Zarc points to an 80% chance of success for planting irrigated rice in a large part of Tocantins

A recent update to the Agricultural Climate Risk Zoning (Zarc) points out that, in the period from October 1st to November 20th, the chance of success in planting irrigated rice in Tocantins is 80%, considering the effects of the climate. The state is today the third largest national producer of this crop and the most prominent in the North Region. Zarc is a fundamental tool to help producers in Tocantins manage risks and contribute to expanding the cultivation area, both in floodplain areas and in irrigated plantations in other areas.

Currently, around 20% of Brazilian rice is produced in a tropical environment, with emphasis on Tocantins, which accounts for around 6% of the national total. The remaining 80% are grown in subtropical conditions, especially in the states of Rio Grande do Sul and Santa Catarina, the first two in the country. 

Production in a tropical environment is important because, in addition to facilitating distribution logistics for the states of the North and Northeast, it reduces supply risks caused by the impacts of severe weather phenomena in the subtropical environment. They are, therefore, places that complement each other in terms of strengthening national production and, above all, the food security of Brazilians.

Climatic factors are those that most influence productivity in various agricultural crops; in the case of rice, it is no different. In the southwest region of Tocantins, the focus of the study, the climatic variables that most limit irrigated rice production are light and high temperatures.

The ideal sowing time, one of the main pieces of information provided by Zarc, plays a fundamental role as a management practice that reduces climate risks. This is because, by following the guidelines, the rural producer increases the chances that the phases considered critical or sensitive of the plant do not coincide with the period of greatest frequency of adverse weather phenomena.

How zoning is done

Zarc's recommendations involve careful and complex work. According to Balbino Evangelista, geographer and research analyst at Embrapa Pesca e Aquicultura (TO), the work “requires sophisticated equipment and advanced data analysis techniques”.

The necessary information and data involve rice production systems, adapted cultivars and their respective development cycles, the need for water, ideal temperatures for cultivation, soil characteristics (chemical, physical and water) and, above all, a long series of climate data, with emphasis on rainfall and temperature. 

ORYZAv3 is a simulation model for the growth, development and productivity of rice crops that has been used accurately in Brazil. It was recently adopted in Zarc's studies due to its good performance, as it generates accurate simulations of the reality in the field.

It is important to highlight that, in the process of calibrating the model so that it can simulate the development and yield of irrigated rice, occurrences of water and nutrient deficiencies, nor biotic stresses during cultivation, are not considered. In other words, the research admits and works with the scenario in which the producer will adopt the technologies and recommended practices, such as pest and disease control and the adequate supply of both water and nutrients.

By parameterizing the model, the coefficients of a cultivar are obtained using data observed in field experiments, such as productivity indices. In this research, data from trials carried out in Goianira (GO) and the region of Formoso do Araguaia (TO) were used to parameterize ORYZAv3 in the simulation of BRS Catiana, one of Embrapa's main rice cultivars.

Publication considers daily data over 36 years

The study, presented in the publication Climatic risk and sowing time for irrigated rice in the state of Tocantins, took into account a climatic base of 36 years of daily data for five municipalities that are very representative of irrigated rice production in Tocantins: Dueré, Cristalândia, Lagoa da Confusion, Formoso do Araguaia and Pium. Together, they produce 96% of Tocantins’ rice. In addition to this base, physical-water data from a hydromorphic soil was used, which is representative of a floodplain, as it has a water table close to the surface for most of the year and is located in flat relief areas that have the conditions that rice needs.

Sowing simulations were carried out for the period from October to January, totaling 13 dates. With the data obtained, the proposal was to indicate the sowing times for irrigated rice in the southwest of Tocantins at three levels of risk of yield loss: 20%, 30% and 40%. Considering it another way, the success probabilities are 80%, 70% and 60%, respectively.

The results show that the ideal sowing period, especially in the Formoso River Basin (where the municipalities responsible for almost all rice production in the state are located), is between October 1st and November 20th. “In case of delay in sowing, the reduction in global solar radiation during the grain filling period and the increase in maximum and minimum air temperatures are responsible for reducing the potential productivity of the crop”, warns Balbino, one of the authors of the publication.  

He notes that using the results presented in this study will bring benefits to producers and other members of the irrigated rice production chain as it will reduce risks and increase crop yields. 

The Embrapa geographer summarizes the work by saying that “Zarc's study indicates 'what', 'where' and 'when' to plant with greater chances of success, which means fewer risks. This allows farmers to plan their investments at low-risk and economically viable levels.” He highlights that, in addition to helping producers reduce damage from loss of productivity, the information generated by zoning supports the government in its policy for releasing rural credit, considering public and private insurance.

“Zarc studies allow the government to optimize resources allocated to insurance, in order to serve a greater number of rural producers. Together, producers and the government contribute to increasing the supply of rice for the local population and the market in general”, explains Balbino. In times of increasingly severe and frequent climate challenges, great care is necessary both on the part of rural producers and the government. And climate risk zoning contributes to this precaution by offering reliable data and information for the production chain of various agricultural crops, including rice.

Rice in Tocantins 

Tocantins is the third largest rice producer in Brazil, behind only Rio Grande do Sul and Santa Catarina. The harvest of the 2023/2024 rice harvest has been completed and the estimate is that 619 thousand tons will be reached with the grain, an increase of around 19% compared to the previous harvest, according to the National Supply Company (Conab). 

This amount is obtained, mainly, in an irrigated system on around 100 thousand hectares, which corresponds to approximately 95% of the total area planted with rice in Tocantins. The main producing municipalities are Formoso do Araguaia and Lagoa da Confusao. Production supplies the domestic market and neighboring states in the North, Central-West and Northeast regions.

Rodrigo Sérgio, analyst at Embrapa Arroz e Feijão (GO), estimates that around 88 thousand hectares (90% of the total rice area) in Tocantins are planted with seeds generated by Embrapa. Eight cultivars with the company's genetics are important for rice farming in the state. In relation to cultivation in an irrigated system, the BRS A706 CL, BRSA705, BRS A704, BRS Catiana and BRS Pampeira stand out. Regarding the highland production system, the main cultivars are BRS A504 CL, BRS A502 and BRS Esmeralda.

The relevance of the role played by Embrapa cultivars in Tocantins has emerged in the last five years and, according to the analyst, reflects the genetic improvement work on rice that has been improved over more than four decades and also goes back to the history of irrigation projects , such as the Rio Formoso Project (1979), which systematized extensive floodplain areas.    

“Tocantins, which has a history of production from the opening of irrigated areas, currently has between 100 thousand and 120 thousand hectares for rice planting, with Lagoa da Confusao being the main producer. There is also potential to reach 300 thousand hectares of tropical floodplains. In the past, at the beginning of this process, there was a lack of genetics adapted to the region and it is this genetics that were generated by research that is currently making a difference”, points out Sérgio.

He recalls that, in the early days of irrigated rice cultivation in Tocantins, the cultivars planted came from the South Region and had genetics adapted for the subtropical environment, but were not improved for local rice farming. With specific genetic improvement work for tropical conditions, more productive cultivars began to emerge for these regions, and one of the differences in this work was the development of disease resistance.   

“To mention just the main disease, blast, Tocantins is a great hotspot (place of intense disease pressure) for testing. If there are 64 mapped blast breeds, 62 occur there. Therefore, seeking to incorporate genetic resistance into the cultivars themselves is always a priority in tropical environments and this work is reflected today with more resistant materials.

Advances also in highlands

For Daniel Fragoso, currently a researcher at Embrapa Pesca e Aquicultura who, for a long time, worked in Tocantins for Embrapa Arroz e Feijão, rice farming in the state has also been advancing in recent years in the highland production system. He says that, mainly following the launch of cultivars with resistance to herbicides, rice is being planted intercropped with forage crops to form and reform pastures along the lines of the Barreirão system, which was widely used in the 1980s. 

Fragoso highlights that this system, now modernized, has been called Barreirão Plus by Tocantins extension agents and allows the growth of various forage species to be temporarily halted with subdoses of herbicide from the imidazolinone group, enabling the development of rice plants.

In addition to Embrapa, the advancement of rice cultivation in Tocantins involves institutions such as the Ministry of Agriculture and Livestock (Mapa), Conab, the Secretariat of Agriculture and Livestock of Tocantins (Seagro), the State University of Tocantins (Unitins), the Federal University of Tocantins (UFT), the Federal Institute of Tocantins (IFTO), the Institute of Rural Development of Tocantins (Ruraltins) and the Union of Rice Beneficiaries of the State of Tocantins (Sindiato). The work also includes partnerships with rice producers and companies in the seed production sector.