Compositional meta-analysis of citrus varieties in the state of São Paulo, Brazil

Brazil is the largest orange (Citrus sinensis) producer worldwide. The nutrient management of orange orchards is designed from experiments on a limited number of varieties. This knowledge is transferred to other varieties by diagnosing tissue nutrient composition. Nutrient diagnostic tools are based on nutrient concentration (critical minimum value or CMV) and ratio (Diagnosis and Recommendation Integrated System or DRIS) norms that disregard the compositional nature of analytical data and the limited number of nutrient ratios that can be diagnosed independently in a given composition. The diagnosis of cationic micronutrients is also biased by contamination from fungicides. Compositional data analysis that can avoid such problems has been first applied to tissue analysis of agricultural crops using centered log ratios (Compositional Nutrient Diagnosis – CND-clr). The isometric log ratio (ilr) transformation is a new approach based on binary nutrient ratios and the principle of orthogonality (CND-ilr). Binary partitions can be defined and varietal nutrient profiles classified based on positive and negative nutrient interactions and meta-analysis. We analyzed 11 nutrients (N, S, P, K, Ca, Mg, B, Cu, Zn, Mn, Fe) in tissue samples across 108 orchard areas, i.e. 31 ‘Valencia’, 22 ‘Hamlin’, 20 ‘Pêra’, and 35 ‘Natal’. Nutrients were partitioned between macro- and micro-nutrients as well as anionic and cationic species. The effect size of varieties over ‘Valencia’ was quantified by the mean and standard deviation of ilr values across ilr coordinates. Specific varietal nutrient profiles and ilr norms were defined. To guide correcting nutrient deficiencies by appropriate nutrient management, compositions can be varied by a perturbation vector on nutrients with to the largest and most negative influence on ilr differences from ilr norms until the Aitchison distance falls below critical value

Mapeamento da produtividade, fertilidade do solo e falhas de plantas em pomar de laranjeiras

The current high competition on Citrus industry demands from growers new management technologies for superior efficiency and sustainability. In this context, precision agriculture (PA) has developed techniques based on yield mapping and management systems that recognize field spatial variability, which contribute to increase profitability of commercial crops. Because spatial variability is often not perceived the orange orchards are still managed as uniform and adoption of PA technology on citrus farms is low. Thus, the objective of the present study was to characterize the spatial variability of three factors: fruit yield, soil fertility and occurrence of plant gaps caused by either citrus blight or huanglongbing (HLB) in a commercial Valencia orchard in Brotas, São Paulo State, Brazil. Data from volume, geographic coordinates and representative area of the bags used on harvest were recorded to generate yield points that were then interpolated to produce the yield map. Soil chemical characteristics were studied by analyzing samples collected along planting rows and inter-rows in 24 points distributed in the field. A map of density of tree gaps was produced by georeferencing individual gaps and later by counting the number of gaps within 500 m² cells. Data were submitted to statistical and geostatistical analyses. A t test was used to compare means of soil chemical characteristics between sampling regions. High variation on yield and density of tree gaps was observed from the maps. It was also demonstrated overlapping regions of high density of plant absence and low fruit yield. Soil fertility varied depending on the sampling region in the orchard. The spatial variability found on yield, soil fertility and on disease occurrence demonstrated the importance to adopt site specific nutrient management and disease control as tools to guarantee efficiency of fruit production

Effect liming, handling and storage of soil samples on N availability indexes as measured by different methods

Um estudo foi conduzido para estabelecer os procedimentos mais adequados de manuseio e armazenamento de amostras de solo, para N inorgânico e frações do N orgânico mineralizável determinado por diferentes métodos. Amostras de solo com umidade natural ou secas, armazenadas em diferentes embalagens e temperaturas foram analisadas em dois experimentos ao longo de 35 ou 349 dias. Os resultados obtidos indicaram que, para as amostras armazenadas com umidade natural de coleta no campo e mantidas a -15°C em sacos plásticos, os teores do N-NH4+ e do N-NO3- não variaram significativamente por um período de 349 dias após a amostragem do solo. O armazenamento de amostras com umidade natural em geladeira provocou alterações significativas, em uma ou duas semanas, nos teores de amônio e nitrato, não sendo, portanto, recomendável. A secagem ao ar mostrou-se eficiente para prevenir alterações no N-NO3- - especialmente nas amostras armazenadas em geladeira - mas não no N-NH4+. No entanto, amostras secas ao ar armazenadas por cerca de 15 ou 20 dias em sacos de plástico em geladeira e, por cerca de 7 dias, em caixas de papelão à temperatura ambiente, apresentaram uma variação máxima de 3 mg kg-1 de N-NH4+. Para o N-NO3, esse mesmo limite de variação foi conseguido com amostras armazenadas secas ao ar em geladeira por vários meses. A menor variabilidade de resultados de N-NH4+ produzido por incubação anaeróbia foi conseguida nas amostras de solo armazenadas em geladeira com a umidade natural, mas o tempo de armazenamento parece não poder exceder 7 dias. Mesmo assim, a variabilidade dos resultados foi maior que a observada nas determinações de N inorgânico. Não foi possível definir um método adequado para a preservação das amostras para a determinação do N-NH4+ extraído pelo método do KCl a quente e pelo método do H2O2/MnO2, em virtude da baixa reprodutibilidade dos resultados em dias diferentes, nas condições testadas. Outro estudo, que visou a determinação da correlação entre índices de disponibilidade de N no solo e a absorção de N pelo milho, foi conduzido em casa de vegetação, com vinte amostras de solos, corrigidas ou não com calcário. O N inorgânico prontamente disponível mostrou a maior correlação com o N absorvido pelo milho (r = 0,98), embora o N-NH4+ produzido por incubação anaeróbia, o N-NH4+ extraído pelo método do KCl 2 M a quente ou do KCl/NaOH, e o N total do solo tenham sido também bons métodos de avaliação da disponibilidade de N no solo (r > 0,64). Resultados pouco consistentes foram obtidos com o método do H2O2/MnO2 e com o C orgânico do solo. O N avaliado pelos métodos testados foi pouco afetado pela calagem aplicada às amostras de solo.An experiment was carried out to study the best handling and storage pretreatment of soil samples for the determination of inorganic N and of mineralizable organic N by different methods. Field moist or dried soil samples, stored in cardboard boxes or plastic bags at different temperatures were analyzed for soil N in short (35 days) and long term (349 days) assays. The results obtained showed that field moist soil samples, stored in polyethylene bags at -15°C, did not present significant variation of the NH4+- and NO3--N contents over 349 days. Storage in refrigerator (5°C) of field moist samples caused significant changes, in one or two weeks, in the concentration of NH4+- and NO3--N. Air drying of soil samples was effective to prevent NO3--N changes - especially in samples stored in plastic bags in the refrigerator. - but not NH4+-N changes. However, air dried samples kept for 15 or 20 days in plastic bags in the refrigerator, or for 7 days in cardboard boxes at room temperature, showed a maximum variation of 3 mg NH4+-N kg-1 of soil. For NO3--N, variation of results could be kept up to that limit in air dried samples stored in refrigerator for several months. The smallest variation in the results of NH4+-N produced by anaerobic incubation was achieved with field moist samples stored in refrigerator, but storage time should not exceed 7 days. It was not possible to define an adequate method to preserve soil samples for the determination of the NH4+-N extracted by the hot KCl or the H2O2/MnO2 procedure, due to the low reproducibility of the analytical results, under the conditions of the test. Another experiment was conducted to establish the correlation between soil N availability indexes and N uptake by maize grown in pots with twenty limed and unlimed soil samples. The readily available inorganic N presented the highest correlation with maize N uptake (r = 0.98), but anaerobic incubation, hot 2 M KCl, or KCl/NaOH extractable N, as well as total N, were good predictors of soil N availability (r > 0.64). The H2O2/MnO2 procedure and the organic C produced inconsistent results. The amounts of N extracted by the methods tested were little affected by lime application

Compositional meta-analysis of Citrus varieties in the state of São Paulo, Brazil

Brazil is the largest orange (Citrus sinensis) producer worldwide. The nutrient management of orange orchards is designed from experiments on a limited number of varieties. This knowledge is transferred to other varieties by diagnosing tissue nutrient composition. Nutrient diagnostic tools are based on nutrient concentration (critical minimum value or CMV) and ratio (Diagnosis and Recommendation Integrated System or DRIS) norms that disregard the compositional nature of analytical data and the limited number of nutrient ratios that can be diagnosed independently in a given composition. The diagnosis of cationic micronutrients is also biased by contamination from fungicides. Compositional data analysis that can avoid such problems has been first applied to tissue analysis of agricultural crops using centered log ratios (Compositional Nutrient Diagnosis – CND-clr). The isometric log ratio (ilr) transformation is a new approach based on binary nutrient ratios and the principle of orthogonality (CND-ilr). Binary partitions can be defined and varietal nutrient profiles classified based on positive and negative nutrient interactions and meta-analysis. We analyzed 11 nutrients (N, S, P, K, Ca, Mg, B, Cu, Zn, Mn, Fe) in tissue samples across 108 orchard areas, i.e. 31 ‘Valencia’, 22 ‘Hamlin’, 20 ‘Pêra’, and 35 ‘Natal’. Nutrients were partitioned between macro- and micro-nutrients as well as anionic and cationic species. The effect size of varieties over ‘Valencia’ was quantified by the mean and standard deviation of ilr values across ilr coordinates. Specific varietal nutrient profiles and ilr norms were defined. To guide correcting nutrient deficiencies by appropriate nutrient management, compositions can be varied by a perturbation vector on nutrients with to the largest and most negative influence on ilr differences from ilr norms until the Aitchison distance falls below critical valu

Comportamento de 16 porta-enxertos para o tangor Murcott na região de Itirapina-SP

Foi monitorado o comportamento de 16 porta-enxertos para o tangor Murcott [Citrus reticulata Blanco x C. sinensis (L.) Osbeck], do clone nucelar J, em experimento instalado em 1990, na Fazenda Raio de Sol, Itirapina-SP. Os porta-enxertos foram: tangelo 'Orlando' (C. reticulata Blanco x C. paradisi Macf.), laranja 'Caipira DAC' [C. sinensis (L.) Osbeck], limão 'Cravo'(C. limonia Osbeck), os trifoliatas 'Kryder 8-5'e 'EEL'[Poncirus trifoliata (L.) Raf.] e as tangerinas 'Cleópatra' (C. reshni hort. ex. Tanaka), 'Sunki' [C. sunki (Hayata) hort. ex. Tanaka], 'Batangas', 'Oneco', 'Swatow', 'Szinkon', 'Satsuma', 'Cravo', 'Dancy', 'Suen Kat' e 'Pook Ling Ming' (C. reticulata Blanco). As produções foram avaliadas de 1996 a 2003 e as maiores médias foram proporcionadas pelas plantas enxertadas nas tangerinas 'Cleópatra', 'Suen Kat', 'Pook Ling Ming' e 'Sunki' (>40 kg planta-1). Dentre os porta-enxetos que induziram as mais baixas produções, estão os dois trifoliatas, a 'Caipira DAC' e a tangerina 'Cravo' (<25 kg planta-1). As características de qualidade apresentadas pelos frutos, referentes aos anos de 1998 e 2002, indicaram não existir diferenças expressivas entre os tratamentos