Nitrogen, Volume 1, Issue 1 (September 2020) – 7 articles

A crop’s health can be determined by its leaf nutrient status; more precisely, leaf nitrogen (N) level, is a critical indicator that carries a lot of worthwhile nutrient information for classifying the plant’s health. However, the existing non-invasive techniques are expensive and bulky. The aim of this study is to develop a low-cost, quick-read multi-spectral sensor array to predict N level in leaves non-invasively. The proposed sensor module has been developed using two reflectance-based multi-spectral sensors (visible and near-infrared (NIR)). In addition, the proposed device can capture the reflectance data at 12 different wavelengths (six for each sensor). We conducted the experiment on canola leaves in a controlled greenhouse environment as well as in the field. In the greenhouse experiment, spectral data were collected from 87 leaves of 24 canola plants, subjected to varying levels of N fertilization. Later, 42 canola cultivars were subjected to low and high nitrogen levels in the field experiment. The k-nearest neighbors (KNN) algorithm was employed to model the reflectance data. The trained model shows an average accuracy of 88.4% on the test set for the greenhouse experiment and 79.2% for the field experiment. Overall, the result concludes that the proposed cost-effective sensing system can be viable in determining leaf nitrogen status. Full article

The study estimated the relationship between the amount of nitrogen (N) that will become available to plants after incorporation of soil of sheep/goat, cattle, swine, and poultry manure and the duration of manure storage prior to soil addition. Manures were periodically sampled from 12 storage piles that were kept for 12 months each and mixed with soil before laboratory incubation for 83 days. The percentage of organic N mineralized after soil incorporation was clearly greater for poultry, ranging between 41 and 85%, in relation to the other three manure types, for which maximum mineralization ranged between 4.5 and 66%. For sheep/goat, cattle, and swine, the interaction between mineralization and immobilization processes showed a distinct pattern with two phases of net N release during the twelve months of storage. The first was separated from the second by a period where mineralization was zeroed and appeared at about six months after storage initiation. It was recommended that farmers should preferably use well-digested manures that have been aerobically stored more than six months to avoid materials that provoke intense immobilization, unless problems associated with the use of fresh manure are managed. Full article

Nitrogen (N) losses from field crops have raised environmental concerns. This manuscript accompanies a database of N loss studies from non-legume field crops conducted across the conterminous United States. Cumulative N losses through nitrous oxide-denitrification (CN₂O), ammonia volatilization (CNH₃), and nitrate leaching (CNO₃⁻) during the growing season and associated crop, soil, and water management information were gathered to determine the extent and controls of these losses. This database consisted of 404, 26, and 358 observations of CN₂O, CNH_3, and CNO₃⁻ losses, respectively, from sixty-two peer-reviewed manuscripts. Corn (Zea mays) dominated the N loss studies. Losses ranged between −0.04 to 16.9, 2.50 to 50.9, and 0 to 257 kg N ha⁻¹ for CN₂O, CNH₃ and CNO₃⁻, respectively. Most CN₂O and CNO₃⁻ observations were reported from Colorado (n = 100) and Iowa (n = 176), respectively. The highest values of CN₂O, and CNO₃⁻ were reported from Illinois and Minnesota states, and corn and potato (Solanum tuberosum), respectively. The application of anhydrous NH₃ had the highest value of CN₂O loss, and ammonium nitrate had the highest CNO₃⁻ loss. Among the different placement methods, the injection of fertilizer-N had the highest CN₂O loss, whereas the banding of fertilizer-N had the highest CNO₃⁻ loss. The maximum CNO₃⁻ loss was higher for chisel than no-tillage practice. Both CN₂O and CNO₃⁻ were positively correlated with fertilizer N application rate and the amount of water input (irrigation and rainfall). Fertilizer-N management strategies to control N loss should consider the spatio-temporal variability of interactions among climate, crop-and soil types. Full article

The ability of foam-based unplanted and green surfaces (Aqualok™) to remove pollutants (total suspended solids (TSS), NO₃, NH₄, total organic carbon (TOC) and total phosphorus (TP)) from direct precipitation and roof runoff passing through the surfaces was assessed. The assessments were conducted using unplanted Aqualok™ and planted Aqualok™ roof panels and a bioswale Aqualok™ installed on two Fire and Emergency Medical Service Stations (FEMSs) in Washington, D.C., USA. During a three-year period, impacts on water chemistry were evaluated by examining overall averages as well as performance over time. Upon installation, all Aqualok™ surfaces released a “pulse” of TSS and NO₃, which decreased over time. TP concentrations from the planted panels were elevated relative to conventional roof runoff throughout the study. TOC was generally higher for planted Aqualok™ compared to unplanted Aqualok™, and did not decrease over time. Excluding the three months post-installation, TSS in throughflow from planted and unplanted Aqualok™ surfaces was 88% and 90% lower, respectively, than in runoff from a conventional tar and gravel roof. No significant differences between green surface throughflow and conventional roof runoff for NO₃ or NH₄ were observed. Full article

Nitric oxide (NO) is a free radical and a component of the N-cycle. Nevertheless, NO is likewise endogenously produced inside plant cells where it participates in a myriad of physiological functions, as well as in the mechanism of response against abiotic and biotic stresses. At biochemical level, NO has a family of derived molecules designated as reactive nitrogen species (RNS) which finally can interact with different bio-macromolecules including proteins, lipids, and nucleic acids affecting their functions. The present review has the goal to provide a comprehensive and quick overview of the relevance of NO in higher plants, especially for those researchers who are not familiar in this research area in higher plants. Full article

The amino acid glutamine (Gln) is an important assimilatory intermediate between root-derived inorganic nitrogen (N) (i.e., ammonium) and downstream macromolecules, and is a central regulator in plant N physiology. The timing of Gln accumulation after N uptake by roots has been well characterized. However, the duration of availability of accumulated Gln at a sink tissue has not been well defined. Measuring Gln availability would require temporal measurements of both Gln accumulation and its reciprocal depletion. Furthermore, as Gln varies spatially within a tissue, whole-organ in situ visualization would be valuable. Here, the accumulation and subsequent disappearance of Gln in maize seedling leaves (Zea mays L.) was imaged in situ throughout the 48 h after N application to roots of N-deprived plants. Free Gln was imaged by placing leaves onto agar embedded with bacterial biosensor cells (GlnLux) that emit luminescence in the presence of leaf-derived Gln. Seedling leaves 1, 2, and 3 were imaged simultaneously to measure Gln availability across tissues that potentially vary in N sink strength. The results show that following root N fertilization, free Gln accumulates and then disappears with an availability period of up to 24 h following peak accumulation. The availability period of Gln was similar in all seedling leaves, but the amount of accumulation was leaf specific. As Gln is not only a metabolic intermediate, but also a signaling molecule, the potential importance of regulating its temporal availability within plant tissues is discussed. Full article