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To find an alternative tool to chemical analysis for assessing the nitrogen (N) nutritional status, the SPAD-Minolta-502 portable chlorophyll meter was tested in one- to three-years-old 'Rocha' pear trees fertilized with 0, 10, 20 and 40 kg N ha-1 year-1. SPAD readings in the third and fourth fully expanded leaves were as responsive to N fertilization as leaves sampled for foliar chemical analysis (medium third of one-year-old shoots), but individual leaves showed heterogeneous chlorophyll patterns. SPAD readings in leaves sampled at 60 and 110 days after full bloom (DAFB) related linearly with leaf N concentration but significant relationships could also be obtained later. Assuming an optimum leaf N concentration of ≥20 g kg-1 dry weight, SPAD readings ≥33 in leaves sampled at 60-110 DAFB corresponded to a good nutritional N status of young pear trees, making this diagnostic technique more practical, non-destructive and inexpensive, compared with chemical leaf analysis. [ABSTRACT FROM AUTHOR]

In Brazilian vineyards planted in sandy soils, nitrogen (N) should be applied at optimal rates and timing that correspond to greatest demand, thus minimizing N losses. The aim of this study was to evaluate the grapevine N distribution and recovery of urea- 15 N applied at budding and bloom. In 2009, in a vineyard ( Vitis vinifera cv. Cabernet Sauvignon) planted in Santana do Livramento, south Brazil, grapevines were treated with 10 kg N ha −1 at budding +10 kg N ha −1 at full bloom (10B + 10F); 20 kg N ha −1 at budding +20 kg N ha −1 at full bloom (20B + 20F); 20 kg N ha −1 at budding (20B); and 40 kg N ha −1 at full bloom (40F). Budding of grapevines in 2009 and 2010 was at the end of August and full bloom in November. In February 2010 and 2011, grapevine organs (leaves, berries, stem and roots) were collected, and in February 2011 soil samples were also collected in the profile. The wine-producing grapevines grown in the sandy soil took up more N derived from 20B treatment, compared with other N treatments, especially in the first crop season. The N derived from fertilizer applied at different rates and time was preferentially distributed in annual plant organs, but most N contained in the plant organs was derived from other sources than the fertilizer N. In the following season, 15 N applied in the previous year was recovered preferentially in leaves and fruits, again in low amounts. Nitrogen derived from fertilizer applied at different rates and time in a sandy soil apparently contributes little to grapevine nutrition. [ABSTRACT FROM AUTHOR]