M. YAMINI, V. MUNASWAMY*, K.V. NAGA MADHURI AND Y. REDDI RAMU

Department of Soil Science and Agricultural Chemistry, S.V. Agricultural College, Tirupati-517502, Andhra Pradesh, India.

ABSTRACT

Status of soil phosphorus fractions under rainfed groundnut monocropping system was studied in a long-term field experiment during Kharif, 2014 being conducted at Regional Agricultural Research Station, Tirupati. The soil of experiment field was slightly acidic, non-saline, low in organic carbon and free CaCO3 contents. The soil was low in available nitrogen, medium in phosphorus and medium to high in potassium. The micronutrients status of the experimental field was above critical levels. Inorganic P fractions like Al-P, Fe-P, O-P, Ca-P, organic P, total P and available P at 0-15 cm depth before sowing of the crop ranged from 20.43 to 37.62, 34.46 to 57.12, 16.97 to 31.31, 14.20 to 22.01, 27.25 to 54.50, 112.87 to 192.78, 27.00 to 45.00 mg kg-1, respectively. At harvest the P fractions like Al-P, Fe-P, O-P, Ca-P, organic P, total P and available P at 0-15 cm depth ranged from 17.06 to 33.20, 31.87 to 53.31, 14.87 to 28.31, 10.62 to 20.25, 30.65 to 56.80, 105.40 to 180.52, 21.00 to 45.00 mg kg-1, respectively. Similarly at 15-30 cm depth the inorganic P fractions like Al-P, Fe-P, O-P, Ca-P, organic P, total P and available P before sowing ranged from 16.91 to 31.90, 32.27 to 49.95, 15.92 to 25.06, 12.57 to 22.72, 25.25 to 51.25, 106.72 to 185.47, 27.00 to 41.00 mg kg-1, respectively and at harvest, these ranged from 15.62 to 29.68, 30.00 to 47.50, 13.75 to 25.25, 14.25 to

20.56, 26.30 to 52.42, 101.97 to 175.77, 23.00 to 36.00 mg kg-1, respectively.

KEYWORDS:

Inorganic P fractions (Al-P, Fe-P, Occluded P and Ca-P), Organic P, Total P