Soil carbon dynamics and fertility may respond differently to land-use systems in the Brazilian semiarid region due to its high environmental and edaphic heterogeneity. This study evaluated soil attributes in degraded, forest, and restoration areas across the states of Ceará (CE), Paraíba (PB), Pernambuco (PE), and Piauí (PI). Surface soil samples (0–10 cm) were analyzed for particle-size distribution, pH, total organic carbon (TOC), humic fractions, available phosphorus, exchangeable cations, and cation exchange capacity (CEC). Soil responses to land use varied markedly among states. Forest areas showed 12% and 57% higher TOC than degraded areas in PB and PI, respectively. Restoration areas showed substantial changes in specific carbon fractions; in PB, humic acid carbon was approximately 85–95% higher and humin carbon 136% higher than in the degraded area. Available phosphorus was also markedly higher in restoration areas in PB and PI. In PI, the restoration area was characterized by high Ca²⁺ and Mg²⁺ contents and CEC, whereas soil pH ranged from approximately 5.0 in the forest area to 8.0 in the degraded area. Overall, restoration areas showed improvements in specific soil attributes, although the magnitude and direction of these responses were strongly modulated by local edaphic conditions.

Lima bean (Phaseolus lunatus L.), an important legume in semiarid environments, often exhibits low yield, requiring strategies to enhance symbiotic nitrogen fixation and nutrient-use efficiency. This study evaluated the effects of single and combined inoculation with Bradyrhizobium elkanii (strain BR 2003) and Azospirillum brasilense (strain Ab-V5) on nitrogen metabolism, nutrient uptake, plant growth, and residual soil fertility in P. lunatus. Four varieties were subjected to four treatments: control (nitrogen fertilization), single inoculation with B. elkanii or A. brasilense, and co-inoculation. All inoculation strategies significantly increased root nodulation, nitrogen assimilation, and the accumulation of key macronutrients. Root nodulation increased from 1 to 12 nodules per plant in the control treatments to up to 277 nodules per plant under inoculation, while shoot nitrogen content increased by up to 91% in ‘Raio de Sol’ and 87% in ‘Cearense’. Increases in P and K were also observed, including a 48% increase in shoot P in ‘Manteiga’ and up to a 100% increase in shoot K in ‘Raio de Sol’, whereas root K increased by up to 90% under co-inoculation. The ‘Raio de Sol’ and ‘Manteiga’ varieties exhibited the most pronounced increases in growth and biomass. Additionally, inoculation improved post-cultivation soil indicators, including pH and available P and K in specific genotype-microbe combinations, and reduced electrical conductivity. These results demonstrate the strong contribution of microbial inoculation to nitrogen assimilation and nutrient acquisition, supporting its use as a promising alternative to conventional nitrogen fertilization in lima bean cultivation.

Soil organic carbon fractions and fertility attributes may differ among land-use conditions in the Brazilian semiarid region due to environmental heterogeneity, soil properties, and land-use history. This study compared soil attributes in degraded, forest, and restoration areas across four desertification hotspots located in Ceará (CE), Paraíba (PB), Pernambuco (PE), and Piauí (PI), Brazil. Surface soil samples (0–10 cm) were collected from four independent plots per land-use condition within each hotspot and analyzed for particle-size distribution, pH, total organic carbon (TOC), humic fractions, available phosphorus, exchangeable cations, and potential cation exchange capacity (CEC). The magnitude and direction of differences among land-use conditions varied across the investigated hotspots. Forest areas exhibited 12% and 57% higher TOC contents than degraded areas in PB and PI, respectively. In PB, humic acid carbon contents were approximately 85–95% higher in forest and restoration areas than in the degraded area, while humin carbon content in the restoration area was 136% higher than in the degraded area. Available phosphorus was markedly higher in restoration areas in PB and PI. In PI, the restoration area exhibited high Ca²⁺ and Mg²⁺ contents and potential CEC, whereas soil pH ranged from approximately 5.1 in the forest area to 8.0 in the degraded area. These findings reveal substantial spatial variation in soil carbon fractions and fertility attributes among land-use categories, potentially associated with differences in soil texture, pedogenic characteristics, and previous land management. The results highlight the importance of considering local edaphic conditions when assessing soil quality across contrasting land-use categories in semiarid environments.

Lima bean (Phaseolus lunatus), an important legume in semiarid environments, often exhibits low yield, requiring strategies to enhance symbiotic nitrogen fixation and nutrient use efficiency. This study evaluated the effects of single and combined inoculation with Bradyrhizobium elkanii (strain BR 2003) and Azospirillum brasilense (strain Ab-V5) on nitrogen metabolism, nutrient uptake, plant growth, and residual soil fertility in P. lunatus. Four varieties were subjected to four treatments: control (nitrogen fertilization), single inoculation with B. elkanii or A. brasilense, and co-inoculation. All inoculation strategies significantly increased root nodulation, nitrogen assimilation, and the accumulation of P, K, Ca, and Mg in plant tissues, demonstrating a robust symbiotic performance superior to mineral fertilization. The ‘Raio de Sol’ and ‘Manteiga’ varieties exhibited the most pronounced increases in growth and biomass. Additionally, inoculation improved post-cultivation soil indicators, including pH and available P and K in specific genotype-microbe combinations, and reduced electrical conductivity. These results support the use of microbial inoculation, either single or co-inoculation, as a promising alternative to conventional nitrogen fertilization, enhancing symbiotic nitrogen fixation and nutrient-use efficiency in lima bean cultivation.