Method developed by Embrapa identifies gaps in pasture carrying capacity by analyzing climate, soil, animals and plants involved in the system. Through two parameters – maximum and critical stocking rates –, the protocol estimates the quantity of animals a given pasture can bear. It also simulates pasture production and estimates climate risks associated with the availability of food for cattle. By identifying the main factors that limit forage production, protocol can support policy and investment decisions. Method shows how to best invest in rehabilitating degraded pastures and in intensifying pasture-based cattle farming. The protocolo has already been incorporated to Animal Farming Climate Risk Zoning launched this year. Embrapa developed a protocol that helps to assess opportunities to intensify pasture-based beef cattle production systems, one of the sector's main challenges towards reducing negative environmental impacts. The yield gap analysis allows for estimating the difference between the current and potential yield of a given crop, identifying opportunities to meet the projected increase in demand for agricultural products, and supporting decision-making in research, public policy, development and investment. The protocol for such gap analysis was applied to estimate productivity gains. The method, which was presented by Embrapa researchers in the international journal Field Crops Research, determines differences in productivity in pasture-based beef cattle production systems under different management scenarios in Central Brazil. “The protocol assesses pasture carrying capacity through two indicators: maximum and critical stocking rates. The maximum stocking rate is reached when all the forage produced is harvested with the maximum efficiency possible, which occurs when the system has full flexibility to adjust the stocking rate. The critical stocking rate expresses the highest constant stocking rate that does not entail lack of food at any period of the year and represents the carrying capacity of managed pastures, limited by seasonal and interannual variability in forage production”, explains Patrícia Menezes Santos, the coordinator of the study and a researcher at Embrapa Southeast Livestock (São Carlos, SP, Brazil). This protocol produces simulations of pasture production and animal stocking rates, and also estimates the climate risk associated with the availability of food for the cattle. “Most protocols tend to overestimate carrying capacity as it does not adequately consider interannual and seasonal variations in forage production. Furthermore, the models do not allow an assessment of the effect of specific technologies, such as fertilization”, the researcher states. According to Santos, there are gaps in the pasture's carrying capacity due to interactions among the climate, soil, plant and animal components of the system. “The method we developed allowed the identification of the main factors that limit forage production and pasture carrying capacity under several environmental conditions and technological levels, and it can be applied to support policies and investment decisions”, he informs. Findings The protocol was applied to central-western and southeastern Brazil, covering parts of the Amazon, Cerrado and Atlantic Rainforest biomes. It combines methods such as homogeneous climate zone definition; systematization of primary data on weather and soil; production scenario definition; long-term forage growth simulations; pasture carrying capacity estimation; and use of agricultural census data to estimate actual stocking rates. In the study, according to Santos, long-term forage production simulations allowed the analysis of the climate risk associated with pasture production in the different climate and soil conditions observed in Brazil's Midwest and Southeast. In addition, it simulated different scenarios, with varying levels of nitrogen fertilization and water availability, which is useful to identify promising technologies to fill yield gaps. The potential for pasture intensification in Central Brazil was estimated based on the indicators of maximum stocking rate and critical stocking rate. The average gap in the maximum stocking rate ranged from 5.81 to 5.12 animal units per hectare (AU/ha) in the potential scenario (without water or nitrogen restrictions), from 4.18 to 2.9 AU/ha in the irrigated scenario and without nitrogen restriction, and from 2.73 to 1.43 AU/ha in the rainfed scenario and only with maintenance nitrogen fertilization. The critical stocking rate varied from 5.44 to 2.91 AU/ha in the potential scenario (without water or nitrogen restrictions), from 1.21 to 0 AU/ha in the irrigated scenario and without nitrogen restrictions, and from 1.04 to 0 AU/ha in the rainfed scenario and only with maintenance nitrogen fertilization. Photo: Gisele Rosso Planning Seasonal forage production poses challenges to pasture-based production systems as the animals' nutritional demands have to be met throughout the year. Such variation in feed production increases the risk of forage shortages and limits pasture carrying capacity. “High yield in a given season cannot be transferred to feed animals in a period of drought, when productivity drops, unless some type of forage conservation practice is adopted, such as haymaking and ensilage”, explains Luís Gustavo Barioni, a researcher at Embrapa Digital Agriculture who also co-authored the paper. Such variation in pasture yield, which is influenced by climate over time and combined with feed demand, will determine the assessment of the pasture's carrying capacity. The cumulative forage deficits used to identify yield gaps are calculated based on a mathematical model developed by Barioni. The study findings showed yield gaps and opportunities to intensify pasture-based beef cattle production, information that can inform planning and public policy. "In areas of high climate risk, it is important to avoid pasture stocking rates that result in narrow differences between forage accumulation and the animals' demand. In the study, the highest risks related to production were observed in locations with low soil water retention capacity, low minimum temperature and low rainfall or poor distribution of rainfall", Patrícia Santos explains. The protocol indicates, for instance, not only where investments in the recovery of degraded pastures and in the intensification of pasture-based cattle farming would be most promising, but also that credit policies need to consider access to complementary technologies to feed the animals during unfavorable periods. “In order to increase stocking rates where there is a forage deficit, it is necessary to either increase pasture yield in times of drought or cold or supplement the herd’s feed, measures that have an economic impact”, Barioni recalls. He adds that integrated crop-livestock systems is an interesting approach to follow the seasonality of forage supply, and the method they developed can be used by farmers to better plan the implementation of such production systems, considering the periods when there would be a forage surplus and the times of scarcity. Another direct benefit is the possibility of using the protocol to inform rural insurance associated with pasture-based cattle production. The accumulated forage deficit has already been applied, for instance, in the survey for the Agricultural Climate Risk Zoning (ARCZ) for beef cattle farming approved by the Brazilian Ministry of Agriculture (Mapa). The Cattle ACRZ, which has been in place since April, aims to identify areas with lower climate risk and define the best regions for Marandu grass-fed cattle in Distrito Federal and 17 Brazilian states. It shows the critical stocking rates of pastures in each town and the months with the highest risk of food shortages in light of the animal stocking rate used. The information supports the offer of rural credit and insurance in the country. Data on the Forage ACRZ can be consulted on the Brazilian Ministry of Agriculture's website or through the app Zarc Plantio Certo. The study can be found here.