ARS | Publication request: Effects of Organic and Inorganic Fertilizers on Marigold Growth and Flowering

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 2010
Publication Date: September 1, 2010
Citation: Bi, G., Evans, W.B., Witcher, A.L., Spiers, J.M. 2010. Effects of Organic and Inorganic Fertilizers on Marigold Growth and Flowering. HortScience. 45:1373-1377.

Interpretive Summary: Recent movements toward naturally managed gardens and the growing interest in managing the environmental impacts of agriculture have led to the development of organic and natural fertilizers that may be suitable for commercial use. Annual broiler chicken production in the U.S. was approximately 50 billion pounds in 2007, and broiler chicken litter (manure plus bedding) may be produced at a rate of at least 1 ton per 1,000 broilers; thus, there is an abundant supply of chicken litter available for fertilizer and other uses. For growers wishing to use these and other natural fertilizers in their production systems, the biggest question is how the fertilizers need to be managed. Two experiments were conducted to evaluate the growth and flowering responses of greenhouse-grown French marigold to various application rates of two non-composted broiler chicken litter-based organic fertilizers and one commonly used synthetic controlled-release fertilizer. Results from both studies demonstrated an increase in synthetic fertilizer a low to high rate resulted in an increase in plant growth. However, the greatest plant growth obtained from the organic fertilizers occurred with the low to intermediate rates. The high rates of each organic fertilizer resulted in stunted plant growth possibly due to high substrate soluble salt concentrations. Results from this study indicated that broiler litter-based materials have the potential to be used as organic fertilizer sources for container production of marigolds in greenhouses. However, growers need to be cautious with the rate applied. Since different crops may respond differently to these natural fertilizers, it is important for growers to test any new fertilizers before incorporating them into their production practices.

Technical Abstract: Two experiments were conducted to evaluate the growth and flowering responses of greenhouse-grown French marigold (Tagetes patula L. ‘Janie Deep Orange’) to two non-composted broiler chicken litter-based organic fertilizers 4-2-2 and 3-3-3, and one commonly used synthetic controlled-release fertilizer 14-14-14. In both experiments, fertilizer 4-2-2 was applied at four rates of 1%, 2%, 4%, and 6% (by volume), 3-3-3 was applied at four rates of 1.34%, 2.67%, 5.34%, and 8.0% (by volume), and 14-14-14 was applied at rates of 0.99, 1.98, 3.96, and 5.94 kg•m-3. In general, substrate containing different rate and source of fertilizers had a pH within the recommended range of 5.0 to 6.5. EC was similar among substrates containing different rates of 14-14-14, however, EC increased with increasing fertilizer rate for substrates containing 4-2-2 and 3-3-3. Substrate EC within each treatment was generally higher earlier in the experiment. For the fertilizer rates used in these two experiments, increasing 14-14-14 fertilizer rate increased plant growth and flowering performance. However, low to intermediate rates of 4-2-2 and 3-3-3 in general produced the highest plant growth index, shoot dry weight, number of flowers per plant, total flower dry weight, and root rating. Plants grown at high rates of 4-2-2 and 3-3-3 showed symptoms associated with excessive fertilization. Plant tissue N, P, K, Fe, and Zn concentrations increased linearly or quadratically with increasing fertilizer rates for all three fertilizers. In general, plants receiving 4-2-2 and 3-3-3 had higher concentrations of N, P, K, Fe, Mn, Zn, and Cu than plants receiving 14-14-14. Results from this study indicated that broiler litter-based 4-2-2 and 3-3-3 have the potential to be used as organic fertilizer sources for container production of marigolds in greenhouses. However, growers need to be cautious with the rate applied. Since different crops may respond differently to these natural fertilizers, it is important for growers to test any new fertilizers before incorporating them into their production practices.