Room‐Induced Changes of Potassium in the Rhizosphere of Lowland Rice uri icon

abstract

  • Potassium (K) deficiency in paddy soils has become the most limiting factor for increasing rice (Oriza Sativa L.) yield. It is important to increase K use efficiency in irrigated rice production systems. In this study, the changes of different K fractions in the rhizopshere of lowland rice were examined at low and adequate K supply using a rhizobox technique. The results obtained indicated that the roots of lowland rice caused changes of soil K fractions in the rhizosphere. The depletion of readily available K and exchangeable K in the rhizosphere could extend over 10 turn from the root surface at both the low and adequate K supply levels. The readily released K and slowly released K in the rhizosphere of lowland rice depleted 6-8mm from the root surface at low K level, whereas up to 2-4mm from root surface were depleted at the adequate K supply. The rice roots also induced the depletion of mineral-K in the rhizosphere, within 0-2mm and 0-3mm from the root surface for the low K and the adequate K treatments, respectively. The depletion of these five fractions of K and decrease of pH in the rhizosphere of lowland rice was greater at low K supply than at the adequate K supply. The fertilizer K applied was mainly in the forms of readily available and exchangeable fractions in the soil. These results imply that rice roots could increase the solubility and availability of potentially available K and even mineral-K in the rhizosphere under submerged condition, partially due to the dramatical decrease of pH by rice plant roots in the rhizsophere. The decrease in pH may partially result from the oxidation of Fe (11) in the rhizophere. High K dramatically enhanced Fe (11) oxidation within 1-2mm from the root surface. It is suggested that improving rice root morphology and physiology for efficiently uptake and use of potentially available K in the rhizosphere would be important for increasing K use efficiency in lowland rice.

publication date

  • 2005
  • 2005
  • 2005