Enriching periphyton with phosphate-solubilizing microorganisms improves the growth and concentration of phosphorus and micronutrients of rice plant in calcareous paddy soil

Periphyton is usually present in most flooded land, especially in paddy fields, and plays an important role in the cycle of nutrients. However, the effects of using the periphyton enriched with its phosphate-solubilizing mi-croorganisms (PSM) on increasing the bioavailability of nutrients, especially phosphorus (P) and microelements and their absorption by rice plant have received little attention. In the research, the effect of natural periphytons and the natural periphytons enriched with PSM on the germination and vital index of rice seed and the bioavailability of P and micronutrients (Fe, Zn, Mn, and Cu) to rice plants in a calcareous soil fertilized with P fertilizer was investigated. Natural periphytons increased the germination index of rice seeds by an average of 42% and PSM-enriched periphytons by an average of 94%. The natural periphytons also reduced the survival of rice seedlings by about 10% on average, but the PSM-enriched periphytons increased this index by about 1%. On average, natural periphytons, due to increasing soil pH and competition with rice plant for nutrients, reduced soil available P, Fe, Zn, Cu and Mn by 15, 18.6, 39.8, 29.7 and 16.2%, respectively, compared to control. However, at the late stage of rice growth the PSM-enriched periphytons increased soil available P by 44%, soil available Fe by 14.6%, soil available Zn by 30.1%, soil available Cu by 25.7%, and soil available Mn by 13.4%, compared to natural periphytons, by releasing accumulated fertilizer P and micronutrients in decomposed periphytons, and thereby increased the rice growth and the concentration of these nutrients in rice grains. It can be concluded that the presence of periphytons in paddy fields, if they are used together with PSM, can be considered as an effective strategy to manage the cycle of P (P fertilizers) and micronutrients in calcareous paddy soils.