Examination of nanoparticulate phosphate rock as both a liming agent and phosphorus source to enhance the growth of spinach in acid soil

To examine the effect of nanoparticulate phosphate rock (NPR) as both a liming agent and phosphorus source in a tropical acid soil. The study examined five rates of NPR (0, 250, 500, 1000, or 2000 kg ha−1), which supplies 30, 60, 120 or 240 kg P ha−1, in a randomized complete pot experiment design with 3 replications. The pots of soil were incubated in a climate-controlled greenhouse for 21 days and then spinach was grown for 49 days. Soil parameters (pH, available P and exchangeable acidity), spinach parameters (leaf area, root hair surface area, root length and dry matter yield) and the effectiveness of NPR dissolution were estimated. The soil and plant parameters and the effective NPR dissolution all increased to the same degree at 1000 and 2000 kg NPR ha−1. Therefore, the use of 1000 kg ha−1 was most economically justified. Although, NPR has been appeared as an effective liming agent and phosphorus source in tropical acid soil. However, a regular application of NPR and further research for economic comparison between NPR and both of lime and superphosphate, as well as the original PR, will be needed.