Nitrogen bound to manure fiber is increased by applications of simple phenolic acids

Abstract

Abstract Background Polyphenolic compounds like tannins can increase nitrogen (N) excreted in feces when consumed by ruminants but less often noted is increased N in fecal acid detergent fiber (ADF-N). Some simple phenolics are thought to facilitate binding interactions between nitrogenous compounds and soil. We hypothesized that contact with common phenolic acids, such as found in crops, could increase ADF-N, in excreted manure. Methods We performed two separate experiments to test our hypothesis. In the first experiment, we applied three solutions (i.e., 0.001, 0.01, 0.1 M) of sodium benzoate (B0), sodium 4-hydroxybenzoate (B1), 3,4-dihydroxybenzoic acid (B2), gallic acid (B3), ammonium benzoate (AB), and ammonium chloride (AC) to dried pulverized manure and measured ADF-N. In the second experiment we modified the methodology, by applying more compounds at a single concentration (0.001 M) and including an added nitrogen (NH4Cl) treatment. Results We found a statistically significant interaction between treatment and concentration in the first experiment (P < 0.0001), but the main effects were inconsistent and there was no significant difference between the treatment means and the control mean (samples treated with water). Conversely, we observed a significant treatment effect in the second experiment (P < 0.0001), but no significant effect of the added N or interaction. Samples treated with water, B0, or B3 were similar and indistinguishable from untreated manure. The treatment with B1, caffeic acid, (CAF), or B2 increased ADF-N from 13.2 to 17.5% while +(−)catechin (CAT), and p-coumaric acid (p-COUM), increased it by 19.7 and 22.2% respectively. Epigallocatechin gallate (EGCG) and ferulic acid (FER) increased ADF-N by 32.6 and 34.1%, respectively. Conclusions The results support our hypothesis that N in manure can complex with manure ADF following exposure to benzoic acid and especially cinnamic acid derivatives. This resulted in greater amounts of N bound to relatively recalcitrant fibers in excreted manure. Thus, N mineralization may be impacted by increasing or decreasing the amount of N bound to manure fibers or other recalcitrant soil compounds such as lignin, but it is unclear whether such N would be less available to plants, or for volatilization, or leaching.

Keywords

• Manure
• Acid detergent fiber
• Nitrogen
• Phenolic acids
• Hydroxybenzoic acids
• Hydroxycinnamic acids