Tropentag 2023, September 20 - 22, Berlin, Germany "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

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

Abstract

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: annyranjakasongmail.com