Composted Horse Manure as Fertilizer

Horse owners who dabble in vegetable gardening need not look far for a source of effective fertilizer. Scientists recommend using horse manure in gardens to increase vegetable yields and maintain soil integrity.

In a 20-year Chinese study of various types of fertilizers and soil conditioners on vegetable crop yields, the best results were found when a mixture of horse manure and nitrogen fertilizer was used. Using horse manure alone produced the second-best results.

The study was carried out by scientists from the Chinese Academy of Sciences and the University of California, Davis. The project also included measurements of soil enzymes and chemical characteristics.

Fertilizer treatments included in the study were no fertilizer, various levels of nitrogen fertilizer, various levels of composted horse manure, and a combination of horse manure and nitrogen fertilizer. Use of straight nitrogen fertilizer increased yield but led to a fall in total organic carbon in the soil. Applications of horse manure, either straight or mixed, resulted in soils with higher enzyme activities, more total organic carbon, and higher levels of total nitrogen, dissolved organic carbon, and microbial biomass carbon.

Overall, horse manure was judged to promote large harvests while sustaining desirable soil characteristics.