Replacement series are used by researchers to understand how competition-related variables influence dynamics from the individual to the population and community levels, but this approach has been criticized because of inherent biases associated with plant size differences and density-dependent responses. The use of functional densities instead of demographic densities was proposed to minimize those biases. This work explored three models to determine reference densities for replacement series experiments based on (1) maximum biomass, (2) biomass at onset of diminishing returns (i.e., inflection point), and (3) nitrogen (N)-uptake equivalency. Replacement series experiments were conducted using redroot pigweed (Amaranthus hybridus L.):maize (Zea mays L.) and giant foxtail (Setaria faberi Herrm.):maize proportions of 1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75, and 0:1. The monoculture density for each species was established according to the three models. Density selection criteria resulted in major differences in competitive interactions between species. The use of functional densities at which the biomass accumulation inflection point for the smaller species allowed both species to exhibit either increases or decreases in biomass production depending on competitive interactions for all interspecific mixtures. Conversely, the maximum biomass model favored the larger species, almost completely inhibiting the growth of the smaller species, which resulted in a poor characterization of competitive responses of the smaller species. The N uptake equivalency model resulted in interactions closer to the predicted neutral competition. The model based on the biomass accumulation inflection point was the most sensitive and informative across all interspecific mixtures for both species. We propose that to reduce bias associated with species size differences when determining reference densities for replacement series experiments, at least two criteria must be met: (1) the experiment sensitivity allows measuring and quantifying the competitive responses for both species in all mixtures, and (2) the balance between density and carrying capacity of the system minimizes intraspecific competition.

The pastoral systems of Eastern Africa have been affected by the alternated incidence of recurrent drought and flood for the last decades, aggravating poverty and local conflicts. We have introduced an innovation to convert floods to productive use using water spreading weirs (WSW) as an entry point to capture and spread the torrential flood emerging in the neighboring highlands into rangelands and crop fields of low-lying pastoral systems in Afar, Ethiopia. The productivity and landscape feature have changed from an abandoned field to a productive landscape within 3 years of intervention. The flood patterns and sediment loads created at least four different crop management zones and productivity levels. Based on moisture and nutrient regimes, we developed land suitability maps for integrating crops and forages fitting to specific niches. The outcome was a fast recovery of landscapes, with 150% biomass yield increment, increased access to dry season feed and food. These positive outcomes could be attributed to the proper design of weirs, joint planning and execution between pastoralists, researchers and development agents, identification and availing best-fitting varieties for each management zone and developing simple GIS-based parcel level maps to guide development agents and pastoralists. The major ‘agents’ were community leaders (‘Kedoh Abbobati’) who keenly debated potential benefits and drawbacks of innovations, enforced customary rules and byelaw and suggested changes in approaches and choices of interventions. In general, an innovation system approach helped to create local confidence, attract attention of government institutions and helped local actors to identify investment areas, develop implementation strategies to increase productivity, define changes as it occurs and minimize conflicts between competing communities. However, the risk of de facto use of a plot of communal land translating into long-term occupation and ownership may be impacting a communal territory and social cohesion that was subject to other collective choice customary rules.

Downy brome (Bromus tectorum L., syn. cheatgrass) is a winter annual grass that invades North American cropping, forage, and rangeland systems. Control is often difficult to achieve, because B. tectorum has a large seedbank, which results in continuous propagule pressure. Pyrenophora semeniperda (Brittlebank and Adam) Shoemaker, a soilborne fungal pathogen, has been investigated as a biological control for B. tectorum, because it can kill seeds that remain in the seedbank, thereby reducing propagule pressure. Temperature influences P. semeniperda and has not been investigated in the context of seeds collected from different B. tectorum locations, that may vary in susceptibility to infection. We compared the effects of temperature (13, 17, 21, 25 C) and B. tectorum seed locations (range, crop, subalpine) with different mean seed weights on infection rates of P. semeniperda using a temperature-gradient table. Infection differed by seed location (P < 0.001) and temperature (P < 0.001), with lighter-weight seeds (i.e., range and subalpine) more susceptible to P. semeniperda infection. Infection increased as temperature increased and was higher at 21 C (66.7 ± 6.7%) and 25 C (73.3 ± 6.0%). Germination was affected by seed location (P < 0.001) and temperature (P = 0.019). Germination was highest for the crop seed location (45.4 ± 4.2%) and overall decreased at higher temperatures (21 and 25 C). Our results suggest that B. tectorum seeds from a crop location are less affected by P. semeniperda than those from range and subalpine locations. Moreover, this demonstrates a temperature-dependent effect on all populations.

Water scarcity is among the main challenges making vulnerable the livestock farming systems in drylands. The water footprint (WF) indicator was proposed as a metric to measure the impacts of livestock production on freshwater resources. Therefore, this study aimed to assess water use in five different Tunisian sheep production systems using the Water Footprint Network methodology. The primary data were obtained from 1050 sheep farms located in 13 Tunisian provinces. A multivariate analysis was performed to characterize the different farming systems. A validation step of the WF modeled values of sheep meat was conducted in 12 sheep farms belonging to two different farming systems. This was done through year-round monitoring of on-farm practices using water metres and recording equipment’s taking into account the direct and indirect water use. The typology analysis came up with five sheep farming systems that are the mixed sheep-cereal (MSC), the agro-sylvo-pastoral (ASP), the agro-pastoral (AP), the extensive agro-pastoral (EAP) and the mixed sheep-olive tree farming systems. The WF of sheep meat produced under the target farming systems ranged from 8654 to 13 056 l/kg live weight. The evaluation of WF of five different sheep production systems figured out that sheep raised under the EAP farming system had the greatest WF per ton of live animal. However, the ASP farming system exhibited the lowest WF. Water used to grow feedstuffs for sheep production accounts for 98% of the total WF of sheep. The green WF accounts for more than 92% of the total WF in all farming systems. Results of monitoring water use at farm scale show that the modeled values of WF are overestimated by an average of 23.3% and 24.1% for the selected farms assigned to the MSC and AP farming systems, respectively. Water use for sheep production is high in most of the Tunisian farms. Therefore, the general assumption that ‘meat production is a driver of water scarcity’ is supported and should be considered as an important focal point in agricultural and water policies. Particular attention should be given to forage crops with low WFs and high contribution to dry matter to provide ration with low WF. The efficient use of green water along the meat value chain is essential to minimize the depletion of blue water resources and to reduce the economic dependency on virtual water through the import of feedstuffs.

In precision agriculture, the selection and use of appropriate sensors determine the type and quality of information that will feed decision-support models. A wide variety of sensors, spectral ranges, data collection and processing approaches are used, sometimes leading to confusion. Whether in transmission or reflectance mode, multispectral or hyperspectral, laboratory or field-based or even satellite-borne, in order to achieve meaningful and accurate measurements it is essential to have a clear understanding of which part of the electromagnetic spectrum the sensors relate to and how the corresponding radiation interacts with the substrate (e.g. soils, crops, livestock products). Sensors in the visible range (390-700 nm) use colour to identify certain properties of the substrate (e.g. chlorophyll and pigments in crops, organic matter contents in soil) and can be used to detect and quantify colour changes that could, in turn, be correlated with changes in those properties. Alternatively, radiation in the near (NIR, 750-2500 nm) and mid infrared (MIR, 2500-25 000 nm) interacts with the molecular bonds that constitute organic and inorganic matter and, therefore, sensors with detectors in these ranges provide different but interrelated information on the chemical composition of the substrate. Shorter wavelength radiation in the form of X-Rays (0.1-10 nm) induces fluorescence in the substrate and XRF sensors provide elemental atomic information that is highly applicable to the study of soils, sediments and fluids. At the James Hutton Institute, we have expertise in the use of all these types of sensors and are developing practical applications based on a thorough understanding of the processes involved. In this paper we provide an overview of the capabilities and applications of the different sensors used in precision agriculture, not only with a theoretical understanding, but also with an awareness of the practicalities involved.

A field experiment was conducted in Urbana, IL, from 1997 to 2000 to evaluate the effect that crop, tillage, and soil depth have on common waterhemp seed-bank persistence. A heavy field infestation of common waterhemp (approximately 410 plants m−2) was allowed to set seed in 1996 and was not allowed to go to seed after 1996. In 1997, 1998, 1999, and 2000, the percentage of the original common waterhemp seed bank that remained was 39, 28, 10, and 0.004%, respectively, averaged over tillage treatments. Initially, germination and emergence of common waterhemp was greater in no-till systems. Consequently, the number of remaining seeds was greater in the till treatments compared with no-till in the top 0 to 6 cm of the soil profile. This reduction was in part explained by the higher germination and emergence of common waterhemp in the no-tillage treatments. Tillage increased the seed-bank persistence of common waterhemp in the top 0 to 2 cm of the soil profile in 1997 and the top 0 to 6 cm in 1998. Crop had no effect on common waterhemp emergence or seed-bank persistence. In 2001, > 10% of the seed germinated that was buried 6 to 20 cm deep compared with 3% for seed 0 to 2 cm deep.

The importance of the crop is often underestimated in poultry production. In addition to storing ingested feed, it also can impact nutrient digestion by digesta softening and the initial activity of feed (endogenous and exogenous) and microbial enzymes. The crop represents the first major defence against poultry pathogens and zoonotic organisms with well established adaptive and innate immune function, and a lactobacilli dominated microbiota capable of reducing the passage of these organisms further along the digestive tract. However, the potential to improve bird productivity and health, as well as affect meat and egg safety, are influenced by the nature of the diet, and in particular feed entry and extended presence in the crop. This is required to promote lactobacilli fermentation, the production of lactic acid and other volatile fatty acids, and the lowering of crop pH. Management practices such as meal feeding and the use of lighting programs with extended dark periods encourage crop utilisation. Further, the use of feed additives such as prebiotics and probiotics may enhance crop function, which in turn contributes to well-being of the entire digestive tract. A healthy and functional crop, along with other segments of digestive tract, has increased importance in an era of reduced antibiotic use in poultry feeds.

This study investigates productive efficiency for a sample of Missouri crop-only (specialized) and integrated crop-livestock (diversified) farms using a cost frontier approach. Results suggest that significant cost inefficiency exists among sample farms. Lower cost efficiency in both types of farms was attributed to improper scale of operations and misallocation of inputs. On average, diversified farms were as technically and scale efficient as specialized farms. Lower allocative efficiency diluted gains in technical efficiency and resulted in greater cost inefficiency for diversified farms than for specialized farms. Technical efficiency was independent of farm size, whereas allocative, scale, and scope efficiencies were not.

The aim of this work was to study the effects of incorporating sugar beet pulp (SBP) into the diet on the development of the crop and performance of geese. A total of 480 1-day-old ganders were divided into three groups differing in the composition and mode of distribution of the diet offered from day 56 to 89. The following two diets were used: a standard diet (nitrogen-corrected apparent metabolizable energy, AMEn 11.44 MJ/kg; 160 g/kg CP) or a diet containing 10% of SBP (SBP diet; AMEn 11.47 MJ/kg; 160 g/kg CP). The swelling capacity (SC) hydration was higher for SBP than for the standard diet (3.62 v. 2.72 ml of H2O/g of dry matter at 60 min; P<0.05). In the Control group, birds were fed with a controlled time of access to a standard diet. Other birds were fed the SBP diet with a controlled time of access (SBPt group) or a controlled quantity offered (SBPq). From day 90 to 104, 88 birds/group were overfed with a mixture containing mainly corn. Body traits including volume of the crop were measured at day 89. Fatty liver weight and commercial grading were measured at d 104. Feed intake from day 56 to 89 was higher in the Control group than in the SBPt group (8097 v. 7545 g; P<0.05), feed intake in the SBPq group being intermediate (7801 g); however, live weights (LW) of the birds were similar in the three groups measured at day 89 (5746 g; P>0.05). At day 89, the volume of the crop tended to be higher in the SBPt compared with the Control group (52.8 v. 48.8 ml/kg of LW; P=0.101). After overfeeding, feed intake (12 922 g), weight gain (2412 g), LW (8170 g), fatty liver weight (875 g) and commercial grading of the fatty liver were similar (P>0.1) for all the three groups. Therefore, SBP could help adapt the digestive tract of waterfowl to high feed intake through an increase in the crop volume, but its method of use – that is, level of incorporation and mode of distribution – should continue to be investigated.

Many crop species are able to hybridize with related weedy or wild relatives, which could lead to transfer of cultivar genes, and among them transgenes, into wild populations. It is not clear, however, whether the hybrids and their descendants are able to survive and reproduce in natural habitats, as inherited cultivar traits may be maladaptive under such conditions. To test this, we produced hybrid (F1) seeds by controlled crosses between wild and cultivated carrots (Daucus carota ssp. carota and ssp. sativa, respectively) and sowed them into three Danish grasslands of different age, in parallel with seeds of wild carrots. Replicate plots were sown in fall and spring. Survival and flowering of the emerging plants were monitored for the following three years. Both hybrid and wild carrots survived and flowered in highest frequency at a recently disturbed site, and much less at two older sites. Hybrids emerged in higher proportions than wild carrots in the first year and survived to similar or slightly lower frequencies at the end of the experiment. Hybrids flowered as frequently or slightly less frequently than wild plants, and developed fewer and smaller umbels. Despite a somewhat lower reproductive potential compared to wild carrots, first generation hybrids between cultivated and wild carrots are likely to survive and produce offspring in natural grasslands in Denmark. This, together with other studies, suggests that cultivar genes may transfer relatively easily into wild carrot populations.

Awareness of the need for biodiversity conservation is now universally accepted, but most often recent conservation activities have focused on wild species. Crop species and the diversity between and within them has significant socioeconomic as well as heritage value. The bulk of genetic diversity in domesticated species is located in traditional varieties maintained by traditional farming systems. These traditional varieties, commonly referred to as landraces, are severely threatened by genetic extinction primarily due to their replacement by modern genetically uniform varieties. The conservation of landrace diversity has been hindered in part by the lack of an accepted definition to define the entity universally recognized as landraces. Without a definition it would be impossible to prepare an inventory and without an inventory changes in landrace constituency could not be recognized over time. Therefore, based on a literature review, workshop discussion and interviews with key informants, common characteristics of landraces were identified, such as: historical origin, high genetic diversity, local genetic adaptation, recognizable identity, lack of formal genetic improvement, and whether associated with traditional farming systems. However, although these characteristics are commonly present they are not always all present for any individual landrace; several crop-specific exceptions were noted relating to crop propagation method (sexual or asexual), breeding system (self-fertilized or cross-fertilized species), length of formal crop improvement, seed management (selection or random propagation) and use. This paper discusses the characteristics that generally constitute a landrace, reviews the exceptions to these characteristics and provides a working definition of a landrace. The working definition proposed is as follows: ‘a landrace is a dynamic population(s) of a cultivated plant that has historical origin, distinct identity and lacks formal crop improvement, as well as often being genetically diverse, locally adapted and associated with traditional farming systems’.

Capillaria contorta is a parasitic nematode of the oesophagus and crop of a number of domestic and wild birds. This study deals with three cases of capillariasis in the red-legged partridge. Infected individuals in two of these cases presented a history of weight loss, weakness, feather alterations and death, while morbidity and mortality were limited. In the third case, deaths occurred only after the birds were freed for repopulation purposes. Congestion of the crop was seen at necropsy. Histological examination revealed the presence of parasites and their eggs in the epithelium of the oesophagus and crop of every partridge. The worms displayed a characteristic distribution in all three cases: adults were found in the basal portion of the epithelium while the eggs were located in the middle. In one bird, parasites were observed in the anterior segment of the proventriculus. The fundamental epithelial lesion consisted of spongiosis of the oesophagus and crop. In the individual with proventricular parasitism, epidermoid metaplasia was also seen. The inflammatory reaction observed in the lamina propria was discrete and diffuse, except in those cases in which epithelial necrosis and bacterial colonies were detected.

In Zambia, termites have been recognized as pests of agricultural crops, plantation trees, structural timber, manufactured wooden goods as well as paper. This makes their control imperative. In line with the concept of pest management, appropriate control measures of termites must take into account their taxonomy, biology and ecology, as well the assessment of crop damage and yield losses. This paper discusses some of the problems inherent in developing such a scheme in Zambia and provides alternative solutions.