Analysis of Petiole Sap Nutrients Using Rapid and Standard Methods and Its Relation to Leaf Analysis of Fertilized <i>Malus domestica</i> cv. Gala
Mariana Mota,
M. João Martins,
Layanne Sprey,
Anabela Maurício,
Cristina Rosa,
João Faria,
Miguel B. Martins,
Miguel L. de Sousa,
Ricardo Santos,
Rui M. de Sousa,
Henrique Ribeiro,
Cristina M. Oliveira
Affiliations
Mariana Mota
LEAF—Linking Landscape, Environment, Agriculture and Food Research Center, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
M. João Martins
CEF—Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
Layanne Sprey
LEAF—Linking Landscape, Environment, Agriculture and Food Research Center, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
Anabela Maurício
FRUBAÇA-Cooperativa de Horto-Fruticultores, C.R.L. Lugar Acipreste Aptd. 12, 2460-471 Alcobaça, Portugal
Cristina Rosa
GRANFER-Produtores de Frutas, CRL. Rua Principal 167, 2510-772 Usseira, Portugal
João Faria
GRANFER-Produtores de Frutas, CRL. Rua Principal 167, 2510-772 Usseira, Portugal
Miguel B. Martins
LEAF—Linking Landscape, Environment, Agriculture and Food Research Center, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
Miguel L. de Sousa
INIAV, I.P., Polo Alcobaça, Estrada de Leiria, 2460-059 Alcobaça, Portugal
Ricardo Santos
CAMPOTEC IN-Cons. e Transformação de Hortofrutícolas, SA. EN 9, 2560-393 Torres Vedras, Portugal
Rui M. de Sousa
INIAV, I.P., Polo Alcobaça, Estrada de Leiria, 2460-059 Alcobaça, Portugal
Henrique Ribeiro
LEAF—Linking Landscape, Environment, Agriculture and Food Research Center, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
Cristina M. Oliveira
LEAF—Linking Landscape, Environment, Agriculture and Food Research Center, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
Currently, fertilization decisions in apple orchards are based on soil and leaf analyses while the leaf material is sampled after the growing season, usually in June–July (90–110 days after full bloom). This approach is inefficient, as the information becomes available later than the growing season and is therefore only useful in supporting fertilization decisions for the next year, not the current one. To establish a method that provides useful information for fertilization decisions earlier in the growth cycle, our research focused on the assessment of the nutrient content of petiole sap using different methods, the standard method and the rapid method using a reflectometer. For this study, in 2021, four ‘Gala’ orchards were fertilized with different N–P–K levels. Macro and micronutrients were determined in leaves and petiole sap at 45 and 90–110 days after full bloom (DAFB) using standard laboratory methods and the reflectometer. When leaf analysis at 45 and 90–110 DAFB was compared with petiole sap analysis at the same time point, no significant correlations were found between the nutrient contents in leaf material and petiole sap, with the exception of calcium. However, positive results were obtained regarding the correlation between reflectometer determination and standard laboratory analyses. The regression analysis revealed high determination coefficients for N-NO3− (R2 = 0.703), K+ (R2 = 0.705), Ca2+ (R2 = 0.715), and Mg2+ (R2 = 0.780) between standard laboratory methods and the reflectometer. These results suggest that the reflectometer enables a real-time diagnostic tool for monitoring nutrient status throughout the growth cycle, particularly key nutrients related to fruit quality. The N–P–K fertilization strategies had no influence on the nutrient content of leaves or petiole sap. The nutrient content of both sample types varied depending on the orchard.
