Use of a chlorophyll meter for evaluating nitrogen fertilization in Tifton 85 bermudagrass

Abstract

The aim of this study was to assess the performance of a chlorophyll meter and its relation to dry matter production of Tifton 85 (Cynodon spp. cv. Tifton 85), in response to nitrogen fertilization. In the first field trial, the total chlorophyll contents extracted from the uppermost fully expanded leaf blade correlated well with chlorophyll meter readings and were affected by N rates and cut number. In the second cut in the first field trial, total chlorophyll contents were higher than the first cut while total dry mass of green shoots responded only to N rates, suggesting that there was a “luxury” production of chlorophylls. In the second field trial, at the end of a single regrowth period of 28 days, total chlorophyll contents, chlorophyll meter readings and dry leaf biomass varied harmonically, according to a quadratic model of response to N dose (0 - 600kg N/ha), without evidence of a supra- optimal production of chlorophylls. Although this last it is probably the normal situation, the refinement of the chlorophyll meter sensitivity to high levels of soil N availability, will demand news studies in order to clarify the status of the nitrogen fractions accumulated in the plant in these conditions.