Effects of tillage, organic resources and nitrogen fertiliser on soil carbon dynamics and crop nitrogen uptake in semi-arid West Africa

Tillage, organic resources and fertiliser effects on soil carbon (C) dynamics were investigated in 2000 and 2001 in Burkina Faso (West Africa). A split plot design with four replications was laid-out on a loamy-sand Ferric Lixisol with till and no-till as main treatments and fertiliser types as sub-treatments. Soil was fractionated physically into coarse (0.250–2 mm), medium (0.053–0.250 mm) and fine fractions (< 0.053 mm). Particulate organic carbon (POC) accounted for 47–53% of total soil organic carbon (SOC) concentration and particulate organic nitrogen (PON) for 30–37% of total soil nitrogen concentration. The POC decreased from 53% of total SOC in 2000 to 47% of total SOC in 2001. Tillage increased the contribution of POC to SOC. No-till led to the lowest loss in SOC in the fine fraction compared to tilled plots. Well-decomposed compost and single urea application in tilled as well as in no-till plots induced loss in POC. Crop N uptake was enhanced in tilled plots and may be up to 226 kg N ha⁻¹ against a maximum of 146 kg N ha⁻¹ in no-till plots. Combining crop residues and urea enhanced incorporation of new organic matter in the coarse fraction and the reduction of soil carbon mineralisation from the fine fraction. The PON and crop N uptake are strongly correlated in both till and no-till plots. Mineral-associated N is more correlated to N uptake by crop in tilled than in no-till plots. Combining recalcitrant organic resources and nitrogen fertiliser is the best option for sustaining crop production and reducing soil carbon decline in the more stabilised soil fraction in the semi-arid West Africa.     

Revisiting the fundamentals of phosphorus fractionation of sediments and soils

Introduction  

Sequential fractionation procedures have been an important tool in the study of phosphorus (P) dynamics in soils and sediments for over 50 years. Throughout this period, the various methodologies have been thoroughly reviewed, and several limitations are widely acknowledged, but there are also aspects of P fractionation that have received little or no discussion. As there are few alternatives to fractionation procedures, in order to advance the usefulness of these techniques, we need to explore the undisclosed variables that may falsely bias our interpretation.     

Identification of the peroxidase-generated intermolecular dityrosine cross-link in bovine α-lactalbumin

The peroxidase-mediated oxidation of calcium-depleted bovine α-lactalbumin generates a mixture of covalently bound protein oligomers with interesting foaming properties. Here, we isolated the initially formed covalent α-lactalbumin dimer and studied its mode of cross-linking. Liquid chromatography-Fourier transform mass spectrometry (LC-FTMS) of proteolytic digests revealed the unambiguous identification of a peroxidase-catalyzed covalent link between Tyr18 and Tyr50. This shows that, although the radical reaction is often regarded as a random reaction, the initial product formation is specific. Protein structural modeling indicates that the conjugation reaction between these tyrosines is sterically favored and involves initial noncovalent protein complex formation through charge compensation, facilitating intermolecular cross-linking. The identification of the Tyr18-Tyr50 cross-link supports the view that the peroxidase-mediated oxidation of apo α-lactalbumin is a sequential process, involving the formation of linear trimers and higher order oligomers.     

Erfl?rung, betressend die allgemeine National?fonomie, herausgegeben von Dr. Leo (Underlind)

Ohne Zusammenfassung     

Prevalence of pigment gallstones in sheep.

In a survey of 666 sheep at a slaughterhouse, gallstones (concretions with a diameter greater than or equal to 1 mm) were found in the gallbladder of 50 sheep (7.5%), sludge (concretions with a diameter less than 1 mm) was found in 9 sheep (1.4%), and sludge plus gallstones were found in 7 sheep (1.1%). Gallstones and sludge were associated, and were more frequent in lambs and females, compared with adults and males. Qualitative analysis of the stones revealed all to be pigment (bilirubin) stones. There was a statistically significant increase of biliary bilirubin (total and indirect quota) only in sheep with gallstones plus sludge, compared with control sheep without sludge or gallstones. Concentrations of bilirubin, cholesterol, phospholipids, total and single bile aids, and total and ionized calcium were similar in the bile of sheep with gallstones, sludge, or both and control sheep. Bacteriologic analysis of the bile in 10 sheep with gallstones and 10 controls revealed bacteria in 50% of the first group and in 75% of the second group (Escherichia coli in all sheep and Salmonella spp also in 1 sheep with gallstones). These findings confirm our earlier findings of a high prevalence of black pigment gallstones in sheep. On that basis, we suggest that gallstones are associated with high total bilirubin concentration in the bile, and deconjugating bacteria are common in the biliary tract of these animals.     

Biochar and fertiliser applications influence phosphorus fractionation and wheat yield

The use of biochar in agriculture to achieve the dual benefits of improving soil quality whilst sequestering carbon (C) has received much attention. However, in low-intensity broadacre agricultural systems where yield is constrained by rainfall and costs associated with phosphorus (P) fertiliser, the application of biochar at rates commonly reported (>10 t ha^?1) are likely to be prohibitively expensive where yield benefits cannot be guaranteed. In marginal areas where calcareous soils dominate, biochar application has no liming effect, reducing its value compared to application in acidic soils. In the present study, we use a field experiment to investigate the interaction between P fertilisation and biochar banding at low application rates (<1 t ha^?1) on wheat yield and soil P fractionation (assessed by a modified Hedley method) in a highly alkaline Haplic Calcisol in a dryland broadacre cropping system. Our results demonstrate no statistically significant effect of low rate biochar banding on wheat yield in this highly P-constrained soil, but a significant effect of both biochar and fertiliser on P fractionation in both years of the study. Higher P fertiliser rates significantly increased wheat yield in all biochar treatments. The interactions between biochar, P fertiliser and P fractionation indicate shifts in potential P availability both as a result of P fertilisation and also biochar application. Further work is required in low productivity calcareous systems such as that studied here to elucidate the potential for biochar amendment to improve productivity and sequester C.     

Eye-specific retinogeniculate segregation independent of normal neuronal activity

The segregation of initially intermingled left and right eye inputs to the dorsal lateral geniculate nucleus (DLGN) during development is thought to be in response to precise spatial and temporal patterns of spontaneous ganglion cell activity. To test this hypothesis, we disrupted the correlated activity of neighboring ganglion cells in the developing ferret retina through immunotoxin depletion of starburst amacrine cells. Despite the absence of this type of correlated activity, left and right eye inputs segregated normally in the DLGN. By contrast, when all spontaneous activity was blocked, the projections from the two eyes remained intermingled. Thus, certain features of normal neural activity patterns are not required for the formation of eye-specific projections to the DLGN.     

Haploid females in the parasitic wasp Nasonia vitripennis

The insect order of Hymenoptera (ants, bees, sawflies, and wasps) consists almost entirely of haplodiploid species. Under haplodiploidy, males develop from unfertilized eggs and are haploid, whereas females develop from fertilized eggs and are diploid. Although diploid males commonly occur, haploid females have never been reported. In analyzing the phenomenon of gynandromorphism in the parasitoid wasp Nasonia vitripennis, we found a line that generates complete phenotypic females from unfertilized eggs. These females have ovaries, can lay eggs, and are haploid, as shown by cytological and flow cytometric analyses. The data show that diploidy is not necessary for female development.