Agronomic effectiveness of partially acidulated rock phosphates with 50 per cent dilute mineral acids. viz. HNO3. HCI. H2SO4 and H3SO4 was tested under field conditions on an acid soil (Inceptisol) with potato (var. Klufri Jyoti) as test crop. Partially acidulated products (PARP) applied @ 80 kg P20S ha−1 resulted in significant increase in tuber yield over untreated Mussoorie (MRP) and Lalitpur (LRP) rock phosphates as well as superphosphate (SSP). Among the different PARP products, the sulphuric acid product (H2SO4-PARP) was found superior and recorded highest tuber yield, maintained highest available P status in soil, higher as similation and uptake of N and P by crop. Further, H2SO4 acidulated product had pronounced effect on availability coefficient ratio (ACR), phosphorus use efficiency (PUE) and relative agronomic effectiveness (RAE). Between the two rock phosphate sources. Lalitpur rock phosphate (LRP) was much more effective than Mussoorie rock phosphate (MRP) with respect to tuber yield. P availability, ACR, PUE and RAE. Among the different acidulants. H2SO4 was the best acidulant followed by H3SO4. HCI and HNO3 for acidulation of rock phosphates. RAE of PARP products followed the order as: H2SO4 - PARP > H3SO4 -PARP > HCI-PARP > HNO3 -PARP > RP > SSP.
Partially acidulated rock phosphate, availability coefficient ratio, agronomic effectiveness, acidulant, Lalitpur rock phosphate, Mussoorie rock phosphate
