Soil phosphorous buffer coefficient as influenced by time and rate of P addition

Abstract

This study was conducted to investigate the effect of time and rate of phosphorus (P) addition on phosphorus availability and phosphorus buffer coefficient in some calcareous soils. Phosphorus was added to the samples at rates of 0, 50, 100, 200, 400, 600 and 800 mg P kg⁻¹ soil. The samples were incubated for 0.041, 1, 7, 14, 21, 30, 60 and 90 days at constant temperature and moisture. Extractable phosphorus was determined after the incubation. The results showed a sharp decrease in available P within 1 h after P addition. There was a linear relation between added P and extractable P in all soils. The buffer coefficients of soils were estimated by Olsen P for above incubation periods. Generally the buffer coefficient decreased with increasing time of incubation. The results indicated that inputs of between 23 – 59 mg kg⁻¹ are required to raise Olsen P by 10 mg kg⁻¹ in these calcareous soils, which assuming 2500 t soil ha⁻¹, gives a required input of 58 – 148 kg P ha⁻¹.

Keywords:

• Phosphorus availability
• phosphorus buffer coefficient
• incubation
• P addition
• P sorption

Acknowledgement

The author grateful to Dr D. L. Rowell (Reading University, Department of Soil Science, UK) who read and commented helpfully on a draft of the paper.