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Mycorrhizal inoculation decreases phosphorus supply dependency of four rice varieties

Rakotoarivelo M., Rahetlah V.B., Trap J., Autfray P.. 2021. Rome : Bioversity International, 1 p.. International Agrobiodiversity Congress. 2, 2021-11-15/2021-11-18, Rome (Italie).

In Madagascar, rainfed rice cultivation is constrained by soil acidity and the bioavailability of phosphorus (P) while farmers expanded upland rice thanks to improved varieties and manure self-production. A commercial biostimulant AGTIV GH 976 of the PREMIER TECH Company was tested in the field with the main hypothesis to improve crop P uptake through the development of a root mycelial system by field mycorrhizal inoculation. A field experiment was carried out over the 2019-2020 growing season with three factors (i) rice genetic (4 varieties), (ii) mycorrhizal inoculation (0 and 16 spores per seed), and (iii) phosphorus apply (0 and 20 P kg ha-1). Nutritional mycorrhizal environment was characterized by in-situ water pH measurements, rice growth indicators were taken at tillering, and grain yields measured at harvest. The results showed a significant increase of 0.6 pH unit (from 4.7 to 5.3), attributable to the localization effect of organic manure in rice holes. During tillering, the interaction of inoculation and phosphorus factors was significant on plant height, nitrogen nutrition (SPAD measurement) and till numbers. At harvest, the interaction of inoculation and phosphorus factors was significant on grain yield, with under 0 P 2.2 t ha-1 and 2.8 t ha-1, respectively with out and with inoculation. Under 20 P no significant effect of inoculation appeared respectively3.8 and 3.9 t ha-1. Our results supported the hypothesis that mycorrhizal inoculation improved, without P fertilizer, rice nutrition and completed manure application, with a final grain yield increase of 28%, whatever the variety used.

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