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Tropentag, September 20 - 22, 2023, Berlin

"Competing pathways for equitable food systems transformation:
trade-offs and synergies"

Synergistic effects of localised application of organic and phosphorus fertiliser on rice growth and yield in P-deficient upland soils of Madagascar

Masinirina Nomenjanahary Anny Ranjakason1, Aung Zaw Oo2, Vivivane Raharinivo1, Yasuhiro Tsujimoto2

1Centre National de Recherche Appliquée au Développement Rural (FOFIFA), Département de Recherche Rizicoles (DRR), Madagascar
2Japan International Research Center for Agricultural Sciences, Crop, Livestock and Environment, Japan


Rice is a crucial crop for Madagascar's agriculture, but upland rice farmers face challenges due to limited access to fertilisers and weathered soils that bind plant-available forms of phosphate. Effective fertiliser management is necessary to increase rice production. Low-cost strategies like P micro-dosing show promise for sustainable intensification, but they are underused due to a lack of awareness and technical capacity. Uncertain soil moisture conditions due to climate change can harm early rice growth through localised P application. Combining and localised application of farmyard manure (FYM)/vermicompost (VC) and P fertiliser can mitigate the risk of chemical injury to seedlings, and increase grain yield, making it a more effective solution.
In a pot trial, both individual treatments and a combination of FYM/VC at 0.8 t ha-1 and P fertiliser at 5 kg and 10 kg P ha-1 applied in the planting hole had a positive impact on early rice growth under consistent and adequate soil moisture conditions. However, when a farmer's field trial was conducted to evaluate the same treatments on shoot biomass and grain yield, applying P locally had a negative effect on the seedlings' initial growth. This was attributed to low soil moisture levels that caused chemical damage to the rice seedlings. However, when localised FYM/VC was used, no negative effects were observed, and shoot biomass increased. When FYM/VC and P were combined, FYM/VC helped to reduce the chemical injury caused by the P fertiliser. This combination further improved early rice growth, even under field conditions with high fluctuations in soil moisture.
At harvest, the response of grain yield to localised P application depended on the P rate. A high P rate (10 kg ha-1) increased grain yield by 7%, while a P rate of 5 kg ha-1 did not show any difference. Grain yield increased by 24% with localised application of FYM/VC than the control. There was no interaction between organic and P fertiliser, and their combined application additively increased grain yield by 51-82% than the control. In conclusion, utilising local organic resources along with localised P micro-dosing promotes sustainable upland rice production in P-deficient soils of Madagascar.

Keywords: Local resource use, Madagascar, micro-dosing, phosphorus, upland rice

Contact Address: Masinirina Nomenjanahary Anny Ranjakason, Centre National de Recherche Appliquée au Développement Rural (FOFIFA), Département de Recherche Rizicoles (DRR), Lot az 89 kii E, Antananarivo, Madagascar, e-mail: annyranjakason@gmail.com

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