Jordi Recasens

Modeling the Emergence of Three Arable Bedstraw (Galium) Species

Abstract Multiyear field data from Spain were used to model seedling emergence for three bedstraw species (Galium) that can coexist in winter cereal fields. The relationships between cumulative emergence and both growing degree days (GDD) and hydrothermal time (HTT) in soil were analyzed as sigmoid growth functions (Weibull). Iterations of base temperature and base water potential were used to optimize the HTT scale. All species were well described with Weibull functions. Both GDD and HTT models provided good descriptions of catchweed bedstraw emergence, as its seedlings have less dependence on soil water potential than false cleavers and threehorn bedstraw, which were described best with HTT. The HTT model for catchweed bedstraw was validated successfully with independent data from the United Kingdom. The models may be useful for predicting bedstraw emergence in semiarid Mediterranean regions and elsewhere. Nomenclature: Catchweed bedstraw, Galium aparine L.; false cleavers, G. spurium L.; threehorn bedstraw, G. tricornutum Dandy.

Demography of Corn Poppy (Papaver rhoeas) in Relation to Emergence Time and Crop Competition

Abstract Twenty-day cohorts of corn poppy were grown in the presence or absence of barley, and seedling survival, biomass accumulation and allocation, plant reproduction, and seed dormancy were measured. Seedling survivorship and biomass accumulation differed strongly among cohorts and were influenced by crop competition. In the absence of crop competition, plants from the first three cohorts (emerging October to January) had 900% higher biomass and 160% more seeds per plant than later cohorts (emerging January to April). Crop competition reduced cohort fitness; for example, in 2003 to 2004, corn poppy biomass was reduced 57 to 96%, and seed production 77 to 97%. Seeds collected from plants that had emerged in spring were less dormant, and thus, germination and emergence of these seeds were higher (25% higher and 200 to 600% higher, respectively) than those for seeds collected from other cohorts. Environmental factors at the time of seed formation may be responsible for the observed differences in dormancy. Cohort-dependent emergence, growth, reproduction, and dormancy have relevant implications for corn poppy management and demography in agricultural systems in northeastern Spain. The dormant seeds produced by autumn to winter cohorts will be the main contributors to the seed bank and weed population shift in subsequent generations. For efficient corn poppy management, the control of cohorts emerging before or with the crop in a cereal field is essential. Nomenclature: Corn poppy, Papaver rhoeas L.; barley, Hordeum vulgare L., ‘Graphic’.

Building bridges: an integrated strategy for sustainable food production throughout the value chain

The food production and processing value chain is under pressure from all sides—increasing demand driven by a growing and more affluent population; dwindling resources caused by urbanization, land erosion, pollution and competing agriculture such as biofuels; and increasing constraints on production methods driven by consumers and regulators demanding higher quality, reduced chemical use, and most of all environmentally beneficial practices ‘from farm to fork’. This pressure can only be addressed by developing efficient and sustainable agricultural practices that are harmonized throughout the value chain, so that renewable resources can be exploited without damaging the environment. Bridges must, therefore, be built between the diverse areas within the food production and processing value chain, including bridges between different stages of production, between currently unlinked agronomic practices, and between the different levels and areas of research to achieve joined-up thinking within the industry, so that the wider impact of different technologies, practices and materials on productivity and sustainability is understood at the local, regional, national and global scales. In this article, we consider the challenges at different stages and levels of the value chain and how new technologies and strategies could be used to build bridges and achieve more sustainable food/feed production in the future.

Effect of ploughing and harrowing on a herbicide resistant corn poppy (Papaver rhoeas) population

ABSTRACT A field trial on winter barley, containing a large infestation of a herbicide resistant Papaver rhoeas population, was established in North-eastern Spain during the cropping seasons 1998–99, 1999–00 and 2000–01. After decades of minimum tillage, ploughing was conducted in Winter 1998, Winter 2000 or in both 1998 and 2000 in part of the field as a preventive weed control strategy. Plant density assessments and quantification of the seed bank at the end of 3 years were taken. Less P. rhoeas emerged in the ploughed plots and the effect was still visible 2 years after ploughing. In the twice ploughed plots, emergence was higher than in the once ploughed plots but lower than in the non-ploughed treatment. Harrowing conducted post-emergence as an annual control method in part of the plots caused a remarkable reduction of the weed population in all three years. The effect caused by the harrowing was more important than the ploughing treatments. However, the combination of single ploughing and harrowing induced the lowest weed plant emergence. The depth distribution of P. rhoeas seed was similar for all treatments but there was a higher total seed bank in the twice ploughed plots. Occasional ploughing was found to be an effective method for placing P. rhoeas seeds in non-optimal germination situations. When the initial weed seed bank is very high as in this field trial, the reduction achieved by ploughing is not sufficient and an additional weed control method should be conducted.

Hydrothermal Emergence Model for Ripgut Brome (Bromus diandrus)

Abstract A model that describes the emergence of ripgut brome was developed using a two-season data set from a no-tilled field in northeastern Spain. The relationship between cumulative emergence and hydrothermal time (HTT) was described by a sigmoid growth function (Chapman). HTT was calculated with a set of water potentials and temperatures, iteratively used, to determine the base water potential and base temperature. Emergence of ripgut brome was well described with a Chapman function. The newly-developed function was validated with four sets of data, two of them belonging to a third season in the same field and the other two coming from independent data from Southern Spain. The model also successfully described the emergence in different field management and tillage systems. This model may be useful for predicting ripgut brome emergence in winter cereal fields of semiarid Mediterranean regions. Nomenclature: Ripgut brome, Bromus diandrus Roth

Phenological and demographic behaviour of an exotic invasive weed in agroecosystems

An experimental work was conducted in Lleida (Spain) aiming to characterise the phenology and to quantify the demographic processes regulating the populations of Abutilon theophrasti Medicus in maize fields. Seedling emergence started a few days after crop sowing in early May and continued during two more months. The vegetative phase was very long due to the late seeding emergence; these later emerged plants showed a slower development, and many of them did not reach the fertility stage. A flowering peak was observed 12 weeks after emergence in late July, and fruit dehiscence and seed setting started in mid August, several weeks before crop harvest. Four different cohorts were identified, and two main peaks of emergence were determined 21 and 49 days after crop sowing nearest related with field irrigation. A functional logarithmic relationship between cumulative growing degree-days (GDD) and cumulative emergence was also described. The resulting demographic diagram reflects greater values relating to seedling survival for May cohorts (90.2 vs 7.9%), to fertility (100 vs 75%) and to fecundity (3774 vs 92 seeds pl−1 ) than those determined for the June cohorts. The late emerged plants are subjected to a high density and are strongly affected by light competition, and their reproductive phase initiation delay is of about 10–20 days. In an assay conducted in Petri dishes, the seeds provided from plants emerged earlier were found more vigorous and germinated more than those from late emerged plants, which seem to be affected by incomplete fruit and seed ripening. Following the crop cycle without any weed control, the population rate increase was about 21.2. These values explain the high invasion capacity of this weed in the local summer irrigated fields, which consists in assuring their presence through a persistent soil seed bank and increasing the probability to spread to other fields.

Spatial distribution and temporal stability of prostrate knotweed (Polygonum aviculare) and corn poppy (Papaver rhoeas) seed bank in a cereal field

Abstract The knowledge of weed distribution in a field is a key factor to manage weeds effectively. The feasibility of using weed distribution maps for site-specific weed control will largely depend on the stability of the spatial distribution of the populations. Seed banks are the most reliable way of telling the areas weediness, but the effect of regular herbicide applications on its stability is largely unknown. A field experiment was conducted during 3 yr in a winter wheat field under herbicide treatments with the aim of studying the seed banks spatial distribution of prostrate knotweed and corn poppy and the spatiotemporal stability of their populations. Soil samples were taken each year on the same locations, and seed abundance was measured by germination in greenhouse. Both species accounted for more than 10% of the broad-leaved weed seed bank and they were selected for further analysis. Prostrate knotweed seed-bank density decreased 76% and corn poppy 88% in 3 yr. Spatial distribution was described by spherical isotropic semivariograms. Distance of spatial dependence (range) of prostrate knotweed and corn poppy decreased 33 and 11% respectively, and the spatial variability (sill) decreased 96 and 99%. Yearly spatial seed distribution was compared for each species and no temporal stability was observed over a 3-yr period. The lack of stability was attributed to the important decrease of seed density over time and the increase in the short-range variability (nugget). However, for prostrate knotweed, the location of minima and maxima were roughly the same between years, allowing farmers to extend the period of use of the weed distribution maps. Although spatial distribution of seed banks can be affected by processes that promote fast changes in the densities of weed populations, this fact does not mean that weed distribution maps could not be used in consecutive seasons. Nomenclature: Corn poppy, Papaver rhoeas L.; prostrate knotweed, Polygonum aviculare L; winter wheat, Triticum aestivum L.

A germination study of herbicide-resistant field poppies in Spain

Field poppy, Papaver rhoeas L., is a very common weed in winter cereals in North-Eastern Spain. Its control is becoming difficult due to expanding herbicide resistance. To control field poppies there are alternative strategies such as non-chemical control that take into account the weed emergence period. However, there is a lack of knowledge of P. rhoeas emergence patterns in semi-arid conditions. Thus, here we conducted pot experiments on the emergence of P. rhoeas. We aimed to describe the emergence period and to quantify the emergence of a susceptible and of a herbicide-resistant P. rhoeas population at two locations in Catalonia, Spain, from 1998 to 2001 and until 2004 at one of them. Therefore, pots containing seeds of both populations were established at the two locations and emergence was recorded monthly. We studied the origin of the population, the sowing location, the effect of cultivation and the sowing year. First, we found that the main emergence peaks in our experiments occurred in autumn, accounting for between 65.7 and 98.5% of the annual emergence from October to December, and only little emergence was recorded in spring. This emergence pattern is different from those found in the literature corresponding to Northern European countries, where in some cases main flushes occur only in autumn, in spring and winter or only in spring. The emergence was mainly affected by cultivation, but the effect of light stimulus was observed several months later. As a consequence, cultivation should be done in early autumn, promoting emergence during the whole autumn and winter so that emerged seedlings can be controlled before sowing a spring crop. Second, most experiments showed that the emergence was significantly higher in the first autumn than in the following seasons, e.g. 4.1% emergence in the first year and only 2.1, 2.3, 0.5 and 0.6% new emergence at one of the locations for the second, third, fourth and fifth years. Thus, after having a severe P. rhoeas infestation causing a big seed rain, emergence should be stimulated by autumn cultivation in the following season and seedlings controlled by trying to deplete the soil seed bank as much as possible. Despite the fact that emergence will be staggered throughout several years and that there was a significant relationship between rainfall and emergence, so that dry years will cause a smaller emergence rate of the weed, these findings define a cultural management strategy to reduce P. rhoeas infestations and to contribute to integrated weed management strategies combining it with other tools.

Management Options for Multiple Herbicide–Resistant Corn Poppy (Papaver rhoeas) in Spain

Corn poppy is the most widespread broadleaf weed infesting winter cereals in Europe. Biotypes that are resistant (R) to both 2,4-D and tribenuron-methyl have evolved in recent decades, thus complicating their chemical control. In this study, field experiments at two locations over three seasons were conducted to evaluate the effects of different weed management strategies on corn poppy resistant to 2,4-D and tribenuron-methyl, including crop rotations, delayed sowing and different herbicide programs. After 3 yr, all integrated weed management (IWM) strategies reduced the initial density of corn poppy, although the most successful strategies were those which either included a suitable crop rotation (sunflower or field peas), or had a variation in the herbicide application timing (early POST or combining PRE or early POST and POST). The efficacy of IWM strategies differed between both locations, possibly due to different population dynamics and the genetic basis of herbicide resistance. Integrated management of multiple herbicide–resistant corn poppy is necessary in order to reduce selection pressure by herbicides, mitigate the evolution of new R biotypes, and reduce the weed density in highly infested fields. Nomenclature: 2,4-D; tribenuron-methyl; corn poppy, Papaver rhoeas L. PAPRH; sunflower, Helianthus annuus L.; field pea, Pisum sativum L.

Fallow management for steppe bird conservation: the impact of cultural practices on vegetation structure and food resources

The potential of fallow lands to favor farmland bird conservation is widely recognized. Since fallows provide key resources for birds within the agricultural matrix, such as nesting sites, shelter and forage, complete understanding of the effect of field-management strategies on vegetation structure and food is essential to fulfill bird requirements and improve habitat management. In this study we experimentally compare the most common field practices (ploughing, shredding, herbicide application and cover cropping) on fallow lands by assessing the resources they provide for birds in terms of vegetation structure and food resources (leaf and seed availability), as well as the economic costs of their implementation. Fallow management treatments are ranked for six target species in a lowland area of the north-eastern Iberian Peninsula, according to the available information on their requirements. The different agronomic practices offer various quantities and types of resources, highlighting the importance of fallow management in bird conservation. Shredding and early herbicide application (February) are estimated to be good practices for Little Bustard (Tetrax tetrax) and Calandra Lark (Melanocorypha calandra), providing both favorable habitat and foraging conditions, while being economical. Meanwhile, superficial tillage in spring is found to be optimum for the rest of the species tested, despite being among the poorest food providers. Alternating patches of the best treatments would improve the effectiveness of agri-environmental schemes by maximizing the harboring habitat for the endangered species.