Movement and conversion of aldicarb and its oxidation products in potato fields

In Spring, the insecticide and nematicide aldicarb in the granular formulation Temik 10G (supplied by Union Carbide) was broadcast on three potato fields and incorporated by rotary cultivation. Ridges were formed by repeated runs with ridging implements. The soil was sampled in layers of 0.1 m up to 0.8 m depth three to four times during the growing season. Aldicarb itself was almost completely converted on a humic sand soil and two loam soils within one month. During the growing season, its sulphoxide and sulphone, which are toxic and are formed by oxidation, were retained mainly in the top 0.3 m of all three soils. Relatively high concentrations were measured only in the top 0.2 m, indicating limited redistribution by leaching.Low to very low contents were found up to 0.8 m depth especially on one of the loam soils where the highest total rainfall was measured from May to October (328 mm). In a humic sand soil, leaching in the furrow was deepter than below the ridge. At the end of the growing season, the sulphoxide plus sulphone corresponded to a mass fraction of 5.7 to 6.7% of the dosage in the two loam soils and to 17% in the humic sand soil. These residues were mainly concentrated in the centre of the ridges.Samenvatting In het voorjaar werd op drie aardappelvelden het insecticide en nematicide aldicarb als Temik 10G breedwerpig toegediend en met een frees ingewerkt. Ruggen werden opgebouwd door herhaalde bewerkingen met aanaardwerktuigen. Gedurende het groeiseizoen werd de grond drie tot viermaal bemonsterd in laagjes van 0,1 m tot op 0,8 m diepte. Aldicarb zelf was binnen een maand bijna geheel omgezet zowel in een humeuze zandgrond als in twee zavelgronden. Gedurende het groeiseizoen bleven het sulfoxide en het sulfon, welke produkten eveneens toxisch zijn en door oxidatie van aldicarb worden gevormd, voornamelijk in de toplaag van 0,3 m bij alle drie gronden. Relatief hoge concentraties werden alleen gemeten in de bovenste 0,2 m, wat wijst op een beperkte herverdeling door uitspoeling.Lage tot zeer lage gehalten werden tot 0,8 m diepte gevonden, met name in één van de zavelgronden waar ook de grootste hoeveelheid neerslag van mei tot oktober (328 mm) werd gemeten. In een humeuze zandgrond was de uitspoeling in de voor groter dan die beneden de rug. Aan het eind van het groeiseizoen kwam de hoeveelheid resterend sulfoxide plus sulfon in de twee zavelgronden overeen met een massafractie van 5,7 tot 6,7% van de dosering en in de humeuze zandgrond met 17%. Deze residuen waren voor het grootste deel geconcentreerd in het centrum van de ruggen.     

Potential of imaging spectroscopy as tool for pasture management

The use of imaging spectroscopy to predict the herbage mass of dry matter (DM), DM content of herbage and crude fibre, ash, total sugars and mineral (N, P, K, S, Ca, Mg, Mn, Zn and Fe) concentrations was evaluated. The experimental system used measured reflectance between 404 and 1650 nm at high spatial (0·28–1·45 mm²) and spectral resolution. Data from two experiments with Lolium perenne L. mini‐swards were used where the degree of sward damage or N‐fertilizer application varied. Regression models were calibrated and validated and the potential reduction in prediction error with multiple observations was estimated. The mean prediction errors for DM mass, DM content and N, total sugars, ash and crude fibre concentrations were 235–268 kg ha^?1, 9·6–16·8 g kg^?1, 2·4–3·4 g kg DM^?1, 16·2–27·7 g kg DM^?1, 5·8–6·5 g kg DM^?1 and 8·4–10·4 g kg DM^?1 respectively. The predictions for concentrations of P, K, S and Mg allowed identification of deficiency levels, in contrast to the concentrations of Na, Zn, Mn and Ca which could not be predicted with adequate precision. Prediction errors of DM mass may be maximally reduced to 95–142 kg ha^?1 with 25 replicate measurements per field. It is concluded that imaging spectroscopy can provide an accurate means for assessment of DM mass of standing grass herbage. Predictions of macronutrient content and feeding value were satisfactory. The methodology requires further evaluation under field conditions.     

Reviewing research priorities in weed ecology,evolution and management: a horizon scan

Weedy plants pose a major threat to food security, biodiversity, ecosystem services and consequently to human health and wellbeing. However, many currently used weed management approaches are increasingly unsustainable. To address this knowledge and practice gap, in June 2014, 35 weed and invasion ecologists, weed scientists, evolutionary biologists and social scientists convened a workshop to explore current and future perspectives and approaches in weed ecology and management. A horizon scanning exercise ranked a list of 124 pre‐submitted questions to identify a priority list of 30 questions. These questions are discussed under seven themed headings that represent areas for renewed and emerging focus for the disciplines of weed research and practice. The themed areas considered the need for transdisciplinarity, increased adoption of integrated weed management and agroecological approaches, better understanding of weed evolution, climate change, weed invasiveness and finally, disciplinary challenges for weed science. Almost all the challenges identified rested on the need for continued efforts to diversify and integrate agroecological, socio‐economic and technological approaches in weed management. These challenges are not newly conceived, though their continued prominence as research priorities highlights an ongoing intransigence that must be addressed through a more system‐oriented and transdisciplinary research agenda that seeks an embedded integration of public and private research approaches. This horizon scanning exercise thus set out the building blocks needed for future weed management research and practice; however, the challenge ahead is to identify effective ways in which sufficient research and implementation efforts can be directed towards these needs.     

Micro-livestock in smallholder farming systems: the role,challenges and opportunities for cavies in South Kivu,eastern DR Congo

Tropical Animal Health and Production - Livestock play multiple roles for smallholder farmers in sub-Saharan Africa. Mixed crop-livestock systems are common in South Kivu, eastern DR Congo, but...     

Monitoring grass swards using imaging spectroscopy

The potential of an imaging spectroscopy system with high spatial (0·16–1·45 mm²) and spectral resolution (5–13 nm) was explored for monitoring light interception and biomass of grass swards. Thirty‐six Lolium perenne L. mini‐swards were studied for a total of eleven consecutive growth periods. Hyperspectral images and light interception (LI) were recorded twice weekly. On two dates ground cover was scored visually (GC_v). At harvest, leaf area index (LAI), fresh‐matter yield and dry‐matter yield (DMY) were determined. Classification of images yielded several estimates of the image ground cover (GC_i) and the index of reflection intensity (IRI). The GC_i was highly correlated with GC_v ( = 0·94), LAI ( = 0·88) and LI ( = 0·95, for dense swards under cloudy skies). However, the relationship between GC_i and LI depended on sky conditions and sward structure. Under cloudy skies, LI was linearly related to GC_i, whereas under clear skies, this relation was logistic. Regression analysis of GC_i and yields showed correlations with of between 0·75 and 0·82. The mean error of DMY estimates was 340 kg. In conclusion, estimates of GC_i and IRI can be used to predict DMY, even for high yield levels (up to 3500 kg DM ha^?1), allowing accurate, non‐destructive monitoring of biomass and light interception of grass swards.     

Variation in trace metal exports from small Canadian shield watersheds

Annual exports of Cu, Pb, and Cd were estimated for eleven headwater and two lake outflow streams in the District of Muskoka, Ontario, Canada. COCl₂-APDC coprecipitation coupled with anodic stripping voltammetry was used to determine metal concentrations. Concentrations of all three metals were similar to those reported from other temperate forested ecosystems, being usually less than 1 ug L^?1 with Cd undetectable (<25 ng L^?1) in many samples. There was limited evidence for a spring peak in metal concentrations associated with the snowpack melt. Annual export (mass per unit area per year) of each metal was calculated; variability between streams was small. Exports of Pb appear to be related to the organic content of the water. Copper export was correlated with watershed area, not with organic acids, implying that a different transport mechanism and possibly a different source are important for this metal. The exports of Pb and Cu were much lower in all streams than the estimated annual atmospheric metal depositions reported for this area in the literature. Terrestrial retention was higher than 95% for all catchments, while lake retention was slightly lower in some cases. Despite the small fractional loss of trace metal from the watersheds, terrestrial inputs can comprise a significant portion of the total metal load to typical lakes in this region because of size of the catchments relative to the lake areas.     

Prediction of barley progeny performance in the presence of genotype environment interaction

Twenty recombinant inbred line (RIL) populations of European two‐row spring barley and their parents were tested in six environments in the Netherlands to investigate the prediction of progeny yield level, yield variance, stability level and stability variance, based on parent information. Progeny yield level is positively correlated with midparent value for average yield. Progeny yield variance is more difficult to predict, but there does appear to be a promising negative correlation between progeny yield variance and Habgood's (1977) parental similarity measure. To quantify yield stability, three statistics were calculated: Finlay and Wilkinson's (1963) regression coefficient b_i, Shukla's (1972) stability variance σs_i² and Eberhart and Russell's (1966) mean squared deviation d_i². The first stability statistic describes a different aspect of the response pattern to change in environment from the last two. Parents with high b_i values appear to have a better average yield, i.e. they react more positively to an improvement in the environment than the other genotypes. The average b_i value of the progeny is positively correlated with the midparent value, indicating its heritable nature. There are also indications that d_i² and σ_i² are heritable but their repeatability is poor. Therefore, it is concluded that only prediction of bi is useful in practical plant breeding. There is a positive correlation between progeny yield variance and progeny variance for b_i but we conclude that the inaccuracy of the stability variance estimates is too high for good predictors for progeny stability variance to be found.     

Transdisciplinary weed research: new leverage on challenging weed problems?

Transdisciplinary weed research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social aspects of ecosystem sustainability. TWR seeks to integrate scholarly and practical knowledge across many stakeholder groups (e.g. scientists, private sector, farmers and extension officers) and levels (e.g. local, regional and landscape). Furthermore, TWR features democratic and iterative processes of decision‐making and collective action that aims to align the interests, viewpoints and agendas of a wide range of stakeholders. The fundamental rationale for TWR is that many challenging weed problems (e.g. herbicide resistance or extensive plant invasions in natural areas) are better addressed systemically, as a part of broad‐based efforts to advance ecosystem sustainability, rather than as isolated problems. Addressing challenging weed problems systemically can offer important new leverage on such problems, by creating new opportunities to manage their root causes and by improving complementarity between weed management and other activities. While promising, this approach is complicated by the multidimensional, multilevel, diversely defined and unpredictable nature of ecosystem sustainability. In practice, TWR can be undertaken as a cyclic process of (i) initial problem formulation, (ii) ‘broadening’ of the problem formulation and recruitment of stakeholder participants, (iii) deliberation, negotiation and design of an action agenda for systemic change, (iv) implementation action, (v) monitoring and assessment of outcomes and (vi) reformulation of the problem situation and renegotiation of further actions. Notably, ‘purposive’ disciplines (design, humanities and arts) have central, critical and recurrent roles in this process, as do integrative analyses of relevant multidimensional and multilevel factors, via multiple natural and social science disciplines. We exemplify this process in prospect and retrospect. Importantly TWR is not a replacement for current weed research; rather, the intent is to powerfully leverage current efforts.     

Assessment of seasonal dry-matter yield and quality of grass swards with imaging spectroscopy

The potential of imaging spectroscopy for the assessment of seasonal dry‐matter (DM) yield and sward quality was studied. Relationships between spatial heterogeneity of tiller density, light interception, ground cover and seasonal DM yield were developed. Sward heterogeneity was quantified by the spatial standard deviation of ground cover and of logarithmically transformed ground cover, and patterns in ground cover transects were quantified by wavelet entropy. An experiment was conducted with eight control (C) swards, eight naturally damaged (ND) swards and twelve artificially damaged (AD) swards. Swards were established in containers and spectroscopic images were recorded twice weekly. Seasonal DM yield was linearly related to a combination of means of ground cover and index of reflection intensity (r² = 0·93). Spatial variation of tiller density was larger for AD and ND swards than for C swards. Values of the spatial standard deviation of ground cover and wavelet entropy were larger for AD and ND swards than for C swards. A single spatial standard deviation of ground cover value of 13% discriminated ND and AD swards from C swards. Seasonal means of wavelet entropy (r² = 0·70) and the spatial standard deviation of ground cover (r² = 0·63) at harvest were linearly related to seasonal DM yield. It is concluded that imaging spectroscopy can be used for assessing seasonal DM yield and sward heterogeneity.