Distribution of available nitrogen forms in soil under Quilombola management systems in Brazilian Cerrado phytophysiognomies

Abstract

ABSTRACT Management of Quilombola systems are primitive agricultural systems based on the ancestral knowledge of Afro-Brazilian enslaved people. Here, the aim was to understand the impact of these primitive farming methods on the distribution of available nitrogen (N) forms in the soil profile of two Brazilian Cerrado phytophysiognomies. The soil was sampled in Cerradão (high Cerrado) and Cerrado Stricto sensu (low Cerrado) at six soil depths (0-10, 10-20, 20-30, 30-40, 40-50, and 50-60 cm). The following management systems were considered: pasture (PP1 and PP2), maize cultivation (M1 and M2), citrus-cassava intercropping (T1), and citrus monoculture (T2). In addition, the soil was sampled in the native area of Cerradão (NC1) and Cerrado Stricto sensu (NC2). Three N forms were determined: i) available nitrogen (Av-N), ii) ammonium (NH4+-N) and iii) nitrate (NO3–-N) contents. The Av-N content decreased with increasing soil depth only in NC1 and NC2. The NO3–-N content was similar at all soil depths for maize and pasture, while the content decreased at soil depth for NC1, NC2, and T1. NH4+-N was similar in M2 and PP2, but it increased in T2, ranging from 6.17 mg kg–1 to 17.54 mg kg–1. Overall, the dynamics of available N forms varied according to the Cerrado phytophysiognomy and the management systems and NO3–-N was the most constant N form in the soil profile. Therefore, although the management of Quilombola systems is less intensive, they negatively affect the dynamics and N availability, mainly where management is less conservative, that is, in maize and citrus monocultures.

Keywords

• Brazilian Cerrado
• tillage
• soil profile assessment
• soil nutrient distribution