Abstract
Abstract The objective of this research was to evaluate the technical feasibility of SPAD index in the diagnosis of N status in ‘Esmeralda’ peach. The field trial, with five N rates applied to the soil (0, 40, 80, 120 and 160 kg ha-1 of N as urea form) was conducted in a randomized block design with four replications. During the years 2014, 2015, 2016 and 2017, SPAD readings were carried out with a Minolta SPAD-502 chlorophyll meter, in the leaf middle part, in 40 leaves per plot. The leaf N content determination was performed in CHN-S Elemental Analyzer. SPAD index and leaf N content increased in a linear way in response to increasing N rates applied in soil. There was a positive linear correlation between SPAD index and N concentration in leaves (0.652; 0.756; 0.762 and 0.767, p<0.05). SPAD index can be used for nutritional N diagnosis purpose in peach when readings are taken between the 13th and 15th weeks after full bloom. In the range between 39 and 49, the SPAD index indicates the leaf N content is included in “normal” class (33 – 45 g kg-1) of agronomic interpretation for the States of Rio Grande do Sul and Santa Catarina, Brazil.
Highlights
IntroductionLevels of leaf nutrients are those that best represent tree nutritional status, the standard period of leaf sampling in peach trees is very close to the fruit harvest season, which makes it difficult to use leaf chemical analysis to adjust fertilization recommendations for the same fruit production cycle (NAVA and CIOTTA, 2013)
The evaluation of nutrient contents in peach tree is based on macro (N, P, K, Ca and Mg) and micronutrient (B, Fe, Cu, Mn and Zn) concentration in leaves collected from the median portion of shoots of the year, between the 13th and 15th weeks after full bloom (CQFS-RS/SC, 2016), a period in which there is greater stability of leaf nutrient concentration and, considered as a standard for leaf sampling for nutritional diagnosis purposes
Levels of leaf nutrients are those that best represent tree nutritional status, the standard period of leaf sampling in peach trees is very close to the fruit harvest season, which makes it difficult to use leaf chemical analysis to adjust fertilization recommendations for the same fruit production cycle (NAVA and CIOTTA, 2013)
Summary
Levels of leaf nutrients are those that best represent tree nutritional status, the standard period of leaf sampling in peach trees is very close to the fruit harvest season, which makes it difficult to use leaf chemical analysis to adjust fertilization recommendations for the same fruit production cycle (NAVA and CIOTTA, 2013). It appears that leaf chemical analysis is a technique that is still little used by peach growers in the State of Rio Grande do Sul, mainly due to cost and delay in receiving results, not allowing to be used for recommendation purposes during the current growing cycle
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