Nitrogen and sulphur in Marandu grass: relationship between supply and concentration in leaf tissues

Abstract

In order to better assess the nutritional status of forage grasses there has been an increasing interest in studying the nutrient concentrations present in different parts of plant shoot. The aim of this work was to evaluate the nitrogen and sulphur concentrations in leaf tissues of Brachiaria brizantha cv. Marandu grown in nutrient solutions with combined rates of both nitrogen and sulphur. An experiment was conducted in a greenhouse during the Spring season in Piracicaba-SP, Brazil, using ground quartz as substrate. A fractionated 5² factorial design was used, with 13 combinations of nitrogen and sulphur rates in the solutions, in mg L-1, as follows: 14 and 3.2; 14 and 32; 14 and 80; 126 and 12.8; 126 and 64; 210 and 3.2; 210 and 32; 210 and 80; 336 and 12.8; 336 and 64; 462 and 3.2; 462 and 32, and 462 and 80. The experimental units were set in a randomized block design, with four replications. Plants were harvested twice. Emerging leaves, recently expanded lamina and mature lamina were sampled separately at each harvest time. In these three types of tissues the nitrogen concentration was closely related to the nitrogen supply in the solution, whereas the sulphur concentration, N:S ratio and chlorophyll meter (SPAD) readings depended upon the supply of both nitrogen and sulphur. Mature lamina did not relate well to the changing in sulphur supply. To properly assess the nitrogen and sulphur concentrations, N:S ratio and SPAD readings for the Marandu grass, the two recently expanded lamina were the best tissues to indicate the availability of both nitrogen and sulphur in the nutrient solution.

<b>Relative chlorophyll contents in the evaluation of the nutritional status of nitrogen from xaraes palisade grass and determination of critical nitrogen sufficiency index

“…Since RCC reached the plateau in the two periods, it may be registered that even if N is added by fertilization, the plant will not produce more chlorophyll. The above behavior is known as photosynthetic maturity and was previously reported for forage grasses (Batista & Monteiro, 2007;Lavres Junior et al, 2010;Lavres Junior & Monteiro, 2006). According to Lavres Junior et al (2010), the behavior suggests the accuracy of CRR and TN in the vegetal tissue as a nutritional assessment tool of nitrogen in tropical grasses.…”

Herbage utilisation efficiency of continuously stocked marandu palisade grass subjected to nitrogen fertilisation

“…; Batista and Monteiro, 2007), revealed higher N concentration for swards fertilised with the higher rates of nitrogen, and sub-optimal levels for those fertilised with 150 kg ha -1 and non-fertilised. In this con-text, the additional supply of nitrogen provided by the 150 kg ha -1 rate resulted in the largest increase in stocking rate relative to that between the remaining rates of nitrogen fertilisation (Table 1).…”

“…Results were used to calculate the sward leaf area index (LAI). At the end of the experiment, samples from the last fully expanded leaf were harvested from each paddock (60 leaves) to determine nitrogen concentration and inferences about the nitrogen nutrition status of plants (Batista and Monteiro, 2007).…”

Macronutrientes em folhas diagnósticas do capim-tanzânia adubado com nitrogênio e cálcio

“…Também estimaram o nível crítico de nitrogênio de 16,0 a 16,5 g kg -1 para o capimmombaça, o que contrasta com os estimados por Volpe et al (2008), que relataram concentração de nitrogênio de 20,0 g kg -1 nas folhas diagnósticas do capim-massai (Panicum maximum) como não limitante ao adequado crescimento desse capim. Batista & Monteiro (2007) observaram que doses de nitrogênio de 1,0 a 33,0 mmol L -1 afetaram a concentração desse mineral nas lâminas de folhas recém-expandidas do capim-marandu (Brachiaria brizantha cv. Marandu), com oscilação de 16,0 a 31,0 g kg -1 na amostragem do primeiro corte e de 9,5 a 17,0 g kg -1 no segundo corte das plantas.…”