Tillage system affects fertilizer-induced nitrous oxide emissions

Since the development of effective N₂O mitigation options is a key challenge for future agricultural practice, we studied the interactive effect of tillage systems on fertilizer-derived N₂O emissions and the abundance of microbial communities involved in N₂O production and reduction. Soil samples from 0–10 cm and 10–20 cm depth of reduced tillage and ploughed plots were incubated with dairy slurry (SL) and manure compost (MC) in comparison with calcium ammonium nitrate (CAN) and an unfertilized control (ZERO) for 42 days. N₂O and CO₂ fluxes, ammonium, nitrate, dissolved organic C, and functional gene abundances (16S rRNA gene, nirK, nirS, nosZ, bacterial and archaeal amoA) were regularly monitored. Averaged across all soil samples, N₂O emissions decreased in the order CAN and SL (CAN?=?748.8?±?206.3, SL?=?489.4?±?107.2 μg kg^?1) followed by MC (284.2?±?67.3 μg kg^?1) and ZERO (29.1?±?5.9 μg kg^?1). Highest cumulative N₂O emissions were found in 10–20 cm of the reduced tilled soil in CAN and SL. N₂O fluxes were assigned to ammonium as source in CAN and SL and correlated positively to bacterial amoA abundances. Additionally, nosZ abundances correlated negatively to N₂O fluxes in the organic fertilizer treatments. Soils showed a gradient in soil organic C, 16S rRNA, nirK, and nosZ with greater amounts in the 0–10 than 10–20 cm layer. Abundances of bacterial and archaeal amoA were higher in reduced tilled soil compared to ploughed soils. The study highlights that tillage system induced biophysicochemical stratification impacts net N₂O emissions within the soil profile according to N and C species added during fertilization.     

Activity-guided identification of (S)-malic acid 1-O-D-glucopyranoside (morelid) and gamma-aminobutyric acid as contributors to umami taste and mouth-drying oral sensation of morel mushrooms (Morchella deliciosa Fr.)

Although morel mushrooms are widely used as tasty ingredients in savory dishes, knowledge of the key compounds evoking their attractive taste is still very fragmentary. In the present study, taste activity-guided fractionation of an aqueous morel extract by means of the recently developed taste dilution analysis (TDA) enabled the localization of several umami-like-tasting fractions as well as a fraction imparting an intense mouth-drying sensation to the oral cavity. Hydrophilic interaction liquid chromatography (HILIC), LC-MS, and amino acid analysis led to the successful identification of gamma-aminobutyric acid as the chemical inducer of the mouth-drying and mouth-coating oral sensations imparted by the morel extract. Besides the well-known umami-like taste contributors L-glutamic acid, L-aspartic acid, and succinic acid, an additional HILIC fraction was isolated and evaluated as tasting umami-like. LC-MS and NMR studies revealed that this fraction consisted of a mixture of (S)-malic acid 1-O-alpha-D-glucopyranoside and (S)-malic acid 1-O-beta-D-glucopyranoside, the structure of which could be successfully confirmed by independent synthesis. To the best of our knowledge, this morel-derived glycoside, which we named (S)-morelid, has previously not been reported in any food products. Sensory analysis of aqueous solutions of the compounds identified revealed threshold concentrations of 0.02 mmol/L for the mouth-drying effect of gamma-aminobutyric acid and 6.0 mmol/L for the umami-like, slightly sour taste of (S)-morelid.     

Analysis of ammonia losses after field application of biogas slurries by an empirical model

Due to energy crises and stricter environmental regulations, renewable energy sources like bio‐methane produced by anaerobic digestion (biogas) become increasingly important. However, the application of slurries produced by biogas fermentation to agricultural land and subsequent ammonia emission may also create environmental risks to the atmosphere and to N‐limited ecosystems. Evaluating ammonia loss from agricultural land by model simulation is an important tool of agricultural‐systems analysis. The objective of this study was the systematical comparison of ammonia volatilization after application of two types of biogas slurries containing high amounts of energy crops in comparison with conventional animal slurries and to investigate the relative importance of factors affecting the emission process through an empirical model. A high number of ammonia‐loss field measurements were carried out in the years 2007/08 in biogas cropping systems in N Germany. The study consisted of simultaneous measurement of NH₃ losses from animal and biogas slurries in multiple‐plot field experiments with different N‐fertilization levels. The derived empirical model for the calculation of NH₃ losses based on explanatory variables gave good predictions of ammonia emission for both biogas and pig slurries. The root mean square error (RMSE) and mean bias error (MBE) of the empirical model for validation data were 2.19 kg N ha^–1 (rRMSE 29%) and –1.19 kg N ha^–1, respectively. Biogas slurries produced highest NH₃ emissions compared to the two animal slurries. In view of the explanatory variables included in the model, total NH$ _4^+ $ application rate, slurry type, temperature, precipitation, crop type, and leaf‐area index were important for ammonia‐volatilization losses.     

Breast cancer prevention by green tea catechins and black tea theaflavins in the C3(1) SV40 T,t antigen transgenic mouse model is accompanied by increased apoptosis and a decrease in oxidative DNA adducts

Tea consumption is associated with a reduced risk of mammary cancer as reflected by epidemiological studies and experiments in carcinogen-induced rodent models of mammary carcinogenesis. We tested the hypothesis that green tea catechins (GTC) or theaflavins from black tea (BTT) interfere with mammary carcinogenesis in C3(1) SV40 T,t antigen transgenic multiple mammary adenocarcinoma (TAg) mice and that GTC/BTT affect tumor survival or oxidation status. TAg mice received GTC/BTT (0.05%) in drinking water for their lifetime. As compared to control mice, they survived longer and had smaller tumors. On microscopic inspection, the size of the largest tumor per mouse was decreased by 40-42% (p<0.01). GTC (0.01%) and BTT (0.05%) increased levels of cleaved caspase 3 in tumor tissue by 67 and 38%, respectively (p<0.05), intimating increased apoptosis. Tumor levels of the malondialdehyde-DNA adduct M1dG in mice receiving GTC or BTT (0.05%) were reduced by 78 (p<0.001) or 63% (p<0.05), respectively, as compared to controls. The results render the exploration of the breast cancer chemopreventive properties of tea preparations in humans worthwhile.     

Photosynthetic water‐use efficiency of irrigated winter and summer crops in a typical mountain oasis of northern Oman

The millenia‐old existence of traditional, surface‐irrigated Omani mountain oases implies a remarkable sustainability of such systems in a hyperarid environment. This study was conducted in the mountain oasis of Balad Seet, situated in the Al‐Jabal‐al‐Akhdar mountains of northern Oman, to investigate the water‐use efficiency (WUE) of these oases and how farmers regulate it. In 2005, gas exchange of single leaves of 9–16 plants was measured for the most important perennial field crop alfalfa in both February and August, for the typical winter crop oat in February, and the dominating summer crop sorghum in August. The measurements were conducted five times a day in subplots irrigated the evening before and in the surrounding control plots, where plants had been withheld from irrigation for 14–16 d. Water deficit at the end of the irrigation interval reduced the stomatal conductance (g_s) strongly in summer alfalfa, oat, and sorghum, but only slightly in winter alfalfa. In oat, the reduction of net photosynthetic rate (P_N) at the end of the irrigation cycle was caused mainly by stomatal closure, in sorghum by nonstomatal factors and in summer alfalfa by both, whereas P_N in winter alfalfa remained unaffected. The ratio of net photosynthetic rate to stomatal conductance (P_N/g_s), the “intrinsic water‐use efficiency”, increased in all investigated crops in response to drought because of a stronger reduction of g_s than of P_N. This increase was small in winter alfalfa, but much stronger in oat, sorghum, and summer alfalfa. The data indicate that alfalfa maintains a relatively high CO₂ assimilation rate year‐round, contributing to a relatively high annual dry‐matter production. The decrease of the light intensity in the late afternoon caused by the shading effect of the surrounding mountains diminishes the crop evapotranspiration in the oasis.     

Nutrient limitation of alpine plants: Implications from leaf N : P stoichiometry and leaf δ15N

Nitrogen (N) deposition can affect grassland ecosystems by altering biomass production, plant species composition and abundance. Therefore, a better understanding of the response of dominant plant species to N input is a prerequisite for accurate prediction of future changes and interactions within plant communities. We evaluated the response of seven dominant plant species on the Tibetan Plateau to N input at two levels: individual species and plant functional group. This was achieved by assessing leaf N : P stoichiometry, leaf δ¹⁵N and biomass production for the plant functional groups. Seven dominant plant species—three legumes, two forbs, one grass, one sedge—were analyzed for N, P, and δ¹⁵N 2 years after fertilization with one of the three N forms: NO$ _3^- $ , NH$ _4^+ $ , or NH₄NO₃ at four application rates (0, 7.5, 30, and 150 kg N ha^–1 y^–1). On the basis of biomass production and leaf N : P ratios, we concluded that grasses were limited by available N or co‐limited by available P. Unlike for grasses, leaf N : P and biomass production were not suitable indicators of N limitation for legumes and forbs in alpine meadows. The poor performance of legumes under high N fertilization was mainly due to strong competition with grasses. The total above‐ground biomass was not increased by N fertilization. However, species composition shifted to more productive grasses. A significant negative correlation between leaf N : P and leaf δ¹⁵N indicated that the two forbs Gentiana straminea and Saussurea superba switched from N deficiency to P limitation (e.g., N excess) due to N fertilization. These findings imply that alpine meadows will be more dominated by grasses under increased atmospheric N deposition.     

GC-based analysis of plant stanyl fatty acid esters in enriched foods

Approaches for the capillary gas chromatographic (GC) based analysis of intact plant stanyl esters in enriched foods were developed. Reference compounds were synthesized by enzyme-catalyzed transesterifications. Their identities were confirmed by means of mass spectrometry. Using a medium polar trifluoropropylmethyl polysiloxane stationary phase, long-chain plant stanyl esters could be separated according to their stanol moieties and their fatty acid chains. Thermal degradation during GC analysis was compensated by determining response factors; calibrations were performed for ten individual plant stanyl esters. For the analysis of low-fat products (skimmed milk drinking yogurts), the GC separation was combined with a "fast extraction" under acidic conditions. For fat-based foods (margarines), online coupled LC-GC offered an elegant and efficient way to avoid time-consuming sample preparation steps. The robust and rapid methods allow conclusions on both, the stanol profiles and the fatty acid moieties, and thus provide a basis for the authentication of this type of functional food ingredients.     

Six new botanical varieties of <Emphasis Type="Italic">Triticum</Emphasis> from Oman

Due to its geographic position on the northeastern tip of the Arabian Peninsula and its sea trade relationships with Asia, East Africa and the Middle East, Oman has for millennia been at the cross-roads of inter-regional exchange of cultivated plants. This is reflected in recent findings of new cultivars of banana (Musa spp.) and wheat (Triticum spp.) in remote oases of the Hajar Mountains in northern Oman. Material collected in 2003 and 2004 contained six new botanical varieties of wheat which are described here. One of them belongs to the tetraploid T. aethiopicum, the others are hexaploid.     

Functional shift hypothesis and the relationship between temperature and soil carbon accumulation

Recent experimental evidence on the relationship between temperature and litter or soil organic matter decomposition suggests that the simple assumption that temperature affects the rate constant of the processes may not be valid. Thermal conditions seem to influence the kinetics of C mineralization by changing, in a qualitatively predictable way, the estimated percentages of initial material that behave as labile or recalcitrant. The consequences of this shift in mineralization dynamics due to temperature, referred to as the functional shift hypothesis, for the long-term C accumulation potential of a soil were investigated using a modified version of Jenny's model. It was concluded that if soils behave according to the functional shift hypothesis, then the utilization of Q₁₀ or other temperature response functions by simulation models leads to significant overestimations of soil C losses due to temperature increase.