Agronomic and Economic Interactions between Sidedressed Nitrogen and Potassium Fertilizations on Atlantic Potato

Abstract Nitrogen (N) and potassium (K) in potato crop planting synergistically increase tuber yield, but there are no studies on this interaction in sidedressing. In two experiments with 'Atlantic' potato combinations of four N rates (0, 50, 100, and 150 kg ha-1) with four K2O rates (0, 100, 200, and 300 kg ha-1) were applied in sidedressing in a 4×4 factorial scheme with three replications in a completely randomized design. Adjacent commercial fields were sampled to economic comparisons with experimental results. Significant interaction between N and K sidedressing rates with tuber yields increase also was confirmed and classified as Liebig-synergism. Compared to the isolated N and K applications in sidedressing, joint N and K fertilizations, respectively, increases by 11% and 48% marketable tuber yields in the summer-fall experiment, and 12% and 7% in the spring experiment. Joint N and K applications as sidedressing was more profitable than planting fertilization, mainly at higher N and K rates. The response of specific gravity of 'Atlantic' potato tubers to the N and K sidedressing rates was mediated by interactions between edaphoclimatic conditions and inputs of N and K. The combined application of N and K sidedressing rates increased specific gravity in the summer-fall experiment, but had a negative effect in the spring experiment. Therefore, our results provide strong evidence that the fertilization management for potato crop in Brazil can be modified by applying higher amounts of N and K in sidedressing to match nutritional needs of the crop.

Organogénesis directa in vitro a partir de hojas de la planta antiplasmodial solanum nudum dunal / Direct organogenesis in vitro from leaves of solanum nudum dunal – antiplasmodial plant

Solanum nudum Dunal (Solanaceae), es una especie vegetal con potencial para desarrollar un tratamiento quimioterapéutico contra la malaria. Este es el primer reporte de un protocolo rápido, eficiente y reproducible de organogénesis directa a partir de segmentos de hoja de plántulas in vitro de esta especie.Los segmentos de hojas de plántulas de 5 meses de germinadas fueron cultivados sobre medio Murashige y Skoog (MS) a mitad de sales y vitaminas, con diferentes concentraciones de Bencilaminopurina (BAP), en combinación con Acido Indolacético (AIA). Se evaluó también el efecto de la iluminación en periodos 0/45, 15/30 y 30/15 días oscuridad/ luz, sobre la inducción de brotes. Se registró un promedio alto de formación de brotes (4,83) en explantes cultivados en medio suplementado con 2,0 mg/L de BAP y 0,1 mg/L de AIA, bajo condición de iluminación por un periodo de 30/15 días oscuridad/luz. Luego de la inducción, los brotes obtenidos fueron transferidos a medio MS suplementado con 0,3 mg/L de Giberelina (GA3), y mantenidos en condiciones de luz donde también enraizaron. Las plántulas regeneradas se llevaron a condiciones de invernadero y fueron morfológicamente similares a las plantas madres.

Solanum nudum Dunal (Solanaceae) is a plant with a potential for developing chemotherapeutic treatments against malaria. This is the first report of a fast, efficient, and reproducible direct organogenesis protocol from leave segments from in vitro seed-grown plantlets.Leaves segments from 5 months old germinated plantlets were placed on half concentration Murashige and Skoog medium (MS), supplemented with several concentrations of Bencilaminopurin (BAP) combinated with Indolacetic Acid (IAA). Dark/ light incubation effect in periods 0/45, 15/30 and 30/15 dark/light days were evaluated on the buds induction. High frequency buds formation was shown (4,83) in explants cultured on MS supplemented with BAP 2,0 mg/L and AIA 0,1 mg/L under a period of 30 days of dark condition incubation. After induction, buds obtained were transferred to MS medium supplemented with gibberellic acid (GA3) 0,3 mg/L and maintained under artificial cool light, there the plantlets rooted. Regenerated plantlets were placed under greenhouse conditions and these were morphologically similar to donor plants.