Agronomic and Environmental Soil Phosphorus Testing in Soils Receiving Liquid Swine Manure
- A. M. Atiab and
- A. P. Mallarino *a
There is uncertainty concerning evaluation of bioavailable P in manured soils. This study assessed P availability in manured Iowa soils by measuring soil P with agronomic and environmental P tests and P uptake by corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Soil and plant samples were collected at the V5-V6 growth stage from trials established at nine locations that received various rates of liquid swine (Sus scrofa) manure, and from farmers' fields that received other animal manures. Soil P was analyzed by the Bray-P1 (BP), Olsen (OP), and Mehlich-3 (M3P) agronomic tests, and by the Fe-oxide impregnated filter paper (FeP), anion-exchange resin membrane (RP), and water (WP) environmental tests. Soil P at a 15-cm depth ranged from deficient to 15 times optimum levels for crops. Extracted P was highest for BP, M3P, and RP, intermediate for OP and FeP, and lowest for WP. Relationships between soil P extracted by the tests were linear, trends were similar for manured and unmanured plots, and correlation coefficients were ≥0.70 (correlations were poorest for WP). There was no conclusive evidence for differences between tests in detecting manure-derived soil P at most sites. However, in some conditions BP, M3P, OP, and RP may extract proportionally more manured-derived P than FeP and WP. Only the agronomic tests were significantly correlated (0.42 for M3P, 0.44 for BP, and 0.47 for OP) with plant P uptake across sites. Agronomic soil tests would predict plant P availability for crops better than environmental P tests in soils receiving liquid swine manure.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2002.