Tillage, cover crops, and nitrogen fertilization effects on soil nitrogen and cotton and sorghum yields

Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha⁻¹) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha⁻¹ than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha⁻¹. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha⁻¹. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha⁻¹ than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha⁻¹ than in rye and weeds with 0 or 60 kg N ha⁻¹. Increased N supplied by hairy vetch or 120–130 kg N ha⁻¹ increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha⁻¹. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha⁻¹. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.     

Studies on pesticides based on coumarin. III. Synthesis and antifungal activity of substituted 4-methyl-coumarins and related compounds

A series of substituted 4-methylcoumarins was synthesised and the members tested for their toxicity towards mycelial growth of seven phytopathogenic fungi in culture. Rhizoctonia solani, Alternaria alternata and Fusarium solani exhibited maximum sensitivity to these compounds whereas Pythium aphanidermatum, Colletotrichum falcatum, Drechslera oryzae and Macrophomina phaseolina were relatively less sensitive. 6-Ethyl-3-n- propyl-7-hydroxy4-methylcoumarin ( I ) was relatively toxic towards all fungi except C. falcatum, P. aphanidermatum and M. phaseolina. The 6-n-butyl ( III ) and 6-(1, 1, 3, 3-tetramethylbutyl) ( VI ) derivatives were highly toxic to R. solani with EC₅₀, values of lμg ml^?1.     

Induction of immune tolerance to caseins and whey proteins by oral intubation in mouse allergy model

This study was designed to evaluate the effect of oral tolerance of caseins (CSN) and whey proteins (WP) in alleviating the allergic response to cow's milk proteins in Swiss albino mice raised on a milk protein–free diet. Oral tolerance was induced by feeding mice with 20 mg of CSN or WP once in a day for 4 days consecutively before immunization with respective protein by intraperitoneal (i.p.) injections (20 μg 200 per μl of PBS) using 2% of alum Al(OH)₃ as adjuvant. Three weeks later, oral tolerance induction was analysed in humoral and cellular compartments of CSN‐ and WP‐fed versus saline‐fed control mice groups by measuring seric and intestinal antibody responses, mRNA abundance in splenic tissue and cytokine secretion patterns. The specific serum immunoglobulin‐E (IgE) levels were significantly suppressed (p < 0.05), while sIgA was enhanced in these groups when compared with their respective saline‐fed mice. Moreover, the mRNA levels of interferon‐γ (IFN‐γ) and interleukin‐4 (IL‐4) in both CSN‐ and WP‐tolerized mice were found to be significantly decreased, while the abundance of interleukin‐10 (IL‐10) and transforming growth factor‐β (TGF‐β) was increased significantly, as compared to respective control groups. Finally, cytokine profiles indicated a reciprocal decrease in IL‐4 and IFN‐γ versus an increase in IL‐10 secretions in supernatants of cultured splenocytes of tolerized mice. Taken together, these results clearly showed that oral administration of cows' milk caseins and whey proteins can induce significant hyposensitization in mice, with the participation of suppressor cytokines.     

One-step continuous coating of silver nanoparticles on well aligned fibers of PAI/PTACM

Highly aligned ultrafine fibers of Poly (amide-co-imide) PAI (torlon)/Poly (trimellitic anhydride chloride-co-4, 4′-methylene dianiline) (PTACM) blends have been prepared by using mechano-electrospinning. Employing a mixed solvent system of DMSO and THF alongwith water coagulation bath as a medium, continuous fibers with improved mechanical properties have been obtained. The continuity of the fibers is strongly dependent on the solvent mixing ratio of DMSO and THF (6:4). Continuous fibers with the most uniform diameter are obtained when a 30 % of PAI and PTACM (1:1) resins by weight is used in the blending solution. The aligned fibers are further coated with silver nanoparticles using a one-step process by passing the electrospunned fibers through PEG solution and a silver precursor solution followed by reduction in a continuous process. The advantage of our method lies in a uniform silver coating on a single fiber that can be coated continuously on a larger length scale (～Km). The mechanical properties of these fibers are dramatically improved after their alignment. Better electrical conductivity is obtained for these fibers after they are coated with silver nanoparticles. The highly aligned silver decorated fibers utilizes a novel electroless continuous process using Polyethylene glycol (PEG), which shows good binding properties and can be used for various bio and electronic applications.     

Sucrose: a constitutive elicitor of phytoalexin synthesis

Extracts of seeds and leaves of the tropical legume Cajanus cajan (L.) Millsp. (the pigeon pea) elicited the accumulation of three phytoalexins when applied as droplets to superficially wounded leaves of the plant. The active component was purified and identified as sucrose. Phytoalexin accumulation was proportional to the logarithm of the concentration of sucrose applied, with maxima ranging from 338 to 455 micrograms per gram (fresh weight) of leaf tissue. The sucrose concentrations required to elicit half these amounts ranged from 20 to 35 micrograms per milliliter, but other sugars had little effect even at 1000 micrograms per milliliter. The elicitor activity of sucrose was abolished by actinomycin D, puromycin, and cycloheximide at a concentration of 10 micrograms per milliliter or greater, suggesting that gene derepression is required for expression of the phytoalexin response.     

Toward the synthesis and biological screening of a cyclotetrapeptide from marine bacteria

The first synthesis of a naturally occurring tetrapeptide cyclo-(isoleucyl-prolyl-leucyl-alanyl) has been achieved using a solution-phase technique via coupling of dipeptide segments Boc-L-Pro-L-Leu-OH and L-Ala-L-Ile-OMe. Deprotection of the linear tetrapeptide unit and its subsequent cyclization gave a cyclopeptide, identical in all aspects to the naturally occurring compound. Bioactivity results indicated the antifungal and antihelmintic potential of the synthesized peptide against pathogenic dermatophytes and earthworms.     

Molecular cloning,sequence characterization,and expression analysis of C-type lectin (CTL) and ER-Golgi intermediate compartment 53-kDa protein (ERGIC-53) homologs from the freshwater prawn,Macrobrachium rosenbergii

Aquaculture International - Lectin protein families are diverse and multi-functional in crustaceans. The carbohydrate-binding domains (CRDs) of lectins recognize the molecular patterns associated...     

Total synthesis and antimicrobial activity of a natural cycloheptapeptide of marine origin

The present study deals with the first total synthesis of the proline-rich cyclopolypeptide stylisin 2 via a solution phase technique by coupling of the Boc-L-Pro-L-Ile-L-Pro-OH tripeptide unit with the L-Phe-L-Pro-L-Pro-L-Tyr-OMe tetrapeptide unit, followed by cyclization of the resulting linear heptapeptide fragment. The chemical structure of the finally synthesized peptide was elucidated by FTIR, 1H/13C-NMR and FAB MS spectral data, as well as elemental analyses. The newly synthesized peptide was subjected to antimicrobial screening against eight pathogenic microbes and found to exhibit potent antimicrobial activity against Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans, in addition to moderate antidermatophyte activity against pathogenic Trichophyton mentagrophytes and Microsporum audouinii when compared to standard drugs--gatifloxacin and griseofulvin.     

Culture-dependent and culture-independent microbial investigation of pine litters and soil in subtropical Australia

Background, aim, and scope  Forest plantations, widely grown for wood production, involve the selective promotion of single-tree species or replacement of natural species by exotic tree species. Slash pine (Pinus elliottii) has been chosen for reforestation of infertile sandy soils in southeast Queensland, Australia. These exotic pine plantations minimize soil and water losses and are important scientific study sites. The soil environment of these plantations, though devoid of sufficient nutrients, organic carbon and other factors, harbors innumerable bacteria that may play a crucial role in maintaining soil quality and ecosystem functions. These soil microorganisms also have the potential for use as sensitive biological indicators to reflect environmental changes. It is therefore essential to understand the interrelationships among bacterial communities and their environment by assessing their structural and functional diversity and their responses to disturbances. The main aim of our investigation was to determine the diversity of bacterial communities in forest litters and soil during the forest leaf litter decomposition using culture-dependent and culture-independent techniques. Materials and methods  A 25-cm (diameter) × 40-cm core sample was collected and fractionated into three subsamples designated E1 (L leaf litter layer), E2 (F leaf litter layer), and E5 (0–10 cm soil layer). Both culture-dependent and culture-independent methods were applied in this study. In the culture-independent study, a strategy of whole-community DNA extraction, polymerase chain reaction (PCR) amplification followed by cloning and 16S rDNA sequence analysis was used; for culture-dependent study, the strategy included sample plating and bacteria isolating, DNA extraction, PCR amplification, and 16S rDNA sequence analysis. The diversity similarities between two bacterial communities and two methods are quantified using Jensen–Shannon divergence. Results  From culture-dependent study, 336 colonies in total were isolated and grouped from the three subsamples, and the 16S rRNA sequence analysis from a representative isolate from each morphogroup (21 isolates) indicated that they belonged to the phyla Actinobacteria, Firmicutes, and Proteobacteria. Culture-independent assessment based on 16S rRNA gene library comprising 194 clones revealed that members of the phylum Actinobacteria were absent in the culture-independent studies. Clones in libraries from E1 consisted exclusively of members of the Firmicutes. The majority of clones from E2 were related to Firmicutes (79%) and Proteobacteria (21%). Clones derived from E5 were mostly affiliated with Acidobacterium (42%), followed by unclassified bacteria (27%), Verrucomicrobiales (12%), Proteobacteria (11%), and Planctomycetes (8%). Discussion  This study showed that bacterial culturabilities in different fractions of leaf litters were similar, and both of them were higher than the bacterial culturability in the soil. Unculturable bacterial diversity in the soil, however, was much higher than the leaf litter bacterial diversity. The bacterial diversity on the top layer of leaf litters was slightly less than that on the bottom layer of leaf litters. This might indicate that forest soils are a more complex environment than leaf litters are and also that they might inhabit more unculturable microorganisms in the forest soils, which would need to be further investigated. The leaf litter layer samples also demonstrate the significant difference between the bacterial community diversity discovered by these two methods in this study. The information provided by assessing the different fractions of leaf litters and forest soil has improved our understanding of the bacterial community distributions within the forest soil and the above-leaf litters in an exotic pine plantation of subtropical Australia. Conclusions  This study represents the first attempt to examine the bacterial community in the different fractions of forest leaf litters and soil in subtropical Australia. The data from this study show that the 16S rDNA clone libraries provided more comprehensive phylogenetic diversity in the soil and leaf litter samples than the culture collections provided, and both the culture-dependent and culture-independent studies revealed that the bacterial diversity present in the leaf litters was very different to that present in the soil. The comparative analysis of bacterial communities in different fractions of leaf litters and soil samples has also provided important baseline information about the bacterial diversity and composition in the exotic pine forest plantations. Recommendations and perspectives  The experimental data provided important information on the bacterial diversity in forest leaf litter and soil samples, though additional surveys and comparisons at different locations would be needed to further characterize. In addition, combined methods that can provide different parts of information on bacterial diversity are encouraged to be used in bacterial community study. The established libraries of diverse 16S rRNA gene fragments from slash pine leaf litters and forest soil can be used to construct specific DNA primers and probes to target bacterial groups of interest. It may then be possible to study the ecology of these bacterial communities and the role of specific bacterial groups that contribute to the many interesting properties of these environments.