A re-examination of Kruizinga and Wells dryland cotton NFUE is warranted due to the availability of new varieties and the potential management and long-term soil resilience implications of the continued removal of mineralised soil N suggested by these high NFUE values.
Data sourced from Roth Rural Trial sites were located in all cotton production irrigation regions. Two more recent N studies Schwenke ; Welsh et al. These lower fertilizer rates may lead to an overall decline in soil N content and potential crop deficiencies, particularly if there is insufficient residual N from the previous season or no legume rotation or addition of organic amendments.
Anecdotal evidence based on cotton picker yield monitoring, however, suggests that lint yields within cotton fields can range between 2. A significant improvement would be the calibration of yield monitoring across the industry. This indicates that factors other than N availability are limiting yield, and that the lower observed NFUE values may be caused by subsoil constraints such as sodicity and compaction Dodd et al. This kind of research will enable growers to manage the causes of their production deficits. Future researches should utilise on-the-go sensing and zonal management to identify, better understand, and target subsoil constraints that are limiting yield.
Unfortunately, the majority of this N is lost via denitrification to the atmosphere, with a portion also lost in surface run-off, transformed and lost as the powerful greenhouse gas nitrous oxide N 2 O , or lost to deep drainage, potentially affecting groundwater systems Macdonald et al.
These losses further emphasise the importance of improving NFUE across the industry. Australian cotton industry consultants and agronomists use a range of fertiliser decision support platforms that include, but are not limited to, Nutrient advantage advice, Back paddock soil mate and NutriLogic Todd Field history, previous experience and standard rates established over a period are also cited in the survey as influencing fertiliser decisions. A comprehensive review of various fertiliser decision support tools and reasons for their adoption or limitations is warranted. Existing fertiliser decision support tools need to be upgraded to assist growers and consultants in improving their NFUE.
Decision tools should account for seasonal weather limitations and their impact on split fertiliser applications, and offer alternate solutions to fertiliser management where water-run fertiliser applications need to be skipped to avoid waterlogging. At national and regional scales, NFUE is below industry expectations. Over fertilising is a particular problem for irrigated cotton systems, and can lead to delayed maturity, defoliation difficulties, boll drop, increased rates of disease, rank cotton and leaf trash in lint Marshall et al. This indicates that the availability of N is not the key production constraint in these trials, that N losses are occurring from the system, and that the industry needs to identify the yield constraining factors.
At the same time, the adoption of existing fertiliser decision support systems that incorporate residual soil fertility, such as Nutrilogic, is limited. A reduction in the application of fertiliser N and the utilisation of myBMP, Nutrilogic and other industry funded guidelines should be adopted. In contrast, the dryland sector may be mining soil N due to low fertiliser inputs that do not match N removal and N losses. Going forward, monitoring and evaluation of the soil resource base are required.
Growers who are not practising myBMP, utilising cover crops, legumes and residue retention should be encouraged to modify their practices to maintain soil resilience. Growers often apply fertiliser N as early pre-plant applications up to eight months prior to sowing. These conditions would have promoted enhanced denitrification of the fertiliser N which contributed to large losses. In drier conditions, the overall losses would be lower. The potential for losses is minimised when the N fertiliser is applied closer to sowing August—September rather than earlier in the year Constable and Rochester ; Humphreys et al.
Significant losses due to denitrification can still occur when the fertiliser is applied nearer to sowing Humphreys et al.
Facts About Nitrogen
The only way to lower the risk of denitrification caused by rainfall is to delay the formation of nitrate-N from the applied fertiliser, either chemically through nitrification inhibitors, or physically, through slow-release coatings of polymers etc. If irrigation techniques are the cause of the denitrification, then methods that reduce waterlogging should be investigated. Marshall et al. This corresponds to findings of Humphreys et al.
Rather than late-season applications, it is more important to obtain a large plant, rich with N, prior to boll production Crowther , which means full fertilisation should occur before boll production. It is at boll production that soil N up-take by the plant dramatically reduces, and translocation of N from the leaves to bolls occurs Crowther The risk of N run-off and leaching loss is greater early in the irrigation season when the crop is small Macdonald et al.
Another timing option increasingly practiced by cotton growers is to split N applications between pre-plant and in-crop applications in conjunction with early season irrigation events. This strategy should be monitored and evaluated in the field, and modelled under a range of conditions to test whether it is suitable for widespread adoption. The split N application includes a risk factor for growers when high rainfall events coincide with the application timing.
The latest cotton yield survey suggests that the average industry yield for irrigated cotton is 2. To increase the higher N uptake and improve the harvest index, future researches need to focus on improving our understanding of N translocation within cotton plants. Variations in irrigation technique are not commonly directly linked with NFUE in the literature, with environmental studies assessing N losses often the best proxies for estimating NFUE. McHugh et al.
This difference in NFUE was further pronounced under reduced water usage, where subsurface drip N losses decreased to negligible levels. Bronson et al. Furthermore, Bronson et al. No appreciable deep drainage and associated N loss were reported for the overhead sprinkler irrigation systems, due to a reduction in waterlogging Bronson et al. In a qualitative review of N and irrigation techniques, Barakat et al. The mounting evidence indicates that furrow irrigation, which is the most common irrigation technique used in Australian irrigated cotton, results in the lowest NFUE of all common irrigation techniques.
Research directly comparing the NFUE of different irrigation methods should be undertaken, building on the work of Bronson et al.
Many Australian studies include data that could theoretically be collated in a meta-analysis to suggest relative NFUE values as a function of irrigation technique furrow irrigation: Antille et al. The NFUE implications of water-running fertilisers as an alternative to solid banded or broadcast or gaseous N delivery methods is also poorly understood in the literature. However, beyond the improvements to NFUE derived from splitting the N applications across several events, the NFUE implications of applying N aqueously over other methods are not well characterised.
Water-running N also has application uniformity problems, with many growers unsure of its efficacy and hesitant to adopt fertigation practices due to restricted N visibility. Theoretically, water-running N should result in a uniform fertiliser application, and indeed Antille and McCarthy comment on the uniformity of N application in their water-run study; however, minimal data exist confirming the uniformity and efficacy of water-run N applications, and this should be a focus of future research.
Recirculation of tail-water is the practice of Australian cotton industry, with moderate concentrations of residual N in supply channels leached from the hills in the fields Macdonald et al. As such, N losses can occur from the irrigation network external to the field regardless of whether intentional fertigation is occurring. Macdonald et al. These fugitive emissions may increase significantly in scenarios of fertigation or N over-application, potentially even exponentially in line with field emission estimates by Grace et al.
Historically, most of the cotton grown in Australia has been on cracking clay soils Constable and Rochester ; Hulugalle and Scott , and as such the bulk of Australian cotton nitrogen researches have taken place on these soils Grace et al. As economic and climatic drivers extend the cotton belt further from its historical centres, cotton is increasingly being grown on different soil types. Deviation in soil attributes fertility, particle size, elemental composition, pH, colour, etc.
Research characterising the effects of specific soil attributes on NFUE would provide the industry with valuable tools for predicting which areas are suitable for cotton expansion. Soil processes are also key constraints to production. It is recommended that improved N mineralisation characterisation be undertaken using a combination of direct sampling measurements, aerial and remote sensing techniques, and modelling.
A common misconception is that the bulk of the fertiliser N not taken up by the plant is immobilised in the soil and will be released in subsequent years. A key aspect of soil management for improved NFUE is to utilise crop rotations with legumes, and to plant cover crops during fallow periods. Soil organic carbon levels are generally declining with cotton monoculture and cotton-wheat rotations due to an insufficient amount of residue returned to the soil Hulugalle and Scott Overall, growing legumes in traditional fallows improve soil organic matter levels, fertility, and soil N Marshall et al.
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To further improve soil health, it is recommended that crop stubbles be incorporated and residue burning avoided Rochester and Peoples While there are on-farm logistical impediments to the adoptation of cover-cropping and legume rotations, and the opportunity cost of soil water use by the cover crop needs to be considered, the yield and long term soil health benefits of rotational cropping can be significant. Soil compaction is another key management practice that contributes to reduced NFUE.
Soil compaction caused through natural flooding or management processes traffic, wet tillage, excessively heavy pickers can reduce NFUE by promoting denitrification Constable and Rochester ; Rochester and limiting plant growth through root inhibition Antille et al. Soil compaction is not permanent and can be mitigated Bennett et al. While this picker is perceived to be labour and time efficient compared with previous cotton pickers, its impact on soil compaction and any indirect effect on NFUE needs to be evaluated.
Changing climate is likely to have a significant effect on cotton yields in Australia and around the world Broughton et al. Increased ambient temperatures are largely predicted to have a negative effect on cotton production. In controlled experiments, early-season biomass was shown to increase under elevated temperature conditions; however, mid- and late-season growth was restricted, with boll-retention increasingly adversely affected with elevated temperatures Broughton et al.
Furthermore, as ambient temperatures increase, so too do crop water requirements Broughton et al. This will likely result in increased irrigation requirements, which will be further exacerbated by the reduced rainfall predicted for much eastern Australia. It forms dense growth patterns that reduce plant and insect biodiversity, and lab assays show that it It forms dense growth patterns that reduce plant and insect biodiversity, and lab assays show that it produces allelopathic compounds that affect microbial activity. Consequently, we hypothesized that V.
We sampled soil from a similar time point within a growing season at each of five sites in New York State where V. We measured bacterial and fungal microbiome composition, available soil nitrogen N , soil respiration CO 2 flux , and soil extracellular enzyme activities. Microbial composition varied across field sites, but only fungal composition was affected by invasion. No significant differences were found between the invaded and uninvaded plots at any of the sites for available soil ammonium, nitrate, or respiration, though extractable N varied greatly between sites.
Microbial hydrolytic extracellular enzyme activities suggest decreased protein degradation and increased oxidative enzyme activity with V. Although V. Chemosymbiotic bivalves contribute to the nitrogen budget of seagrass ecosystems.
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In many seagrass sediments, lucinid bivalves and their sulfur-oxidizing symbionts are thought to underpin key ecosystem functions, but little is known about their role in nutrient cycles, particularly nitrogen. We used natural stable We used natural stable isotopes, elemental analyses, and stable isotope probing to study the ecological stoichiometry of a lucinid symbiosis in spring and fall.
Chemoautotrophy appeared to dominate in fall, when chemoautotrophic carbon fixation rates were up to one order of magnitude higher as compared with the spring, suggesting a flexible nutritional mutualism. In fall, an isotope pool dilution experiment revealed carbon limitation of the symbiosis and ammonium excretion rates up to tenfold higher compared with fluxes reported for nonsymbiotic marine bivalves.
These results provide evidence that lucinid bivalves can contribute substantial amounts of ammonium to the ecosystem. Given the preference of seagrasses for this nitrogen source, lucinid bivalves' contribution may boost productivity of these important blue carbon ecosystems. Effects of uranium concentration on microbial community structure and functional potential. This study aimed to understand the impact of uranium concentration on microbial communities, in order to identify and describe potential breakpoints in microbial ecosystem services.
Changes to microbial communities were characterised through the use of amplicon and shotgun metagenomic next-generation sequencing. Saltwater intrusion history shapes the response of bacterial communities upon rehydration. Saltwater intrusion SWI can result in the loss of dominant vegetation from freshwater habitats.
In northern Australia, sea level is predicted to rise cm by This will exacerbate the impact of SWI, threatening This will exacerbate the impact of SWI, threatening Ramsar-listed habitats. Soil bacteria in these habitats play a significant role in biogeochemical cycling, regulating availability of essential nutrients such as nitrogen to vegetation. However, there is limited understanding as to how SWI will impact these soil bacteria.
A SWI event was simulated over 7 days with treatments of saltwater and freshwater.
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Bacterial community composition before and after treatment were measured using next generation sequencing of bacterial DNA. Sites with no history of SWI showed no significant changes in community taxonomic composition following treatments, suggesting the community at these sites have broad functional capacity which may be due to their historic conditioning over many years.
Sites with a history of SWI showed a significant response to both treatments. Following saltwater treatment, there was an increase in sulfate-reducing bacteria, which are known to have an impact on carbon and nitrogen cycling. We suggest that the impact of SWI causes a shift in the soil bacteria which alters the community to one which is more specialised, with implications for the cycling of essential elements and nutrients.
Nitrogen is an essential component of basic bio-molecules.
Atmospheric nitrogen is inaccessible to living organisms because of its inert nature but it can be fixed into usable forms by nitrogen-fixing microbial communities. The microbial The microbial nitrogen cycle is a complex process which occurs through the coordinated functioning of several microbial genes, many of which have been identified primarily from cultivable microbes. However, for unculturable microbes belonging to the community of a given environment, metagenomics is used as an alternative approach to the classical methods of genomics, including polymerase chain reaction based gene identification and restriction fragment length polymorphism.
A few metagenomic studies of terrestrial and aquatic environments, including some under moderate and extreme conditions, have been carried out which focus on nitrogen-fixing microbial communities and their functional diversities.
The nitrogen nutrition potential of arable soils | Scientific Reports
This could boost plant growth and help sequester carbon — but not fast enough to avert climate change, as some pundits have claimed. America's drinking water infrastructure is aging and needs billions of dollars in upgrades. Two extension educators urge consumers to monitor their water and have it tested if they suspect problems. Pollution has increased carbon in our soils - which is good for climate change. But this carbon may not stay there for long. Somehow we need to grow more food to feed an expanding population while minimising the problems associated with nitrogen fertiliser use.
With current modes up against their limits, we need new data storage solutions. Tiny defects in diamonds' atomic structure might turn them into a new medium for memory. Increasing legume production can turn the tide for African farmers who struggle with poor soils, declining farm yields and worsening nutrition in one fell swoop.