Abstract Phosphorus (P) deficiency is a major yield constraint for lowland rice production on highly weathered soil in Sub-Saharan Africa. To overcome this constraint, we examined the effect of dipping seedling roots into a P-enriched slurry before transplanting (P-dipping) on yield and P use efficiency in the typical P-deficient lowlands in the central highlands of Madagascar. Experiment 1 was conducted at a high-elevation site (Site1) and consisted of three levels of P treatments, 0 P (no P applied), 60BP (60 kg ha–1 of P2O5 broadcasted), and 30DP (30 kg ha–1 of P2O5 applied via P dipping), combined with two levels of N treatments, −N (no N applied) and +N (total of 60 kg ha–1 applied). Experiment 2 was conducted continuously at Site1 and additionally at middle-elevation site (Site 2) following the same design but adding the 30BP treatment (30 kg ha–1 of P2O5 broadcasted). The 30DP treatment significantly and consistently accelerated initial biomass production with high crop growth rate (CGR) and shortened days to heading by 14 days compared to 0 P and by 6 to 9 days compared to 30BP and 60BP. The 30DP treatment increased grain yields by 59–171% relative to 0 P and, more importantly, by 9–35% relative to 30BP and 60BP, with a significant site × P-treatment interaction. The effect of P-dipping was consistent between the N treatments. The effect of P-dipping was particularly significant at a high-elevation and cool climate site (Site 1), which was partly attributable to the improved grain fertility by avoiding cold stresses at the reproductive stage. Furthermore, P-dipping achieved remarkably high agronomic P use efficiency (increase in grain yield per kilogram of P applied): 85–198 kg kg–1 across the sites. A set of on-farm trials revealed that P-dipping can increase both grain yields and P use efficiency, even with shorter growth durations, than equivalent or doubled P application rates via broadcasting. Because lowland rice production in Sub-Saharan Africa is widely subjected to environmental stresses and to highly P-deficient soils, P-dipping could be an efficient P fertilization technique for resource-limited farmers in the region. Further participatory farmers’ trials are expected to assess the farmers’ appreciation and potential constraints for adopting this technique.

中文翻译：

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将水稻幼苗浸入富含磷的泥浆中可提高谷物产量并缩短在马达加斯加中部高地缺磷低地的抽穗天数

摘要 磷（P）缺乏是撒哈拉以南非洲高度风化土壤上低地水稻生产的主要制约因素。为了克服这一限制，我们研究了在马达加斯加中部高地典型的缺磷低地，在移栽前将幼苗根浸入富含磷的泥浆中（浸磷）对产量和磷利用效率的影响。实验 1 在高海拔地点（Site1）进行，包括三个水平的磷处理，0 P（不施磷）、60BP（60 kg ha-1 P2O5 喷洒）和 30DP（30 kg ha-1的 P2O5 通过浸磷施用），结合两个水平的 N 处理，-N（不施用 N）和 +N（施用 60 kg ha-1）。实验 2 在站点 1 和另外的中海拔站点（站点 2）按照相同的设计连续进行，但增加了 30BP 处理（撒播 30 kg ha-1 P2O5）。30DP 处理显着且一致地加速了初始生物量生产，具有高作物生长率 (CGR)，与 0 P 相比，抽穗天数缩短了 14 天，与 30BP 和 60BP 相比，抽穗天数缩短了 6 至 9 天。30DP 处理相对于 0 P 增加了 59-171% 的谷物产量，更重要的是，相对于 30BP 和 60BP 增加了 9-35%，具有显着的位点×P 处理相互作用。P 浸渍的效果在 N 处理之间是一致的。P-浸渍的影响在高海拔和凉爽气候站点（站点 1）特别显着，这部分归因于通过避免生殖阶段的冷胁迫来提高谷物肥力。此外，浸磷实现了非常高的农学磷利用效率（每公斤施磷的谷物产量增加）：整个地点为 85-198 kg kg-1。一组农场试验表明，即使生长持续时间较短，浸磷也可以提高谷物产量和磷的利用效率，与通过撒施施磷量相当或翻倍相比。由于撒哈拉以南非洲的低地水稻生产广泛受到环境压力和高度缺磷的土壤的影响，对于该地区资源有限的农民来说，浸磷可能是一种有效的磷肥技术。预计进一步的参与式农民试验将评估农民对采用这种技术的欣赏和潜在限制。