Responses of nine tropical grasses to nitrogen fertilizer under rain-grown conditions in south-eastern Queensland. 2. Concentrations and uptakes of nitrogen, phosphorus and potassium in plant tops

Abstract

Nitrogen, phosphorus and potassium concentrations were determined in plant tops harvested every four weeks from nine tropical grasses fertilized with nitrogen on ten occasions at eight week intervals. Nitrogen was applied at three rates-25, 50 and 100 kg/ha (N25, N50, N100)-on each occasion. Grasses were rain-grown without grazing at a site near Gympie with an average annual rainfall of 1160 mm. Overall, nitrogen concentration in the tops increased and potassium concentration decreased with increasing nitrogen application. Phosphorus concentrations were constant at N25 and N50, but were lower at N 100. Mean nitrogen concentration was highest at 2.4% in Pennisetum clandestinum cv. Whittet, and lowest at 1 .9% in Chloris gayana cvv. Callide and Katambora, with intermediate concentrations occurring in Digitaria decumbens, Setaria sphacelata var. sericea cv. Narok, Panicum maximum cvv. Gatton and Makueni, Brachiaria decumbens cv. Basilisk and Paspalurn plicatulum cv. Bryan. Phosphorus concentration was highest in Whittet at 0.38% and lowest in Bryan at 0.25%. Potassium concentration was highest in Whittet at 2.53% and Narok at 2.29% and lowest in Katambora at 1 .48%. The implications of these concentrations and calculated nutrient uptakes are discussed in relation to animal and plant nutrition.

Rendimento e diagnose foliar dos capins Aruana e Mombaça cultivados em latossolo vermelho-amarelo adubado com doses de nitrogênio

“…Resultados de pesquisa com colonião têm mostrado que aplicações de nitrogênio não alteram significativamente os teores de cálcio nessa gramínea (Crespo et al, 1986e Alvim et al, 1990, ou causam sua redução (Mattos & Wemer, 1979e Monteiro et al, 1980 (Malavolta, 1980e Mengel & Kirkby, 1987. Malavolta et al (1974) Griffith et al (1964 ), CIAT (1981 ), Monteiro et al (1980), Cook & Mulder (1984) e Carvalho & Saraiva (1987).…”