Nitrogen efficiency in marandupalisadegrass pastures under increasing nitrogen levels / Eficiência do nitrogênio em pastagens de capim-marandu adubadas com doses crescentes de nitrogênio

The use of nitrogen (N) in pastoral ecosystems leads to increased productivity, as it allows the plant to elongate its leaves and, therefore, grazing herbivores harvest the green leaves. However, there are very volatile N sources, which can be replaced by ammonium nitrate, which is less volatile and less dependent on the application in rainy days. The treatments are compound of Marandu palisade grass pastures managed under continuous stocking at a canopy height of 25 cm, with different levels of N fertilizer: 0, 75, and 150 kg ha-1year-1, as ammonium nitrate (32% of N), with four replicates (pastures) in a completely randomized design. Nitrogen uptake (54.9, 96.5, 113.8 kg N ha-1) and N nutrition index (0.67, 0.98, 1.15) were different between N level, respectively, 0, 75 and 150 kg ha-1 year-1. The N recovery (58.3, 40.9 %) differed between 75 and 150 kg ha-1 year-1, respectively. The dose of 75 kg N kg ha-1 year-1 results in better N utilization, while the dose of 150 kg N ha-1 year-1 enables greater stocking rate; therefore, requiring less grazing area.

O uso de nitrogênio (N) em ecossistemas pastoris leva ao aumento da produtividade, pois permite que a planta alongue suas folhas e, portanto, os herbívoros colham as folhas verdes. Porém, existem fontes de nitrogênio muito voláteis, que devem ser substituídas por nitrato de amônio, que é menos volátil e menos dependente da aplicação em dias chuvosos. Os tratamentos foram compostos por pastagens de capim-marandu, manejadas sob lotação contínua, na altura do dossel a 25 cm, com diferentes doses de N: 0, 75 e 150 kg ha-1 ano-1, na forma de nitrato de amônio (32% de N), com quatro repetições (piquetes), em delineamento inteiramente casualizado. A absorção de nitrogênio (54,9; 96,5; 113,8 kg N ha-1) e o índice nutricional de N (0,67; 0,98; 1,15) foram diferentes entre as doses de N, respectivamente, 0, 75 e 150 kg ha-1 ano-1. A recuperação de N (58,3; 40,9%) diferiu entre 75 e 150 kg ha-1 ano-1, respectivamente. A dose de 75 kg N kg ha-1 ano-1 resultou em melhor aproveitamento do N, enquanto a dose de 150 kg N ha-1 ano-1 possibilita maior taxa de lotação; portanto, exigindo menos área de pastagem.

Effect of hairy vetch cover crop on maize nitrogen supply and productivity at varying yield environments in Southern Brazil.

Cover crops play a critical role on conservation and sustainable agriculture due to their well-documented benefits on both soil and crop productivity. Inclusion of legumes (e.g., hairy vetch, Vicia villosa Roth) in the farming system can reduce the nitrogen (N) fertilizer needs for cereals such as maize (Zea mays L.) crop while maintaining or increasing its productivity. The aims of this research study were to quantify the effect of hairy vetch as a cover crop on: i) successor maize yield under varying yield environments (YEs) and fertilizer N rates, and ii) maize N status [N uptake, N nutritional index (NNI), and N fertilizer replacement value (NFRV)] at flowering time. Two field studies were carried out in Southern Brazil under varying YEs. The factors investigated were: YE (low, medium, and high), hairy vetch cover crop (with and without), and fertilizer N rate (0, 60, 120, 180, and 240 kg N ha-1). Under the combination of low YE and low fertilizer N rates (0-60 kg ha-1) with previous vetch, maize displayed the largest yield response and an improvement in its N status. The NNI determined at maize flowering was an efficient index of the vetch effect, increasing delta maize yield response (yield with- minus without-vetch) as the NNI reduced, with more than 10% delta yield response with NNI below 0.85. The NFRV of the hairy vetch represents potential N savings of 151 kg N ha-1 for the LYE, 95 kg N ha-1 for the MYE and from 59 to 45 kg N ha-1 for the HYE depending on the tested fertilizer N rate. The N coming from the legume cover crop in addition to the N fertilization was critical for supplying N to maize and boosting productivity across all YEs.

Integrative Control Between Proton Pumps and SOS1 Antiporters in Roots is Crucial for Maintaining Low Na+ Accumulation and Salt Tolerance in Ammonium-Supplied Sorghum bicolor.

An effective strategy for re-establishing K+ and Na+ homeostasis is a challenge for the improvement of plant performance in saline soil. Specifically, attempts to understand the mechanisms of Na+ extrusion from plant cells, the control of Na+ loading in the xylem and the partitioning of the accumulated Na+ between different plant organs are ongoing. Our goal was to provide insight into how an external nitrogen source affects Na+ accumulation in Sorghum bicolor under saline conditions. The NH4+ supply improved the salt tolerance of the plant by restricting Na+ accumulation and improving the K+/Na+ homeostasis in shoots, which was consistent with the high activity and expression of Na+/H+ antiporters and proton pumps in the plasma membrane and vacuoles in the roots, resulting in low Na+ loading in the xylem. Conversely, although NO3--grown plants had exclusion and sequestration mechanisms for Na+, these responses were not sufficient to reduce Na+ accumulation. In conclusion, NH4+ acts as an efficient signal to activate co-ordinately responses involved in the regulation of Na+ homeostasis in sorghum plants under salt stress, which leads to salt tolerance.

Efficient production of lignocellulolytic enzymes xylanase, ß-xylosidase, ferulic acid esterase and ß-glucosidase by the mutant strain Aspergillus awamori 2B.361 U2/1.

The production of xylanase, ß-xylosidase, ferulic acid esterase and ß-glucosidase by Aspergillus awamori 2B.361 U2/1, a hyper producer of glucoamylase and pectinase, was evaluated using selected conditions regarding nitrogen nutrition. Submerged cultivations were carried out at 30 °C and 200 rpm in growth media containing 30 g wheat bran/L as main carbon source and either yeast extract, ammonium sulfate, sodium nitrate or urea, as nitrogen sources; in all cases it was used a fixed molar carbon to molar nitrogen concentration of 10.3. The use of poor nitrogen sources favored the accumulation of xylanase, ß-xylosidase and ferulic acid esterase to a peak concentrations of 44,880; 640 and 118 U/L, respectively, for sodium nitrate and of 34,580, 685 and 170 U/L, respectively, for urea. However, the highest ß-glucosidase accumulation of 10,470 U/L was observed when the rich organic nitrogen source yeast extract was used. The maxima accumulation of filter paper activity, xylanase, ß-xylosidase, ferulic acid esterase and ß-glucosidase by A. awamori 2B.361 U2/1 was compared to that produced by Trichoderma reesei Rut-C30. The level of ß-glucosidase was over 17-fold higher for the Aspergillus strain, whereas the levels of xylanase and ß-xylosidase were over 2-fold higher. This strain also produced ferulic acid esterase (170 U/L), which was not detected in the T. reesei culture.

Efficient production of lignocellulolytic enzymes xylanase, -xylosidase, ferulic acid esterase and -glucosidase by the mutant strain Aspergillus awamori 2B.361 U2/1

The production of xylanase, -xylosidase, ferulic acid esterase and -glucosidase by Aspergillus awamori 2B.361 U2/1, a hyper producer of glucoamylase and pectinase, was evaluated using selected conditions regarding nitrogen nutrition. Submerged cultivations were carried out at 30 ºC and 200 rpm in growth media containing 30 g wheat bran/L as main carbon source and either yeast extract, ammonium sulfate, sodium nitrate or urea, as nitrogen sources, in all cases it was used a fixed molar carbon to molar nitrogen concentration of 10.3. The use of poor nitrogen sources favored the accumulation of xylanase, -xylosidase and ferulic acid esterase to a peak concentrations of 44,880, 640 and 118 U/L, respectively, for sodium nitrate and of 34,580, 685 and 170 U/L, respectively, for urea. However, the highest -glucosidase accumulation of 10,470 U/L was observed when the rich organic nitrogen source yeast extract was used. The maxima accumulation of filter paper activity, xylanase, -xylosidase, ferulic acid esterase and -glucosidase by A. awamori 2B.361 U2/1 was compared to that produced by Trichoderma reesei Rut-C30. The level of -glucosidase was over 17-fold higher for the Aspergillus strain, whereas the levels of xylanase and -xylosidase were over 2-fold higher. This strain also produced ferulic acid esterase (170 U/L), which was not detected in the T. reesei culture.(AU)

Efficient production of lignocellulolytic enzymes xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by the mutant strain Aspergillus awamori 2B.361 U2/1

The production of xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by Aspergillus awamori 2B.361 U2/1, a hyper producer of glucoamylase and pectinase, was evaluated using selected conditions regarding nitrogen nutrition. Submerged cultivations were carried out at 30 ºC and 200 rpm in growth media containing 30 g wheat bran/L as main carbon source and either yeast extract, ammonium sulfate, sodium nitrate or urea, as nitrogen sources; in all cases it was used a fixed molar carbon to molar nitrogen concentration of 10.3. The use of poor nitrogen sources favored the accumulation of xylanase, β-xylosidase and ferulic acid esterase to a peak concentrations of 44,880; 640 and 118 U/L, respectively, for sodium nitrate and of 34,580, 685 and 170 U/L, respectively, for urea. However, the highest β-glucosidase accumulation of 10,470 U/L was observed when the rich organic nitrogen source yeast extract was used. The maxima accumulation of filter paper activity, xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by A. awamori 2B.361 U2/1 was compared to that produced by Trichoderma reesei Rut-C30. The level of β-glucosidase was over 17-fold higher for the Aspergillus strain, whereas the levels of xylanase and β-xylosidase were over 2-fold higher. This strain also produced ferulic acid esterase (170 U/L), which was not detected in the T. reesei culture.

Diagnosis tools useful in the management of nitrogen nutrition in Urochloa / Ferramentas diagnósticas úteis no manejo da nutrição nitrogenada em Urochloa

The N management on pasture requires methods for analyzing and predicting the need for fertilization, aiming at greater efficiency of fertilizer application, adjusting the forage requirements for biomass productivity with quality and sustainability. Nitrogen Nutrition Index (NNI) defined as the ratio between the actual N concentration and the N concentration critical, corresponding to the actual standing biomass. NNI is an indicator well connected with the physiological regulation of N concentration, but it cannot be used directly in farm conditions. Leaf N concentration has been shown to be with greenness (chlorophyll meter readings), as measured by SPAD 502, giving instantaneous values that could be used for estimating directly the N concentration and indirectly the NNI. The main of this work was to test the usefulness N concentration and SPAD to diagnose the N status of four genotypes Urochloa. The experimental design was a randomized block in a factorial 4 x 4, genotypes of Urochloa (U. brizantha cv. Piata, U. brizantha cv. Marandu, and two hybrids H69 and H12) and nitrogen levels (0, 75, 150 and 225 mg dm-3) whose source urea, with five replications, in pots (3.34 dm3) with Psament soil. Evaluations were performed on plants aged 52 days after sowing. Data were analyzed by the mixed procedure of SAS V. 9.2; average qualitative treatments were compared by Tukey test at 5% pr

O artigo não apresenta resumo em português.

Diagnosis tools useful in the management of nitrogen nutrition in Urochloa / Ferramentas diagnósticas úteis no manejo da nutrição nitrogenada em Urochloa

The N management on pasture requires methods for analyzing and predicting the need for fertilization, aiming at greater efficiency of fertilizer application, adjusting the forage requirements for biomass productivity with quality and sustainability. Nitrogen Nutrition Index (NNI) defined as the ratio between the actual N concentration and the N concentration critical, corresponding to the actual standing biomass. NNI is an indicator well connected with the physiological regulation of N concentration, but it cannot be used directly in farm conditions. Leaf N concentration has been shown to be with greenness (chlorophyll meter readings), as measured by SPAD 502, giving instantaneous values that could be used for estimating directly the N concentration and indirectly the NNI. The main of this work was to test the usefulness N concentration and SPAD to diagnose the N status of four genotypes Urochloa. The experimental design was a randomized block in a factorial 4 x 4, genotypes of Urochloa (U. brizantha cv. Piata, U. brizantha cv. Marandu, and two hybrids H69 and H12) and nitrogen levels (0, 75, 150 and 225 mg dm-3) whose source urea, with five replications, in pots (3.34 dm3) with Psament soil. Evaluations were performed on plants aged 52 days after sowing. Data were analyzed by the mixed procedure of SAS V. 9.2; average qualitative treatments were compared by Tukey test at 5% pr

O artigo não apresenta resumo em português.