Biological Nitrification Inhibition—A Novel Strategy to Regulate Nitrification in Agricultural Systems

Human activity has had the single largest influence on the global nitrogen (N) cycle by introducing unprecedented amounts of reactive-N into ecosystems. A major portion of this reactive-N, applied as fertilizer to crops, leaks into the environment with cascading negative effects on ecosystem functions and contributes to global warming. Natural ecosystems use multiple pathways of the N-cycle to regulate the flow of this element. By contrast, the large amounts of N currently applied in agricultural systems cycle primarily through the nitrification process, a single inefficient route that allows much of the reactive-N to leak into the environment. The fact that present agricultural systems do not channel this reactive-N through alternate pathways is largely due to uncontrolled soil nitrifier activity, creating a rapid nitrifying soil environment. Regulating nitrification is therefore central to any strategy for improving nitrogen-use efficiency. Biological nitrification inhibition (BNI) is an active plant-mediated natural function, where nitrification inhibitors released from plant roots suppress soil-nitrifying activity, thereby forcing N into other pathways. This review illustrates the presence of detection methods for variation in physiological regulation of BNI-function in field crops and pasture grasses and analyzes the potential for its genetic manipulation. We present a conceptual framework utilizing a BNI-platform that integrates diverse crop science disciplines with ecological principles. Sustainable agriculture will require development of production systems that include new crop cultivars capable of controlling nitrification (i.e., high BNI-capacity) and improved agronomic practices to minimize leakage of reactive-N during the N-cycle, a critical requirement for increasing food production while avoiding environmental damage

Genetic variability of drought-avoidance root traits in the mini-core germplasm collection of chickpea (Cicer arietinum L.).

Extensive and deep root systems have been recognized as one of the most important traits for improving chickpea (Cicer arietinum L.) productivity under progressively receding soil moisture conditions. However, available information on the range of variation for root traits is still limited. Genetic variability for the root traits was investigated using a cylinder culture system during two consecutive growth seasons in the mini-core germplasm collection of ICRISAT plus several wild relatives of chickpea. The largest genetic variability was observed at 35 days after sowing for root length density (RLD) (heritability, h 2 = 0.51 and 0.54) across seasons, and followed by the ratio of plant dry weight to root length density with h 2 of 0.37 and 0.50 for first and second season, respectively. The root growth of chickpea wild relatives was relatively poor compared to C. arietinum, except in case of C. reticulatum. An outstanding genotype, ICC 8261, which had the largest RLD and one of the deepest root system, was identified in chickpea mini-core germplasm collection. The accession ICC 4958 which was previously characterized as a source for drought avoidance in chickpea was confirmed as one with the most prolific and deep root system, although many superior accessions were also identified. The chickpea landraces collected from the Mediterranean and the west Asian region showed a significantly larger RLD than those from the south Asian region. In addition, the landraces originating from central Asia (former Soviet Union), characterized by arid agro-climatic conditions, also showed relatively larger RLD. As these regions are under-represented in the chickpea collection, they might be interesting areas for further germplasm exploration to identify new landraces with large RLD. The information on the genetic variability of chickpea root traits provides valuable baseline knowledge for further progress on the selection and breeding for drought avoidance root traits in chickpea

Eu31 Luminescence, Ce41 r Eu31 Energy Transfer, and White-Red Light Generation in Sr2CeO4

Photoluminescence studies on pure and Eu31-doped Sr2CeO4 compounds are presented. The pure compound displays a broad band in its emission spectrum when excited with 254 nm, which peaks at 467 nm and is due to the energy transfer between the molecular orbital of the ligand and charge transfer state of the Ce41 ion. The excitation spectrum shows a broad band which peaks at 300 nm. From the spectral properties, it is established that Sr2CeO4 has good potential for application as a blue phosphor in low pressure mercury vapor lamps and in TV tubes. The Eu31 spectral features, when doped at the Ce41 site either singly or along with La31, have been studied and compared with the results obtained by doping the Eu31 ion at the Sr21 site. At low Eu31 concentrations (#4 mol %), the observed excitation and emission spectra reveal excellent energy transfer between Ce41 and Eu31. This energy transfer generates white light with a color tuning from blue-white to red-white, the tuning being dependent on the Eu31 concentration. At high Eu31 concentrations (5-15 mol %), these compounds exhibit efficient red emission under 254, 355, and 466 nm excitations. The observed luminescence properties of these compounds are similar to those of the known Y2O3:Eu31 red phosphor. The emission intensity of Sr2CeO4:Eu (>0.05) under 466 nm excitation is twice that of Y2O3:Eu. The results establish that the compound Sr2CeO4 is an efficient “single host lattice” for the generation of white and red lights under UV irradiation