Ammonium/nitrate ratio and total ion concentration in the nutrient solution on Chrysanthemum growth. I. Growth and flowering

Three chrysanthemum cultivars were grown under hydroponic gravel culture by subirrigation using Steiner's solution to determine the influence of N-Nhsub4 (1.5, 3.0, and 4.5 meq Lsup-1) on the mutual ratio between the cations and N-NOsub3 (10.5 and 13.5 meq Lsup-1), on the mutual ratio between the anions as well as the nutrient solutions osmotic pressure (0.54, 0.72 and 0.90 atm), over the growth and the partitioning of the dry matter. A control treatment without ammonium, with 13.5 meq Lsup-1 of N-NOsub3, was added. All factors were studied using a randomized factorial 3x2x3x3 with three replications and distributed in a split block design. Both the ammonium ratios and cultivars influenced significantly plant growth whereas the osmotic levels and nitrate ratios did not affect it. With 4.5 meq Lsup-1 N-NOsub3- taller plants were obtained with greater number of inflorescences and total aboveground dry or fresh matter. The partitioning of dry matter indicated that the increase of ammonium in the nutrient solution allowed a better growth of branches which represented an important portion of the aerial dry matter at harvest. The control treatment produced less dry matter En un sistema hidroponico por subirrigacion se estudiaron los efectos de las concentraciones de N-Nhsub4 (1.5, 3.0 y 4.5 meq Lsup-1 ) en la relacion de cationes y de N-NOsub3 (10.5 y 13.5 meq Lsup-1 ) en la de aniones y la influencia de la presion osmotica (0.54, 0.72 y 0.90 atm) de la solucion nutritiva de Steiner sobre el crecimiento y particion de biomasa aerea en tres variedades de crisantemo (Dendranthema x grandiflorum (Ramat.) Kitam. tipo racimo: Puma, Funflower e Improved Funshine. Se adiciono un tratamiento testigo sin amonio y con 13.5 meq Lsup-1 de N-NOsub3. Los diferentes factores fueron estudiados en un diseno factorial 3x2x3x3 aleatorizado con tres repeticiones y con arreglo en parcelas divididas. A diferencia de los niveles osmoticos y de nitratos empleados, las concentraciones de amonio y variedades difirieron significativamente (alfa=0.05) en su influencia sobre el crecimiento vegetal. Con el nivel de 4.5 meq Lsup-1 de N-Nhsub4 en combinacion con 10.5 o 13.5 meq Lsup-1 de N-NOsub3, se lograron plantas mas altas, con mayor numero de inflorescencias y peso fresco o seco de biomasa aerea. Al incrementar la adicion de amonio a la solucion nutritiva se favorecio el crecimiento de brotes laterales y constituyo una porcion importante de la biomasa aerea (33% del total) al momento de l