Resumo de Mineral Parameters Evaluation And Dris Norms For Panicum Maximum Jacq. Cv Tanzânia.

Mineral parameters evaluation and dris norms for panicum maximum jacq. cv Tanzânia.The objective of this research was to evaluate the effects of grazingmanagement and season of the year on Mineral concentrations in fourparts of Panicum maximum Jacq. cv. Tanzânia (EL ? expanded leaf, RELB ?recent expanded leaf blades, MLB ? mature leaf blades and SS ? stemsplus sheaths), and on mineral intake and recycling through grazingcattle. One experiment was done from October 1999 to October 2000 on anirrigated area under rotational grazing. Treatments imposed were threepost-grazing residues, 1000, 2500 and 4000 Kg/ha of green dry matter,respectively in a four randomized complete blocks design. Season of theyear affected mineral concentrations in every part of the plant. FromOctober till beginning of February (period 1) there was lowconcentration of nitrogen and phosphorous in all parts of the plant.Potassium concentrations varied among season of the year; its lowestconcentrations occurred from February to May (period 2). Calciumconcentration of the RELB and MLB, also varied along seasons of theyear occurring highest values in period 2. The highest concentrationsof magnesium and sulphur occurred for June to October (period 3).Grazing intensity had small influence on plant mineral concentrations.The MLB showed higher concentrations of N, P, S and Zn on the lowpost-grazing residue. Mineral intake was higher on the low post-grazingresidue; intake levels during one grazing cycle at the low post-grazingresidue were 44.9 Kg N; 4.0 kg P; 54.2 kg K; 6.1 kg Ca; 8.3 kg Mg e 2.6kg S per hectare. A higher mineral percentage of the pre-grazing foragemass was returned to the soil via feces and urine when the pasture wasmanaged with low post-grazing residue. Differences between intake andmineral recycling related to the grazing intensity can be used toestablish the adequate fertilization for pasture maintenance andproduction. The DRIS norms for the Tanzania grass were determined usingdata colleted during two periods: October 1999 through October 2000 andFebruary 2002 through January 2003. The DRIS method, based on theestablished norms, was accurate to diagnose deficiencies, balance andexcess nutrients in leaf tissue. There was a low relationship betweenNBI (Nutritional Balance Index) and dry matter yield. The methodproposed by Jones (1981) showed smaller variations between DRIS indexesand showed no relationship between NBI and dry matter yield. Methodsproposed by Beaufils (1973) and Elwali & Gascho (1984) were moresuitable to estimate DRIS index.

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