CORESTA Meeting, Agronomy/Phytopathology, 2017, Santa Cruz do Sul, AP 19

Organic fertilizer programs for tobacco seedling production

(1) North Carolina State University, Department of Crop & Soil Sciences, Raleigh, NC, U.S.A.; (2) North Carolina Department of Agriculture & Consumer Services, Agronomic Division, Raleigh, NC, U.S.A.

Organic tobacco production in North Carolina has increased in recent years. Despite increasing interest, little is known regarding the appropriate management of organic nitrogen sources in a seedling float system. Research was conducted in North Carolina to evaluate three organic nitrogen programs and their effects on float water nutrition and seedling growth. Treatments evaluated consisted of Peruvian Seabird Guano (SG), sodium nitrate (SN), or a combination of SG+SN. A conventional fertilizer source (SQM 16-5-16) was included for comparison. Treatments containing SN as the sole source of nitrogen failed to produce usable seedlings due to the absence of phosphorus in the selected fertilizer program. Seedling growth and development was acceptable in treatments comprised of SG or SG+SN, and was similar to that of 16-5-16. Ammonium float water concentration was greatest in SG treatments 25 days after seeding (DAS), but declined rapidly over the following 20 to 30 days. The decline in ammonium concentration was complimented by an increase in nitrate concentration during the same period. Bicarbonate concentration was greatest in SG only (≥12.0 meq/L) and SG+SN (≥3.0 meq/L) treatments 25 DAS but was <1.0 meq/L in SN only treatments, further implicating SG as a source of bicarbonates in organic float systems. Despite the high bicarbonate concentrations documented in SG treatments, seedling growth was not impacted. Seabird Guano and SG+SN based fertility programs produced seedlings comparable to 16-5-16 and appear to be suitable for the production of organic tobacco seedlings. These fertility programs should be managed to include additional nutrients, such as phosphorus, in order to provide a complete nutrition program. Furthermore, bicarbonates should be monitored and corrected accordingly.