Resumo -O objetivo deste trabalho foi avaliar a dinâmica de nutrientes na solução do solo após a aplicação, via fertirrigação, de nitrogênio, fósforo e potássio a laranjeiras. O experimento foi realizado entre setembro de 2007 e outubro de 2009, em pomares de laranjeiras 'Valência' e 'Hamlin', enxertadas sobre citrumeleiro 'Swingle'. Foram avaliadas cinco doses de N, P 2 O 5 e K 2 O (0, 25, 50, 100 e 200% da dose recomendada). A solução do solo foi extraída a 30 e 60 cm de profundidade, com o auxílio de extratores com cápsulas porosas. Foram realizadas 11 avaliações durante o período experimental, com as extrações iniciadas após 12 horas das fertirrigações. O aumento das doses reduziu o pH (pH~3,5, na maior dose), e aumentou a condutividade elétrica (CE~1,5 dS m -1 , na maior dose) e os teores de NH 4 , NO 3 , P, K, Mn e Zn na solução do solo, nas duas profundidades amostradas. Nos meses com maior precipitação pluvial, houve perda potencial de nutrientes por lixiviação, pois maiores concentrações de NO 3 , K e B foram observadas à profundidade de 60 cm. A análise da solução do solo, obtida por extratores com cápsula de cerâmica porosa, pode ser considerada ferramenta auxiliar para monitorar e avaliar a disponibilidade de nutrientes às plantas.Termos para indexação: Citrus sinensis, acidificação, cápsula porosa, extrator de solução, fertirrigação, lixiviação. Nutrient dynamics in soil solution in a fertigated citrus orchardAbstract -The objective of this work was to evaluate nutrient dynamics in soil solution after fertigated application of nitrogen, phosphorus, and potassium to orange trees. The experiment was carried out from September 2007 to October 2009, in 'Valência' and 'Hamlin' orange orchards grafted onto citrumelo 'Swingle' rootstock. Five doses of N, P 2 O 5 and K 2 O (0, 25, 50, 100 and 200% of the recommended dose) were evaluated. Soil solution was extracted from 30 and 60 cm soil depths using extractors with porous cups. Eleven evaluations were done during the experimental period, with extractions beginning 12 hours after fertigation. Increasing nutrient doses decreased pH (pH~3.5, at the highest dose), and increased electrical conductivity (CE~1.5 dS m -1 , at the highest dose) and the amounts of NH 4 , NO 3 , P, K, Mn, and Zn in the soil solution, in both sampled depths. In the months with heavier rainfall, there was nutrient potential losses by leaching, since higher concentrations of NO 3 , K, and B were observed at the 60 cm soil depth. Soil solution analysis, obtained by extractors with porous ceramic cups, can be considered an auxiliary tool for monitoring and assessing nutrient availability to plants.

A análise de nutrientes na seiva vem destacando-se como ferramenta sensível no estudo do estado nutricional de plantas perenes, sendo útil também na avaliação da disponibilidade de nutrientes no solo para as plantas. Este experimento foi conduzido com o objetivo de avaliar a concentração de nutrientes na seiva de duas variedades de laranja, quando fornecidas cinco doses de N, P2O5 e K2O via fertirrigação. A seiva foi extraída mensalmente do ramo da brotação nova com éter etílico, durante duas safras consecutivas. Para compreender a dinâmica dos nutrientes na seiva, também foram feitas, simultaneamente, análises de folha e de solução do solo. Os valores de pH na seiva mantiveram-se constantes, em torno de 5,5, independentemente dos tratamentos. A análise da seiva mostrou-se sensível às variações da adubação, pois as concentrações de N e K na seiva aumentaram conforme as doses de nutrientes aplicadas e correlacionaram-se de forma positiva com os valores desses nutrientes na folha e na solução do solo. Alta concentração de K foi observada na seiva, em torno de 4,0 g L-1, sendo esta maior que todos os outros nutrientes analisados. Observou-se diferença significativa no teor de N-NO3 entre as duas variedades de copa estudadas: a variedade de copa Hamlin, de ciclo precoce, apresentou concentração na seiva cerca de 20% superior à variedade Valência, que é de ciclo tardio. Os resultados sugerem que a análise da seiva pode ser empregada como ferramenta auxiliar na avaliação do estado nutricional de plantas cítricas.

The fertigated area of the Brazilian citrus industry has grown rapidly during recent years, and an efficient management of nitrogen (N) application at these sites is required for sustainable citrus production. Therefore, a field trial with Valencia orange trees [Citrus sinensis (L.) Osbeck] on Swingle citrumelo rootstock (Citrus paradise Macfad. x Poncirus trifoliata L. Raf.) was conducted for 8 years to evaluate the effects of N rates (80, 160, 240 and 320 kg ha–1 y–1) applied by fertigation, either as ammonium nitrate (AN) or calcium nitrate (CN), on soil solution dynamics, fruit yield, nutritional status, and N‐use efficiency (NUE) of trees. The maximum fruit yield was reached with 240 kg N ha–1 for AN, whereas a linear response and greater fruit yield was observed for N supplied as CN. The NUE was reduced for both N forms with increasing N rates. However, the NUE for CN was 14 to 38% greater than the NUE for AN. The lower fruit yield and NUE for AN compared to CN‐treated trees was associated with the increased acidification of the soil solution with increased AN rates (pH ≤ 4.0). This limited nitrification resulted in a high ammonium (NH$ _4^+ $) concentration in the soil solution and a reduction in the net absorption of cations by the trees, particularly calcium (Ca). Due to the improved ion balance as well as the higher pH of the soil solution (pH ≥ 6.3) and diminished NH$ _4^+ $ availability, gains in both fruit yield and NUE in fertigated citrus groves in tropical soils can be obtained with the use of CN as a source of N.

No abstract

The present study had the objective to evaluate the effect of blends of KCl and K2SO4 fertilizers and their influence on the yield and the nutritional state of coffee plants, as well as on the chemical composition and quality of the coffee beverage. The experimental design was in randomized blocks with four repetitions and six treatments (T1: 100% KCl; T2: 75% KCl + 25% K2SO4; T3: 50% KCl + 50% K2SO4; T4: 25% KCl + 75% K2SO4; T5: 100% K2SO4; and a control, without application of K). The following analyses were performed: K and Cl content in the leaves and the soil, stocks of Cl in soil, yield, removal of K and Cl with the beans, cup quality of the beverage, polyphenol oxidase activity (PPO), electric conductivity (EC), potassium leaching (KL), the content of phenolic compounds, the content of total sugars (TS), and total titratable acidity (TTA). The stocks of Cl in the soil decreased as the proportion of KCl in the fertilizer was reduced. The fertilization with KCl reduces the cup quality and the activity of the polyphenol oxidase, probably due to the ion Cl. The increase in the application of Cl directly relates to the increase in potassium leaching, electric conductivity, and titratable acidity. Indirectly, these variables indicate damages to the cells by the use of Cl in the fertilizer. The activity of the polyphenol oxidase enzyme and the cup quality indicate that the ion Cl- reduces the quality of the coffee beverage. K content in the leaves was not influenced by the application of blends of K fertilizer while Cl content increased linearly with KCl applied. The application of KCl and K2SO4 blends influenced coffee yield and the optimum proportion was 25% of KCl and 75% of K2SO4. The highest score in the cup quality test was observed with 100% K2SO4.