Organic fertilizers such as manure, bonemeal, bloodmeal and other soil supplements from plants, animals or minerals can add nutrients back into the soil and encourage stronger, healthier plant growth. These fertilizers are used in organic farming and gardening instead of chemical alternatives. Because these substances occur in nature, many people view them as safer than chemical fertilizers. However, risks are involved with the use of any kind of fertilizer--including organic.
Damage to Plants
Too much of any kind of fertilizer can burn plants, whether that fertilizer is chemical or organic. The University of Utah Cooperative Extension cautions that many organic fertilizers contain high levels of salts which can be damaging to plants when over-applied.
Improperly composted fertilizer may take nitrogen from the ground to use in the decomposition process, temporarily robbing plants of the nutrients they need. Use only well-composted materials in the garden.
Organic fertlizers such as manure can contain harmful bacteria. Be careful when handling any fertlizers. Don't breathe in the dust from bonemeal and bloodmeal, and wear gloves to handle any kind of fertilizer. If you come in contact with the fertilizer, wash with soap and water as soon as possible.
The use of uncomposted manure in gardens can lead to contamination of the garden with E. coli, a bacteria that can cause stomach upset, illness and in severe cases, death, according to the Colorado Extension Service. Always compost manure thoroughly to prevent contamination. Wash all produce before eating and wash your hands after working in the garden.
If more fertilizer is applied to the land than plants can readily use, the excess nutrients can be washed away during rainstorms or routine irrigation. This can release too much nitrogen, phosphorus and other nutrients into waterways, resulting in algae bloom, killing fish, and otherwise damaging the water way. Only use the amount of fertilizer necessary to meet the nutritional needs of the plants. Levees around fields near streams or waterways can help prevent run-off during periods of excess rain.