Tipos de solo e a orientação para o mercado influenciam na escolha das variedades de mandioca (Manihot esculenta Crantz) nos sistemas de produção do Baixo Rio Tapajós, Pará

Abstract

Manioc (Manihot esculenta Crantz) is the main agricultural crop in Amazonia, with great economic and cultural importance, as it is the basis of the diet of rural and urban populations, especially traditional and indigenous communities that manage a large number of manioc varieties. Ecological, socioeconomic and cultural factors, such as soil type, soil fertility and market orientation, influence the forms of management and the diversity of cassava varieties cultivated by different cultural groups. This study investigates how different soil types (especially anthropogenic soils and adjacent soils) and market orientation influence the selection of manioc varieties managed by smallholder farmers in the Resex Tapajós-Arapiuns, lower Tapajós River, Pará, Brazil. Sixty-one fields of 30 family farms were studied in three riverside communities, with different soil types and different degrees of market orientation. A total of 41 manioc varieties were found (36 bitter manioc, 3 sweet manioc and 2 manicuera varieties). Six varieties are cultivated in all communities, 6 are unique to Enseada do Amorim, 8 to Parauá and 10 to Surucuá. The different soil types were grouped into three categories, defined according to soil fertility, color and presence of ceramic artifacts: Terra preta, with high fertility, dark brown or black color and abundant ceramic fragments; transitional soils, with high levels of phosphorous, organic matter and aluminum, light brown color and occasional occurrence of ceramics; adjacent soils, with low fertility, light color and without ceramic artifacts. Twenty five varieties are cultivated in all soils, with seven common to the three soil types, 2 exclusive to Terra preta, eleven to transitional and three to adjacent soils. Farmers prefer to grow short cycle varieties in the most fertile soils and long cycle varieties in less fertile soils. Terra preta are managed more intensively, with a shorter fallow period (4.0±1.2 years) and more consecutive productive cycles (3.6±0.5); transitional soils have intermediate fallow durations (6.0±1.6 years) and number of consecutive production cycles (2.9±0.4), while adjacent soils have longer fallows (10.0±1.2 years) and fewer consecutive production cycles (2.0±0.0). The market orientation of manioc flour production is related to the size of fields and the area occupied by "commercial varieties". Farmers that allocate between 50 and 80% of the market produce areas of 1.65 ± 0.49 ha, each with 0.66 ± 0.20% of the area occupied by commercial varieties; Families that destine more than 80% manage larger areas, 2.61 ± 1.07 ha, and commercial varieties occupy 0.73 ± 0.17% of the area of the plantations. In contrast, families that allocate less than 50% of cassava flour production to the market manage smaller areas, 0.58 ± 0.12 ha and commercial varieties proportionally occupy a smaller area 0.49 ± 0.19%. In conclusion, the composition of manioc varieties, as well as the management of family farming systems in the Lower Tapajós River region are influenced by soil type. The orientation of production to the market influences the characteristics of the cropping system, as well as the size of the area managed and the proportion of area in the fields occupied by commercial.