7 minute read

The efficient use of the BRS Mandarim legume intercropped with the Marandu cultivar of bread grass and the Basilisk cultivar of signal grass increased weight gain in cattle and emitted less methane per kilogram obtained. The daily gas emission per kilogram of weight gain was 614.05 grams in the intercropped pasture, about 70% less than in degraded pasture, which had 2,022.67 grams.

Productivity was also higher in the intercropped treatment with pigeon peas – the animals gained 478 grams per day, while in the degraded pasture the average weight gain was of 302 grams per day. An increase of 58% over degraded pasture.

The technology can represent advantage not only for cattle farmers, but also for Brazil, which, in 2021, during the 26th UN Climate Change Conference of the Parties (COP26), in Glasgow, Scotland, made a commitment to reduce methane emissions by 30% by 2030.

According to the General Head of Embrapa Southeast Livestock (São Paulo, Brazil), Alexandre Berndt), any technology that reduces methane, at low cost, and that contributes to the efficiency of the production system and to sustainability is desirable and should be implemented.

The study, which was developed in partnership between Embrapa Southeast Livestock, the School of Veterinary Medicine and Animal Science of the University of São Paulo (FMVZ/USP) and the Center of Nuclear Energy in Agriculture of the University of São Paulo in Piracicaba, São Paulo, assessed the performance and emission of enteric methane resulting from the digestive process of Nellore steers in three different production systems, including the intercropping with BRS Mandarim pigeon peas.

The researchers presented the study's abstract during the 8th International Greenhouse Gas and Animal Agriculture Conference (GGAA 2022), held June 5-7 in Orlando, Florida, USA.

Experiment combined intercropped forage and pasture recovery

The experiment happened from July 2020 to July 2021, at Canchim Farm, headquarters of Embrapa Southeast Livestock's research center. The 27 animals that were used, of 15 to 16 months of age, were weighed monthly and the methane was measured by through the sulfur hexafluoride (SF6) tracer gas technique for five consecutive days in the rain and drought seasons.

The treatments were:

  1. recovered pasture with Urochloa decumbens cv. Basilisk signal grass cultivar and Urochloa brizantha cv. Marandu bread grass cultivar with liming and corrective fertilization with phosphorus (P), potassium (K), sulfur (S) and micronutrients and nitrogen fertilization with 200 kilograms of nitrogen (N) per hectare per year in the rainy season divided into three applications, with moderate animal stocking rate
  2. degraded pasture with low stocking rate
  3. pasture that was recovered with liming and corrective fertilization with P, K, S and micronutrients intercropped with Urochloa decumbens cv. Basilisk signal grass cultivar and Urochloa brizantha cv. Marandu bread grass cultivar intercropped with BRS Mandarim pigeon peas, with moderate stocking rate

The veterinarian Althieres Furtado, master's scholar in Animal Nutrition and Production at FMVZ/USP, advised by professor Paulo Henrique Mazza Rodrigues, says that three repetitions of each treatment were carried out, with adjustment of the stocking rate by the put-and-take technique. This method places and removes the animals on and from the pasture, according to the forage supply at each time of the year.

The cattle's annual average weight gain per day was 478 grams in the pigeon peas intercrop treatment, 387 grams in the recovered pasture and 302 grams in the degraded pasture.

The daily methane emission per kilogram gained was 2,022.67 in the degraded pasture, 1,053.55 in the recovered pasture and 614.05 in the intercropped one. The recovery with the pigeon pea intercropping emitted 70% less than the degraded pasture, while the recovery with the use of nitrogen fertilizer emitted 48% less.

According to Embrapa's researcher André Pedroso, this result was possible because the pigeon peas intercropping and the recovery of pastures not only lower enteric methane emissions but also improve the animals' performance with an increase in average daily gain.

Furtado says that the researchers expected this effect. 

"There are several ways to reduce methane production by the animal. In addition to improving the nutritional intake available to cattle, the tannins present in the structures of the BRS Mandarim pigeon peas plant work inside the rumen and, consequently, reduce the emission," he explains.

Inserting legume in intercrops is viable for sustainable cattle raising

For Embrapa's researcher Patrícia Perondi Anchão Oliveira, the degraded pasture is always the worst-case scenario. In general, the degradation process is characterized by increased loss of pasture productivity (low productivity), large areas of exposed soil, weeds, erosion, obvious symptoms of nutritional deficiency in plants and animals, and slower growth rate of plants which are reflected in environmental issues.

"Under these conditions, the soil is exhausted, which compromises not only the forage's production and quality but also the animals' performance. These factors increase the emission of enteric methane and make the soil lose organic matter which impairs carbon sequestration," she points out.

Oliveira recalls that the recovery of pastures through the insertion of legumes is a widely sought solution in the technical-scientific environment, a challenge of several decades, because through biological nitrogen fixation the legume provides nitrogen both for animal feed and soil improvement. "In times of scarcity and high prices for nitrogen fertilizers and protein mineral supplements, as well as concerns about enteric methane emissions, this type of technology is even more relevant," she adds.

Studies with intercropped grasses and legumes can improve animal performance with sustainability, Furtado believes. 

"Further research is still needed. However, when thinking about grass-fed meat production, with low emissions, this would be a possible alternative," he underscores.

Technologies for methane reduction are available to cattle farmers

Photo courtesy of Althieres Furtado

According to Berndt, methane is a short-lived gas.

"If we can reduce methane emissions, the impact on global warming will be faster. Its lifespan is of 10 to 20 years, while carbon dioxide's – CO₂ – is of 100 years," he explains.

Other studies by Embrapa Southeast Livestock assess technologies to meet this challenge. The research center has been investing in studies on greenhouse gas (GHG) emissions for more than 20 years, both in beef and dairy production systems, seeking low emissions of gases such as enteric methane in order to reduce the impact of the activity on the planet.

Many are already available to cattle farmers such as recovery of degraded pastures, good animal and plant management practices, adequate use of inputs, animal welfare, life cycle reduction and nutritional management. For Berndt, the implementation of these technological solutions and good practices, such as integrated systems, intensive pasture management and the use of additives in animal nutrition is able to offset the emissions generated by livestock and make the production system more sustainable.

Legume intercropping is a good example of technology that can contribute to methane reduction within pasture management. Some, such as BRS Mandarim pigeon peas, have some compounds in their structures, such as tannins and saponins, which can work on rumen microorganisms and, therefore, interfere with fermentation, reducing the populations of methanogenic organisms, which produce methane.

From the researcher’s point of view, Brazil’s main challenge is the scale adoption of these technological practices and solutions to significantly reduce the emission of enteric methane.

How to measure methane?

Methane is collected from the animals by automated or manual means. At Embrapa Southeast Livestock, both forms are used. In the experiment, the measurement was made manually. A capillary tubing is attached to a halter that is placed behind the bovine's head and stores the gases emitted by the animal for 24 hours. One of these gases is the tracer gas that is provided to the animal and has a known emission rate, which allows measuring the emission of other gases. After this time, the capillary tubing is removed and is sent to the laboratories for analyzes. Collections are made from a sample of animals for a certain time in different periods of the year.

On the other hand, GreenFeed is an automated technology used to measure, in a faster and more accurate way, the emission of methane (CH4) and carbon dioxide (CO2) of animals. The equipment recognizes the bovine by its electronic ear tag and delivers a quantity of food to the animal as soon as a sensor detects its presence in the trough; at the same time, it absorbs and measures the gases emitted during feeding. Thus, the emission is continuously monitored.

Contribution to SDGs

The results of this study contribute to alternatives for adaptation and mitigation of the effects of climate change, toward the more sustainable development of Brazilian cattle farming and to directly meet the United Nations' (UN) Sustainable Development Goal (SDG) number 13, which is “Take urgent action to combat climate change and its impacts”.

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