Nutrient Uptake by Poa Pratensis From Oxidation of Elemental Sulfur Impregnated with Micronutrients.

Iron has been shown to improve verdure of Kentucky bluegrass (KBG; Poa pratensis L.) and other micronutrients are potentially beneficial. New fertilizers consisting of elemental S impregnated with Fe alone (S-Fe) or Fe, Zn, Mn, and Cu (S-micro) may provide an alternative source of Fe and other micronutrients. The effect of the S-Fe fertilizer on KBG was evaluated in three glasshouse studies, namely: (1) with or without Fe fertilizer applied as S-Fe, ferrous sulfate (FS), or Fe-EDDHA to soil (49 kg ha^-1 Fe), or foliar Fe-EDDHA (5 kg ha^-1 Fe) to one soil and two KBG cultivars; (2) increasing rates (0, 49, 197, or 592 kg ha^-1 Fe) of S-Fe either deep mixed or surface mixed with two soils; (3) 0 or 49 kg ha^-1 Fe applied as S-Fe to one soil and four cultivars. A field study comparing 0 or 49 kg ha^-1 Fe, Mn, and Zn soil applied as S-micro to KBG was also conducted. Results show that Fe from S-Fe was as efficiently absorbed as Fe from Fe-EDDHA applied to soil or foliage. Leaf Fe increased significantly with increasing rate in a curvilinear response when deep mixed with soil and a linear response when surface mixed. Leaf Fe, Zn, and Mn all increased as a function of field applied S-micro in relation to the untreated control. Thus, micronutrient uptake by shoots of KBG support S-Fe and S-micro as an equal replacement for chelated sources and better than other sources tested. However, there was no impact on growth or verdure from any treatment tested in these studies. These results are surprising in light of steps taken (over watering, N application and adding CaCO₃) in these studies to promote Fe chlorosis after none developed naturally and of previous reports of verdure improvements of KBG with Fe application. These data suggest that intensive breeding programs have produced KBG cultivars that are no longer highly susceptible to Fe-deficiency chlorosis stress. However, if Fe chlorosis is confirmed, S-Fe is a viable alternative to expensive and/or labor-intensive Fe chelates.