Department of Soil Sciences and Water Management, Himachal Pradesh Krishi Vishva Vidyalaya, Palampur, 176 062, Himachal Pradesh
*Present address: Fertiliser Association of India, Near Jawaharlal Nehru University, New Delhi 110 067
A field experiment was conducted for two years on an acid (pH 5.6) and phosphorus responsive soil at Palampur (H.P.), to evaluate the suitability of phosphoric or nitric acid acidulated rock phosphate as a source of phosphorus in a wheat-black gram cropping sequence. Results revealed that (i) raw rock phosphate (without acidulation) was of no fertilizer value, (ii) acidulation at all the levels improved its effectiveness significantly, and (iii) samples acidulated with nitric acid proved as effective as those prepared with phosphoric acid at almost all the comparable levels of acidulation, in respect of crop yield, total phosphorus uptake and the apparent recovery of applied phosphorus. Further, it was observed that acidulation of rock phosphate to the extent of 50% with either of the two acidulants proved as effective as superphosphate. As regards the method of application of partially acidulated rock phosphate (PARP), band placement was inferred to be the best.
Acidulated rock phosphate, Alfisols, wheat-blackgram yield, P uptake
