Water and nitrate budgets in a rendzina cropped with oilseed rape receiving varying amounts of fertilizer

Pollution of the environment by nitrogen (N) has emerged as a serious concern in agriculture, especially in the case of crops such as oilseed rape. To assess the effect of N fertilization on N dynamics, the movements of water and nitrate were determined in a rendzina near Châlons-en-Champagne (eastern France) cropped with oilseed rape with three levels of fertilizer N and in a bare control. From in situ micrometeorological measurements, actual evapotranspiration rates were computed with an energy budget and used to calibrate an evapotranspiration model based on meteorological data and crop leaf area index. Water flow below 120 cm was then deduced from periodic measurements of soil moisture contents and precipitation, and the associated nitrate leaching fluxes were calculated from the NO₃ concentration measured at the same depth. Denitrification rates and ammonia volatilization were monitored in the field after fertilizer applications, and crop assimilation of nitrogen was determined frequently during the growth cycle. A nitrate budget gave an approximation of the in situ net mineralization fluxes. The water balance was influenced by the crop and its fertilization: the crop's canopy and roots enhanced the water loss by evapotranspiration and contributed to diminish the soil water storage, whereas drainage volumes were about the same for all cropped treatments, and significantly greater in the bare soil. The rainy winter was particularly favourable to leaching, and losses were much greater (+ 41%) under the over-fertilized crop than under the non-fertilized one, but remained less (– 42%) than those under the bare control soil. Bilans hydriques et azotés d'une culture de colza sur rendzine avec différentes doses d'engrais Les pollutions de l'environnement par l'azote sont devenues une préoccupation majeure en agriculture, particulièrement dans le cas des cultures comme le colza. Pour évaluer les effets de la fertilisation azotée sur la dynamique de l'azote, les transferts d'eau et de nitrate d'une rendzine ont été mesurés près de Châlons-en-Champagne (Est de la France) sur des parcelles expérimentales de colza avec trois niveaux de fertilisation azotée et sur une parcelle témoin en sol nu. A partir de mesures micrométéorologiques in situ, l'évapotranspiration réelle a été calculée par bilan énergétique de la surface du sol, et un modèle d'évapotranspiration ayant pour entrées des données météorologiques classiques et l'indice foliaire de la culture a été calibré. Le flux net d'eau sous 120 cm a été alors déduit de mesures périodiques de teneur en eau du sol et de précipitations, et les flux de nitrate associés ont été calculés à partir des concentration mesurées à la même profondeur. Les flux de dénitrification et la volatilisation d'ammoniac ont été mesurés au champ après les apports d'engrais; l'absorption d'azote par la culture a été déterminée fréquemment pendant le cycle de croissance. Enfin, un bilan azoté a donné l'ordre de grandeur de la minéralisation nette. Le bilan hydrique a été influencé par la culture et sa fertilisation: le couvert végétal et les racines ont accentué les pertes d'eau par évapotranspiration et par conséquent le stock d'eau, tandis que la lame d'eau drainée était à peu près la même pour tous les traitements cultivés, et significativement plus élevée pour le sol nu. L'hiver particulièrement pluvieux a été très favorable au lessivage, et les pertes ont été beaucoup plus fortes (+ 41%) sous la culture sur-fertilisée que sur la culture non-fertilisée, mais elles sont restées inférieures (– 42%) à celles sous sol nu. Nomenclature     

Antifeedant activity of vicolides from Pentanema indicum

Vicolides A–D (0.2–2000 ppm) from Pentanema indicum showed antifeedant activity against Euproctes fraterna and Pericallia ricini V stage larvae.     

Dry-matter production and botanical composition of multispecies and perennial ryegrass swards under varying defoliation management

Multispecies swards, comprised of different plant functional groups have comparable production potential to high N input L. perenne swards at reduced N when legumes are included. However, information on the appropriate management of multispecies swards is limited. The effect of differing management practices on the herbage dry-matter (DM) production and botanical composition of different sward types was investigated using a 3 × 2 × 2 factorial design plot experiment. The experiment consisted of three sward types: L. perenne-only receiving (LP; 250 kg N ha⁻¹ a⁻¹); L. perenne-Trifolium repens (LP-TR); multispecies sward containing L. perenne, Phleum pratense, Trifolium repens, Trifolium pratense, Plantago lanceolata and Cichorium intybus (MSS). LP-TR and MSS received 90 kg N ha⁻¹ a⁻¹. Harvesting of plot herbage took place every 21 or 28 days to a defoliation height of 4 or 6 cm, over two growing seasons (March to November 2020 and 2021 inclusive). Annual herbage produced by both LP and LP-TR was not significantly affected by defoliation frequency. However, MSS produced 1923 kg DM ha⁻¹ a⁻¹ more herbage when harvested less frequently. Unsown species contributed significantly less to the herbage DM of MSS compared to LP and LP-TR and remained similar in 2020 and 2021, whereas the contribution of unsown species to herbage DM increased in LP and LP-TR from 2020 to 2021, with noxious species more associated with LP and LP-TR than MSS. Results demonstrate the role of multispecies swards in improving the sustainability of grass-based agricultural systems in an environment of reduced fertilizer inputs.     

Characterization of the trade in manta and devil ray gill plates in China and South‐east Asia through trader surveys

相似文献   

Assessing Environmental Influences on Solvent Retention Capacities of Two Soft White Spring Wheat Cultivars

The solvent retention capacity test (SRC) (AACC Approved Method 56‐11) of flour is used to evaluate multiple aspects of wheat (Triticum aestivum L.) quality including pentosan content, starch damage, gluten strength, and general water retention based on the ability of flour to retain a range of solvents. The objectives of this study were to evaluate the effects of grain production environment in general and crop irrigation and fertility management in particular on SRC of soft wheat flour, and to evaluate the ability of SRC to predict end‐use quality across diverse environments. Two soft white spring wheat cultivars ‘Pomerelle’ and ‘Centennial’ were produced in a range of irrigated and rain‐fed production environments. SRC profiles and milling and baking quality parameters were measured. In a two‐year study at Aberdeen, ID, with two late‐season irrigation management regimes and two crop nitrogen fertility treatments, only wheat genotype significantly affected flour SRC. In two‐year studies at Tetonia, ID, one conducted under rain‐fed conditions and the other under irrigation, additional fertilizer applied at anthesis did not affect SRC. Correlations among quality parameters were determined using the Aberdeen and Tetonia flour samples, as well as samples of the same genotypes grown in fertility trials under rain‐fed conditions at Havre and Bozeman, MT, and under irrigation at Bozeman. Patterns of correlations among SRC values were similar for both genotypes. Grain test weight was negatively correlated with sodium carbonate and sucrose SRC of both genotypes. Flour protein was strongly positively correlated with sucrose and lactic acid SRC of both genotypes. The optimal regression models for predicting sugar snap cookie diameter (AACC Approved Method 10‐52) as a function of protein, SRC, flour extraction, and kernel hardness were different for the two cultivars. SRC evaluations of flours from these trials were consistent with large genotype and environment effects, yet minimal genotype × environment interaction. This suggests that selection among genotypes within an environment will produce a gain‐from‐selection observable in multiple and diverse environments.     

Mixed stream channel morphologies: implications for fish community diversity

• 1. Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant.
• 2. Twenty‐five stream reaches in north‐western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool‐riffle, mixed (i.e. pool‐riffle/cascade, pool‐riffle/other) and forced pool‐riffle stream morphological groups. Stream reach surveys included cross‐sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys.
• 3. Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon–Weaver Index (H′); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P?0.05), with pool‐riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool‐riffle the lowest.
• 4. These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool‐riffle/cascade and pool‐riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool‐riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies.
• 5. These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional‐distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts.

Copyright © 2008 John Wiley & Sons, Ltd.     

Looking beyond the horizon: An early warning system to keep marine mammal information relevant for conservation

相似文献   

Microalgal paste production of the diatom <Emphasis Type="Italic">Chaetoceros calcitrans</Emphasis> using electrolytic flocculation method at optimum culture conditions

The optimum culture conditions of the local strain Chaetoceros calcitrans were determined to improve biomass and reduce cost of production. Under outdoor culture conditions, higher cell density was attained when the cultures were enriched with Tungkang Marine Research Laboratory (TMRL) medium composed of cheap technical grade reagents and cultured at 25 g L^?1 salinity. The cultures were lighted with two 40 W cool-white GE fluorescent tubes (24–35 μmol photon m^?2 s^?1). Using semi-continuous culture system under established optimum culture conditions, C. calcitrans can be re-cultured thrice and concentrated at each culture cycle using electrolytic flocculation method to produce 4.6 kg m^?3 of diatom paste. The viability of concentrated C. calcitrans after 3 months of storage was comparable to live diatom cells. Simple preservation technique by low-temperature storage is convenient for storing algal concentrates for use as starter cultures and for feeding invertebrates. The paste costs USD 8.24 kg^?1 inclusive of the assets and flocculation materials for culturing and harvesting the diatom, respectively. This study established the suitable conditions for mass culture of C. calcitrans and produced concentrated diatoms in paste form that is readily available for aquaculture hatcheries at a lower cost.     

Use of thraustochytrid <Emphasis Type="Italic">Schizochytrium</Emphasis> sp. as source of lipid and fatty acid in a formulated diet for abalone <Emphasis Type="Italic">Haliotis asinina</Emphasis> (Linnaeus) juveniles

The effects of using thraustochytrid Schizochytrium sp. as source of lipid and fatty acids in a formulated diet on growth, survival, body composition, and salinity tolerance of juvenile donkey’s ear abalone, Haliotis asinina, were investigated. Treatments consisted of diets either containing a 1:1 ratio of cod liver oil (CLO) and soybean oil (SBO) (Diet 1) or thraustochytrid (Diet 2) as source of lipid and fatty acids at 2 % level. Natural diet Gracilariopsis heteroclada (Diet 3) served as the control. No significant difference in growth was observed in abalone fed Diet 3 (SGR: 5.3 % BW day^?1; DISL: 265 μm day^?1) and Diet 2 (SGR: 5.2 % BW day^?1; DISL: 255 μm day^?1). Survival ranged from 78 to 85 % for all treatments and was not significantly different from each other. A 96-h salinity stress test showed highest survival of 84 % in abalone fed Diet 2 compared with those fed diets 1 and 3 (42 %). The high growth rate of abalone fed Diet 2 and high tolerance to low salinity could be attributed to its high DHA content (8.9 %), which resulted to its high DHA/EPA ratio of 10.5 %. These fatty acids play a significant role in abalone nutrition. The fatty acid profile of abalone meat is a reflective of the fatty acid profile of the oil sources in the diet. The present study suggests that the use of Schizochytrium oil in lieu of CLO and SBO can support good growth of abalone which is comparable with abalone fed the natural seaweeds diet.