Economic trade-offs to limit nonpoint sources of agricultural pollution

A national model has been built which allows analysis of physical and economic trade-offs as soil loss per acre is limited to specified levels in each major land group of the nation. Crop variables with their associated conservation practices are developed for each of 1891 land groups in 223 agricultural producing regions and 51 water supply regions. The regions and soil groups are made interdependent through regional commodity demands and a transportation submodel. Hence, changes in cropping systems and erosion control practices in one region are simultaneously expressed in effects on other regions. Soil loss limits are set at 10, 5, and 3 t per acre. The 10 t limit does not have a large impact on interregional production patterns and farm comodity prices. However, the 5 and 3 t limits, either singularly or in combination with different export levels, cause rather marked increases in commodity prices. Also at limits of 5 and 3 t, considerable shifts take place among regions in the crops grown and the erosion control methods used. Regions with erosive soils sacrificed in reduced income; regions with level soils can crop more intensely and gain greater income. Conservation practices such as reduced tillage increase the amount of pesticides needed in some regions and pose special environmental problems. The South Atlantic region is affected most by soil loss limits to control nonpoint pollution. The Great Plains regions with more level land and limited rainfall are affected least.     

Effect of Density at Harvest on the Growth Performance and Profitability of Hatchery‐reared Spotted Rose Snapper,Lutjanus guttatus,Cultured in Floating Net Cages

This study evaluated the effect of the density at harvest on the performance and profitability of hatchery‐reared spotted rose snapper cultured in cages. The fish were stocked at harvest densities of 15, 20, and 22 kg/m³ in cages of 222 and 286 m³. More than 39,000 snapper fingerlings with an initial weight of 14 g were stocked. The fish were fed an extruded diet and cultured over a 360 d period. The thermal growth coefficient ranged from 0.04 to 0.05 and survival was 95% for all treatments, with the highest final weight (436.8 g) observed for fish reared at a density of 20 kg/m³. The allometric value b indicated that hatchery‐raised, cage‐cultured snapper were heavier than their wild counterparts. The major costs were feed (ranging from 44.7–45.9%), labor (22.4–32.6%), and seed costs (20.2–26.1%). The total production cost ranged from US$ 6.5 to US$ 7.5/kg. The baseline scenario was not economically feasible. However, a 10% increase in the sales price resulted in increases in the internal rate of return (183%) and net present value (US$ 97,628.9). These results suggest that L. guttatus has the potential for commercial production in cages.     

Larval traits of the Caribbean amphidromous goby Sicydium punctatum (Gobioidei: Sicydiinae) in Guadeloupe

Amphidromous fish are the biggest contributor to the diversity of fish communities in river systems of Caribbean islands. Among them, Sicydium punctatum Perugia, 1896, which is endemic to the West Indies, represents the vast majority of fish in these rivers. The otolith microstructure and the biometry of S. punctatum postlarvae from Guadeloupe were investigated to explore the dispersal modalities of this species through an appreciation of the growth pattern, the pelagic larval duration (PLD) and the size‐at‐recruitment. The study was made on one cohort of 83 recruited postlarvae, fished at the Capesterre River's mouth on 2 November 2011. The mean (±SD) size‐at‐recruitment of the postlarvae was 24.6 ± 1.3 mm (range of 20.5–28.1 mm, n = 83). We found a mean (±SD) PLD of 72.2 ± 10.5 days (range of 54–101.5 days, n = 67). The growth rate estimated from the otolith increments showed a globally decreasing pattern during the marine larval phase. Growth rates at the beginning of the larval stage were significantly different between hatching periods, suggesting a relation between the hatching period and the growth rate in S. punctatum. This study adds on to the general understanding of the life cycle of S. punctatum in Guadeloupe that will help implement strategies to manage amphidromous fish populations in the Caribbean region.     

The Sustainability of Quinoa Production in Southern Bolivia: from Misrepresentations to Questionable Solutions. Comments on Jacobsen (2011, J. Agron. Crop Sci. 197: 390–399)

Reviewing the situation of quinoa production in southern Bolivia, Jacobsen (2011, J. Agron. Crop Sci. 197: 390) argues that the booming export market has a negative effect on the environment and on the home consumption of quinoa, thereby leading to an environmental disaster in the region. In view of the scarcity of scientific knowledge on the rapid social and environmental dynamics in the region, we consider that Jacobsen’s review misrepresents the situation of quinoa production in southern Bolivia. Specifically, we argue that (i) the data presented by Jacobsen (2011, J. Agron. Crop Sci. 197: 390) do not support any drop in quinoa crop yield supposed to reflect soil degradation and (ii) his demonstration regarding home consumption of quinoa is ill‐founded from both a nutritional and a cultural point of view. We suggest that the diffusion of the arguments exposed by Jacobsen (2011, J. Agron. Crop Sci. 197: 390), because of their flaws, might have strong negative impacts on those concerned with sustainable food production and fair‐trade with developing countries. We conclude that, rather than reinforced agro‐technical controls on local farmers, the rising competition in the international quinoa market requires a shift towards an ethical economy and ethical research cooperation with quinoa producers.     

Linking the abundance of aspen with soil faunal communities and rates of belowground processes within single stands of mixed aspen–black spruce

The occurrence of aspen (Populus tremuloides Michx.) patches within stands dominated by black spruce (Picea mariana Mill. BSP) has been shown to increase litter decomposition and nutrient cycling rates by improving soil physical and chemical properties. It is well known, however, that these processes are also influenced by the structure of the soil biota, but this factor has received less attention. In this study, relationships between forest floor properties and soil invertebrates were studied along black spruce–trembling aspen gradients in three stands of the eastern boreal forest of Canada. The forest floor layer of 36 plots differing in aspen basal area was sampled and analyzed to determine physical and chemical properties, the rates of decomposition of standard substrates, net N mineralization, as well as microbial basal respiration and metabolic quotient. Soil invertebrates were also collected using funnel-extraction and pitfall trapping methods. Based on redundancy analyses, we found that forest floor properties, the abundance and composition of soil invertebrates, and the rates of belowground processes changed along the spruce–aspen gradient. The increase in aspen basal area was associated with a reduction in forest floor thickness, moisture content and microbial biomass, and with an increase in the concentration of nutrients. It was also accompanied by changes in soil faunal communities, as soil invertebrates were associated with specific soil properties. In general, macroinvertebrates (i.e., Lumbricidae, Formicidae, Carabidae, Staphylinidae and Gastropoda) were related to the nutrient-rich forest floor associated with aspen, whereas microarthropods and Enchytraeidae tended to be negatively related to aspen basal area. According to mixed linear models, decomposition rates of standard substrates and net ammonification significantly increased along the spruce–aspen gradient. Given the functional significance of macroinvertebrates in soils, these results suggest that aspen favours the elaboration of a macrofaunal community, which in turn accelerates the rate of soil processes by having either direct or indirect influence on microbial activity. Moreover, this study shows that the changes in soil processes and in the biodiversity of soil organisms related to the presence of mixed stands can operate only in the immediate surroundings of a given tree species. Therefore, coarse-scale tree species mixing in a forest stand may have a different effect on soil biodiversity and soil processes than fine-scale mixing.     

Behaviour of domestic ducks exposed to mobile predator stimuli. 1. Flock responses

1. Small flocks of ducks (Anasplatyrhynchos domesticus) were exposed to two stimuli, a small mobile vehicle and a walking human, to investigate their flight responses. 2. Experiment 1. Flocks were herded around an annular arena by each stimulus at 0.5 ms(-1) and the flight distance between the stimulus and the centre of the flock, and individual positions within the flock were recorded every 10 s. Flocks maintained a significantly longer distance from the human (6.0 m) than the vehicle (5.1 m) and usually did not maintain visual contact with either stimulus. Significant consistency in individual positions within the flock was found within and between trials. 3. Experiment 2. Flocks were exposed to each stimulus which approached them as they were feeding in a circular arena. The latencies for cessation and resumption of feeding were recorded and the paths followed by the flocks described. Ducks showed a significantly shorter latency to cease feeding in response to the human (4.9 s) compared with the vehicle (6.9 s). 4. Domestic ducks apparently perceive an approaching human as a greater threat than a small vehicle. The findings are discussed in relation to the development of herding robots.     

Application of a putative fatty-acid binding protein to discriminate serologically the two European quarantine root-knot nematodes, Meloidogyne chitwoodi and M. fallax, from other Meloidogyne species

Two major proteins, Mcf-A67 and Mcf-B66, were identified by mini two-dimensional polyacrylamide gel electrophoresis in order to distinguish the two European quarantine root-knot nematodes, Meloidogyne chitwoodi and M. fallax, from eight other species. These quarantine proteinic markers have been microsequenced after enzymatic digestion. The internal amino acid sequences exhibit similarities to members of a family of low molecular weight intracellular lipid-binding proteins. Moreover, to explore a simple, rapid, and inexpensive way to identify the two quarantine nematodes, dot blot hybridizations were performed using an antiserum (A67) produced from the longest amino-acid sequence of the protein Mcf-A67. Although several proteins stained on the M. chitwoodi and M. fallax western blot membranes, the two nematodes were easily distinguished from other root-knot nematodes, on dot blot assays with soluble proteins extracted from a single female. Because of its specificity and sensitivity, the use of the A67 antiserum to improve the diagnosis of the two European quarantine root-knot nematodes is discussed.     

Dilemma of virulence of Streptococcus suis: Canadian isolate 89-1591 characterized as a virulent strain using a standardized experimental model in pigs

Virulence of Streptococccus suis capsular type 2 strain 89-1591 has been controversial in literature. A standardized experimental model with specific-pathogen free piglets was used for a new evaluation of this strain. Twenty-nine piglets were allotted in 4 separated groups. Group 1 consisted of negative control animals which received broth medium. Groups 2, 3, and 4 were intravenously challenged with 2 mL of S. suis, strains 1330, 89-1591, and 166', respectively. The strain 1330 is a recognized avirulent Canadian strain. The strain 166' is a reference French virulent isolate. Pigs inoculated with strain 1330 did not present clinical signs of a S. suis infection. Contamination in organs and bacterial blood circulation were rare and lesions were almost non-existent. Infection of pigs with S. suis strain 89-1591 (group 3) and 166' (group 4) caused severe clinical problems, animals infected with S. suis 166' were the most affected. Pigs presented with clinical signs such as high body temperature, lameness, nervous symptoms, and even mortality. Lesions associated with S. suis were numerous for both strains, but more evident in animals of group 4. It can be concluded that S. suis strain 89-1591 is virulent, although its virulence seems to be lower than that of the French strain. Results of an experimental infection with strain 89-1591 may depend on different factors such as the route of inoculation and the immunological status of the animals used. Using conventional animals, with an unknown status regarding previous S. suis infections, equivocal results may be obtained, and this may explain differences reported by some authors with the same strain.     

Evaluation of Natural Chemical Compounds Against Root-lesion and Root-knot Nematodes and Side-effects on the Infectivity of Arbuscular Mycorrhizal Fungi

The survival of two species of plant parasitic nematodes: the root-lesion nematode Pratylenchus brachyurus, and the root-knot nematode Meloidogyne javanica, was evaluated in saturated atmospheres of 12 natural chemical compounds. The infectivity of two isolates of arbuscular mycorrhizal fungi: Glomus mosseae and Glomus intraradices, under identical experimental conditions, was also determined. All the compounds tested exerted a highly significant control against M. javanica and among them, benzaldehyde, salicilaldehyde, borneol, p-anisaldehyde and cinnamaldehyde caused a mortality rate above 50% over P. brachyurus. The infectivity of G. intraradices was inhibited by cinnamaldehyde, salicilaldehyde, thymol, carvacrol, p-anisaldehyde, and benzaldehyde, while only cinnamaldehyde and thymol significantly inhibited mycorrhizal colonization by G. mosseae.