Browsing by Author "Martin, Peter J."

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    Effects of soil compaction and mechanical damage at harvest on growth and biomass production of short rotation coppice willow
    (Springer Science Business Media, 2004-06) Souch, C. A.; Martin, Peter J.; Stephens, William; Spoor, G.
    The effects of soil compaction and mechanical damage to stools at harvesting on the growth and biomass production of short rotation coppice (SRC) of willow (Salix viminalis L.) were monitored on clay loam (CL) and sandy loam (SL) soils. Moderate compaction, more typical of current harvesting situations did not reduce biomass yields significantly. Even heavy compaction only reduced stem biomass production by about 12% overall; effects were statistically significant only in the first year of the experiment on sandy loam. Heavy compaction increased soil strength and bulk density down to 0.4 m depth and reduced soil available water and root growth locally. Soil loosening treatments designed to alleviate the effects of heavy compaction did not markedly improve the growth of willow on compacted plots. Hence the focus fell on harvesting. Extensive mechanical damage to stools caused a 9% and 21% reduction in stem dry mass on the clay loam and sandy loam soils as a result of fewer stems being produced. The particularly severe effect on the sandy loam soil probably resulted from a combination of dry conditions in the year of treatment, root damage and soil compaction under stools and might have been aggravated by the young age of the plants (1 year) at the time of treatment.
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    A rate-based approach to cleaning-in-place
    (American Chemical Society, 2017-05-18) Trinh, Linda; Willey, A. Roy; Martin, Peter J.; Ashley, Jon; Tothill, Ibtisam E.; Rodgers, Thomas Lawrence
    Fouling is a major problem in the food industry. In cases where allergens are involved, excessive cleaning of food processing equipment often takes place to ensure allergen levels are reduced to acceptable levels. Experimental trials were conducted in a pilot scale cleaning rig to assess the effect of fluid flow rate and temperature on the removal rate of milk paste during cleaning-in-place. Conductivity measurements taken during trials were analysed to produce an equation enabling calculation of the cleaning rate with water temperature, flow rate, initial deposit mass, and time. The rate of cleaning with detergent was also investigated. This methodology produces a rate based expression for cleaning which can be applied to other products, and can be used to determine the time when cleaning is complete, the extent of a cleaning process, or when the pre-rinse should be replaced with a detergent rinse. This prevents over-cleaning and therefore reduces the costs associated with over-cleaning through energy, material and loss of production time.
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    Willow growth in response to nutrients and moisture on a clay landfill cap soil. I. Growth and biomass production
    (Elsevier, 2005) Martin, Peter J.; Stephens, William
    This paper describes studies into the effect of soil factors and water stress on the growth and biomass production of willow (Salix viminalis L.) on a clay landfill cap soil. Individual plants were grown in lysimeters containing Oxford clay and using different soil amendments, bulk densities and watering regimes. Three years from planting, stem biomass production in well-watered plants was least (0.28 kg plant-1) with high bulk density soil (1480 kg m-3) and no nutritional amendment but was increased 10-fold (2.53 kg plant-1) by reducing soil bulk density (1200 kg m-3) and adding thermally dried sewage sludge and fertilisers (N, P and K). This was low, however, compared with production on a sandy loam soil (6.23 kg plant-1) with the same amendments and a similar bulk density. These large treatment differences were also reflected in number of stems plant-1, stem basal area plant-1 and plant leaf area. Plants growing on the Oxford clay had higher root:stem ratios than those on the sandy loam. Water stress reduced stem biomass production by 26 - 37% and caused higher root:stem ratios. Foliar and soil analyses and pot trials indicated that the effects of the soil amendments could be attributed to the addition of N and P which are low in Oxford clay. The research suggests that reasonable biomass production from willow SRC on Oxford clay landfill caps will be dependent on the application of nutritional amendment to the soil at these sites.
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    Willow growth in response to nutrients and moisture on a clay landfill cap soil. II: Water use
    (Elsevier, 2005) Martin, Peter J.; Stephens, William
    This paper describes studies into the effects of soil factors and water stress on water use by willow (Salix viminalis L.) on a clay landfill cap soil and a sandy loam. Individual plants were grown in lysimeters containing these soils under different watering regimes and with different soil amendment treatments. Stemflow and throughfall were measured to determine rainfall entering the lysimeters and evapotranspiration (ET) calculated from a water balance. With plentiful water, seasonal ET increased annually in most treatments, reflecting increases in plant leaf area and dry matter production. For the most vigorous plants, in the sandy loam treatment, it increased from about 360 l plant-1 in the establishment year to almost 1200 l plant-1 in the third year. Seasonal ET was highly correlated with leaf area duration. Nutritional amendment of Oxford clay resulted in plants with larger leaf area and higher dry matter production and seasonal ET than in the unamended treatment. Water stress reduced seasonal ET by up to 41%, as a result of defoliation and stomatal closure. In unstressed plants, in the sandy loam treatment, daily ET rates per unit leaf area reached a maximum of about 1.5 l m-2 d-1 in July. Without nutritional amendment, water use efficiency (WUE) calculated from plant ET and root, stump and stem dry weight, was low for the unamended Oxford clay treatment (1.4 g kg-1) but was similar in the amended clay (5.0 g kg-1) and sandy loam (4.9 g kg-1) treatments. The study has shown the dependence of biomass production by willow on Oxford clay on both nutritional amendment and water availability. Although both nutrients and water could be supplied at these sites by growing SRC within a leachate management system, there are several practical issues like the narrow window of opportunity for mechanised operations and concerns about long-term sustainability which still need to be addressed.