Phosphorus reserves and availability in soils receiving long-term manure applications
Indiati, R.R.ssi, N.
Communications in soil Science and plant analysis 3(9-10): 1589-1605
ISSN/ISBN: 0010-3624 DOI: 10.1081/css-120004301
In agricultural areas where intensive farming practices are common, applications of phosphorus (P) in amounts larger than crop requirements have led to an increased incidence of soils with a high P concentration. Accumulation of P in soil generally results in a greater potential for P enrichment of surface runoff and P losses during drainage. Estimating the size of the available P pool and the P supplying capacity of such soils is useful for calculating P-use efficiencies as related to agronomic practices and can be useful for assessing soil P characteristics that may have a negative impact on the environment. In this work, the available P content of 29 soils from farms with intensive confined animal operations was determined using eight traditional and three P-sink methods. The results obtained are discussed in relation to the degree of P saturation (DPS) of the same soils. The residual P availability status was evaluated via successive anion exchange resin membrane extraction of the soils. The cumulative P removed after eleven extractions fitted well a first-order equation, the asymptote of which represents the potential amount of desorbable P (Ultimate Releasable P). Relationships between the soil P test values and both the Ultimate Releasable P and the DPS lead to the conclusion that about 50% of the soils examined have a high potential for releasing P to surface and ground waters.