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Research Summaries

Manure Nutrients

Research Purpose

The objectives of this research project are to:

1. determine the optimum condition for maximal enrichment of volatile fatty acids (VFAs) and ammonia (NH3) in liquid swine manure through anaerobic digestion in laboratory scale experiments; and
2. investigate the toxic effect of conditioned manure on soybean cyst nematodes (SCN) eggs and juveniles through laboratory assays; and the efficacy in reducing infection of soybean roots by SCN and in lowering SCN population density through greenhouse experiments.

Recent Activities

The project has been completed according to the objectives listed above with all the information being collected and analyzed, and conclusions drawn.

What We Have Learned

Experimental results showed that the levels of VFA and ammonia would peak after 10 and 25 days of anaerobic digestion, respectively. The effect of raw and anaerobically digested liquid swine manures on the hatch and viability of the SCN was examined in both lab and field tests. The results showed that all filtrates of the raw, VFA-enriched, and NH4+-enriched manures at 10-250× dilutions inhibited SCN hatch, and the reduction of hatch increased with increasing concentration of the manure. The cumulative hatch at day 21 was only 2.1-3.7% in 10× dilution manures while that in water was 21-27.3%.

The high concentrations of manure appeared to be lethal to some eggs. Most of the SCN second-stage juveniles (J2) were killed when incubated for 8 hours in the manure filtrate at original concentrations (>90% mortality) or for 48 hours at the 64× dilution (>82% mortality). When J2 were treated with manures at 10-250× dilutions for 4 hours, only the 10× dilution of VAF-enriched and raw manures resulted in a lower number of J2 that penetrated soybean roots as compared with lower concentrations. The VFA-enriched manure was most, raw manure moderate, and NH4+-enriched manure least, effective in inhibiting SCN hatch and killing eggs.

Why is This Important?

Currently, rigorous efforts have been put forth to research alternative ways of using swine manure to recuperate its values besides fertilizer, with emphasis primarily on energy recovery through anaerobic digestion and fermentation. However, the beneficial use of swine manure should not be only limited to the energy sector and needs to be diversified to better promote waste recycling and reuse.

A promising area that has largely been untouched is the possibility of converting liquid swine manure into a pesticide, such as nematocide to deal with soybean cyst nematode (SCN), a known problem but with few effective controlling techniques available. Therefore, research is needed to develop either chemical or biological processes in order to engineer swine manure into a product with SCN control capability.

For More Information

Contact us at Jun Zhu, zhuxx034@umn.edu or (507)837-5625. For more information, read the following articles:

Xiao, J., J. Zhu, S. Chen, W. Ruan, and C. Miller. 2007. A Novel Use of Anaerobically Digested Swine Manure to Potentially Control Soybean Cyst Nematode. J. Environ. Sci. & Health Part B B42(6): 749-757.

Xiao, J., J. Zhu, S. Chen, W. Ruan, and C. Miller. 2007. Control of the Soybean Cyst Nematode Using Anaerobically Digested Liquid Swine Manure. Journal of Nematology 39(1): 73-73 (Abstract).

By Jun Zhu, Senyu Chen, Jianli Xiao, Curtis Miller, University of Minnesota

This report was prepared for the 2008 annual meeting of the regional research committee, S-1032 "Animal Manure and Waste Utilization, Treatment and Nuisance Avoidance for a Sustainable Agriculture". This report is not peer-reviewed and the author has sole responsibility for the content.