ABSTRACT Soil fertility evaluation through soil analysis traditionally does not consider interaction among elements. To include the interaction effect in interpretation of soil analyses, an experiment was conducted to evaluate the effect of nitrogen fertilization (0, 0.5, 1.0, and 2.0 kg N per plant per cycle) with urea (45 % N) and potassium fertilization (0, 0.55, 1.1, and 2.2 kg K2O per plant per cycle) with potassium chloride (60 % K2O) on soil cationic balance. The experiment was carried out in an irrigated commercial production area of ‘Paluma’ guava, for five consecutive cycles, 2009 through 2012, using the concept of isometric log ratio (ilr) to evaluate soil cationic balance through [K, Ca, Mg | H+Al], [K | Ca, Mg] and [Ca | Mg] balances. The compositional data analysis showed to be a suitable tool to interpret the soil cationic balance given that the soil cationic balances value was changed by nitrogen fertilization and potassium as well as the soil pH value and the concentration of K in the soil. The soil cationic balances also changed by the variations of in climate conditions at period of soil sample. An application rate of 0.55 kg K2O per plant per cycle was considered sufficient to keep K soil concentration above 1.6 mmolc dm-3.

ABSTRACT Guava response to fertilization can be monitored through plant tissue analysis. Correct interpretation of these results, based on standard levels, is of great importance for correct nutrient management of the crop. However, standard levels are constantly criticized for not considering interactions among elements. To improve the nutritional diagnosis of ‘Paluma’ guava (Psidium guajava L., Myrtaceae), an experiment was conducted using nitrogen fertilization (0, 0.5, 1.0, and 2.0 kg per plant per cycle of N, with urea as a source with 45 % N), and potassium fertilization (0, 0.55, 1.1, and 2.2 kg per plant per cycle of K2O, with potassium chloride as a source with 60 % K2O) in an irrigated commercial area for five consecutive cycles, 2009 through 2012, observing the influence of fertilizers and climate and assessing yield and leaf element content, using the concept of isometric log ratios (ilr) to interpret leaf analysis results (N, P, Ca, Mg, K, and S). This paper showed that nutrient balances and nutrient concentration values can be interpreted coherently using compositional data analysis. Ranges of nutrient balances also were established for “Paluma” guava and validated through ranges grounded in nutrient contents currently used in Brazil. Nitrogen fertilization increased “Paluma” guava yield. The 0.5 kg N application rate per plant and the other studied treatments practically showed the same results, and their values were affected by pruning time as well as the nutrient balances.

RESUMOA adequada adubação mineral de pomares de goiabeira, sob manejo intensivo, é fator preponderante na produtividade, e o acompanhamento do estado nutricional das plantas contribui para a eficiência desta prática agronômica.Objetivou-se pesquisar o efeito de diferentes doses de nitrogênio e potássio sobre o estado nutricional de goiabeiras‘Paluma’. O experimento foi conduzido em Vista Alegre do Alto-SP, em pomar irrigado, com sete anos deidade, manejado com podas de frutificação, durante quatro ciclos de produção consecutivos. O solo é o Argissolo Vermelho-Amarelo distrófico. O delineamento experimental foi em blocos ao acaso, com trêsrepetições, em esquema fatorial com quatro doses de nitrogênio (0; 0,5; 1,0 e 2,0 kg planta-1 de N) e quatro depotássio (0;0,55; 1,1 e 2,2 kg planta-1 de K2O). A adubação nitrogenada promoveu aumento nos teores foliares de N e Mn e decréscimo nos teores de P e B, observados do segundo ao quarto ciclo produtivo. A adubaçãonitrogenada elevou os teores de Ca e Mg, respectivamente, no segundo e terceiro ciclos. Com exceção doprimeiro ciclo produtivo, os teores foliares de K e Mn aumentaram em função da adubação potássica, enquanto os teores de Mg, no segundo e quarto ciclos, diminuíram em função dessa adubação.

ABSTRACTThe proper mineral fertilization of guava orchards under intensive management, is a major factor in productivity and monitoring the nutritional status of the plants contributes to the efficiency of this agronomic practice. The aim of this study was to investigate different doses of nitrogen and potassium in the nutritional status of guava ‘Paluma’. The experiment was conducted at Vista Alegre do Alto, São Paulo, in a 7 year old irrigated orchard, managedwith fruiting pruning during four consecutive growing seasons. The soil is a dystrophic Ultisol. The experimental design was randomized blocks, in factorial, with four nitrogen doses (0, 0.5, 1 and 2 kg of N plant-1) and four of potassium (0, 0.55, 1.1 and 2.2 kg of K2O plant-1), with three replications. Nitrogen fertilization promoted increased levels of leaf N and Mn and the decrease in the levels of P and B; effects observed from the second to the fourth production cycle. Nitrogen fertilization increased the Ca and Mg levels, respectively, in the second and third cycle. Except for the first production cycle, K and Mn foliar concentrations increased with increasing potassium fertilization, whereas the levels of Mg, in the second and the fourth cycle, decreased as a function of fertilization.

O oeste do estado de São Paulo responde por cerca de 40% da produção estadual de batata-doce, mesmo sem a adoção, pelos agricultores da região, de tecnologias fundamentais para o aumento da produtividade. Este trabalho avaliou o impacto de viroses sobre variáveis da produção de batata-doce. O experimento foi conduzido em área comercial no município de Presidente Prudente, São Paulo, Brasil, utilizando plantas de Ipomoea batatas L, grupo rosada, cv. Canadense. Como material de propagação foram utilizadas mudas livres de vírus produzidas em viveiros e mudas originadas de lavoura comercial infectada por vírus. Na colheita foram demarcadas três parcelas de 10 x 4 m em cada uma das metades do campo (com e sem vírus), quando se avaliou, aleatoriamente, número, massa, comprimento e diâmetro dos tubérculos de dez plantas localizadas na área central de cada parcela. As parcelas sem vírus produziram cerca de 50% a mais e o dobro em massa (kg) de tubérculos colhidos em relação aos provenientes das parcelas com vírus. Os tubérculos obtidos das plantas não infectadas apresentaram maior massa (p < 0,01), comprimento (p < 0,01) e diâmetro médio (p < 0,05) do que os colhidos das plantas infectadas. Foi constatada também uma frequência de 65% de tubérculos com classificação 2A (150 a 299 g) para o grupo rosada-CEAGESP, que representa 70% do volume comercializado no CEAGESP, o que confere maior lucratividade ao produtor.

ABSTRACT The Western region of São Paulo State, Brazil, is responsible for approximately 40% of the production of sweet potato (Ipomoea batatas L.) in the state, even under low-technology. The study aimed to evaluate the impact of viruses on sweet potato production variables. The experiment was conducted in Presidente Prudente, São Paulo, Brazil, in a commercial sweet potato crop of pink group, cv. Canadense, with and without virus. In three randomly chosen plots of 10 x 4 m in each half of the field (with and without virus), ten central plants were randomly collected. The number, weight, length and diameter were evaluated. The plots without virus produced 50% more tubers and 100% more weight during harvesting. Tubers obtained from virus-free seedlings showed a greater mass (p < 0.01), height (p < 0.01) and mean diameter (p < 0.05) than those harvested from infected plants. From free-of-virus seedlings, 65% of tubers were classified as 2A (150 to 299 g), the standard that represents 70% of the trading volume at a Food Market place, which provides greater profitability to the producer.