PS 24-3 - Assessing the response of above- and below-ground communities to various fertilizer regimes in small scale agroecosystems

Thursday, August 11, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
Raymon Shange1, Niyi S. Omidire2, Victor Khan1, Russell Bean1, Jewell Bean1 and Ramble O. Ankumah2, (1)Carver Integrative Sustainability Center, Tuskegee University, Tuskegee, AL, (2)Department of Agricultural and Environmental Sciences, Tuskegee University, Tuskegee, AL

Researchers have often been engaged in demonstrating the impacts of both organic and chemical fertilizers in terms of nutrient availability and the long-term effects on soil, plants, and the environment. This research study was conducted to assess the difference in above and belowground ecology of an agroecosystem under differential fertilizer regimes under plastic mulch/drip irrigation. The treatments were Inorganic fertilizer (NPK 13:13:13 + ammonium nitrate mixed in 3:1 ratio); Inorganic/Organic fertilizer “Farmer’s Mix” (NPK 13:13:13 + ammonium nitrate mixed in 3:1 ratio + Bio-grow) plus microbe mix; and Organic Fertilizer – Mighty Grow (4-3-4) with a microbe mix. All fertilizers were applied prior to mulch application after which the following crops squash (Cucurbita pepo L.), cucumber (Cucumis sativus L.), and okra (Abelmoschus esculentus L. Moenchwere directly seeded in a complete randomized design.


Aboveground results showed that the inorganic fertilizer had higher yields (lbs/acre) and numbers of fruit (nos/acre) than organic fertilizer (p<0.05). The addition of microbes to the inorganic fertilizer consistently increased the numbers of cucumbers and squash per acre with their highest yields being 72,791.33 and 31,931.33 respectively. Overall, Inorganic fertilizer with the addition of microbes significantly increased yields and numbers (of  fruits) for all crops compared to the organic-based fertilizer. Soil bacterial results demonstrated communities with a significant response to fertilizer treatment under plastic mulch. Actinobacteria (copiotroph) showed a significant drop in the Inorganic fertilizer treatment only, while Acidobacteria (oligotroph) populations responded negatively to the presence of inorganic fertilizer in both the “Inorganic Fertilizer” and the “Farmer Mix”. Additionally, both diversity (Shannon Wiener Index) and richness estimates are greater in the “Farmers Mix” than the control with no significant differences amongst the fertilizer treatments. Given these results, both treatments are seen as beneficial to belowground ecology, while the “Farmers Mix” presents the largest increase in yield. Further studies into the shifts in species as well as the nutrient cycling enzymes will elucidate more about the functional and structural dynamics of the soil community.