LAUSR

Phosphorus is the most limited nutrient in Brazilian soils for plant growth, resulted of low availability and poor P content in bedrock. The aim of the study was to evaluate the dynamic of P fractions in a sand soil typical Quartzipsamment cropped with common bean under the effects of P and Si-fertilizer rates. The research was carried out in a soil with sand texture and clay mineralogy constituted mainly by kaolinite, classified as Neossolo Quartzarenico Ortico típico (RQo). The greenhouse location was the campus of Universidade Federal de Lavras located in the city of Lavras, state of Minas Gerais, Brazil (approximately 21o13'46.54" S and 44o58'26.30" W, average altitude 932 m above sea level). The experimental design used was entirely random, arranged in a 4 × 3 factorial design, with four repetitions, with amount of 48 experimental units. The treatments included four P rates (0, 80, 240 and 410 mg dm-3) and four Si rates (0, 240 and 410 mg dm-3). Phosphorus fractions in soil are little affected by Si-fertilizer rates. P uptakes by bean plants are correlated to the labile and moderately labile fractions. P-fertilizer rates increment majority the stable P fraction in soil and in lower proportion the labile and moderately labile P fractions in soil. Po-NaHCO3 is the only that contributes to bean plant nutrition.