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This article in JEQ

  1. Vol. 14 No. 2, p. 246-251
     
    Received: May 4, 1984
    Published: Apr, 1985


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doi:10.2134/jeq1985.00472425001400020018x

Reaction of Fertilizer and Liquid Manure Phosphorus with Soil Aggregates and Sediment Phosphorus Enrichment1

  1. V. K. Bhatnagar,
  2. M. H. Miller and
  3. J. W. Ketcheson2

Abstract

Abstract

Phosphorus enrichment ratios (PER) were estimated for sediment from six runoff events from plots that had been under one of three management systems for at least 5 yr: no-till (NT), no-till manured (NTM), and fall plowed manured (FPM). Sodium bicarbonate-extractable P enrichment ratios (Ext-PER) in sediment were 2.15, 1.30, and 1.10 for NT, NTM, and FPM treatments, respectively. The higher Ext-PER on the NT treatment could not be explained solely by a higher clay enrichment.

A laboratory experiment was conducted to test three hypotheses developed to explain the difference in Ext-PER values. Phosphorus in the form of either inorganic salt (KH2PO4) or liquid poultry manure (chicken, Gallus gallus domesticus) was added to soil at rates up to 400 mg P kg−1. Soils were passed through 7-d wetting and drying cycles for 235 d and sampled periodically. Most of the added P from both the manure and inorganic P treatment was associated with the clay fraction. The proportion of P that was desorbable increased as the amount of P added increased. This may, in part, explain the lower Ext-PER on the manured plots, which had a greater amount of P added. Manure increased water stability of soil aggregates. In addition, the Ext-P concentration in water-stable aggregates from the manure treatment increased with increasing aggregate size, whereas the inorganic P source had no effect. Manure did not alter the size distribution of dry-sieved aggregates, but Ext-P was increased to a greater extent in the larger aggregates, indicating that there was a preferential sorption of manure P by larger-sized aggregates. This conclusion was supported by results from a small field trial. The preferential sorption of P from liquid manure by larger, more stable aggregates may result in a lower Ext-PER in sediment from manured fields.

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