The Influence of Manure Phytic Acid on Phosphorus Solubility in Calcareous Soils

Abstract

Manure characteristics can influence the potential for P transfer in runoff following land application of manures. This research assessed the influence of manure characteristics on P solubility in calcareous soils using manures from poultry (Gallus Domisticus) fed a variety of grain-based diets with the manures containing a range of total P (5.6-16.4 g P kg-1), water-extractable P (WEP, 0.9-4.7 g P kg -1), phytic acid P (0.1-7.6), total N/P ratios (2.6-5.1), and total C/P ratios (19.5-75.7). In addition, mono-ammonium phosphate fertilizer and reagent grade inositol hexaphosphate (phytic acid [PA]), were included, as well as a control treatment with no P additions. Treatments were incorporated into two soils (Portneuf [Coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcids] and Millville [Coarse-silty, carbonatic, mesic Typic Haploxerolls]) at three rates (10, 20, and 40 mg P kg -1) and incubated for a total of 18 wk with subsamples taken at 2, 5, 9, and 18 wk. Soil samples were analyzed for inorganic and organic NaHCO 3 (Olsen) extractable P and select soils were analyzed at 0 and 12 wk by 31P nuclear magnetic resonance spectroscopy (NMR) for soil P characterization. The percentage of WEP and PA (of total P) in the manures were linearly related (r 2 = 0.94). Increases in Olsen P over time were positively related to the percentage of monoester P in the treatments. At 2 wk, there was a strong negative correlation between the amount of PA added in the treatments and increases in Olsen P. However, by 18 wk, Olsen P was more closely related to the amount of C or N added with the treatments. Changes in PA content of manures due to dietary modification may influence P sorption on calcareous soils in the short-term while other characteristics such as C/P ratio may exert a stronger influence over changes in soil test P over longer time periods.

Phytate utilization and phosphorus excretion by broiler chickens fed diets containing cereal grains varying in phytate and phytase content

“…This finding supports previous work where analysis of excreta from broilers fed diets containing various cultivars of barley revealed that only trace amounts of phytate P were excreted, irrespective of the phytate P concentration of the initial feed (Leytem et al, 2007). However, as the diets in the studies by Maguire et al (2004) and Leytem et al (2006) also contained appreciable amounts of inorganic Ca and P, it could be expected that differences in the proportion of phytate P in the excreta were due to the detrimental effects of these minerals on intestinal phytate P hydrolysis.…”

“…Maguire et al (2004) reported that litter from birds fed maize-based diets contained 0.26-0.56 of P as phytate P, while concentrations in manure from layers fed maize-based diets ranged from 0.35 to 0.80 of total P (Leytem et al, 2006). Based on these findings, it was expected that there would be reasonable concentrations of phytate P in the excreta in the present study.…”

“…The environmental fate of phosphorus (P) in poultry manure is determined in part by its chemical composition (Leytem et al, 2006). Soil sorption capacity differs among the various forms of P with phytate P being very tightly bound to soil while other P forms such as phosphates are more mobile (Celi and Barberis, 2005).…”

Phosphorus utilization and characterization of excreta from swine fed diets containing a variety of cereal grains balanced for total phosphorus1

“…Therefore, manures that have a greater proportion of phytate P will have decreased WSP concentrations and WSP:TP. Examination of the available literature reveals a similar trend in swine feces (Baxter et al, 2003;Leytem and Thacker, 2008), broiler litter (Maguire et al, 2004;Toor et al, 2005), and manure from laying hens (Leytem et al, 2006).…”

“…Therefore, one would expect that storage of the manures in the present study would result in a further decrease in phytate content, possibly resulting in an increase in manure WSP. Additionally, Leytem et al (2006) reported that once manures are incorporated into soils, the manure phytate will break down over time, releasing soluble P, thereby ameliorating differences in manure WSP attributable to phytate content. Although the feces from the swine fed the corn diet had greater concentrations of phytate, and therefore less soluble P, the breakdown of phytate in storage and soils will release soluble P over time and will therefore ameliorate any benefits of this reduction in WSP.…”