Combined effect of intercropping and minimum tillage on soil carbon sequestration and organic matter pools in the semiarid region of Brazil Stoécio Malta Ferreira Maia A,E , Adriana Tamie Otutumi B , Eduardo de Sá Mendon¸ ca C , Júlio César Lima Neves D , and Teógenes Senna de Oliveira D A Federal Institute of Education, Science and Technology of Alagoas, Rua Lourival Alfredo, 176, 57160-000, Marechal Deodoro, Alagoas, Brazil. B Soil Science Department, Federal University of Ceará, Fortaleza, Ceará, Brazil. C Department of Plant Production, Federal University of Espírito Santo, 29500-000, Alegre, Espírito Santo, Brazil. D Soil Science Department, Federal University of Vi¸ cosa, Avenida P. H. Rolfs, s/n, 36570-000, Vi¸ cosa, Minas Gerais, Brazil. E Corresponding author. Email: stoecio.maia@ifal.edu.br Abstract. This study aimed to evaluate the effect of two intercropping systems and minimum soil tillage in the semiarid region of Brazil on soil organic carbon (SOC) and pools of soil organic matter (SOM), compared with the native vegetation (NV). The first intercropping was cultivated with beans, sesame and pigeon pea, whereas the second was cultivated with cotton, maize, beans, sesame and pigeon pea. Two areas under NV, adjacent to the crop areas, were also sampled. Soil sampling were collected from 0–5, 5–10, 10–20, 20–30 and 30–50 cm layers in three plots per area to characterise the SOM (SOC, soil nitrogen, humic substances, microbial biomass, and mineralisable carbon). Our results demonstrated that, when compared with the NV, intercropping systems conducted with minimum soil tillage were effective in maintaining and sometimes increasing the levels and stocks of SOC and some SOM fractions such as microbial C and humic substances, and therefore, these systems can be an alternative form of sustainable soil management in the semiarid region of Brazil. Additional keywords: semiarid soils, soil organic matter, soil quality, soil tillage. Received 17 December 2017, accepted 4 February 2019, published online 14 March 2019 Introduction Arid and semiarid regions cover around 41% of the land surface of the Earth and are home to more than 38% of the global population (MEA 2005; Qiu et al. 2012). In Brazil, the semiarid region comprises a total area of 980133.079 km 2 , representing 11.5% of the country and 11.8% of the population (Medeiros et al. 2012). The Brazilian semiarid region is characterised by high temperatures, low rainfall, slightly weathered soils and small production of phytomass. In addition to unfavourable conditions of soil and climate, farming is completely extractive and overgrazing by livestock is considerable. Agriculture is developed at the expense of indiscriminate deforestation, burning and inadequate periods of fallow (Maia et al. 2006). As a result of these conditions, the productivity of crops such as beans and maize (the main annual crops) in the semiarid region remains well below the national average. For example, in the semiarid region, beans and maize have an average productivity of 327.0 and 440.0 kg ha –1 respectively, whereas the averages for Brazil are 1028 and 5250 kg ha –1 respectively (municipal agricultural production database – IBGE, https://sidra.ibge.gov. br/pesquisa/pam/tabelas). In addition, although the productivity of these crops has increased by 150–180% in the last 25 years in Brazil as a whole, in the semiarid region there has been almost no increase in beans, with maize increasing by only 18%. These data show that agriculture continues to stagnate in the semiarid region of Brazil, as well as in other semiarid regions worldwide (El Tahir et al. 2009; Rathore et al. 2014; Campiglia et al. 2015; Camilli et al. 2016). In this context, the identification of suitable cropping systems that make the best use of available resources and provide higher yields is important if the diverse needs of farming communities and environmental sustainability in arid and semiarid regions are to be catered for (Rathore et al. 2014). Thus, practices such as intercropping, crop rotation, organic fertiliser and conservation tillage systems have been assessed for application under semiarid conditions around the world Journal compilation Ó CSIRO 2019 www.publish.csiro.au/journals/sr CSIRO PUBLISHING Soil Research, 2019, 57, 266–275 https://doi.org/10.1071/SR17336