63ª Reunião Anual da SBPC

E. Ciências Agrárias - 1. Agronomia - 1. Ciência do Solo

Phosphate levels and foliar-applied phosphorus forms on P uptake efficiency, P utilization efficiency, and P translocation in Phaseolus vulgaris

Vicente Filho Alves Silva 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:

Phosphate anions (H2PO4-, HPO42- and PO43-) are considered mains phosphorus forms assimilated by plants, and these can induce adequate growth and development with consequences in yield. However, another P form known as phosphite has been widely marketed either as fungicide or as a superior P source for plant nutrition. Phosphite anions (H2PO3- and HPO32-) are reduced forms of phosphate anions, in which one hydroxyl group is substituted by hydrogen. Aim of this research was to evaluate different soil phosphate levels and foliar-applied phosphorus forms on P uptake efficiency, P utilization efficiency, and P translocation 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 (Table 1). 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 applied via foliar (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.Shoot and root dry mass were ground and analyzed for total P concentration colorimetrically after nitric-perchloric digestion of the plant material. Data from shoot and root dry wt and total P concentration were used to calculate P uptake efficiency (P total accumulation in plant / root dry wt), P utilization efficiency ((plant dry wt)2/ (P total accumulation in plant)), and P translocation from root to shoot (P total accumulation in shoot / P total accumulation in plant). 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:

Either one or two foliar applications of potassium phosphate and phosphite had not significant effects (p > 0.05) on P uptake efficiency such as ability to take up P from soil, and also P translocation such as ability to transporter P from root to shoot (Figure 1). Nevertheless, limiting phosphate availability in soil reduced P uptake efficiency and P translocation by common bean. When the phosphate availability to plants is insufficient, P translocation from root to shoot decreases, increasing the root growth rate in detriment shoot growth rate. Foliar-applied treatments did not affect P utilization efficiency of phosphate-sufficient plants, whereas under limiting phosphate availability in soil, foliar-applied phosphite decreased P utilization efficiency of common bean. This result was due to the inhibitory effect of phosphite on biomass yield of the phosphate-starved plants, since accumulated P of the plants was not affect (data not shown).

CONCLUSÃO:

Results on one or two foliar applications of potassium phosphate and phosphite had not significant effects on P uptake efficiency and translocation.

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