The influence of organic and conventional fertilisation and crop protection practices, preceding crop, harvest year and weather conditions on yield and quality of potato (Solanum tuberosum) in a long-term management trial

The effects of organic versus conventional crop management practices (fertilisation, crop protection) and preceding crop on potato tuber yield (total, marketable, tuber size grade distribution) and quality (proportion of diseased, green and damaged tubers, tuber macro-nutrient concentrations) parameters were investigated over six years (2004–2009) as part of a long-term factorial field trial in North East England. Inter-year variability (the effects of weather and preceding crop) was observed to have a profound effect on yields and quality parameters, and this variability was greater in organic fertility systems. Total and marketable yields were significantly reduced by the use of both organic crop protection and fertility management. However, the yield gap between organic and conventional fertilisation regimes was greater and more variable than that between crop protection practices. This appears to be attributable mainly to lower and less predictable nitrogen supply in organically fertilised crops. Increased incidence of late blight in organic crop protection systems only occurred when conventional fertilisation was applied. In organically fertilised crops yield was significantly higher following grass/red clover leys than winter wheat, but there was no pre-crop effect in conventionally fertilised crops. The results highlight that nitrogen supply from organic fertilisers rather than inefficient pest and disease control may be the major limiting factor for yields in organic potato production systems

Changes in growth and gene expression induced by sulphur deficiency in garlic

Sulfur deficiency in garlic Allium sativum L. caused a reduction in growth together with chlorosis and necrosis of leaves. Large differences in shoot sulfur and sulphate concentrations between deficient and high sulfur treatments were only observed after 54 days growth. Using the mRNA differential display technique, a novel cDNA was isolated from shoots grown in sulfur depleted nutrient solution for 24 days. This novel cDNA was constitutively expressed in the shoots during further growth in sulfur depleted solution, but it was undetectable following 30 days recovery with sulfur supplementation. The cDNA sequence demonstrated a high degree of identity with a coat protein gene of a garlic latent carlavirus. The results suggest a possible relationship between low plant sulfur status and the induction of a latent carlavirus in garlic

Variation between two near isogenic barley (Hordeum vulgare) cultivars in expression of the B subunit of the vacuolar ATPase in response to salinity.

A gene encoding the barley vacuolar ATPase subunit B (BSVAP) was differentially expressed between two near isogenic barley cultivars, Golden Promise and Maythorpe. This gene (BSVAP) was isolated by the mRNA differential display technique (DDRT-PCR). BSVAP was salt inducible under long-term salinity stress in the salt sensitive cultivar Maythorpe but less so in the relatively salt tolerant Golden Promise and was more highly expressed under control conditions in Maythorpe. The physiological consequences of altered vacuolar ATPase expression are discussed in relation to the salt sensitivity of Maythorpe

Kinetics of maize cob and bean straw pyrolysis and combustion

Kinetic studies are important for the design and optimisation of thermochemical processes. This study involved analysis of the pyrolysis and combustion behaviour of the agricultural residues (bean straw and maize cob) by non-isothermal thermogravimetric analysis. Increasing the heating rate from 10 to 40 K min−1 during both combustion and pyrolysis increased the degradation rate of both feedstocks and the gaseous yields of H2O, CO and CO2. The activation energies determined by the Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods varied which reveals that the pyrolysis and combustion of these agricultural residues are complex processes involving multiple reactions. The average activation energy of maize cob and bean straw were 214.15 and 252.09 kJ mol−1 for pyrolysis and 202.26 and 165.64 kJ mol−1 for combustion, respectively. The order of reaction ranged between 9.0-10.3 and 6.3–13.3 for both feedstocks in combustion and inert environments, respectively. Modelled data is important to enable the optimisation of reactor design for pyrolysis and combustion for energy generation from agricultural residues

Salinity induced differences in growth, ion distribution and partitioning in barley between the cultivar Maythorpe and its derived mutant Golden Promise

Dry matter changes and ion partitioning in two near isogenic barley cultivars Maythorpe (relatively salt sensitive) and Golden Promise (relatively salt tolerant) were studied in response to increasing salinity. Although the growth of both cultivars was significantly reduced by exposure to NaCl, the effect was greater in Maythorpe, whilst Golden Promise maintained an increased ratio of young to old leaf blade. Golden Promise maintained significantly lower Na+ concentrations in young expanding tissues compared with Maythorpe. Partitioning of Cl– was evident in that both varieties maintained lower Cl– concentrations in mesophyll than in epidermal cells. Golden Promise maintained higher K+/Na+ and Ca2+/Na+ ratios in young leaf blade and young sheath tissues than Maythorpe when exposed to salt. Differences in ion partitioning and the maintenance of higher K+ and Ca2+ to Na+ ratios, especially in young growing and recently expanded tissues, would appear to be important mechanisms contributing to the improved salt tolerance of Golden Promise

Evolution of the Labor Market in a Regional City:

This paper draws on micro-level data to fully inform the debate on decentralization and regional development. Using labor-income trajectories of emigrants from Mexico City, the paper analyzes how the labor market in a regional city, Leon, evolves. Results from the econometric model suggest that migrants' labor-income trajectories differ between the large agglomeration and the regional city in an early stage of the evolution of the labor market, but converge in a later stage. Specifically, the slope of the earning function for recent migrants is steeper and statistically different from the slope for early migrants. The findings presented in this paper enrich the existing theory by providing microfoundations to a typically macroeconomic area of research and enable policy makers to better understand the processes underpinning the evolution of regional labor markets. Copyright Blackwell Publishers, 2005