1,720,970 research outputs found
Soil carbon, nitrogen and phosphorus dynamics as affected by solarization alone or combined with organic amendment
No full textSoil solarization, alone or combined with organic amendment, is an increasingly attractive approach for managing soil-borne plant pathogens in agricultural soils. Even though it consists in a relatively mild heating treatment, the increased soil temperature may strongly affect soil microbial processes and nutrients dynamics. This study aimed to investigate the impact of solarization, either with or without addition of farmyard manure, in soil dynamics of various C, N and P pools. Changes in total C, N and P contents and in some functionally-related labile pools (soil microbial biomass C and N, K2SO4-extractable C and N, basal respiration, KCl-exchangeable ammonium and nitrate, and water-soluble P) were followed across a 72-day field soil solarization experiment carried out during a summer period on a clay loam soil in Southern Italy. Soil physico-chemical properties (temperature, moisture content and pH) were also monitored. The average soil temperature at 8-cm depth in solarized soils approached 55 C as compared to 35 C found in nonsolarized soil. Two-way ANOVA (solarization organic amendment) showed that both factors significantly affected most of the above variables, being the highest influence exerted by the organic amendment.
With no manure addition, solarization did not significantly affect soil total C, N and P pools. Whereas soil pH, microbial biomass and, at a greater extent, K2SO4-extractable N and KCl-exchangeable ammonium were greatly affected. An increased release of water-soluble P was also found in solarized soils. Yet, solarization altered the quality of soluble organic residues released in soil as it lowered the C-to-N ratio of both soil microbial biomass and K2SO4-extractable organic substrates. Additionally, in solarized soils the metabolic quotient (qCO2) significantly increased while the icrobial biomass C-to-total organic C ratio (microbial quotient) decreased over the whole time course. We argued that soil solarization promoted the mineralization of readily decomposable pools of the native soil organic matter (e.g. the microbial biomass) thus rendering larger, at least over a short-term, the available fraction of some soil mineral nutrients, namely N and P forms. However, over a longer prospective solarization may lead to an over-exploitation of labile organic resources in agricultural soils. Manure addition greatly increased the levels of both total and labile C, N and P pools. Thus, addition of organic amendments could represent an important strategy to protect agricultural lands from excessive soil resources exploitation and to maintain soil fertility while enhancing pest control
Effect of imazamethabenz-methyl on nitrate uptake in wheat (Triticum durum L.)
No full textThe effect of the herbicide imazamethabenz-methyl (IMZM), a mixture of the two isomers methyl (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-4-methylbenzoate (para isomer) and methyl (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxa-1H-imidazol-2-yl]-5-methylbenzoate (meta isomer), on the uptake of nitrate by wheat grown hydroponically was studied. IMZM stimulates the nitrate uptake in both "induced" (NO3--pretreated) and "uninduced" (NO3--starved) seedlings, most likely as a response to a plant stress. The decrease in acetohydroxy acid synthase (AHAS; EC 4.1.3.18) activity and in protein content of IMZM-treated roots supports this hypothesis. The presence of valine, leucine, isoleucine, and IMZM prevents the effects of the herbicide treatment in both induced and uninduced plants. The addition of IMZM to humic acid enhances the nitrate uptake, although to a lower extent than with the herbicide alone. Possible traces of imazamethabenz acid (IMZA) in growing units do not seem to be responsible for the greater N demand observed
Genetic analysis of root adaptive traits in sugar beet
No full textGenetic improvement of sugar beet requires better knowledge of genetic basis of root adaptive traits to nutritional stress. This study was conducted to determine combining ability and heritability for morphological and physiological root traits involved in nutrient acquisition in a diallel set of crosses of 5 sugar beet genotypes. Total root length, root surface area, number of root tips, glucose and fructose concentration in the root tips, and sulfate uptake rate were evaluated after sulfate deprivation on six-teen day old seedlings grown under hydroponic conditions. Significant differences were observed among genotypes for the morphological and physiological traits evaluated, and such traits were significantly correlated with the productivity. The genetic analysis showed that general and specific combining ability effects were significant for all traits, with a predominance of additive gene effects. All traits exhibited high coefficients of heritability, suggesting their response to the selection process. The inheritance of the investigated traits could be considered in breeding programs aimed at increasing sugar yield under nutritional stress
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The "glucose effect" in callus cultures of Nicotiana plumbaginifolia is enzyme specific.
No full text
- …
