Nitrate Nitrogen Uptake Research Articles

Impacts of Watershed Characteristics and Crop Rotations on Winter Cover Crop Nitrate-Nitrogen Uptake Capacity within Agricultural Watersheds in the Chesapeake Bay Region.

The adoption rate of winter cover crops (WCCs) as an effective conservation management practice to help reduce agricultural nutrient loads in the Chesapeake Bay (CB) is increasing. However, the WCC potential for water quality improvement has not been fully realized at the watershed scale. This study was conducted to evaluate the long-term impact of WCCs on hydrology and NO3-N loads in two adjacent watersheds and to identify key management factors that affect the effectiveness of WCCs using the Soil and Water Assessment Tool (SWAT) and statistical methods. Simulation results indicated that WCCs are effective for reducing NO3-N loads and their performance varied based on planting date, species, soil characteristics, and crop rotations. Early-planted WCCs outperformed late-planted WCCs on the reduction of NO3-N loads and early-planted rye (RE) reduced NO3-N loads by ~49.3% compared to the baseline (no WCC). The WCCs were more effective in a watershed dominated by well-drained soils with increased reductions in NO3-N fluxes of ~2.5 kg N·ha-1 delivered to streams and ~10.1 kg N·ha-1 leached into groundwater compared to poorly-drained soils. Well-drained agricultural lands had higher transport of NO3-N in the soil profile and groundwater due to increased N leaching. Poorly-drained agricultural lands had lower NO3-N due to extensive drainage ditches and anaerobic soil conditions promoting denitrification. The performance of WCCs varied by crop rotations (i.e., continuous corn and corn-soybean), with increased N uptake following soybean crops due to the increased soil mineral N availability by mineralization of soybean residue compared to corn residue. The WCCs can reduce N leaching where baseline NO3-N loads are high in well-drained soils and/or when residual and mineralized N availability is high due to the cropping practices. The findings suggested that WCC implementation plans should be established in watersheds according to local edaphic and agronomic characteristics for reducing N leaching.

Response of four fall-seeded cover crops to residues of selected herbicides

Currently, there are no published data available to describe the influence of herbicide residues on establishment and function of fall-seeded cover crops. Field experiments were conducted in 2012/2013 and 2013/2014 in Ontario, Canada, to characterize the effects of soil residues of selected herbicides on establishment and function of oat (Avena sativa L.), hairy vetch (Vicia villosa L.), oilseed radish (Raphanus sativus L.) and cereal rye (Secale cereale L.). These cover crops were planted three months after application of imazethapyr at 100 and 200 g ha−1, s-metolachlor/atrazine plus mesotrione at 2880 + 140 and 5760 + 280 g ha−1, and saflufenacil/dimethenamid-p at 735 and 1470 g ha−1. Imazethapyr residues caused up to 65 and 30% visible injury to oilseed radish at 1 and 4 WAE, respectively. Plant light attenuation, shoot dry weight and shoot nitrate-nitrogen uptake from imazethapyr residues three months after application were reduced up to 77, 34 and 43%, respectively in oilseed radish compared to non-treated control. Oat, hairy vetch and cereal rye were not negatively impacted by any of the herbicide residues tested. Preliminary evidence suggests that oat, hairy vetch and cereal rye may be safely seeded three months after saflufenacil/dimethenamid-p, s-metolachlor/atrazine plus mesotrione, and imazethapyr applied PRE at the currently registered rates. It is recommended however, that oilseed radish not be seeded three months after imazethapyr application.

Field‐based Selection Method Creates Alfalfa Populations That Differ in Nitrate Nitrogen Uptake

Sustainable agricultural systems could benefit from alfalfa (Medicago sativa L.) germplasm that reduce N losses to the ground water and decrease N fertilizer inputs. With the goal of producing alfalfa populations with altered nitrate N uptake, our objectives were to develop, assess, and refine an inexpensive selection method using Br− as an analog for nitrate under field conditions. Two selection schemes using divergent herbage Br− concentration and/or divergent herbage Br− uptake, both in combination with high herbage N content, produced two Cycle 1 and four Cycle 2 alfalfa populations. We evaluated these populations for both Br− uptake and nitrate N uptake (estimated by N derived from fertilizer, Ndff [15N‐labeled]) for one regrowth period in two locations in each of 2 yr. Weak associations between Br− uptake and Ndff were found during the establishment year, but strong correlations were found between Br− concentration and fraction of Ndff (fNdff) (r = 0.83) and between Br− uptake and Ndff (r = 0.85 to 0.90) when populations were evaluated during the first production year. Populations selected for high Br− concentration or uptake had greater Br− concentration and uptake, fNdff, and Ndff than populations selected for low Br− Our method of selecting alfalfa plants for differences in herbage Br− concentration or uptake in combination with high herbage N content is the first to successfully produce alfalfa populations that differ in nitrate N uptake in a field environment.

Uptake of Nitrate-Nitrogen in Intensive Shrimp Culture Ponds by Sterile Ulva sp.

We studied nitrate-nitrogen uptake by sterile Ulva sp. under various conditions including tropical ones. The Sterile Ulva sp., which was collected from Yokohama, Japan, removed nitrate-nitrogen in the culture medium. The algae took in nitrate-nitrogen even without light. The uptake rate of nitrate-nitrogen decreased with the increase of the nitrate-nitrogen content in algal cells. The ambient ammonia-nitrogen lowered the rate of nitrate-nitrogen uptake, whereas the ambient nitrate-nitrogen did not affect the ammonia-nitrogen uptake.

Nitrogen Uptake by Gracilaria gracilis (Rhodophyta): Adaptations to a Temporally Variable Nitrogen Environment

The physiology of nitrogen acquisition was determined for Gracilaria gracilis (Stackhouse) Steentoft, Irvine et Farnham in a series of perturbation experiments with the aim of examining uptake kinetics in response to transiently variable N. Experiments were designed to determine how variables such as history of exposure to nutrients, NO 3 - -N and NH 4 + -N concentrations and interactions, temperature and water motion affect parameters of linear and Michaelis-Menten models. A third 'Michaelis-Menten parameter' (a) is introduced here and used to extract additional ecological relevant information from the model. Ammonium-nitrogen uptake was best described by a linear, rate-unsaturated response, with the slope increasing with N-limitation, indicating that Gracilaria is more efficient at acquiring nutrients when internally stored N pools were impoverished. Temperature also affected the slope of the linear regression in the case of N-replete material. Nitrate-nitrogen uptake was suppressed by approximately 38 % in the presence of NH 4 + -N at concentrations above 5 μM, and the seaweed displayed a higher affinity for NH 4 + -N than for NO 3 - -N at low temperatures. Nitrate-nitrogen uptake followed a rate-saturating mechanism best described by the Michaelis-Menten model. Increased temperature enhanced the affinity for NO 3 - -N only in N-limited thalli, while nutrient limitation enhanced affinity irrespective of temperature. The maximal velocity of uptake (V m a x ) and the half saturation constant (K s ) appeared to vary with experimental conditions, but these differences were not statistically significant. Water motion was shown to reduce 'diffusion transport limitation' experienced by the alga under conditions of low external dissolved inorganic nitrogen (DIN) concentrations, so that the rate of N uptake responds with a 4.5-fold increase under conditions of enhanced water motion. All results suggest that Gracilaria gracilis is well suited to remain productive in an upwelling environment dominated by the transient availability of DIN through the use of a high affinity system for NO 3 - -N and non-saturable uptake of NH 4 + -N. Water motion interacts strongly with nutrient concentration, and may alleviate N limitation by reducing boundary-layer resistance to diffusion. Practical application of the results of this study is discussed in terms of significance to mariculture.

Constitutive and inducible aspects of nitrate-nitrogen uptake by Chlamydomonas reinhardtii

Constitutive and inducible aspects of nitrate-nitrogen uptake by Chlamydomonas reinhardtii

Nitrogen uptake and storage by the red alga Gracilaria tikvahiae (McLachlan, 1979)

Nitrogen-starved plants of the red alga Gracilaria tikvahiae (McLachlan, 1979) assimilate ammonium-nitrogen very rapidly, doubling their total tissue nitrogen content in 8 h or less. Uptake of nitrate-nitrogen is less rapid. Ammonium uptake is initially the same in the dark as in full sunlight, but the light-exposed seaweeds continue to assimilate the nitrogen longer. N-starved plants soaked in a full nutrient medium including NH 4 +-N for as little as 6 h and returned to unenriched flowing sea water will grow at non-nutrient-limiting rates for as much as 2 weeks before they again become nutrient-deficient and their growth rate declines.

Kinetics of nitrate and ammonium uptake by the tropical freshwater macrophyte Pistia stratiotes L.

The kinetics of nitrogen uptake were examined for a common freshwater macrophyte Pistia stratiotes. Nitrate-nitrogen and ammonium-nitrogen uptake were monitored in response to a wide range of substrate concentrations. Nitrate uptake rates were higher after 24 h of exposure to the nitrate source than immediately after exposure. The rate of uptake of nitrate-nitrogen was greater in the light than in the dark. Nitrate uptake followed a pattern which could be adequately described by the Michaelis—Menten expression. Ammonium-nitrogen uptake response to substrate concentration appeared to be linear. Rates of ammonium-nitrogen uptake were similar in the dark and in the light. For any given dissolved nitrogen concentration, the rate of ammonium-nitrogen uptake was greater than the rate of nitrate-nitrogen uptake.

STUDIES ON THE MECHANISM OF FUNGICIDAL ACTION OF CRYSTAL VIOLET ON MYCELIAL FELTS OF FUSARIUM CULMORUM.

Crystal violet, when incorporated in culture media of mycelial felts of Fusarium culmorum, reduced, or in certain cases stopped, the uptake of nitrate-nitrogen, protein and peptide synthesis, and carbon dioxide output by the mycelial mats.