Reclamation status of a degraded pasture based on soil health indicators

Pasture degradation is a concern, especially in susceptible sandy soils for which strategies to recover them must be developed. Microbiological and biochemical soil health indicators are useful in the guindace of soil management practices and sustainable soil use. We assessed the success of threePanicum maximum Jacq. cultivars in the reclamation of a pasture in a sandy Typic Acrudox in the northwest of the state of Paraná, Brazil, based on soil health indicators. On a formerly degraded pasture withUrochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, a trial with threeP. maximum (cv. Massai, Tanzânia, or Mombaça) was conducted. Lime and phosphate were applied at set-up, and mineral N and K as topdressing. A remnant of degraded pasture adjacent to the trial was used as control. Twenty-three chemical, physical, microbiological and biochemical attributes were assessed for the 0-10 cm topsoil. The procedures for reclamation improved most of the indicators of soil health in relation to the degraded pasture, such as soil P, mineral N, microbial biomass C, ammonification rate, dehydrogenase activity and acid phosphatase. CO2 evolution decreased, whereas microbial biomass C increased in the pasture under reclamation, resulting in a lower metabolic quotient (qCO2) that points to a decrease in metabolic stress of the microbial community. The reclamation of the pasture withP. maximum, especially cv. Mombaça, were evidenced by improvements in the microbiological and biochemical soil health indicators, showing a recovery of processes related to C, N and P cycling in the soil

Compartimentos de carbono orgânico em Latossolo cultivado com hortaliças sob diferentes manejos

Resumo: O objetivo deste trabalho foi avaliar os teores de carbono orgânico total (COT) e das frações granulométricas da matéria orgânica de um Latossolo Vermelho cultivado com hortaliças, sob diferentes sistemas de manejo e de cultivo de plantas de cobertura. O experimento foi realizado por seis anos, em delineamento de blocos ao caso, em arranjo fatorial 3x2, com três sistemas de manejo do solo - plantio direto (SPD), preparo reduzido (PPR) e preparo convencional (SPC) - e dois cultivos de cobertura, um de milho solteiro e outro de milho consorciado com mucuna-cinza (Stizolobium niveum) (MM), com quatro repetições. Os teores de COT, estimados para a camada 0,00-0,30 m, foram maiores em SPD e PPR. Independentemente da profundidade avaliada, o consórcio MM promoveu os maiores teores de carbono orgânico particulado (COP), que foram fortemente influenciados pela incorporação da palhada. Em todas as camadas, observaram-se correlações negativas entre os teores de COP e os de carbono orgânico associado a minerais (COAM), indício de ocorrência do efeito "priming". Os teores de COT correlacionaram-se positivamente aos de COAM, o que destaca a importância de mecanismos de estabilização da matéria orgânica no incremento dos teores de COT no solo