Dipping rice seedlings in phosphorus (P)-enriched slurry at transplanting increases yield and avoids cold stress under P-deficient soils in the tropics
Phosphorus (P) deficiency is a major yield constraint for lowland rice production in Sub-Saharan Africa. Plant P uptakes are restricted not only by low P content in soils but also by high P-fixing capacity with abundant Al- and Fe-oxides in soils in the region. To overcome this constraint, we examined the effect of dipping seedling roots into a P-enriched slurry before transplanting (P-dipping) as shown in Figure 1.
First, we identified that initial rice growth can be substantially improved by the P-dipping (Fig. 2). The optimal duration of dipping and the P concentration in the slurry are less than 2 hours and 1.8%–2.6%, respectively. We further clarified that P-dipping can facilitate plant P uptakes by creating a soluble P hotspot at the plant base or near the root zone even in high P-fixing soils where P incorporation has no effect on rice growth (Fig. 3). Then, subsequent on-farm trials confirmed that P-dipping can significantly increase both grain yield and applied P use efficiency in the typical P-deficient lowlands of Madagascar (Fig. 4). The effect of P-dipping was particularly significant at a high-elevation and cool climate site, where the improved grain fertility is attributable to the avoidance of cold stresses at the reproductive stage because the technique shortens days to heading by 14 days compared to control (no fertilization) and by 6 to 9 days compared to conventional P application via broadcast.
Fig. 1. An illustration of the P-dipping technique
Fig. 2. Effect of P concentration in slurry and duration of P-dipping on initial plant growth
Fig. 3. Effect of P-dipping on plant growth and spatial distribution of soluble P content in the soils differing in P-fixing capacity
Both P-dipping and P incorporation treatments applied P at 40 mg pot−1. The numeric number in the spatial map indicates the average soluble P content (mg L−1) in the pot.
Fig. 4. Effect of P-dipping on grain yield and on cold degree days and fertility rate
Cold degree days is the sum of daily mean temperatures below 22 ºC from 15 days before to 7 days after heading. Fertility rate is the product of filled grain weight and filled grain rate.
Japan International Research Center for Agricultural Sciences Crop, Livestock and Environment Division
- Program name
- Research Project
Breakthrough in Nutrient Use Efficiency for Rice by Genetic Improvement and Fertility Sensing Techniques in Africa
- Term of research
- Responsible researcher
Tsujimoto Yasuhiro ( Crop, Livestock and Environment Division )KAKEN Researcher No.: 20588511
Oo Aung Zaw ( Crop, Livestock and Environment Division )
Kawamura Kensuke ( Social Sciences Division )
Nishigaki Tomohiro ( Crop, Livestock and Environment Division )KAKEN Researcher No.: 80795013
Rakotoarisoa Njato Mickaël ( Centre National de Recherche appliquée au Développement Rural, Madagascar )
- Publication, etc.
Oo AZ et al. (2020a) Agronomy 10(2):240https://doi.org/10.3390/agronomy10020240Oo AZ et al. (2020b) Scientific Reports 10:11919https://doi.org/10.1038/s41598-020-68977-1Rakotoarisoa N et al. (2020) Field Crops Research 254:107806https://doi.org/10.1016/j.fcr.2020.107806
- Japanese PDF
- English PDF
- Poster PDF
＊ Affiliation at the time of implementation of the study.