Nitrogen uptake and biochemical activity in maize rhizosphere during growth on acidic and neutralized soils

This work aimed to understand the effects of liming and no tillage on the pH stability and inorganic N uptake in the rhizosphere of maize plants on an acidic soil depleted in organic matter, reclaimed by liming and no tillage in a long-term field trial. We analyzed the inorganic N dynamics, respiration, microbial biomass and enzyme activities in the rhizosphere and bulk soil of maize plants grown in rhizoboxes on acidic soil under conventional tillage or no tillage management with or without liming and amendment (sugar beet foam and red gypsum). Analysis of inorganic N in the rhizosphere showed preferential NH4+-N uptake and reduced NO3−-N uptake by maize plant grown on acidic non tilled soil. With few exceptions, soil respiration, microbial biomass and enzyme activities were higher in the maize rhizosphere than in bulk soil. Soil respiration and enzyme activities were generally higher in the rhizosphere of non-tilled soils, whereas microbial biomass was higher in the rhizosphere of the amended soils. The study, based on rhizobox, showed effectiveness of sugar beet lime and red gypsum in the neutralization of the pH value in the rhizosphere during the early stages of maize growth, and the limited capacity of the plant to neutralize the acidic soil pH value in the rhizosphere of the non-amended soil. Positive interactive effects of tillage and liming were observed on the biochemical activity in the plant rhizosphere that could contribute to explain the positive effects of this management practice on the soil fertility observed at field scale on the long term.