ABSTRACT The goal of this paper was to apply a method for the delineation of vegetation homogeneous zones (HZs) to map the profitability of cotton ( Gossypium sp.) using NDVI (Normalized Difference Vegetation Index) data from RPA imagery. Two irrigated cotton crops, at the FAU (103 ha) and FRP farms (106 ha), located in the western region of Bahia State, Brazil, were studied. The NDVI images were classified into three HZs: “high”, “medium” and “low” plant vigor; using the k-means clustering method. In each HZ the yield was measured, and the profitability estimated. In FAU we found that the lower the HZ’s NDVI values, the lower its profitability, because there was profit in the “high vigor” HZ, of US$ 829.40 ha-1, and loss in the “low vigor” HZ, of about US$ ‒1.256.09 ha-1 (‒251.44% compared with the “high vigor”). In the FRP plantation, the lower the NDVI values, the lower the loss of the plantation, as there were losses in all HZs: from “high” to “low vigor” HZ, the percentage difference in profitability was ‒343.43%. Thus, the use of a low-cost modified near-infrared Canon S100 on an RPA enabled the mapping of crop profitability, aiding the search for the factors behind yield variability.

RESUMO Com a expansão da produção agrícola, há a substituição de áreas de Cerrado nativo por outras formas de uso do solo. Assim, objetivou-se avaliar alterações no fracionamento físico do carbono orgânico em áreas submetidas a diferentes usos do solo no Cerrado. Os tratamentos, com cinco repetições, corresponderam às seguintes formas de uso: área sob plantio convencional, área sob plantio de pastagem, área sob plantio de eucalipto e área sob vegetação nativa de Cerrado nas profundidades de 0-5, 5-10, 10-15 e 15-20 cm no munícipio de Luís Eduardo Magalhães, BA. Os maiores teores e estoques de carbono foram encontrados para a área de eucalipto, iguais à área sob vegetação nativa de Cerrado. Já os estoques de carbono particulado foram superiores na área sob pastagem na profundidade de até 10 cm, não diferenciando da área sob Cerrado nativo. A pastagem e o eucalipto apresentaram efeito positivo no índice de manejo do carbono, independentemente da profundidade.

ABSTRACT With the expansion of agricultural production, native Cerrado areas are replaced with other forms of land use. Thus, the objective of this study was to evaluate changes in the physical fractionation of organic carbon (C) in areas under different forms of land use in the Cerrado. The treatments, with five repetitions, corresponded to the following forms of use: area under conventional tillage, area under pasture plantation, area under eucalyptus plantation and area under native Cerrado vegetation, at the depths of 0-5, 5-10, 10-15 and 15-20 cm in the municipality of Luis Eduardo Magalhães, BA, Brazil. The highest C contents and stocks were found in the eucalyptus area, which were equal to those of the area under native Cerrado vegetation, while particulate C stocks were higher in the area under pasture at the depth up to 10 cm, not differing from the area under native Cerrado. Pasture and eucalyptus had positive effect on C management index, regardless of depth.

RESUMO O solo representa um importante componente no ciclo biogeoquímico do carbono (C) e do nitrogênio (N). Objetivou-se, nesta pesquisa, avaliar as mudanças provocadas por diferentes formas de uso do solo sobre os estoques de carbono e nitrogênio em áreas de Cerrado em profundidade de até 60 cm: área sob plantio convencional, plantio direto, pastagem, eucalipto e área sob vegetação nativa de Cerrado na região de Luís Eduardo Magalhães, BA. O maior teor de C foi encontrado para área de plantio direto na camada superficial até 10 cm; porém, houve decréscimo em seu teor ao longo das profundidades. Áreas sob plantio convencional apresentaram valores menores de estoque de C na camada superficial (0-5 cm) e abaixo de 20 cm. Entre estas, os estoques de C foram significativamente inferiores em comparação à utilização de pastagem e eucalipto na profundidade de até 40 cm. Considerando a profundidade de 0-60 cm, o maior estoque de C foi encontrado nas áreas sob vegetação nativa, com 62,81 Mg ha-1, seguida pela área sob cultivo de eucalipto, com 60,70 Mg ha-1. Os menores estoques de C foram encontrados nas áreas sob uso convencional, com 44,87 Mg ha-1. O plantio convencional reduziu os estoques de N em até 61 e 56% em relação às áreas sob vegetação nativa de Cerrado e plantio de eucalipto, respectivamente, ambas na profundidade de até 10 cm. Portanto, práticas de uso do solo como eucalipto e plantio direto contribuem para armazenar carbono e nitrogênio ao longo do tempo.

ABSTRACT The soil is an important component in the biogeochemical cycling of carbon (C) and nitrogen (N). The objective of this study was to evaluate the changes caused by different types of land use on the C and N stocks in areas of Cerrado at different depths: area under conventional tillage, no-tillage, grazing, eucalyptus and area under native vegetation of Cerrado in the municipality of Luis Eduardo Magalhães, BA, Brazil. The highest C content was found for no-tillage area in the surface layer up to 10 cm; however, there was a decrease in its content along the depths. Areas under no-tillage had lower values of C in the surface layer (0-5 cm) and below 20 cm. Among these, C stocks were significantly lower compared to the use of grass and eucalyptus at the depth of up to 40 cm. Considering the depth of 0-60 cm, the highest C stock was found in areas under native vegetation, 62.81 Mg ha-1, followed by the area under cultivation with eucalyptus, 60.70 Mg ha-1. The lowest C stocks were found in areas under conventional use, 44.87 Mg ha-1. Conventional planting reduced N stocks by up to 61 and 56% when compared to areas under native Cerrado vegetation and eucalyptus plantations, respectively, both at a depth of up to 10 cm. Therefore, land use practices such as eucalyptus cultivation and no-tillage contribute to C and N storage over time.