Effectiveness of arbuscular mycorrhizal colonization at nursery-stage on growth and nutrition in wetland rice (Oryza sativaL.) after transplanting under different soil fertility and water regimes

Abstract

Abstract In order to analyze the effectiveness of colonization by arbuscular mycorrhizal fungi (AMF) at the nursery stage on the growth and nutrient concentration of wetland rice after transplanting, the experiments were conducted under glasshouse conditions using two types of soil, namely (i) sterilized paddy soil (PS) and (ii) sterilized paddy soil diluted with sterilized Andosol subsoil 5 times (DS) under two water regimes, (i) flooded conditions changed to non-flooded conditions 30 d before harvest (F-NF) and (ii) continuous flooding (CF) up to harvest. Treatments consisting of mycorrhizal inoculation (+AMF) and non-inoculation ( — AMF) were applied only at the nursery stage when the seedlings were produced under dry nursery (60% moisture of maximum water holding capacity) conditions. Seedlings grown in PS showed a significantly higher biomass yield and nutrient concentrations than in DS. At 90 and 105 d after transplanting, the mycorrhizal plants showed a higher biomass than non-mycorrhizal plants in PS whereas there were no differences in DS except for roots. Mycorrhizal colonization at the transplanting stage was higher in DS than in PS. However, after transplanting opposite results were obtained, the level in PS being relatively higher than in DS. Grain yield and P concentration of unhulled grain and shoots in PS were higher in the +AMF treatments than in the -AMF treatments under both water regimes. Contents of micronutrients (Zn, Cu, Fe, and Mn) were higher in the +AMF plants than in the -AMF ones at all growth stages up to maturation irrespective of soil fertility and water regimes. These results suggest that AMF inoculation at the nursery-stage was beneficial for wetland rice after transplanting to flooded conditions in terms of growth promotion and increase of nutrient concentrations.