Crop rotation: peanuts and sugar cane

Sugarcane is among Brazil's most important agro-industrial resources and, for a long time, was the basis of the colonial economy. Today, the country stands out on a large scale with the production of sugar and ethanol, the main biofuel for the vehicle fleet. Climatic factors and water availability are the elements that most influence sugarcane production and make Brazil the largest producer in the world - with 660 million tons, according to the National Supply Company (Conab).

The main agricultural activity in the State of São Paulo, sugar cane uses large areas of land for planting, which results in the agronomic effects generated by monoculture. An effective solution to alleviate the problem, and highlighted by agronomists, is the rotation of production with the cultivation of leguminous plants. 

During sugarcane field renewal, it is common to use known plant species, such as green manures, whose objective is to obtain superficial coverage to maintain or improve the physical, chemical and biological properties of the soil, including at depth. The cultivation of short-cycle species in sugarcane renewal areas provides the producer with another series of agronomic, financial, political and social advantages, such as savings in sugarcane field reform, soil conservation, due to the maintenance of coverage at a specific time. high rainfall, weed control during the annual sugarcane cultivation, indirect pest control, increased productivity and food production.

For the renovation of the sugarcane field, one can opt, among legumes, for planting Crotalaria juncea, soybeans or peanuts, and the choice must be made depending on the location to be used, the slope of the area, the predisposition to soil pests and the availability of machines and implements to found the activity.

One of the most interesting crops for this process is peanuts, as they have low fertility requirements on the land, have a well-developed root system and good adaptation to various types of soil, and also contribute to increasing the productivity of sugarcane fields during the renovation intervals. Furthermore, the practice with the grain has provided important economic gains, as it contributes to the good maintenance of the land, balancing nutrients such as nitrogen, essential for the development of sugarcane, and considerable soil recovery.

In addition to the benefits already mentioned, this system allows for social advantages and economic gains. Within the social scale is the employee's use during the off-season, which avoids the seasonality of income and work. Part of the sugarcane infrastructure can also be used for peanuts, optimizing the machinery.

Around 85% of the peanuts grown in Brazil are found in São Paulo. Of this amount, a large part of the planting is concentrated in areas for sugarcane field renewal, in addition to an important portion for updating pastures.

In the Ribeirão Preto region, more than 40 thousand hectares of land are renewed annually with peanut planting during the sugarcane off-season. The process allows the producer to reduce sugarcane renewal costs by up to 50%.

In the case of peanut cultivation, some factors are considered relevant to the success of crop rotation with sugar cane. Among the main ones is the management of foliar diseases, such as brown spot, caused by the fungus Cercospora arachidicola which occurs at the beginning of flowering, and early blight, caused by the fungus Cercosporidium personatum and predominantly considered the most severe foliar disease of peanut crops in the final part of flowering.

The causes that favor the development of brown spot and black spot are temperatures between 20^oC and 26 ^oC, periodic rains during the crop cycle and leaf wetness, due to high air humidity.   

These diseases are responsible for losses of up to 50% of productivity and the damage is a consequence of early defoliation. To effectively control this scenario, management must contain active ingredients such as Chlorothalonil, a protective fungicide that, when applied sequentially, improves the effectiveness of specific fungicides.