Eucalyptus are widely planted in regions with low rainfall, occasioning frequent drought stresses. To alleviate the stress-induced effects on plants growing in these environments, soil fertilization with potassium (K) may affect drought-adaptive plant mechanisms, notably on tropical soils with low K availability. This work aimed to evaluate the K dynamic nutrition in eucalyptus in response to soil-K and -water availabilities, correlating the K-nutritional status with the physiological responses of contrasting eucalyptus clones to drought tolerance. A complete randomized design was used to investigate the effects of three water regimes (well-watered, moderate water deficit, and severe water deficit) and two K soil supplies (sufficient and low K) on growth and physiological responses of two elite eucalyptus clones: "VM01" (Eucalyptus urophylla × camaldulensis) and "AEC 0144" (E. urophylla). Results depicted that the K-wellnourished E. urophylla × camaldulensis clone under severe water deficit maintained shoot biomass accumulation by upregulating the K-content in leaves and stems, gas exchange, water-use efficiency (WUE I ), leaf water potential (Ψw), and chlorophyll a fluorescence parameters, compared to E. urophylla clone. Meanwhile, E. urophylla with a severe water deficit showed a decreased of K content in leaves and stem, as well as a reduction in the accumulation of dry mass. Therefore, the K-use efficiency and the apparent electron transport rate through photosystem II were positively correlated in plants grown in low K, indicating the importance of K in maintaining leaf photochemical processes. In conclusion, management strategy should seek to enhance K-nutrition to optimize water-use efficiencies and photosynthesis.

-The objective of this study was to evaluate the development of grass Paspalum millegrana Schrad propagated through seeds and tillers, subjected to different levels of water and phosphorus to be used in erosion control on slopes. The experimental trial was conducted in greenhouse with propagation of tillers and seeds of Paspalum grass, at the Federal University of Sergipe, São Cristóvão, Brazil. The design was the completely randomized design with sixteen treatments and four replications, arranged in a factorial scheme corresponding to (0, 100, 200, 300 and 400 mg kg -1 ), two water contents in the soil (60% and 100% of total pore volume) filled with water and two types of propagation (tillers and seeds). Plants were harvested at the end of four months of conducting the experiment and evaluated the following variables: number of tillers (NT), number of inflorescences (NI), Shoot Length (SL), Root Length (RL), Shoot Dry Weight (SDW) and Root Dry Weight (RDW). The phosphorus and water levels interacted positively with the variables studied and showed that this grass, presented biotech important features like good tillering, and the consequent formation of dense aerial biomass and root required for slope protection against erosion. The specie Paspalum millegrana showed a better development among the variables analyzed under conditions of less water availability with 60% VTP and the best responses of the simple superphosphate dosages were between 200 and 300 mg kg -1 .

-This study aimed to evaluate the effects of combination of nitrogen and sulphur fertilizations on water consumption and water use efficiency by marandu palisadegrass (Brachiaria brizantha cv. Marandu). The experiment was carried out in a greenhouse, using a Typic Quartzipsamment. Five nitrogen rates (0; 100; 200; 300 and 400 mg dm -3 ) were combined with five sulphur rates (0; 10; 20; 30 and 40 mg dm -3 ) in a fractionated 5 2 factorial, with four replications. The leaf area was harvested three times at intervals of approximately 30 days. Soil moisture was maintained at 70% of capacity retention through a self-irrigating system. There was an increase in consumption and water use efficiency by the forage grass due to the supply of nitrogen and sulphur. Nitrogen fertilization increased the consumption and efficiency of water use in the first growth period (35 days after the transplanting of seedlings). Nitrogen and sulphur supply were more effective in increasing water consumption in the third growth period. For water use efficiency this fact was observed in the second and third growth periods of the Marandu palisadegrass.Key words: Marandu palisadegrass. Plants and water. Plants-nitrogen effect. Plants-sulphur effects.RESUMO -Neste estudo objetivou-se avaliar a combinação de doses de nitrogênio e enxofre no consumo e eficiência do uso da água pela Brachiaria brizantha cv. Marandu. O experimento foi conduzido em casa de vegetação, utilizando-se um solo classificado como Neossolo Quartzarênico Órtico típico. Cinco doses de nitrogênio (0; 100; 200; 300 e 400 mg dm ) e m um f a tori al 5 2 fracionado, com quatro repetições. A parte aérea do capim foi cortada três vezes em intervalos aproximados de 30 dias. A água do solo foi mantida a 70% da capacidade de retenção por meio de um sistema autoirrigante. Ocorreu aumento no consumo e na eficiência do uso da água pela gramínea forrageira em razão do fornecimento de nitrogênio e enxofre. A adubação com nitrogênio incrementou o consumo e a eficiência no uso da água no primeiro período de crescimento (35 dias após o transplantio das mudas). O fornecimento simultâneo de doses de nitrogênio e enxofre foi mais efetivo no aumento do consumo de água no terceiro período de crescimento. Para a eficiência no uso da água esse efeito foi observado no segundo e terceiro períodos de crescimento do capim-marandu.Palavras-chave: Capim-marandu. Plantas e água. Plantas-efeito do nitrogênio. Plantas-efeito do enxofre.

Tropical grass pastures are broadly split between those that use high N fertilizer rates and those that use little or none. Maximizing the efficiency of N application in pastures requires understanding which features and adaptations species utilize to take advantage. This study was designed to determine the variation in growth of Brachiaria cultivars (Basilisk, Marandu, Piatã and Xaraés) and Panicum cultivars (Aruana, Massai, Mombaça and Tanzania) under two N supply rates (low and high) in order to understanding forage-grass species adaptive mechanisms for high and low N supply. Changes in growth were determined based on the following characteristics: number of leaves and tillers, leaf area (LA), shoot dry matter (SDM) production, root surface area (RSA), root length (RL) and root dry matter(RDM) production. The experimental design consisted of 8 forage-grass cultivars x 2 N rates (30 and 300 mg dm-3) in a randomized block design with four replications. At low N supply, Marandu, Xaraés, Piatã, Basilisk and Mombaça cultivars maintained a constant number of tillers but showed a decrease in the number of leaves and LA compared to high N. Tanzania cultivar maintained a constant number of tillers and LA but showed a decrease in the number of leaves under low N. In contrast, cultivars Aruana and Massai showed an increased number of tillers and a reduced LA. At low N rate, Brachiaria cultivars prioritized roots growth but with high N supply increased leaf and tiller growth. Brachiaria cultivars demonstrated high plasticity of reserve allocation, suggesting that these cultivars may better withstand N stress, ensuring their persistence. Panicum cultivars exhibited vigorous roots growth which may improve the capture of soil N and reduce losses from leaching and volatilization, and also can contribute to reduce environment contamination.

-The development of root system of forage grasses is influenced by the supply of mineral nutrients. The experiment was carried out in a greenhouse in Piracicaba, São Paulo State, with the objective of evaluating the effect of nitrogen and magnesium rates on dry mass yield, total length and surface, specific length and surface, and concentrations of nitrogen, magnesium, calcium and potassium in the root system of Brachiaria brizantha Stapf. cv. Marandu. It was studied five rates of nitrogen (2, 9, 16, 23 and 30 mmol L -1 ) and five rates of magnesium (0. was a randomized block with four replications. Plants had two growth periods, and after the second harvest the roots were separated from the plant tops. Combination of the high rates of nitrogen and magnesium resulted in expressive increases in rooty dry matter yield, in the length and in the root surface of marandu palisadegrass. High rates of nitrogen and magnesium resulted in short root specific length and surface. Combinations of high rates of nitrogen and magnesium increased nitrogen concentration or decreased potassium concentration in the roots. Calcium concentration in the roots was increased by nitrogen rates and decreased by magnesium rates. Magnesium rates resulted in increase in magnesium concentration in the roots of marandu palisadegrass.

An improved N use in grasses is necessary to increase the nutrient use efficiency and the species persistence in the production systems. However, it is not known if the same grass cultivars should be used in high or low N situations to achieve high nitrogen use efficiency (NUE). This study aimed to analyze whether Brachiaria brizantha cv. Marandu, B. brizantha cv. Xaraés, B. brizantha cv. Piatã, B. decumbens cv. Basilisk, Panicum maximum cv. Mombaça, P. maximum cv. Tanzania, P. maximum cv. Aruana and P. maximum x P. infestum cv. Massai grasses modify the N partition to an improved nutrient use efficiency when growing in an environment with low and high N availability. The experiment was carried out in a greenhouse with an Entisol collected in a degraded pasture area. The experiment was set up with 8 cultivars (four cultivars each of Brachiaria spp. and Panicum spp.) x 2 N rates in a complete randomized block design, with four replications. The studied grasses modified the N partition and the nitrate and ammonium concentrations in shoots and roots at high and low N supplied rates. These differences reflect the higher NUE by Mombaça and Tanzania compared with the other six cultivars.

No abstract

The interaction of natural reactive phosphate with poultry litter may increase the production of forage grasses as a result of phosphorus (P) uptake. This study's goal was to analyze growth, production and P concentration of diagnostic leaves of forage grasses fertilized by an Arad reactive phosphate + poultry litter association. The experiment employed a 2 3 factorial, with the following factors: forage grasses (Urochloa brizantha and Panicum maximum), Arad rates (0 and 50 mg dm-3 P 2 O 5), and poultry litter (0 and 7.5 g dm-3). At the first harvest, the highest dry-matter production of leaves, sheaths + stems and shoots occurred in the interaction P. maximum × Arad × poultry litter. P concentrations in diagnostic leaves as well as number of leaves were similar between forage grasses, but higher in the interaction between Arad + poultry litter when compared to isolated fertilizers. At the second harvest, dry-matter production of shoots and sheaths + stems was higher in the U. brizantha + poultry litter interaction than in other interactions. Compared to the other fertilizers, P concentration in the diagnostic leaves at second harvest was higher in grasses fertilized with poultry litter. At second harvest, the number of leaves and tillers was highest in the U. brizantha + Arad + poultry litter interaction, followed by the Arad + poultry litter interaction. The association of Arad and poultry litter promotes adequate P nutrition and biomass production of forage grasses, and can therefore be considered an important instrument for the establishment of these grasses.