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Integrated Pest Management (IPM) has long been promoted as a means of reducing reliance on pesticide inputs as compared to conventional farming systems. Reduced pesticide application could be beneficial due to the links between intensive pesticide use and negative impacts upon biodiversity and human health as well as the development of pesticide resistance. Work assessing the potential of IPM in cereal production is currently limited, however, and previous findings have generally covered the subject from the perspective of either field trial data or social science studies of farmer behaviour. This thesis attempts to help to address this knowledge gap by providing a more holistic assessment of IPM in Scottish spring barley production (selected because of its dominance in Scotland’s arable production systems), in relation to three of its most damaging fungal pathogens: Rhynchosporium commune, Blumeria graminis f.sp. hordei, and Ramularia collo-cygni. Several IPM techniques of potential relevance to the sector were identified, and the prospects of three in particular – crop rotation, varietal disease resistance, and forecasting disease pressure – were assessed in several ways. Preliminary analysis of experimental field trial data collected from 2011 – 2014 across Scotland found that the majority of spring barley trials in this period (65%) did not show a statistically significant impact of fungicide treatment on yield, with the average yield increase due to fungicide application being 0.62 t/ha. This initial analysis was expanded upon using stepwise regressions of long-term (1996 – 2014) field trial data from the same dataset. Here, the difference between treated and untreated yields could be explained by disease resistance, average seasonal rainfall (whereby wetter seasons saw an increased impact of fungicide use on yield), and high combined disease severity. Stakeholder surveying provided information about current practice and attitudes towards the selected IPM techniques amongst a group of 43 Scottish spring barley farmers and 36 agronomists. Stakeholders were broadly open to taking up IPM measures on farm; sowing of disease resistant varieties was most frequently selected as the best technique in terms of both practicality and cost, though individual preference varied. However, a disparity was seen between farmer perception of their uptake of IPM and actual, self-reported uptake for both varietal disease resistance and rotation. Farmers and agronomists also overestimated the impact of fungicide use as compared with the field trials results – the majority of stakeholders believed fungicide treatment to increase yields by 1 - 2 t/ha, while the majority of 2011 – 2014 field trials had a yield difference of under 1 t/ha. The reasons behind these differences between perception and practice are not currently known. Finally, an annual survey of commercial crops, gathered from 552 farms across Scotland (from 2009 – 2015), highlighted two gaps where IPM practice could be improved upon. Firstly, relatively few of the varieties listed in the commercial crops database were highly resistant to the three diseases – 26.1% were highly resistant to Ramularia, 14.2% to Rhynchosporium, and 58.1% to mildew. Secondly, 71% of the farms included in the database had planted barley in at least two consecutive seasons, indicating that crop rotation practices could be improved. The overarching finding of this project is that there is scope for IPM uptake to be improved upon and fungicide use to be reduced while maintaining high levels of yield in Scottish spring barley production. Incorporating experimental field data, stakeholder surveying, and commercial practice data offered a unique view into the potential for IPM in this sector, and provided insights which could not have been gained through the lens of a single discipline.

Scientists, policymakers, and growers are increasingly interested in the use of biochar, or pyrolyzed biomass, as an agricultural soil amendment. The number of published biochar studies has increased at a near exponential rate, from one publication per annum in the early 2000s, to over 4,100 in 2020. Policymakers have also taken notice, resulting in biochar included as a leading natural climate solution in the 2018 Intergovernmental Panel on Climate Change (IPCC) Special Report, and in California, the creation of the Biochar Research Advisory Group by the Governor’s Office of Planning and Research. As scientific and policy interest in biochar grows, so too does the size of the biochar market. Since 2009, 920 patent applications mentioning biochar have been submitted to the United States Patent and Trademark Office. While interest in biochar is evident, many questions remain about the efficacy of biochar as a soil amendment. Due to its high surface area, low bulk density, reactive surface functional groups, and recalcitrant carbon, the material is purported to deliver many agronomic and environmental benefits when added to the soil. These benefits include increased water holding capacity, nutrient retention, crop yield, and soil carbon stocks, as well as enhanced microbial activity and the promotion of soil health. Despite the proliferation of biochar studies, research shows inconsistent results on the ability of biochar to deliver these benefits, due to differences in biochar feedstock, production methods, soil properties, climate, and cropping systems. It is especially difficult to interpret results for the fertile agricultural soils of California’s Mediterranean climate, as biochar has been shown to have the greatest impact in more acidic, nutrient-limited soils. Furthermore, results from the scientific literature have limited relevance to production agriculture, as biochar studies are dominated by short-term laboratory experiments that are difficult to extrapolate to field-scale. To inform the use and regulation of biochar in California, it is essential that farmers and policymakers have access to reliable, location-based data that evaluates biochar across scales. This project fills a gap in the literature by providing mechanistic laboratory studies that are linked to pot trials and long-term, field-scale data about the agronomic and soil health potential of biochar as a soil amendment in California. To carry out this work, seven biochars were obtained from commercial companies at multiple production temperatures from various feedstocks. The potential for these biochars to impact the soil physical, chemical, and microbial environment was investigated across scales. In the laboratory, biochars were tested for their ability to physically or chemically retain nitrate and ammonium. Nearly every biochar tested exhibited a strong chemical affinity for ammonium, likely due to the attraction between their negatively charged surfaces and the positively charged ammonium ion. This was evident in that ammonium retention was strongest in biochars with high cation exchange capacity (CEC), oxygen-containing functional groups, and high oxygen to carbon ratios. Biochars exhibited little to no chemical affinity for nitrate, though one biochar reduced nitrate leaching, to a small extent, in soil column studies. This result was linked to the biochar’s high surface area and low CEC. The ability of biochar to alter the soil physical environment was most evident in its effect on saturated hydraulic conductivity (Ksat). Broadly, biochars increased Ksat in a silt loam but had a mixed effect in a sandy loam. An additional small-scale study was carried out in a growth chamber, in which biochar-amended soil was observed to substantially increase the yield of romaine lettuce (Lactuca sativa) when compared to the unamended control. Collectively, the short-term laboratory experiments in this study demonstrated that these biochars could improve ammonium retention, water conductivity, and crop yield when added to the soil. However, in three-year field trials with the same biochars in the same soils, similar benefits were not observed. Seven biochars were amended to soils at two rates, combined with two synthetic nitrogen (N) fertilizer rates, in two California locations. Processing tomatoes (Solanum lycopersicum) were grown for three years, and data was collected on the influence of biochar on plant and soil properties. Biochar had minor effects on soil pH, EC, and N content, though the effects varied by biochar, location, and year, and were not substantial enough to impact plant yield or quality parameters. Under no combination of experimental conditions was biochar observed to increase processing tomato yield, plant nitrogen uptake, or soil moisture. Field trial results are consistent with those from other studies, which indicate biochar may confer limited benefits in soils which do not require conditioning for the successful growth of crops. Furthermore, the discrepancy between results from experiments at different scales demonstrate that short-term laboratory trials are not sufficient to make conclusions about field-scale agriculture. While biochar did not deliver tangible agricultural benefits in field trials, further investigation was made into its influence on parameters that constitute current notions of soil health. Soils were sampled 2.5 years after amendment with almond shell biochars produced at 500 or 800 °C, or a softwood biochar produced at 500 °C, for a comprehensive soil health assessment. To varying effects, biochars were observed to increase labile carbon, water stable aggregates, pH, and EC in both the silt loam and sandy loam. In the finer textured silt loam, which had higher fertility and organic matter concentration, results were not substantial enough to influence the microbial community. Phospholipid fatty acid (PLFA) analysis from the silt loam revealed that biochar had no effect on community composition or on the PLFA ratios typically interpreted to denote microbial stress. In the coarser, more nutrient-limited sandy loam, however, a canonical correspondence analysis (CCA) revealed microbial communities responded to the increase in water stable aggregates, pH, and potassium conferred by the addition of biochar. This resulted in a distinct community composition, as well as reduced indicators of microbial stress. Results were greatest in plots amended with almond shell biochars, likely due to the high potassium content of almond shell, and to the high pH and ash concentration of these biochars. The soil health assessment indicates that, while biochar may not deliver agronomic improvements in fertile agricultural soils, it may confer other ecological or environmental benefits, or have the potential to deliver agronomic benefits across a longer time horizon. Importantly, results from multiple scales indicate biochar may be added to agricultural soils with few negative consequences for cropping systems. However, there is a growing body of research which suggests some biochars may contain potentially toxic properties that pose a threat to human health when airborne biochar is inhaled. In order to optimize the ecological benefits of adding biochar to soils, care should be taken to select biochars which conform to quality standards established by the International Biochar Initiative or the European Biochar Certificate. Care should also be taken to amend biochars to soils under conditions which minimize dust emissions, and to equip farmworkers with respirators and appropriate protective attire. As there may be limited financial incentive for California growers to add biochar to their soils, cost-share and incentive programs should be considered. Together, data from this project can assist policymakers and land managers in California in making decisions about amending biochar to working lands. Realistic expectations should be established for the agronomic benefits of adding biochar to California cropping systems. Meanwhile, carbon sequestration or soil health projects may be pursued with minimal consequence, given the safe and appropriate selection of biochars.

The goal of this study was to assess the feasibility of producing open pollinated (O.P) corn varieties as a grain source for the production of specialty whiskies. Low profit margins on corn grain as a commodity make it difficult for small to medium size farmers to grow corn competitively. Such farmers could benefit from a cash crop that could offer a higher profit margin. There is current popular interest in heirloom (old-time) grains, including O.P varieties. This may provide an opportunity for a distiller to develop a market for a specialty whisky using O.P. varieties. An advantage for O.P corn as a specialty crop for corn growers is the similarities in equipment, cultural practices, and inputs. No major conversion is needed. Field studies were initiated to determine the production potential and reliability of O.P. varieties in New York environments, and to identify the best varieties. Comparative yield trials were conducted over two growing seasons in various locations. Varieties were selected on the basis of anticipated adaptation to New York growing conditions, potential for grain production and commercial availability of seed. In 2001, seventeen open pollinated varieties along with a modern hybrid check were tested at Aurora, (central) and Kingston, (eastern), NY. In 2002, twenty varieties were planted at Aurora. Those considered earlier varieties were also planted at Bliss, (western). Also, in 2002, later varieties were planted at Kingston, and Pittsford, (western). All trials were set up in randomized complete block designs. Treatments consisted of two adjacent rows of each variety with approximately 36-40 seeds planted within each block. Each trial consisted of three blocks. The plots were thinned to a density of 18,000 plants/acre. Several major obstacles were observed First, yields of O.P. varieties were lower and more variable than yields of hybrids. The mean corn yield in bushels for New York State is 100.7 bu/acre (www.nass.usda.gov) averaged over the three years. (1999-2001). Many of the varieties in these trials occasionally performed at or above this level, but none consistently, except the hybrid checks. Stalks were also weak, blowing down in winds, and making harvest difficult. Perhaps most significantly, the data showed wide variation in variety performance between years and locations, even among the same varieties. Premium alcoholic beverage producers could tolerate high O.P. grain costs if they could develop a market for a high value specialty whiskey featuring an O.P. corn source. However they would need reliable grain supplies. In these studies O.P. corn production was erratic, and not dependable from year to year, or site to site. This lack of dependability would present an unacceptable business risk. One possible solution might be to develop a product based mostly on readily available, inexpensive hybrid corn grain, mixed with a small amount of open pollinated grain. If a business plan could be developed that protects against fluctuations of availability, the concept of using O.P. corn to differentiate a small batch premium alcoholic beverage might have potential for success. This could provide employment in the processing, distilling and bottling processes. And O.P corn might provide a profitable niche crop for a limited number of corn growers.

The effect of desiccation on yarrow (Achillea millefolium L.) rhizomes was studied in three series of experiments at Lincoln College during 1982. Desiccation in growth cabinets at 11°, 18° and 25°c led to the total death of 5 cm long rhizome fragments within 10 - 14 hours. Rates of death and moisture loss increased with increasing temperature. Water content was found to be a more reliable analysis of water stress than water potential. There was a linear relationship between moisture content and survival of the rhizomes, and 50% viability occurred at moisture contents between 40 and 49%. High soil moisture decreased the effect of desiccating temperatures on rhizome viability. On the surface of soil at field capacity, 0 88% of the rhizome fragments were viable after 12 hours at 20°C, while on air dry soil all the rhizomes were dead. Seven per cent of the rhizomes were still viable after 6 days burial in air-dry soil. Viability decreased slowly in rhizomes buried in wilting-point soil. No rhizomes survived longer than 3 days when placed on the soil surface during hot, dry weather in February, but there was no apparent loss in viability over 8 days of rhizomes placed on the soil during cool,wet weather in April. Emergence of buried rhizomes in the February trial was about 40% less than those considered viable in the laboratory. Total death of rhizomes placed on the soil surf ace in May did not occur until 14 weeks had passed. Initial death was rapid though, and less than 15% remained viable after 4 weeks. It was concluded that the desiccation of yarrow rhizome fragments on the soil surface was a successful method of controlling the rhizomes. Tillage techniques would need to be devised to enable a significant proportion of the rhizomes to be brought to the soil surface. Warm, dry weather and dry soil would be optimum conditions for desiccation.

During the latter part of the 1973-74 growing season, levels of damage to potato crops caused by potato tuber moth, Phthorimaea operculella (Zeller), were monitored by regular sampling. This revealed a significantly lower level of damage among tubers grown in sandy loam rather than silt loam. Similarly there was a higher proportion of infested seed grade tubers than larger table grade. As the haulms died off there was an increase in infestation among green tubers; this was the result of larvae moving from the haulms seeking alternative food sources. The 1974-75 season involved a more comprehensive study of tuber moth population growth and behaviour. This entailed the sampling of tubers and haulms for larvae and the use of suction traps; these were able to segregate the catch into specific time intervals and continuous recordings were made of weather conditions. This made it possible to study the relationship between abiotic factors and flight behaviour. Flight activity was found to reach its peak at dusk, and nightly catches were proportional to the total number of hours that occurred above 14°C. Fourteen degrees Celsius was found to be the field threshold temperature of flight. Although windspeed inhibited flight, the moths were found to fly in considerable breezes (up to 6 msec ⁻¹) and rarely left the boundary layer. At no time was there any detectable difference in the aerial density of tuber moths over the Ilam Hardy and Rua crops which are purported to be susceptible and resistant respectively. Six weeks after harvest the level of infestation among cull tubers had risen by 88%. This clearly shows the significance of discarded tubers as overwintering sites and the importance of a clean harvest. Laboratory work revealed there was no difference between infestation levels of Pentland Dell, (resistant), and Ilam Hardy tubers (susceptible), when subjected to identical infestation pressures. However it was shown that the three volatile components extracted from fresh potato leaves by steam distillation were capable of eliciting an excited response from adult moths, It is suggested that this highly volatile fraction ,could play an important. role in tuber moths' ability to detect crops. Field trials with a variety of compounds showed pyridine to be attractive to males and 3-ethyl pyradine attractive to females.