Nitrogen supply reduces the earthworm-silicon control on rice blast disease in a Ferralsol

Blanchart Eric, Ratsiatosika Onja, Raveloson Harinjaka, Razafimbelo Tantely Maminiana, Razafindrakoto Marie-Antoinette, Sester Mathilde, Becquer Thierry, Bernard Laetitia, Trap Jean. 2020. Nitrogen supply reduces the earthworm-silicon control on rice blast disease in a Ferralsol. Applied Soil Ecology, 145:103341, 8 p.

https://doi.org/10.1016/j.apsoil.2019.08.003

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Quartile : Q2, Sujet : SOIL SCIENCE

Résumé : Revealing belowground-aboveground relationships (BAR) is essential to drive ecological processes to address agriculture dysfunctions, especially in the management of aboveground plant diseases. Earthworms are one of the most important soil organisms involved in BAR, and silicon (Si) has been identified as a crucial element regulating aboveground plant health. How earthworm-Si interactions induce BAR in poor- and rich-nutrient soil contexts is still poorly understood, despite a growing interest in agricultural sustainability. We investigated the potential of BAR induced by the earthworm-silicon interaction to control the severity of rice blast disease in a Ferralsol in Madagascar, with or without NPK fertilization. We conducted a greenhouse microcosm experiment in which we manipulated the presence of the endogeic earthworm Pontoscolex corethrurus and the fungus Pyricularia oryzae in a Ferralsol supplied or not with Si and fertilized with macronutrients (nitrogen, phosphorus and potassium, i.e., NPK). After eight weeks of growth, plant biomass, nutrition and disease severity were measured. Our results validated the hypothesis that a dual treatment of earthworm inoculation and Si fertilization in a nutrient-poor tropical soil confers a higher tolerance of rainfed rice to P. oryzae, in comparison with treatments with only earthworms or Si, providing the optimal agronomic balance between a gain in biomass (and nutrition) and a reduction in disease severity. The supply of macronutrients altered this positive BAR by favouring the phenomenon of N-induced susceptibility. The aboveground plant C:N ratio of 15 is a threshold below which any increase in N per C unit likely enhances blast disease. The role of belowground interactions to counteract agricultural dysfunctions is supported by our study. To accomplish ecological intensification and provision of ecosystem services such as disease regulation, our findings recommend replacing excessive use of macronutrient fertilizer with sustained agricultural practices promoting the development of earthworm populations, such as organic matter inputs, superficial or no tillage, and the use of cover crops or conservation agriculture.

Mots-clés Agrovoc : Pyricularia oryzae, Oryza, pyriculariose du riz, nutrition des plantes, ver de terre, fertilisation, azote, ferralsol

Mots-clés géographiques Agrovoc : Madagascar

Mots-clés complémentaires : Pyriculariose, Pontoscolex corethrurus

Mots-clés libres : Belowground-aboveground relationships, Disease severity, Plant nutrition, Pontoscolex corethrurus, Pyricularia oryzae, Madagascar

Classification Agris : H20 - Maladies des plantes
F61 - Physiologie végétale - Nutrition
F04 - Fertilisation

Champ stratégique Cirad : CTS 4 (2019-) - Santé des plantes, des animaux et des écosystèmes

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