The effect of phosphorus on the growth, chemical composition, and critical phosphorus percentages of some tropical pasture grasses

Abstract

Nine tropical pasture grasses were grown in pots of a phosphate-deficient solodic soil with varying additions of phosphate. Growth responses and chemical composition of the plant tops were recorded, and from these, critical percentages of phosphorus were established. All species responded to phosphate addition. Under the conditions of this experiment Melinus minutiflora was the most responsive species and Pennisetum clandestinum the least responsive. Critical percentages of phosphorus in the tops of Melinus minutiflora, Cenchrus ciliaris, Paspalum dilatatum, Panicum maximum, Chloris gayana, Sorghum almum, Setaria anceps, Digitaria decumbens and Pennisetum clandestinum sampled at the immediate pre-flowering stage of growth were 0.18, 0.25, 0.25, 0.20, 0.22, 0.20, 0.21, 0.16, and 0.22% respectively of the dry matter. Phosphate applications decreased the concentration of plant potassium, had no significant effect on calcium, increased magnesium in most species, and in four species increased sodium. The increases in magnesium and sodium are considered to result in part from reduced potassium uptake and the plant's ability to preserve cation balance. Three species, C. gayana, P. maximum and D. decumbens, had relatively high concentrations of sodium (58, 46, and 46% of total cations respectively). In contrast S. anceps had a relatively high concentration of potassium (56 % of total cations) and low sodium (7%). Phosphate applications decreased the concentration of nitrogen, and had little effect on chloride.

Dry Matter Yield, Chemical Components and Dry Matter Degradability of Ten Sorghum Cultivars (Sorghum bicolor L. Moench) Grown on Oxic Paleustult Soil

“…This could be considerably inadequate for metabolic process of microorganisms in the ruminant animals. The results attained were similar to the work reported by Andrew and Robins (1971). Nevertheless, if these sorghum plant materials must be used for feed stuffs then some additional amount of calcium and phosphorous at the ratio of 1:1 must be added.…”

Nutrientes na fitomassa de capim-marandu em função de fontes e doses de nitrogênio

“…(HOPKINS et al, 1994), embora o teor de Mg tenha diminuído com o aumento das doses de N, o teor de Mg e a relação K/Mg se mantiveram na faixa de 7 a 10, considerada adequada por Malavolta (1980). O N estimula a absorção e translocação do P (ANDREW & ROBINS, 1971). Com o NA os teores de P permaneceram adequados e com a uréia ficaram acima -0,8 a 3,0 g kg -1 .…”

Field response of three subtropical pasture legumes to lime, P and K on an acid sandy soil

“…According to Andrew & Robins (1971) phosphate applications also decreased the concentration of plant potassium in tropical grasses. Depending on the type of animal, ruminant dietary K requirements vary between 0,67 and 0,81 g 100 g-l. Potassium deficiency is, however, not a cominon problem in ruminants owing to the high K content of most forages (Devlin, Roberts & St. Orner, 1969).…”