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The preferable N source for tropical grasses and its effects on the nutritional status are still matters of priority investigation. This study aimed to explore the effects of N sources and N deprivation on growth and uptake of elements in a newly-released ruzigrass cultivar, BRS Integra. Plants were grown under controlled conditions in vermiculite and were supplied with nutrient solution containing either NH4+, NH4++NO3-, NO3- or no N added in solution making. Plant biomass, chlorophyll content, transpiration, N status, and levels of selected elements were evaluated. NH4+ improved biomass production and aboveground N contents. Other elements exhibited high (N, K and Na), medium (Mn), low (Ca, Cd, Cr, Cu, Mg, Ni and Zn) or non-detected (Al and Fe) translocation. Cd was included in the study because of its hazardous concentrations in agricultural soils in Brazil and its influence on N uptake and translocation in the genus Urochloa. All N sources increased the uptake of whole plant Cu and K and Al, and root Fe and Mg. Other favorable relations prevailed in the roots, specifically of NO3- on Ca and Ni, NH4+ and NH4++NO3- on Cr, and NH4+ on Cd. Removal of N supply caused increases on Mn and Na aboveground and Zn in roots. Overall, the more evident N source-induced uptakes were, in order of decrease, of NO3- on Ca, NH4++NO3- on Ni, and NH4+ on Cr, Cu and Mn. It is concluded that NH4+ is more efficient for fertilizing ruzigrass by improving growth and N uptake compared to NH4++NO3- or NO3-. In addition, the diverse effects of varying N sources on the uptake of 12 elements indicate such interactions should be taken into account to further improve fertilizer formulations. [ABSTRACT FROM AUTHOR]

In this study, two experiments were conducted to evaluate the plant response of Brachiaria brizantha cv. MG5 to nitrogen forms and different pH of nutrient solution. For this, nutrient solutions containing ammonium and ammonium nitrate were fixed at pH 4, 6 or 8, and nutrient solution containing nitrate was fixed at pH 6. The pH adjustment was done by different compounds including MES, calcium hydroxide, calcium carbonate and sulfuric acid. In another experiment the seedlings were grown in nutrient solution with different N forms, but without pH adjustment. The results showed that plants in ammonium or ammonium nitrate at pH = 4 had better growth and performance, followed by pH = 6, compared to plants grown at pH = 8 (buffered with calcium carbonate). Calcium carbonate (bicarbonate) especially in higher amounts in nutrient solution (pH = 8) significantly reduced plant growth particularly root growth as the toxic effects were visible on the roots. The adverse effect of carbonate at high pH was more than those at low pH. High concentration of carbonate in presence of ammonium also was toxic for plants probably due to additional toxic effect of ammonia. However, plants were able to grow normally with different N forms under hydroponics culture, independent of pH effect. When pH was not controlled under different N-forms, there was no significant difference between root and shoot biomass production or leaf SPAD value and protein concentration. So, the presence of carbonate but not pH, was determined as an inhibiting factor for growth of Palisadegrass plants. [ABSTRACT FROM AUTHOR]

Macroalgal growth in temperate coastal ecosystems is primarily regulated by light and inorganic nitrogen availability. The effect of light (photon irradiance) on NO3- and NH4+ uptake, and NO3- - assimilation, were studied in the red macroalga, Hemineura frondosa, which does not operate a carbon concentrating mechanism (non-CCM). Non-CCM macroalgae grow in low and high light environments but become increasingly dominant with depth, suggesting a mechanism for 'preserving energy' under low light levels. H. frondosa was acclimated to limiting (30 µmol photons m-2 s-1) and saturating (150 µmol photons m-2 s-1) irradiances for 8 days. Then, NO3- and NH4+ uptake rates were measured under limiting and saturating irradiances at six concentrations ranging from 2--64 µM. NO3- uptake did not follow saturating uptake kinetics at both irradiances suggesting multiple uptake mechanisms. NH4+ uptake saturated at concentrations <32 µM under limiting but not under saturating irradiance. Saturating irradiance resulted in greater maximum uptake rates of both NO3- and NH4+. There was no evidence that irradiance regulated NO3- reduction by nitrate reductase. Also illustrated is the importance of measuring nitrate reductase activity on fresh material, as freezing in liquid nitrogen and storage at -80°C for 7 days caused a 65% decline in activity. Photosynthetic pigments, soluble tissue nitrogen and % total tissue nitrogen were all higher in limiting irradiance. In this first study of the nitrogen physiology of a non-CCM seaweed, we show that light regulates NO3- and NH4+ uptake but not NO3- assimilation. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential element for living organisms because it is a crucial constituent of biomolecules. Inadequate supply of usable nitrogen reduces plant growth and crop yield. The primary nitrogen sources for plants are nitrate and ammonium in soils, and plants have multiple layers of sensing and adaptive mechanisms that respond to the availability of these nutrients. The adaptive responses are called ‘nitrogen responses,’ which include morphological and physiological responses enabling plants to efficiently take up nitrogen and adapt to spatiotemporal fluctuations in nitrogen abundance in the field. In this review, we summarize the strategies that plants use to respond to changes in the nitrogen nutrient status in the soil and discuss different effects produced by nitrate and ammonium, emphasizing the important role of nitrate for plant growth. Recent studies revealed the molecular mechanism mediating the primary response to nitrate provision and the molecular mechanisms that coordinate the nitrogen response with responses to another macronutrient, phosphorus. We thus discuss these molecular mechanisms as well. [ABSTRACT FROM PUBLISHER]

Co-composting of chicken slurry and rice straw with clinoptilolite zeolite and urea as additives was conducted to determine the characteristics of a compost and their effects on controlling ammonium (NH4+) and nitrate (NO3−) losses from urea. Quality of the compost was assessed based on temperature, moisture content, ash, pH, electrical conductivity, carbon/nitrogen (C/N) ratio, NH4+, NO3−, macronutrients, heavy metals, humic acid, microbial population, germination index, and phytotoxicity test. Moisture content and C/N ratio of the compost were 43.83% and 15, respectively. Total N, humic acid, ash, NH4+, NO3−, phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) increased after co-composting rice straw and chicken slurry. Copper, iron (Fe), manganese (Mn), zinc (Zn), and microbial biomass of the compost were low. The germination rate of Zea mays on distilled water and Spinacia oleracea growth on peat-based growing medium (PBGM) and compost were not significantly different. Urea amended with compost reduced N loss by retaining NH4+and NO3−in the soil. [ABSTRACT FROM AUTHOR]