63ª Reunião Anual da SBPC

E. Ciências Agrárias - 1. Agronomia - 5. Agronomia

Growth in Phaseolus vulgaris subjected to different soil phosphate levels and foliar-applied phosphorus

Diego Correia Sodré 1 Eldenira Barbosa Uchôa 1 Argemiro Pereira Martins Filho 1 Fabricio William de Ávila 2 Valdemar Faquin 2 Allan Klynger da Silva Lobato 1

1. Núcleo de Pesquisa Vegetal Básica e Aplicada, Universidade Federal Rural da Amazônia 2. Departamento de Ciência do Solo, Universidade Federal de Lavras

INTRODUÇÃO:

In terms of plant nutrition, phosphite-based products have been recommended as fertilizers for foliar application. Phosphite salts are recommended as fertilizer because they contain a cation that may be plant nutrient, such as K+, NH4+, Ca2+, Mg2+, Cu2+ or Zn2+, and the P in form of phosphite anion. However, results of studies that investigated nutritional value of phosphite anion as a P nutrient are inconclusive. Aim of this study was to investigate interference produced by different soil phosphate levels, as well as action produced by foliar-applied phosphorus forms (phosphite and phosphate), and if number of foliar application can act on growth in common bean (Phaseolus vulgaris cv. Radiante) plants.

METODOLOGIA:

Study was implemented in Departamento de Ciência do Solo of the Universidade Federal de Lavras, Brazil. Plants remained in glasshouse environment under natural conditions day/night. Substrate used was composed by Oxisol placed in plastic pots with capacity of 6 L. For plant material was used common bean (Phaseolus vulgaris cv. Radiante) plants.Experiment was organized in factorial scheme completely randomized using 2 soil phosphate levels (Pi-starved and Pi-sufficient), combined with 3 nutrient sources supplied via foliar application (KH2PO3, KH2PO4, and KCl used as control), and 2 foliar application numbers (single and two applications). This study had 3 replicates, and each experimental unit consisted of one pot containing two plants, and all variables measured were expressed as mean of two plants. Plants were harvested at full flowering stage and separated into shoot and root. Both shoot and root were rinsed in deionized water and dried at 60°C for 72 h prior to dry weight determination. Results were submitted to variance analysis and applied to Tukey test at 5% level, as well as the standard errors were calculated in all evaluated points.

RESULTADOS:

Variables in this study were not significant affected by foliar application numbers during single application timing and two application timings. Common bean plants grown under limiting phosphate availability (Pi-starved) showed considerable reductions in the root and shoot dry wt and increased root to shoot ratio. The increase root to shoot ratio by phosphate-starved plants is a mechanism for overcoming P deficiency. Foliar application of potassium phosphite and phosphate had no significant effect on biomass yield in phosphate-sufficient common bean, when compared with the control. However, for plants grown under limiting phosphate availability, shoot and root dry wt were significantly decreased by foliar-applied potassium phosphite. Most plausible hypothesis to date is that plants do not metabolize phosphite anion. Furthermore, phosphite inhibits some mechanisms involved in overcoming of phosphate deprivation, such as increased synthesis of phosphatases, phosphodiesterases, and high-affinity P transporters.

CONCLUSÃO:

Shoot dry weight and root dry weight were not significantly affected by foliar application numbers. Foliar application of potassium phosphite and phosphate had no significant effect on biomass yield in phosphate-sufficient common bean, when compared with the control.

Palavras-chave: Phaseolus vulgaris, phosphorus, nutrition plant.