The benefits of mycorrhizal inoculation on growth, yield and nutrition of plants are well documented. However, mycorrhiza use in pepper and sweet pepper crops (Capsicum spp.) is still rarely exploited compared to other crops of economic importance. The current paper reviews the main aspects of the association between arbuscular mycorrhizal (AM) fungi and plants of pepper and sweet pepper. It includes topics about the effects of AM fungi on nutrition, growth and yield in Capsicum spp., paying particular attention to AM fungi-pathogen interactions, responses to some environmental stresses, as well as biochemical and physiological aspects of AM fungi-plant interaction in Capsicum annuum L.
A warmer and potentially drier future climate is likely to influence the production of forage crops on dairy farms in the southeast dairy regions of Australia. Biophysical modelling was undertaken to explore the resilience of forage production of individual forage crops to scalar increases in temperature, atmospheric carbon dioxide (CO2) concentration and changes in daily rainfall. The model APSIM was adapted to reflect species specific responses to growth under elevated atmospheric CO2 concentrations. It was then used to simulate 40 years of production of forage wheat, oats, annual ryegrass, maize grown for silage, forage sorghum, forage rape and alfalfa grown at three locations in southeast Australia with increased temperature scenarios (1, 2, 3 and 4 degrees C of warming) and atmospheric CO2 concentration (435, 535, 640 and 750 ppm) and decreasing rainfall scenarios (10, 20 or 30% less rainfall). At all locations positive increases in DM yield compared with the baseline climate scenario were predicted for lucerne (26-932% increase), wheat (89-374% increase), oats (61-359% increase) and annual ryegrass (97-667% increase) under all future climate scenarios. The response of forage rape and forage sorghum varied between location and climate change scenario. At all locations, maize was predicted to have a minimal change in yield under all future climates (between a 26% increase and a 68% decrease). The future climate scenarios altered the seasonal pattern of forage supply for wheat, oats and lucerne with an increase in forage produced during winter. The resilience of forage crops to climate change indicates that they will continue to be an important component of dairy forage production in southeastern Australia.
Following the surface application of granulated urea to grassland, high ammonia (NH3) losses of up to 30% have been reported. The addition of a urease inhibitor (UI) to urea granules could be a way to abate these losses. Field experiments were conducted at two intensive grassland sites in 2007 and 2008 to evaluate the potential of the new UI N-(2-nitrophenyl) phosphoric triamide (2-NPT; concentrations of 0.75, 1.0 and 1.5 g N/kg) to reduce NH3 emissions resulting from the application of granulated urea. Ammonia losses were continuously measured on plots fertilized with urea, urea + 2-NPT, calcium ammonium nitrate and a control (0N). The measurements were made with a dynamic chamber system. All measurement periods were started after a period of precipitation with a following rainless period being forecasted. Results over measurement periods of 10 days following fertilization are presented. Ammonia losses following the application of granulated urea varied between 4.6 and 11.8 kg N/ha, corresponding to 4.2 up to 14.0% of the applied nitrogen. The addition of 2-NPT to urea granules at three concentrations significantly reduced NH3 losses by 69-100%. Comparable losses of NH3 were observed for urea containing the UI 2-NPT as well as calcium ammonium nitrate, and were not significantly different from the control treatment. No relationships between losses, meteorological factors and soil moisture were observed. The addition of the UI 2-NPT to urea granules applied on grassland effectively reduced NH3 losses.
The objective of the present study was to evaluate the effects of isovalerate supplementation on growth performance and ruminal fermentation in pre-and post-weaning dairy calves. Forty-eight Chinese Holstein male calves at 15 days of age and 45.1 +/- 0.36 kg body weight (BW) were assigned randomly to four groups. The treatments were: control, low-isovalerate, moderate-isovalerate (MIV) and high-isovalerate (HIV) with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. Isovalerate was hand-mixed into milk in pre-weaning calves and the concentrate portion in post-weaning calves. The study lasted 75 days, including a 15-day adaptation period followed by a 60-day sampling period. Weaning was conducted when calves were 60 days old. Six calves were chosen from each treatment at random and slaughtered at 30 and 90 days of age. Average daily weight gain increased linearly whether during pre-weaning or post-weaning period with increasing isovalerate supplementation. Dry matter intake linearly increased at 90 days of age with increasing isovalerate supplementation. During weaning, ruminal pH and ammonia nitrogen (N) decreased linearly, whereas total ruminal volatile fatty acid concentration increased linearly with increasing isovalerate supplementation. The ratio of acetate to propionate increased linearly with increasing isovalerate supplementation due to increased acetate concentration and the unchanged propionate concentration. Activities of caboxymethyl-cellulase, cellobiase, xylanase and pectinase linearly increased at 90 days of age, alpha-amylase and beta-amylase activities linearly increased at 30 and 90 days of age. Relative quantities of Butyrivibrio fibrisolvens, Ruminococcus albus, Fibrobacter succinogenes and Ruminococcus flavefaciens increased linearly with increasing isovalerate supplementation. Ruminal fermentation, enzyme activities and cellulolytic bacteria were higher for HIV and MIV than for the control. The present results indicate that isovalerate accelerated growth of calves by improving ruminal fermentation, microbial enzyme activities and cellulolytic bacteria growth during weaning. In the experimental conditions of the current trial, the optimum isovalerate dose was about 6.0 g isovalerate per calf per day.
Biased assessment of tillage impacts on soil organic carbon (SOC) sequestration are often associated with a lack of information on the initial level of SOC stocks. The present study reported the changes in SOC concentrations and stocks following 10-year different tillage practices relative to the initial SOC levels. The tillage trial included no tillage (NT), ridge tillage (RT) and mouldboard plough (MP) on a Black soil (Hapludolls) in Northeast China. Results showed that tillage, soil depth and time significantly affected SOC concentration and SOC stock. Tillage and crop residue retention had great impacts on the SOC concentrations in the top 0.1 m layer. Compared with MP and NT, RT resulted in higher SOC concentration and SOC stock in the plough layer (0-0.2 m), which became more obvious with time. The soil under NT and RT had higher stratification ratios (SR) of SOC (SR, the ratio of SOC concentration in 0-0.05 m to that in 0.1-0.2 m) than under MP. Significant positive and nearly identical linear relationships between the SR of SOC and the duration of tillage practices occurred for both NT and RT soils; the increased SR in NT resulted from both SOC increase in surface and SOC decrease in subsurface soils, but in RT, the increased SR was only from a substantial SOC increase in surface soil. Accordingly, the present study highlights that RT was more helpful than NT in carbon sequestration for the studied Black soil in Northeast China.
Effects of soil tillage systems and nitrogen (N) fertilizer management on spring wheat yield components, grain yield and N-use efficiency (NUE) were evaluated in contrasting weather of 2013 and 2014 on a clay soil at the Royal Agricultural University's Harnhill Manor Farm, Cirencester, UK. Three tillage systems - conventional plough tillage (CT), high intensity non-inversion tillage (HINiT) and low intensity non-inversion tillage (LINiT) for seedbed preparation - were compared at four rates of N fertilizer (0, 70, 140 and 210 kg N/ha). Responses to the effects of the management practices were strongly influenced by weather conditions and varied across seasons. Grain yields were similar between LINiT and CT in 2013, while CT produced higher yields in 2014. Nitrogen fertilization effects also varied across the years with no significant effects observed on grain yield in 2013, while in 2014 applications up to 140 kg N/ha increased yield. Grain protein ranged from 10.1 to 14.5% and increased with N rate in both years. Nitrogen-use efficiency ranged from 12.6 to 49.1 kg grain per kg N fertilizer and decreased as N fertilization rate increased in both years. There was no tillage effect on NUE in 2013, while in 2014 NUE under CT was similar to LINiT and higher than HINiT. The effect of tillage and N fertilization on soil moisture and soil mineral N (SMN) fluctuated across years. In 2013, LINiT showed significantly higher soil moisture than CT, while soil moisture did not differ between tillage systems in 2014. Conventional tillage had significantly higher SMN at harvest time in 2014, while no significant differences on SMN were observed between tillage systems in 2013. These results indicate that LINiT can be used to produce similar spring wheat yield to CT on this particular soil type, if a dry cropping season is expected. Crop response to N fertilization is limited when soil residual N is higher, while in conditions of lower residual SMN, a higher N supply is needed to increase yield and improve grain protein content.
Drought and salinity are two major environmental factors limiting faba bean growth, leading to considerable reduction in their productivity. The WRKY gene family act as major transcription factors that might play an important role in abiotic stress tolerance. In the present study, two partial sequences sharing significant homology with known WRKY genes were isolated from faba bean by polymerase chain reaction (PCR) amplification using degenerate primers targeting the well-conserved WRKY domain. The isolated WRKY gene fragments were designated as VfWRKY1 and VfWRKY2 showing 62% similarity between them. Sequence and phylogenetic analyses revealed that VfWRKY1 and VfWRKY2 belong to WRKY group I and could be grouped with their orthologues from other plant species. The gene expression profile of VfWRKY1 and VfWRKY2 in faba bean showed that they are significantly accumulated in various plant organs. Further, quantitative real-time PCR analysis showed that both transcripts were responsive to drought and salt stress, and also they are genotype dependent, meaning that different faba bean cultivars respond in a different way to drought and salt challenge. The expression patterns obtained suggest the important roles of VfWRKY1 and VfWRKY2 in drought and salt stress response and tolerance. This knowledge might be helpful in the identification of drought-tolerant cultivars and provide potential candidate markers for faba bean breeding in order to develop osmotic-stress-tolerant cultivars.
The spatial distribution of soil organic carbon (SOC) can be affected by environmental factors such as land use change, type of vegetation, soil redistribution processes and soil management practices. Because data are scarce in mountain agroecosystems, improving knowledge on the relationships between land use, soil redistribution processes and SOC fractions is of interest, especially in rapidly changing Mediterranean landscapes. Typically, SOC is divided into two distinct carbon fractions: the active and decomposable fraction (ACF) with rapid turnover rates, which acts as a short-term carbon reservoir, and the stable carbon fraction (SCF) with lower turnover rates that acts as a long-term reservoir. In the present study SOC, ACF and SCF contents were measured by the dry combustion method and converted to inventories expressed as mass per unit surface area (kg/m(2)). The SOC distribution patterns were related to land use and soil redistribution processes in soil profiles along a representative mountain agroecosystem toposequence in northeast Spain. The soil depth profiles were identified as stable, eroded and depositional sites using fallout (137)caesium (Cs). Significantly higher amounts of SOC were found in forest soils (36 +/- 20.2 g/kg) compared to abandoned (21 +/- 14.3 g/kg) and cultivated arable land (11 +/- 6.3 g/kg), suggesting that cultivation decreases SOC content. In addition, stable soil profiles had significantly higher SOC content (42 +/- 24.3 g/kg) than at depositional and eroded profiles (18 +/- 14.5 and 17 +/- 13.1 g/kg, respectively). A positive and statistically significant relationship between SOC and Cs-137 inventories suggested that both are moved and associated with similar soil redistribution processes.
Delineating site-specific management zones within fields can be helpful in addressing spatial variability effects for adopting precision farming practices. A 3-year (2008/09 to 2010/11) field study was conducted at the Postgraduate Agricultural Research Station, University of Agriculture, Faisalabad, Pakistan, to identify the most important soil and landscape attributes influencing wheat grain yield, which can be used for delineating management zones. A total of 48 soil samples were collected from the top 300 mm of soil in 8-ha experimental field divided into regular grids of 24 x 67 m prior to sowing wheat. Soil and landscape attributes such as elevation, % of sand, silt and clay by volume, soil electrical conductivity (EC), pH, soil nitrogen (N) and soil phosphorus (P) were included in the analysis. Artificial neural network (ANN) analysis showed that % sand, % clay, elevation, soil N and soil EC were important variables for delineating management zones. Different management zone schemes ranging from three to six were developed and evaluated based on performance indicators using Management Zone Analyst (MZA V0.1) software. The fuzziness performance index (FPI) and normalized classification entropy NCE indices showed minimum values for a four management zone scheme, indicating its appropriateness for the experimental field. The coefficient of variation values of soil and landscape attributes decreased for each management zone within the four management zone scheme compared to the entire field, which showed improved homogeneity. The evaluation of the four management zone scheme using normalized wheat grain yield data showed distinct means for each management zone, verifying spatial variability effects and the need for its management. The results indicated that the approach based on ANN and MZA software analysis can be helpful in delineating management zones within the field, to promote precision farming practices effectively.
The cropping systems of the Eastern Gangetic Plains of Bangladesh, India and Nepal are based on rice. There is a scope to intensify such systems through diversification with lentil, the most popular food legume. Two strategies were evaluated to fit lentil into the short fallow between successive monsoonal (i.e., T. aman) and pre-monsoonal (aus) or irrigated rice (boro) crop. These were early-flowering sole-cropped lentil and relay-sown lentil into rice. Firstly, 18 early-flowering lentil lines at three contrasting sowing dates were tested over two seasons on a research station at Ishurdi in Bangladesh. Secondly, relay sowing was evaluated at the same location with six early-flowering lines and two control cultivars in two seasons. It was also assessed on ten farms in Western Bangladesh, comparing relay with sole cropping over 3 years. Flowering in the early-flowering lentil lines was consistently 9-17 days earlier, than the control cultivars, but they did not achieve an economic yield (<10 t/ha). Relay sowing with an existing cultivar produced an economic yield of lentil, which was comparable or higher than sole-cropped lentil in all situations. The relay-sown lentil matured in sufficient time to allow the land to be prepared for the succeeding rain-fed rice crop. It was concluded that the substitution of relay-sown lentil for fallow in the monsoonal rice-fallow-rain-fed rice cropping pattern is a useful option to intensify and diversify cropping in the Eastern Gangetic Plain.
A field study was carried out to examine the response of microbial communities of a clay loam soil to long-term (30 years) effects of residue return and fertilization. The experimental design was a split-plot arrangement of treatments, consisting of three residue treatments (crop residues returned at rates of 0, 2500 and 5000 kg/ha) in combination with eight fertilization treatments (control, no fertilizer; N, mineral nitrogen (N) fertilizer; P, mineral phosphorus (P) fertilizer; K, mineral potassium (K) fertilizer; NP, mineral NP fertilizer; NK, mineral NK fertilizer; PK, mineral PK fertilizer; and NPK, mineral NPK fertilizer). Soil microbial communities were characterized by phospholipid fatty acid analysis. Results indicated that the more crop residues were returned, the lower ratio of fungi to bacteria was observed. However, soil microbial biomass was only found to be significantly higher in plots with residues returned at a rate of 5000 kg/ha but not 2500 kg/ha. This suggested there was a threshold for microbial biomass to increase under residue return for the clay loam soil studied. The fertilization effect on soil microbial biomass gradually decreased with increases in the amount of crop residues returned. A significant composition change was observed under N fertilization. Structural equation modelling indicated that soil microbial communities were influenced directly by residue return and indirectly by residue-induced change in ratio of carbon to N and fertilization-induced change in soil pH.
Hazard identification is the first step in assessing the risk of a genetically modified (GM) crop. It employs the concept of substantial equivalence to evaluate crop safety. The current process relies on subjective opinions to integrate various comparisons among the GM crop, the non-GM counterpart and an assortment of non-GM references over an array of key endpoints measured in field trials. The pre-eminent need to control the consumer's risk in hazard identification has been left unaddressed. The current paper develops statistical strategies to resolve this issue. Hypotheses of individual tests are explicitly defined to reflect the study objectives. They are then grouped into families and connected by logical operators according to decision rules commonly used in crop safety evaluation. This pre-specification of hypotheses arranged in an organized layout leads to a simple, transparent decision-making process where the consumer's risk can be managed directly. A two-stage multiplicity adjustment procedure is created by applying fundamental principles for multiple testing to the newly assembled families of hypotheses. The practical utility of the proposed procedure is shown in a real-world example. Besides being easy to implement and convey, the proposed statistical strategies accommodate the addition of supportive evidence for safety and allow the nature of the genetic modification to be taken into account.
The historical temperature (1981-2007) and phenological (1986-2011) data were analysed for the region of Sremski Karlovci, one of the oldest grapevine growing areas in Europe, with the aim of detecting trends of changes in the data, evaluating the sensitivity of grapevine phenology to temperature and revealing diversity among cultivars in their response to observed changes in temperature. The onset dates of four major phenological stages (budburst, flowering, veraison and harvest), along with the corresponding growth intervals between them, were examined for 20 wine grape cultivars. A number of climatically important parameters for viticulture were calculated for the calendar year, growing season and different grapevine growth periods. Significant increases were detected in average and heat-related extreme temperature indices. The greatest rate of change in temperature variables across the growing season was observed during the period from the beginning of flowering to the beginning of veraison and the smallest during the ripening period. Linear trends indicated that all phenological stages, except budburst, have advanced significantly. Averaged across all cultivars, detected trends were -0.4, -0.7 and -0.6 days/year for the beginning of flowering, the beginning of veraison and harvest date, respectively. Observed warming and change in the timing of phenological events did not significantly affect the duration of the growth intervals, which can be explained by significant inter-correlation between the phenological stages' onset. Ripening was occurring under warmer conditions due to earlier flowering and veraison, rather than because of considerably higher temperatures preceding harvest or shortening of the ripening period. Most of the variation in phenology timing (74-90%) can be explained by a linear relationship between the onset date of phenological stage and temperature, with mean and maximum temperatures being more important than minimum temperatures. According to the current results, a 1 degrees C increase in the most influential temperature variable during the most relevant periods for the onset of phenological stages led to an advancement in the beginning of budburst, the beginning of flowering, the beginning of veraison and harvest by 3.6, 3.1, 5.2 and 7.4 days, respectively, on average for all cultivars. Among the cultivars studied, Pinot Noir displayed the greatest phenology advancement in response to increased temperature.
Grazing season length (GSL) on grassland farms with ruminant production systems can influence farm economics, livestock disease transmission, environmental impact, milk and meat quality, and consumer choice. Bioclimatic variables are biologically meaningful climate variables that may enable predictions of the impact of future climate change on GSL on European farms. The present study investigated the spatial relationship between current GSL (months) measured by EUROSTAT on dairy, beef and sheep farms in 706, 774 and 878 regions, respectively, and bioclimatic variables. A stepwise multiple regression model revealed a highly significant association between observed GSL and bioclimatic variables across Europe. Mean GSL was positively associated with the mean temperature of the coldest quarter and isothermality, and negatively associated with precipitation in the wettest month. Extrapolating these relationships to future climate change scenarios, most European countries were predicted to have a net increase in GSL with the increase being largest (up to 25 months) in the north-east of Europe. However, there were also predictions of increased variability between regions and decreases in GSL of up to 15 months in some areas such as the west of France, the south-west of Norway and the west coast of Britain. The study quantified and mapped the potential impact of climate change on GSL for dairy, beef and sheep farms across Europe.
Palm oil comprises mainly triacylglycerols (TAG) that account for about 095 of its composition. Lipolysis of TAG releases free fatty acids that are then oxidized, impairing oil quality. Lower endogenous lipase activity is therefore desirable for better quality oil. Identifying genotypes for this should allow production of oils with improved shelf-life. A novel non-radioactive cold-activation titration assay was used to assay for lipase activity in 49 randomly selected Elaeis guineensis palms using the novel method as well as the traditional radioactive method. The results confirmed significant correlation between the radioactive and novel non-radioactive methods. A total of 148 E. guineensis palms originating from Angola, Cameroon, Guinea Conarky, Nigeria, Senagal, Sierra Leone, Tanzania and Zaire were then screened for lipase activity using the novel non-radioactive method. The analysis revealed genotypes with significantly different lipase activities, indicating that the activity is genotype-dependent. Quantitative polymerase chain reaction indicated similarity in pattern between gene expression and lipase activity determined by the novel assay. Several low and high lipase genotypes were identified. The findings pave the way for selection and breeding for low lipase genotypes. They are also relevant to genetic marker development for oil quality. Evidence is presented for the presence of at least two different lipases that determine oil quality in the oil palm mesocarp.
The effects of planting pattern and irrigation on the soil water content, stomatal conductance, leaf relative water content, leaf water potential and leaf water use efficiency of winter wheat were investigated in North China during the 2008/09 and 2009/10 growing seasons. A field experiment was conducted using a randomized complete block design that consisted of three planting patterns: (i) a uniform row spacing of 25 cm, and alternating wide-narrow row spacing of 40 and 20 cm tested as (ii) flat and (iii) furrow-ridge seedbeds. In addition, irrigation treatments of 90, 135 and 180 mm were used. The planting pattern, irrigation treatments and interactions between them significantly affected soil water content, stomatal conductance, leaf relative water content, leaf water potential and leaf water use efficiency. The soil water content, stomatal conductance, leaf relative water content, leaf water potential, grains/spike, thousand grain weight, leaf water use efficiency and yield were highest in the furrow-ridge seedbed planting pattern and increased with increasing irrigation (except for the leaf water use efficiency). The leaf water use efficiency in the 135 mm irrigation treatment was significantly greater than in the other treatments. In addition, soil water content, stomatal conductance, leaf relative water content, leaf water potential, grains/spike and thousand grain weight were positively correlated with leaf water use efficiency and yield of winter wheat. The interaction between the furrow-ridge seedbed planting pattern and 135 mm irrigation increased soil water content, leaf water indices, grains/spike, thousand grain weight, leaf water use efficiency and yield. These results indicated that a beneficial response occurred for wheat yield. The furrow-ridge seedbed planting pattern combined with 135 mm of irrigation improved the soil and leaf water status and could increase wheat yield while using less water.
Safety evaluation of a genetically modified (GM) crop is accomplished by establishing its substantial equivalence to non-GM reference crops with a history of safe use. Testing hypotheses of equivalence rather than difference is the appropriate statistical approach. A necessary first step in this regard is to specify a reasonable equivalence criterion that includes a measure for discrepancy between the GM and reference crops as well as a regulatory threshold. The present work explored several equivalence criteria and discussed their pros and cons. Each criterion addresses one of three ordered classes of equivalence: super, conditional and marginal equivalence. Their implications were investigated over an array of parameter values estimated from a real-world dataset. Marginal equivalence was identified as adhering most closely to the concept of substantial equivalence. Because conditional equivalence logically implies marginal equivalence and is practically quantifiable from current field designs, the present work recommends conditional equivalence criteria while encouraging producers to improve their design to enable testing marginal equivalence in the future. Contrary to concerns of the ag-biotech industry, empirical evidence from recent publications indicates that a linear mixed model currently implemented by the European Food Safety Authority is adequate for assessing equivalence despite its lack of genotype-by-environment interaction terms.
Although forage lipid is generally rich in polyunsaturated fatty acids (PUFA), recovery of these fatty acids (FA) in milk and meat of ruminant origin is generally low, due to microbial biohydrogenation (BH) taking place in the rumen. Since lipolysis is a prerequisite for BH, the latter process is expected to be enhanced when (conserved) forages contain lower levels of esterified FA (particularly polar lipids; PL). However, this was not observed in former studies with red clover (Trifolium pratense L.). Furthermore, red clover inclusion in the herbivore's diet was associated with decreased rumen BH as compared with other forages. Differences in plant lipase activity during wilting and ensiling has been attributed to changes in disappearance from the PL fraction, but a potential role of microbial lipases in silo has not yet been elucidated. Therefore, the aims of the present study were to assess whether BH of red clover FA is linked with PL levels of the (conserved) starting material and to clarify the possible role of in silo microbial activity on PL disappearance. In order to obtain sufficient variation in forage PL and microbial activity, laboratory-scale silages were made by wilting and ensiling damaged or undamaged red clover using molasses or formic acid as ensiling additive, while perennial ryegrass (Lolium perenne L.) was used as a control. Distribution of lipids within three lipid fractions (PL, free FA and neutral lipids) in forages was determined and BH calculated after 24 h in vitro rumen incubation. Results indicated microbial lipases in silages did not enhance FA disappearance from the PL fraction. A gradual decrease of FA in the PL fraction upon conservation was found, both in red clover and ryegrass, irrespective of the degree of damage. In red clover PL losses started from the wilting phase, while substantial PL disappearance from ryegrass only started upon ensiling. Proportions of PUFA remaining in the PL fraction after wilting and ensiling of red clover were positively correlated with PUFA BH, while this effect was not observed for ryegrass. Red clover PUFA seemed to be partially protected against ruminal BH, while disappearance of FA from the PL fraction did not seem to be hampered. Results indicated the encapsulation mechanism as a consequence of protein-bound phenol formation induced by polyphenol oxidase is still the most probable hypothesis to explain red clover's increased flow of PUFA across the rumen.
Thirty-two lambs (n=8 per treatment) were fed a total mixed ration (TMR) formulated either with palm oil (CTRL; 34g palm oil/kg TMR) or flaxseed (FS) (85g FS/kg TMR) alone or enriched with quercetin (QCT, 34g palm oil plus 2g QCT/kg TMR; FS-QCT, 85g FS plus 2g QCT/kg TMR). The animals were slaughtered after being fed for at least 5 weeks with the experimental diets and samples of ruminal contents and ruminal liquid were collected for quantitative real-time polymerase chain reaction analyses of ruminal microbial species and fatty acid profile or in vitro fermentation, respectively. Results demonstrated that Butyrivibrio vaccenic acid (VA) and Butyrivibrio stearic acid (SA) producing bacteria copy numbers were decreased when FS was added to the diet of fattening lambs, which seemed to be in agreement with numerically (but not significantly) lower values for gas production, methane production and butyric acid during in vitro incubation. Ciliate protozoa were significantly enhanced by QCT, which was in accordance with numerically (but not significantly) higher values for in vitro methane production. Moreover, the modifications observed in ruminal microbial populations (Butyrivibrio and ciliate protozoa) when FS and QCT were included together (but not separately) in the diet of fattening lambs were probably related to a trend towards significantly higher values of rumenic acid (RA) in ruminal content. In conclusion, when FS and QCT were administered together in the diet of fattening lambs quantitative changes in the ruminal microbiota were observed, which might have promoted an increment of RA concentration in ruminal contents.
Three different explanatory indicators for reduced light use efficiency (LUE) under limited nitrogen (N) supply were evaluated. The indicators can be used to adapt dry matter production of crop simulators to N-limited growth conditions. The first indicator, nitrogen factor (NFAC), originates from the CERES-Wheat model and calculates the critical N concentration of the shoot as a function of phenological development. The second indicator, N nutrition index (NNI), calculates a critical N concentration as a function of shoot dry matter. The third indicator, specific leaf nitrogen (SLN) index (SLNI), has been newly developed. It compares the actual SLN with the maximum SLN (SLNmax). The latter is calculated as a function of the green area index (GAI). The comparison was based on growth curves and fitted to empirical data, and was carried out independently from a dynamic crop model. The data set included four growing seasons (2004-2006, 2012) in Northern Germany and seven modern bread wheat cultivars with varying N fertilization levels (0-320 kg N/ha). The influence of N shortage on LUE was evaluated from the beginning of stem elongation until flowering. With the exception of 2005, the highest productivity was observed for the highest N level. A moderate N shortage primarily reduced GAI and therefore light interception, while LUE remained stable under moderate N shortage. The relative LUE (rLUE) of a specific day was defined as the ratio of actual to maximal LUE. None of the indicators was proportional to rLUE, but the relationships were described well by quadratic plateau curves. The correlation between simulated and measured rLUE was significant for all explanatory indicators, but different in terms of mean absolute error and coefficient of determination (R-2). The performance of SLNI and NNI was similar, but the goodness of prediction was much lower for NFAC. Compared with NNI and NFAC, SLNI corresponded to leaf N and was therefore sensitive to N translocation from leaves to growing grains during the reproductive stage. For this reason, SLNI may have the potential to improve simulation of dry matter production in wheat crop simulators.