Eficiência de absorção de fósforo por diversas espécies de adubos verdes e aproveitamento desse nutriente pelas culturas de cana-de-açúcar e de arroz / Efficiency of phosphorus uptake by several species of green manure and use of this nutrient by crops of sugar cane and rice

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Integration of green manures species, which immobilize P, with supplying mineral P sources is one of the most promising agronomic practices for improving the availability of P for the main crop in order to recover soil fertility, increasing soil organic matter and thus optimize the efficiency of mineral fertilizers. The objectives of this work was to select among the green manure species the most efficient in absorbing the less available form of P, and by isotopic labeling of this plants, quantify the use of this nutrient from the green manures and mineral fertilizer by the sugar cane and rice crops, determining their real contributions as a P source. It was developed in three phases, in dystrophic Typical Hapludox, low-P, in the greenhouse in CENA / USP. The first experiment was conducted to identify and select the green manure species the more efficient one in absorbing P by isotopic dilution techniue. The plants were grown in a completely randomized design with three replications. With 25 species of green manures and 13 variables statistical analysis of principal components (PCA) and hierarchical clustering (HCA) were carried out in order to group the most similar ones. The PCA was explained by the first two components, defined as plant accumulated P and the L value, resulting three groups, and the white lupin being the most efficient in absorbing less available P, so there is difference between species on the ability to absorb the less available form of soil P absorption. From these groups some species of green manure were selected to evaluate the P use efficiency (PUE), from green manure and triple superphosphate (TSP), both labeled with ³²P, by sugar cane (experiment II) and rice plant (experiment III) through the isotopic dilution technique. Brachiaria, sunnhemp, dwarf pigeon pea, stylosante cv. campo grande were selected for sugar cane and sunnhemp and dwarf pigeon pea for rice, and four rates of TSP (0, 30, 60 and 120 mg P/ pot). On average, the AVs had low PUE, begin 0.1% by the root of sugar cane, 0.8% by shoot of sugar cane and 2.0% by rice. For TSP, the PUE by sugar cane roots were 1.0%, 9.9% by shoots and 4.0% by rice plants. Thus PUE of TSP is greater than that of green manure for both crops, regardless of green manure species. The highest PUE of TSP for both crops was obtained at rate of 30 mg P/pot. The green manure P is not sufficient to meet total demand for the main crop, but improves the absorption of P by the crop when associated with SFT.

ASSUNTO(S)

radioisótopos. estilosante adubo verde cana-de-açúcar green manure-³²p isotope dilution sunnhemp triple superphosphate brachiaria diluição isotópica arroz brachiaria guandu l value pigeon pea: stylosante. crotolária fósforo

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