Chile peppers (Capsicum annuum) were discovered by Spanish explorers in Central and South America and have been popular ever since for the robust heat they give to dishes. They have growing requirements similar to bell peppers, although they need less water and fertilizer, including manure. Chiles are grown throughout the milder climates of the United States as a food crop, and are usually consumed roasted, or dried and ground into powder. Some chiles are too hot to consume, but make decorative ornamental plants.
Excessive manure (or synthetic nitrogen fertilizer) reduces the amount of capsaicin in chiles. Capsaicin is the chemical compound that gives chiles their characteristic heat. Chile heat is determined partly by genetics, but also by growing conditions. For hotter chiles, use little or no manure, especially late in the growing season.
The primary nutrient in manure is nitrogen. Too much nitrogen-rich manure causes peppers to produce lush vegetative growth, but few fruits, according to Cornell University's horticulture website. Instead, fertilize peppers with a balanced vegetable fertilizer that contains phosphorus. Bonemeal, bat guano, and rock phosphate are organic sources of phosphorus.
Raw manure contains bacteria that may cause foodborne illnesses. These pathogens can contaminate peppers and other crops when manure is used incorrectly as a fertilizer. Manure should be thoroughly rotted or sterilized before application, according to the University of Minnesota Extension's Food Safety website. Apply raw manure to the soil the previous fall before planting your peppers to ensure that any bacteria has been killed.
As raw manure breaks down, it produces high levels of nitrogen. These nutrients can burn the leaves and roots of chile plants if placed too closely. Use well-rotted manure and work it into the soil at least two to three weeks before planting chile peppers to prevent root burn.
While excessive fertilizer-use may have negative effects, chiles do need some additional nutrients. A manure tea made by soaking manure in water provides nutrients at just the right concentration. Wet the soil thoroughly with manure tea immediately after planting and again four weeks later for healthy plants, suggests a horticulture agent at Colorado State University Cooperative Extension.
Synthetic fertilizers also burn chile peppers if applied too closely.