Change point in phosphorus release from variously managed soils with contrasting properties
2005
Neri, U. | Diana, G. | Indiati, R.
Investigating the relation between concentration or release of phosphorus (P) into soil solution (CaCl2-P, determined by 0.01 M CaCl2 extraction of soils) and soil test phosphorus (Olsen P, or 0.5 N NaHCO3-extractable soil phosphorus) for 10 widely ranging and variously managed soils from central Italy, a change point was evident where the slopes of two linear relationships meet. In other words, it was possible to distinguish two sections of the plots of CaCl2-P against Olsen P, for which increases of CaCl2-P per unit of soil test P increase were significantly (p < 0.05) greater above than below these change points. Values of change point ranged from 14.8 to 253.1 mg kg(-1) Olsen P and were very closely correlated (p < 0.001) to phosphorus sorption capacity of soils. Similar change points were also previously observed when Olsen P (and also Mehlich 3 P) of surface soils was related to the P concentration of surface runoff and subsurface drainage. Because insufficient data are available relating P in surface soils and amount of P loss by overland, subsurface, or drainage flow, using the CaCl2 extraction of soil can be convenient to determine a change point in soil test P, which may be used in support of agricultural and environmental P management.
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