Food security for a growing population presents a significant challenge for crop production, with increasing pressures upon agriculutral productivity. There is a vast need to improve crop yield and quality using an efficient approach that does not present negative environmental impacts. A novel interrogation technique that is able to provide information of the overall health of a plant, would be extremely beneficial in an agriculutral, as well as research, setting. This information could be utilised to better understand the mechanisms of plant functions, including stress responses. Vibrational spectroscopy encompasses a range of techniques that are able to derive chemically specific information from a biological sample in a rapid, nondestructive and cost-effective manner. Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy are two such approaches and have been readily implemented across biological samples. However, their applications in the field of plant science have been relatively underexploited. This is largely associated with the presence of water and fluorescent metabolites found in plant tissues. The application of attenuated total reflectance (ATR)-FTIR and spontaneous Raman spectroscopy for in vivo plant monitoring to elucidate spectral alterations indicative of healthy plant growth in a non-destructive manner. These approaches are able to characterise the biochemical signature of leaves at distinct developmental stages, and correspond to known biological processes within the leaf such as cell wall expansion. This information is useful prior to monitoring studies as normal leaf growth could be considered background variance. No significant local or systemic effects manifest as a consequence of interrogation with these techniques, establishing this as a non-destructive approach for plant system investigations. Raman microspectroscopy as a tool for monitoring nutrient uptake at the leaf surface is also considered, alongside complementary ion probe and elemental analysis. Such a technique is useful in the agrochemical production of foliar fertilisers, where the efficiency of specific formulae can be rapidly compared. This can also further the current understanding of nutrient transport into plant tissues, as well as translocation. Agriculturally relevant levels of calcium were applied to the leaf surface and uptake was successfully illustrated at concentrations as low as 15 mM using Raman microspectroscopy. Ion probe analysis also complemented these findings, with elemental analysis unable to detect this subtle uptake of nutrients. This assay is now being implemented in agrochemical practise as a fertiliser screening method. Deficiencies in essential nutrients such as calcium are detrimental to crop yield and thus are a potential target for improving crop production. A range of spectroscopic methods, including the use of synchrotron radiation, were utilised to presymptomatically detect these deficiencies prior to their onset in live samples. Coupled with multivariate analysis, these techniques discriminate between deficient and control samples with high sensitivity and specificity, without extensive sample preparation that traditional analytical techniques require. These results suggest that Raman and ATRFTIR spectroscopic approaches could highly valuable in the field, where plant health and nutrient status could be assessed rapidly in situ. Here it is shown that these issues can be overcome and that qualitative spectral measurements can be obtained from plant samples. Due to the non-destructive nature of these approaches, they can be applied for a wider range of crop screening investigations, including the efficiency of nutrient uptake, as well as distinguishing nutrient deficiencies presymptomatically. As such, these spectroscopic methods may be implemented to unearth further details regarding nutrient use efficiency during crop production.

No description available.

Field experiments were carried out to determine the effect of nitrogen on the yield, nitrogen uptake and grain nitrogen concentration of spring barley grown for malting. The effects of the rate, timing of application and the form in which the fertiliser nitrogen was applied were studied. The form of fertiliser nitrogen applied had little effect on grain nitrogen concentrations, except under dry soil conditions, when concentrations were higher using calcium nitrate fertiliser. Calcium nitrate also improved grain yields at low fertiliser rates, but at rates nearer recommended levels there was little difference in yield between fertiliser forms. Split or late applications of fertiliser nitrogen only improved yields when applied as calcium nitrate, and then only when early applications had been followed by heavy rain. At low fertiliser rates, the efficiency of recovery of fertiliser nitrogen (<SUP>15</SUP>N) in plant shoots was greater, when applied as calcium nitrate than when applied as ammonium sulphate or ammonium nitrate. Efficiency of recovery fell at higher rates in calcium nitrate treatments, but rose in ammonium sulphate treatments. Under the dry soil conditions in 1989, the efficiency of recovery was significantly increased in all fertiliser treatments. Uptake of fertiliser nitrogen was rapid in the calcium nitrate and ammonium nitrate treatments, usually reaching a maximum by anthesis. There was evidence of losses between anthesis and harvest of fertiliser nitrogen previously taken up by the crop. The uptake of soil nitrogen in the calcium nitrate treatments remained constant over the range of rates and timings of fertiliser application. There was evidence of increasing uptake of soil nitrogen with increased rates of ammonium sulphate fertiliser at several sites, possibly due to 'pool substitution' of <SUP>15</SUP>N-labelled fertiliser. Uptake of soil nitrogen was less rapid than fertiliser nitrogen before anthesis, but continued right up to harvest in most treatments.

Continuous measurements of atmospheric ammonia (NH₃) exchange were conducted for a period of 19 months (May 1998-November 1999) over intensively managed grassland (cut twice for silage and grazed) in southern Scotland using the aerodynamic gradient method. The mean NH₃concentration and flux for the whole measurement period were 1.52 μg m^-3 and 13.9 ng m^-2 s^-1, respectively. Enhanced emissions of NH₃ were observed following three separate grass cutting events (June 1998, August 1998 and June 1999) with peak emissions of 380, 200 and 539 ng m^-2 s^-1, respectively. The magnitude of these emissions was up to an order of magnitude greater than the emissions observed from the grassland prior to cutting. Enhanced NH₃ emissions from cut grassland have been observed, but not quantified prior to this study. The NH₃ exchange was bi-directional with large diurnal and seasonal variation, which was strongly linked to grassland management in addition to meteorological conditions. The grassland varied from being a net sink for NH₃ during winter months (-6.0 g NH₃-N ha^-1 d^-1) and prior to cutting of the grass (-4.9 g NH₃-N ha^-1 d^-1) to being a net source after the grass was cut (29.3 g NH₃-N ha^-1 d^-1) and after nitrogen fertilisation (153.6 g NH₃-N ha^-1 d^-1). Net emission was also observed during grazing periods (33.0 g NH₃-N ha^-1 d^-1). The pattern of Nh₃ exchange was similar for 1998 and 1999. The net annual budget of NH₃ exchange for the grassland for May 1998-April 1999 was emission of NH₃ of 1.9 kg N ha^-1 yr¹, equating to 1.6% of the fertiliser N applied. The gross emission flux for the year was 4.2 kg N ha^-1 yr^-1. Scaling up these gross emissions across the whole of the UK improved grassland (60,500 km²) would lead to 25 kt NH₃-N, equivalent to 9.5% of the UK total emissions. These results indicate that the gross emission from all processes in fertilised grassland, including emissions from fertilisation, grazing and from cutting, make a significant contribution to the NH₃ emission budget of the UK.

No description available.

This study aimed at contributing to the understanding the physiology, structural distribution and management of Napier grass (<i>Pennisetum purpureum</i> Schum.) since its versatility promoted its wide distribution in tropical and subtropical areas of the world. A series of three experiments were developed to determine growth dynamics, sward structure, and forage quality at different physiology ages.  In the first study in long established pasture of Napier grass were applied three fertilizer levels of dairy cattle manure and three cutting intervals. A second experiment included two inorganic nitrogen fertilizer levels and two cutting intervals. The third experiment assessed the physiological performance of the pasture applying destructive sampling every 10 days, from 10 to 80 days. The general objective was to adapt the CROPGRO growth model to Napier grass included in the DSSAT program. Model calibration has been based in a review of Napier grass physiology and in experimental data to provide a structural and quantitative framework for describing crop response to environment and management. The Specie (SPE), Cultivars (CUL) and Ecotype (ECO) files were modified, based first on literature information and secondly, on optimisation against field data. Root Square Mean Error (RMSE) values were 42, 26, 16 and 5% for aboveground biomass, stem biomass, leaf number per stem and plant height, respectively. The Index of Agreement (d) for the same variables was 0.9, 0.8, 0.97 and 0.99 respectively. The incorporation of the Napier grass model into the Cropping System Model (CSM)-CROPGRO Version 4.0 framework confirmed that the new crop model has good potential to assess management strategies for optimising forage production of Napier grass.

No description available.

Phosphate fertilizers are a finite resource, thus sustainable crop production will most likely depend on the utilization of P sources naturally found in soil, in particular predominant organic P forms. To date we know little of the biochemical sensing and adaptation of crops to different organic and inorganic P that potentially affects its assimilation. Furthermore, the use of inoculants of beneficial soil microorganisms has become of increasing interest due to their ability to mobilize P from organic and inorganic sources naturally occurring in soil. However, many factors including nutrient type and status, plant species and the presence of other microbes have a positive or detrimental affect on microbial fitness and activity and as a result on crop P uptake and growth. Therefore, the aim of this PhD thesis was to improve our understanding of the biochemistry of phosphorus sensing, mobilization and uptake in wheat from various sources, and subsequently address the impact of mycorrhizal fungi as well as plant growth promoting rhizobacteria on these processes. Mesocosm studies provided detailed evidence that wheat root metabolism and the secretion of root exudates are sensitive to organic and inorganic P forms. In addition and with respect to P uptake and growth, wheat responsiveness to mycorrhizal fungi and plant growth promoting rhizobacteria colonization was highly dependent on the present P form. However, long-term changes in root metabolism were mainly driven by the P source. Based on these results, it is still necessary to ascertain if these metabolic changes are general responses of wheat or cultivar specific. Further, it is essential to link these responses to P uptake mechanisms and determine their effect on rhizosphere microorganisms in order to develop cultivars that not only have enhanced soil P exploitation and utilization capacities, but also positively respond to beneficial rhizomicroorganisms.

No description available.

Predicting N release in agricultural soils amended with organic residuals is essential to ensure there are sufficient nutrients for crops, and minimal losses to the environment. Factors such as moisture, temperature, soil type and organic residuals type may affect the amount of mineralised nutrients. Information is required to describe microbial N immobilisation in biosolids-amended soil, which may vary between soil types influencing extent and rate of nutrient release. Industrial biowastes are increasingly being used as soil amendments as a diversion from landfill disposal; these materials result from a diverse range of processes and vary greatly in physical and chemical characteristics. There is little published or advisory information regarding their agronomic benefit, therefore research is required to quantify their fertiliser value. The aims of this research were to quantify mineralisation of N, and investigate other agronomic benefits of biosolids and biowastes, and to investigate microbial biomass N (MBN) dynamics, with the aim of improving fertiliser guidelines. A field trial was established at the Imperial College field station in Wye, Kent, in spring 2005, to investigate N transformations in contrasting soil types amended with conventional and enhanced treated biosolids. Analysis of MBN in biosolids-amended soil indicated that there were differences in N immobilisation processes in soils of differing fertility status, with greater immobilisation observed in the lower fertility soil in some cases. Despite initial differences in rate of mineralisation and nitrification, overall extent of N release was similar in both soils. A programme of field trials was established at Imperial College Silwood Park campus in 2006-2007 to quantify the agronomic value of a range of industrial biowastes. Biowastes from the vegetable, meat and dairy industries and from aerobic and anaerobic digestion plants were investigated. Yield response and N offtake of perennial ryegrass to biowastes, at five rates of application, in comparison to mineral N fertiliser, was used to calculate the replacement N fertiliser value. The results of a laboratory incubation experiment, to investigate MBN and mineral N in biowastes-amended soil, demonstrated lower recoveries of N in fine textured soil with low stability waste. Denitrification was suspected as the potential mechanism for this observation. Interactions between soil type and biowaste type on N availability, and the implications for gaseous N losses to the environment from biowastes-amended soils require further research.