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Food fraud surfaces regularly, anywhere in the world. Not only the companies involved in food fraud suffer from losses when food fraud occurs, other actors in the supply chain and branch of industry are often painted with the same brush. Milk has been a common fraud target in the past and, therefore, fraud is a concern for companies involved in milk production. In order to manage and prevent fraud in the milk supply chain, a good insight into the vulnerabilities of companies and their supply chain networks is pivotal. The aim of the current study is to understand (a) the fraud vulnerability of the general milk supply chain in the Netherlands and its tiers (farmers, processors, retailers) and (b) the differences in fraud vulnerability of farmers producing organic milk, green intermediate ‘pasture milk’ and conventional milk. The SSAFE food fraud assessment tool was slightly adapted to the milk supply chain and used to examine the fraud vulnerability of the 38 businesses of the three tiers in the study: 30 farmers, 4 milk processors and 4 retailers. Forty-eight fraud factors related to opportunities, motivations and control measures were examined. Subsequently, key fraud factors were identified. The three tier groups showed major similarities in motivation related fraud factors, and large differences in fraud opportunities and controls. There were also differences observed between the organic and non-organic farmers, with organic farmers being slightly more vulnerable than their non-organic counterparts. From this study it appears that the milk supply chain in the Netherlands is low to medium vulnerable to fraud but the key factors contributing to the vulnerability differ between the tiers (farmers, processors, retailers). Management of the fraud risks requires consideration of these differences.

In Chile, cow carcasses present the highest bruise prevalence compared with other cattle categories; however, the causes of the bruises are frequently unknown. In this study, 52 cull cows were transported to the slaughterhouse in three batches under identical transport conditions. A combination of direct observation and video analyses was used to determine moment, pre-slaughter stage and cause of potential bruising events during the period from loading on the farm until stunning at the slaughterhouse. After slaughter, number of bruises, location on the carcass and characteristics of the bruises were assessed. Seventy-eight bruises were observed on 37 carcasses. Fifty-two bruises were linked back to their causal event. Results showed that 46% of these bruises were a result of interactions between animal and facility, and most of them were inflicted in the stunning box, 27% of the bruises originated from animal–animal interactions and were mostly inflicted during lairage, another 27% was a result of human–animal interactions and were mostly inflicted during loading and unloading of animals. The percentages of potential bruising events resulting in a bruise were 43%, 9% and less than 1% for animal–facility, human–animal and animal–animal interactions, respectively. Most bruises on the back site were inflicted when the animal was in the stunning box (91.2%), whereas bruises on the pin site were mostly (75%) inflicted during loading at the farm. One may conclude that in relative short journeys (=4 h) directly from farm to the slaughterhouse and long lairage times (>12 h), most bruises are the result of circumstances at the slaughterhouse. A substantial amount of these bruises could be avoided by proper animal handling and adequate stunning facilities.

Since both the spatial and vertical heterogeneities in soil properties have an impact on crop growth and yield, accurate characterization of soil properties at high sampling resolution is a preliminary step in successful management of soil-water-plant system. Conventional soil sampling and analyses have shown mixed economical returns due to the high costs associated with labor-intensive sampling and analysis procedures, which might be accompanied with map uncertainties. Therefore, the conventional laboratory methods are being replaced or complemented with the analytical soil sensing techniques. The objective of this chapter is to review different soil sensing methods used to characterize key soil properties for management of soil-water-plant system. This will cover laboratory, in situ in the field, and on-line measurement methods. This review chapter is furnished with an overview of background information about a sensing concept, basic principle and brief theory, various factors affecting the output of the sensor, and justification of why specific soil properties can be related with its output. The literature review is succeeded with an integration and analysis of findings in view of application in the precision agriculture domain. Potentials and limitations of current sensor technology are discussed and compared with commonly used state-of-the-art laboratory techniques. As sensing is commonly addressed as a very technical discipline, the match between the information currently collected with sensors and those required for site-specific application of different inputs, and crop growth and development is discussed, highlighting the most accurate method to measure a soil property for a given application.

The objective of this study was to test the reliability of the post-mortem evaluation of bruise characteristics using a newly extended protocol. Intra-observer reliability of the observations was assessed with three meat graders, each of whom blindly examined 50 photos of bovine carcasses in two sessions, with 1 week in between. The agreement was “substantial” for number of bruises per carcass, and size and shape of the bruises; whereas it was “moderate” for colour and severity grade. Inter-observer reliability of the observations was assessed with four meat graders who each examined the same 46 carcasses at the slaughter-line. Inter-observer agreement for number of bruises per carcass ranged between observer pairs from “fair” to “moderate.” The agreement for number of bruises scored per anatomical site was “very low” for all observers. The most concordant bruise feature was size, followed by colour and shape. The bruise scoring protocol was associated with high level of intra-observer reliability and low inter-observer reliability. A further calibration of the observer judgments is needed to reach a more uniform scoring of the observers.

Emissions of air pollutants from livestock houses may raise environmental problems and pose hazards to public health. They can be reduced by scrubbers installed at the air outlets of livestock houses. In this study, three multi-stage scrubbers were evaluated in terms of their effectiveness in reducing emissions of airborne dust, total bacteria, ammonia, and CO2 from pig houses in winter. The three multi-stage scrubbers were one double-stage scrubber (acid stage+ bio-filter), one double-stage scrubber (acid stage + bio-scrubber), and one triple-stage scrubber (water stage + acid stage + bio-filter). Results showed that these scrubbers reduced concentrations of PM10 by 61% to 93%, concentrations of PM2.5 by 47% to 90%, concentrations of airborne total bacteria by 46% to 85%, and concentrations of ammonia by 70% to 100%. Concentrations of CO2 were not affected. Most of the airborne bacteria emitted from the pig houses were larger than 3.3 µm (73% to 95%). The multi-stage scrubbers removed 53% to 92% of them, compared with -42% to 20% removal effectiveness of the bacteria in the size range of 0.65 to 3.3 µm. The triple-stage scrubber was the most efficient in removing dust and ammonia. Compared to single-stage scrubbers, all three multi-stage scrubbers performed more consistently in reduction of PM10, PM2.5, total bacteria, and ammonia emissions from livestock houses and removed these pollutants more efficiently. It should be noted that all measurements were performed in winter at low ventilation rates, thus at low loadings of the multi-stage scrubbers

In an airborne transmission experiment, Campylobacter in the air was sampled by three types of bioaerosol samplers (all-glass impinger AGI-30, Andersen six-stage impactor, and OMNI-3000) in four broiler rooms. In each room, five 14-day- old broilers inoculated with Campylobacter jejuni were kept in a central cage located in the middle of the room. Another ten broilers, as susceptible animals, were kept individually in ten cages surrounding the central cage at a distance of approximately 75 cm. Air samples were taken on eight days: the day before inoculation (BI) as a negative control, and 1, 3, 6, 9, 14, 21, and 29 days post-inoculation (PI). Presence of C. jejuni was investigated with the culture method for culturable bacteria and with the PCR test for bacterial DNA. Results showed that Campylobacter infection of susceptible broilers occurred in all four rooms; however, no culturable C. jejuni could be detected in any of the air samples. This might have been the result of the low number of broilers in the room and the unfavorable conditions for Campylobacter survival, leading to Campylobacter concentrations below the detection limits of the bioaerosol samplers. The PCR test showed that DNA of C. jejuni was detected in the air samples on the first day PI, but no bacterial DNA was detected on the following days. It is concluded that the three samplers used in this study are not able to alarm Campylobacter outbreaks through an airborne route when low bacterial concentrations are present. Developments of new sampling techniques with low detection limits are required for biosecurity assessment.

BACKGROUND: An apparently large disparity still exists between developed and developing countries in historical trends of the amounts of nitrogen (N) fertilizers consumed, and the same situation holds true in China. The situation of either N overuse or underuse has become one of the major limiting factors in agricultural production and economic development in China. The issue of food security in N-poor regions has been given the greatest attention internationally. Balanced and appropriate use of N fertilizer for enriching soil fertility is an effective step in preventing soil degradation, ensuring food security, and further contributing to poverty alleviation and rural economic development in the N-poor regions. RESULTS: Based on the China Statistical Yearbook (2007), there could be scope for improvement of N use efficiency (NUE) in N-rich regions by reducing N fertilizer input to an optimal level (=180 kg N ha-1), and also potential for increasing yield in the N-poor regions by further increasing N fertilizer supply (up to 116 kg N ha-1). For the N-rich regions, the average estimated potential of N saving and NUE increase could be about 15% and 23%, respectively, while for the N-poor regions the average estimated potential for yield increase could be 21% on a regional scale, when N input is increased by 13%. CONCLUSION: The study suggests that to achieve the goals of regional yield improvement, it is necessary to readjust and optimize regional distribution of N fertilizer use between the N-poor and N-rich regions in China, in combination with other nutrient management practices.

A novel centre of gravity measurement system for small tractors with the principle of the three-point reaction is presented. According to the prototype of a small tractor gravity centre test platform, a mathematic multi-body dynamics prototype was built to analyze the measurement error in the centre of gravity measurement system. For the precision evaluation, interrelationships among the factors were studied which included the test platform structural parameters, the error of measurement sensors and the displacement of drive-pillar and the mass of measurement object. In succession, a virtual collaborative model of the centre of gravity measurement system was built and verified by a real prototype-based measurement platform. A modified gray model GM(1,1), which was used for forecasting the gravity height of small tractors, was proposed to avoid deviation of test data and so improved the measurement accuracy. A series of standard test object experiments were carried out, and the results showed that the relative error of the gravity height was up to 0.93%

The guidance of a vehicle in an outdoor setting is typically implemented using a Real Time Kinematic Global Positioning System (RTK-GPS) potentially enhanced by auxiliary sensors such as electronic compasses, rotation encoders, gyroscopes, and vision systems. Since GPS does not function in an indoor setting where educational competitions are often held, an alternative guidance system was developed. This article describes a guidance method that contains a laser-based localization system, which uses a robot-borne single laser transmitter spinning in a horizontal plane at an angular velocity up to 81 radians per second. Sensor arrays positioned in the corners of a flat rectangular table with dimensions of 1.22 m × 1.83 m detected the laser beam passages. The relative time differences among the detections of the laser passages gave an indication of the angles of the sensors with respect to the laser beam transmitter on the robot. These angles were translated into Cartesian coordinates. The guidance of the robot was implemented using a uni-directional wireless serial connection and position feedback from the localization system. Three experiments were conducted to test the system: 1) the accuracy of the static localization system was determined while the robot stood still. In this test the average error among valid measurements was smaller than 0.3 %. However, a maximum of 3.7 % of the measurements were invalid due to several causes. 2) The accuracy of the guidance system was assessed while the robot followed a straight line. The average deviation from this straight line was 3.6 mm while the robot followed a path with a length of approximately 0.9 m. 3) The overall performance of the guidance system was studied while the robot followed a complex path consisting of 33 sub-paths. The conclusion was that the system worked reasonably accurate, unless the robot came in close proximity (

This paper describes a model to calculate the concentrations of (Z)-3-hexenol, a-pinene, a-terpinene, ß-caryophyllene, and methyl salicylate in a greenhouse on the basis of their source and sink behaviour. The model was used to determine whether these volatile organic compounds (VOCs) can be used to indicate Botrytis cinerea infection in a large-scale tomato production greenhouse with a volume of 5 × 104 m3 containing 2.2 × 104 plants. Seven experiments were done to parameterise the model for these VOCs. Based on model predictions, the B. cinerea-induced increase in concentration of methyl salicylate is detectable in a large-scale tomato production greenhouse when: (a) windows are fully opened, and (b) the increase continues for at least 1 h, and (c) 5% of the plants are infected. The B. cinerea-induced increase in concentration of methyl salicylate is also detectable when: (a) windows are closed, and (b) the increase continues for at least 6 h, and (c) 5% of the plants are infected. The B. cinerea-induced increase in concentration of (Z)-3-hexenol is detectable under all conditions studied. However, it is expected that besides infected plants, many additional sources of (Z)-3-hexenol exist including plant debris and nearby field crops especially upon harvest or stress. The B. cinerea-induced increases in concentration of a-pinene, a-terpinene and ß-caryophyllene are probably undetectable in a large-scale tomato production greenhouse. Therefore, it is recommended to focus on the detection of methyl salicylate to indicate B. cinerea infections in large-scale tomato production greenhouses.

The objectives of this study were to determine the reflectance properties of volunteer potato and sugar beet and to assess the potential of separating sugar beet and volunteer potato at different fields and in different years, using spectral reflectance characteristics. With the ImspectorMobile, vegetation reflection spectra were successfully repeatedly gathered in two fields, on seven days in 2 years that resulted in 11 datasets. Both in the visible and in the near-infrared reflection region, combinations of wavelengths were responsible for discrimination between sugar beet and volunteer potato plants. Two feature selection methods, discriminant analysis (DA) and neural network (NN), succeeded in selecting sets of discriminative wavebands, both for the range of 450–900 and 900–1650 nm. First, 10 optimal wavebands were selected for each of the 11 available datasets individually. Second, by calculating the discriminative power of each selected waveband, 10 fixed wavebands were selected for all 11 datasets analyses. Third, 3 fixed wavebands were determined for all 11 datasets. These three wavebands were chosen because these had been selected by both DA and NN and were for sensor 1: 450, 765, and 855 nm and for sensor 2: 900, 1440, and 1530 nm. With the resulting three sets of wavebands, classifications were performed with a DA, a neural network with 1 hidden neuron (NN1) and a neural network with two hidden neurons (NN2). The maximum classification performance was obtained with the near-infrared sensor coupled to the NN2 method with an optimal adapted set of 10 wavebands, where the percentages were 100 ± 0.1 and 1 ± 1.3% for true negative (TN) classified volunteer potato plants and false negative (FN) classified sugar beet plants respectively. In general the NN2 method gave the best classification results, followed by DA and finally the NN1 method. When the optimal adapted waveband sets were generalized to a set of 10 fixed wavebands, the classification results were still at a reasonable level of a performance at 87% TN and 1% FN for the NN2 classification method. However, when a further reduction and generalization was made to 3 fixed wavebands, the classification results were poor with a minimum performance of 69% TN and 3% FN for the NN2 classification method. So, these results indicate that for the best classification results it is required that the sensor and classification system adapt to the specific field situation, to optimally discriminate between volunteer potato and sugar beet pixel spectra

Pathogen attack and herbivore infestation have a major impact on plant health. In a model study, these two plant health issues were simulated to study whether plant health can be monitored at greenhouse scale through the analysis of volatile organic compounds (VOCs) in greenhouse atmosphere. To simulate pathogen attack and herbivore infestation, we repeatedly stroked the stems of tomato plants (Lycopersicon esculentum) and repeatedly removed their side shoots. In addition, we studied the effect of fruit picking on the concentration of plant-emitted VOCs in greenhouse atmosphere. Analysis of air samples obtained before these treatments revealed up to 17 VOCs that are known to be released from tomato plants, of which the most dominant one was the monoterpene ß-phellandrene. When plants were 7 weeks old, the concentration of this VOC was approximately 0.06 ppbv before treatment. When plants were 12 weeks old, this concentration was raised to approximately 0.14 ppbv. Stroking of the stems, removing the side shoots and fruit picking resulted in an increase in the concentrations of all mono- and most sesquiterpenes up to 60-fold, which was expected because these VOCs are well-known constituents of trichomes. The treatments did not result in substantially increased concentrations of the stress-related compounds ¿-copaene, methyl salicylate and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. In contrast to stroking and fruit picking, shoot removal resulted in the emission of the lipoxygenase-derived product (Z)-3-hexenol in greenhouse atmosphere expressing cell membrane degradation. The findings presented in this paper focus on the feasibility of monitoring plant health through the analysis of VOCs in greenhouse air, but findings might also be relevant for atmospheric chemistry.

Aims of this study are to analyze growth pattern and development Of Cut chrysanthemum and test simple regression models in relation to light level and plant density. Cut chrysanthemum (Chrysanthemum morifolium), cv. Reagan Improved, was grown at four different plant densities of 16, 32, 64 or 80 plants m(-2) combined with three different light levels of 100%, 66% or 43% of light in three greenhouse compartments in summer at Wageningen University in the Netherlands. Plant fresh and dry mass, stem strength, number of flowers and stem length had shown interactive effects between light level and plant density. All these parameters increased with increased light level and with increased plant density; however, the decrease as a result of light reduction was much larger at low plant densities except for stem length. Stem length increased with increased plant density, following a saturation-type of response, except for the lowest light level, where an optimum-response was observed, resulting in a reduced stem length at the highest density. Dry mass production per m(2) greenhouse area and final leaf area index increased with increased light level and with increased plant density. Light use efficiency (LUE, unit dry mass per unit of cumulative intercepted PAR) was 48% higher at lower light levels than 100%. LUE also showed a quadratic response to plant density in range of 16 and 80 plant m(-2). Using an existing empirical linear model for plant, fresh mass and number of flowers for cut chrysanthemum showed overestimation in plant fresh mass and under estimation for number of flowers at the lowest plant density in all light level in this study. Plant shape, calculated as a ratio between stern length and a length between a node with first lateral stem to top point of plant, linearly decreased with increased LAI. Plant qualities hence strongly varied depending on crop canopy like leaf area index. Although the simple regression models are good tools for summary of experiment, it does not fit at lower plant density. To produce a constant product quality throughout the year, optimal number of plant m(-2) with amount of available light should be considered through the growing period.

Animals have various behavioural and physiological needs that are important for welfare. Fulfilment of these needs depends on the quality of housing, management and animal characteristics. The objective of this study was to develop a model to assign welfare scores to husbandry systems for dairy cattle, based on scientific results, and thereby supporting the design of new, welfare-friendly systems. COWEL is a computer-based decision support system that contains attributes regarding housing and management conditions. These attributes are technical specifications that contain various technical units called levels. These levels are ranked from best-to-worst regarding welfare, based on scientific information about animal-based parameters. This information, inserted in the model as statements, was weighted depending on the impact it has on welfare by using weighting categories. Thereafter, a weighting factor was calculated for each attribute which determines how important an attribute is for welfare. The COWEL model contains 2,343 statements on dairy cattle welfare from 476 sources found during a literature survey. The model was applied to four husbandry systems, namely a tie-stall, cubicle housing, a straw yard and a pasture-based system. The welfare scores, calculated by COWEL for these husbandry systems, correspond with the general opinion about these systems. A tie-stall receives a low and a pasture-based system a high welfare score: 211 and 271, respectively. A husbandry system can receive a maximum of 313 on the welfare scale of COWEL. We conclude that COWEL can be used to rank husbandry systems on a welfare scale, and may be a useful tool to develop new, sustainable and welfare-friendly systems for dairy cattle

A hermetically sealed ferrocement bin was conceived by application of a systematic design process. It consisted of a frustum of a cone with a conical bottom supported by three vertical columns with V-shaped cross-section. A labour and material saving model was developed to contain 2.5 tons of paddy. After detailed designing of the bin, it was constructed and the actual cost incurred was investigated before introducing to the farmer who requires this type o fbin for on-farm storage of paddy.

The objective of this paper is to demonstrate the need of a multiple design parameter approach to greenhouse design. To illustrate this need, we determined the combined effects of cover design parameters on tomato production of a passive greenhouse, that is a greenhouse with only natural ventilation and seasonal whitewash for climate management. The design parameters investigated in this research were the transmission of the cover for photosynthetically active radiation (PAR) and near infrared (NIR) radiation, the emission coefficient for long wave radiation of the cover and the ventilation area. First, we developed a model to link the tomato yield to the cover design parameters, through their effects on greenhouse climate. The model was validated by comparing the simulated greenhouse climate and yield with data obtained from field studies conducted in Almería, Spain. Thereafter, the sensitivity of the yield to the cover design parameters was analysed for three greenhouse configurations. This analysis gave insight into the effects of the cover design parameters on crop yield. Results showed that the sensitivity of the yield to a single design parameter depended on the absolute values of the other ones. For example, the yield in a greenhouse with a high ventilation capacity was the most sensitive to PAR transmission (0.45 % more yield for each 1% increase of PAR transmission) while in a greenhouse with a low ventilation capacity the crop yield is most sensitive to the ventilation area (0.63 %) and NIR transmission (-0.56 %). In addition, the yield sensitivity to the design parameters also varied over time because of changing outdoor climate conditions. In conclusion, a significant improvement of greenhouse design can be attained only through a multifactorial approach that accounts for the joint effect of design parameters, local climate and desired production period upon crop yield.

Earlier research has revealed that considerable energy savings can be achieved by maintaining an average temperature in the greenhouse in stead of maintaining rigid pre-defined temperature `blue-prints¿. A model based optimal control approach has proven to be a suitable framework to tackle these kind of control problems and it has been shown that these algorithms can be implemented on-line. But, when on-line optimal temperature control is considered, interesting questions arise, some of which are still unresolved. The issue tackled in this paper concerns the relation between the resolution of the control strategy (sample time) and energy savings of the control strategy. One would expect that an accurate and frequent anticipation to changing outdoor climate conditions might result in reduced energy consumption. It was indicated in the literature that a sample-time of 0.25 h or 1 hour should be sufficient, but these choices were hardly motivated. In this research, the relation between the control resolution and energy savings was quantitatively investigated using a dynamic greenhouse climate model and measurements of Dutch outdoor climate conditions containing high-frequency components. The results indicate that for an open-loop optimal control problem concerning the realization of an average temperature during a fixed period of one day using a minimum amount of energy with full a-priori knowledge of the outdoor weather, a resolution of the heating profile between half an hour and a hour suffices to produce accurate results in terms of energy conservation. These results were not much affected by parameter variations (heat capacity of the air, the solar heating efficiency) or opening and closing of thermal screens.

The objective of this paper is to demonstrate that optimal greenhouse design must account for (and be combined to) optimal climate management. We prove this by showing that different strategies and set-points to control the greenhouse ventilators result in different ¿optimal sets¿ of design parameters. We determined these optimal sets for a passive greenhouse in Almería, Spain where tomatoes were grown. The greenhouse design parameters investigated in this research were: 1) the transmission of the cover for photosynthetically active radiation (PAR), 2) the transmission of near infrared (NIR) radiation and 3) the emission coefficient for longwave radiation of the cover. Six optimal sets of design parameters were determined by maximising the marginal revenues (crop yield minus costs of design parameters), under given climate conditions, and for different ventilation control strategies. Each ventilation control strategy had different set-points for the air temperature and carbon dioxide concen¬tration to control the greenhouse ventilators. To solve this optimization problem we used a dynamic crop-greenhouse model and an optimization algorithm. The model described the combined influence of the relevant design parameters, outdoor climate and ventilation control upon economic crop yield, through their effect on indoor climate. The yearly costs of the design parameters were empirically derived from prices, physical properties and lifespan of a number of greenhouse cover materials. Results showed that indeed for different strategies and set-points to control the green¬house ventilators different ¿optimal sets¿ of design parameters and marginal revenues were obtained. For example, the difference between the highest optimal NIR trans¬mission 1.00 and the lowest optimal NIR transmission 0.40 was 60%, while the highest marginal revenues 16.94 ¿m-2 differed 18,7% with the lowest marginal revenues of 13.77 ¿ m-2. Additionally, it was found that the cover design parameters were time dependent. In conclusion, only a combined optimal control and design approach that takes into account the best climate control strategy and the time dependency of the design parameters will ensure optimal design parameters and maximum marginal revenues.

The poultry sector in the Netherlands is confronted with the EU ban on conventional cages, the public debate on the welfare of hens in furnished cages, the limited perspectives of currently used more welfare-friendly single- or multi-tiered systems (either indoor or outdoor), and with questions about the natural behaviour of animals and the robustness of current production systems. To arrive at new and sustainable husbandry systems for laying hens a new design approach was developed and applied. The work-scheme of the approach consisted of four phases: (1) collecting information and network building, (2) a thorough analysis of problems followed by making strategic choices, (3) developing a structured design, and (4) reporting and communication. The approach incorporated interdisciplinary and multi-stakeholder interactive methods, integrating scientific and tacit knowledge. The main results of the study were (1) a Brief of Requirements for the laying hen, the farmer and the citizen/consumer as key players in a sustainable development, and (2) two new attractive and feasible husbandry concepts for future egg production. The approach succeeded in identifying the underlying needs and requirements of actors, bridging the gap between seemingly conflicting requirements and stimulating new initiatives towards sustainable development.

The paper presents results of research on inverse kinematics algorithms to be used in a functional model of a cucumber harvesting robot consisting of a redundant manipulator with one prismatic and six rotational joints (P6R). Within a first generic approach, the inverse kinematics problem was reformulated as a non-linear programming problem and solved with a generic algorithm. Solutions were easily obtained, but the considerable calculation time needed to solve the problem prevented on line implementation. To circumvent this problem, a second, less generic approach was developed consisting of a mixed numerical-analytic solution of the inverse kinematics problem exploiting the particular structure of the P6R manipulator. This approach facilitated rapid and robust calculation of the inverse kinematics of the cucumber harvester. During the early stages of the cucumber harvesting project, this inverse kinematics algorithm was used to off-line evaluate the ability of the robot to harvest cucumbers using 3D-information of a cucumber crop obtained in a real greenhouse. Thereafter, the algorithm was employed successfully in a functional model of the cucumber harvester to determine if cucumbers were hanging within the reachable workspace of the robot and to determine a collision-free harvest posture to be used for motion control of the manipulator during harvesting.

Traditional tillage systems practiced by farmers in semi-arid regions of Ethiopia are characterized by repeated and cross plowing with an indigenous plow called Maresha . Repeated and cross plowing have led to land degradation. Conservation tillage systems that advocate minimum soil disturbance can alleviate land degradation problems. However, before introducing reduced tillage systems, it was found necessary to study why farmers undertake repeated plowing. The study was undertaken in two semi-arid areas called Melkawoba and Wulinchity located in the central rift valley of Ethiopia and on two major crops; Tef ( Eragrostis Tef (Zucc.)) and maize ( Zea mays XX ). Fifty farmers from each area were randomly selected and interviewed using a structured questionnaire. The results showed that farmers in the study area plow repeatedly in order to completely disturb unplowed strips of land left between adjacent furrows. Unplowed strips are the results of the V-shaped furrows created by the Maresha plow. Farmers generally do not plow before the soil is wetted by rainfall. Wetting and drying cycles due to dry spells occurring between rainfall events force farmers to plow frequently to avoid moisture losses through surface runoff, evaporation and weed transpiration. Tef fields are plowed 4–5 times while maize fields are plowed 3–4 times. Tillage frequency increased with the education level and experience of farmers; with their perception about the purpose of tillage such as moisture conservation, weed control and soil warming; and with resource availability such as area of land and family labor. Tillage frequency was higher for Tef than for maize and in heavy soils than in light soils.

Crop production in the dryland farming areas of northern China is constrained by low and variable rainfall. This article presents the analysis of the relationships between variations in rainfall and yields of winter wheat and spring maize. The analysis is based on data from both several short-term and our ongoing long-term field experiments in dryland farming research projects in Tunliu, Linfen, Shouyang, and Luoyang. Grain yields of wheat and maize ranged from 1,548 to 5,169 and from 2,612 to 8,789 kg ha-1 respectively, with differences up to above 200% (between dry and wet years). Wheat yields are sensitive to growing season rainfall but also correlated to water use (ET), whereas maize yields are sensitive to the critical time of water supply (especially June rainfall) but not correlated to ET. The ratio of grain yields to soil water at sowing is an important indicator, showing close relationships between yields and soil water-related ratio within the rainfed crops site. Comparison between the indices of water use efficiency (WUE) and precipitation use efficiency (PUE) suggests that the index WUE is more grain-related indicator than the PUE used for assessing rainfed crop water use by both maize and wheat. The index PUE should be used in caution, especially for wheat crops in dry years. Our results indicate that options to alleviate crop moisture stress must be tailored to the rainfall pattern. This holds especially for conservation tillage with response nutrient management practices that aim at enhancing water use efficiency.

A long-term experiment was carried out in the dryland of northern China to assess the effects of applications of maize stover, cattle manure and NP (1:0.44) fertilizer on partial nitrogen (N), phosphorus (P) and potassium (K) balances, extractable soil N (SEN), P and K, and soil organic matter (SOM) in a spring maize cropping system, under reduced tillage conditions. The experiment was set-up according to an incomplete, optimal design, with three factors at five levels and 12 treatments, including a control with two replications. Statistical analyses using multiple regression models showed that the partial N, P and K balances were strongly influenced by annual variations in the amounts of soil water at seeding (SWS) and growing season rainfall (GSR). Most treatments had positive P but negative N and K balances. Cumulative P and K balances were reflected in extractable soil P (P-Olsen) and K (exchangeable K), but the weak relationships indicated that the sorption of P and buffering of K were strong. Cumulative balances of effective organic carbon (C) were weakly related to soil organic C (SOC) content after 12 years. Negative C balances were related to decreases in SOC, but positive C balances were not translated into increases in SOC. The analysis of nutrient balances and soil fertility indices revealed that nutrient inputs in most treatments were far from balanced. It is concluded that the concepts of `ideal soil fertility level¿ and `response nutrient management¿ provide practical guidelines for improving nutrient management under the variable rainfall conditions of dry land areas in northern China.

Soil and residue manipulation can assist weed management by killing weeds mechanically, interfering in weed lifecycles, facilitating operations and enhancing crop establishment and growth. Current tillage systems often compromise these functions, resulting in heavy reliance on herbicides, particularly in no-till systems. Herbicides are an exhaustible resource, so new approaches to merge soil conservation and non-chemical weed management are needed. This paper broadly reviews various preventive and curative non-chemical weed management tactics. It also demonstrates how innovations can be derived from functional requirements of weed management operations, and from biological processes and weaknesses in weed's lifecycles. Mechanical weeding and enhancement of weed seed mortality are highlighted as examples. Major limitations with mechanical weeding include limited weed control in crop rows at early vulnerable crop stages, weather-dependent effectiveness, and difficulties in handling crop residues. Precise steering and depth control, improved seedbed friability and lighter tractors or controlled traffic could bring considerable improvements. To expose weed seeds to predators, position them for fatal germination, viability loss or low emergence may require completely different soil displacement patterns than those of current implements and systems. Controlled traffic and precise strip tillage offer good opportunities for implementing these weed management strategies in minimum-tillage systems.

The farmers in Sri Lanka's dry zone are the main contributors to the paddy production in the country. However, due to various reasons, they face difficulties in obtaining a reasonable income for their produce at harvesting time. According to the survey carried out in the paddy producing regions, it was found that one possible solution to reduce this problem is to enable the farmers to sell their produce at a time when prices are higher than at harvest time. To enable the farmers to keep their paddy on-farm for some time with a minimum loss of quality and quantity, some reliable and affordable storage facility has to be developed. To achieve this, an airtight storage system of 2.5 tons was developed by a four-step approach, which consists of: preliminary study to investigate the actual need, definition of the core problem, definition of the main function to be fulfilled by the designed system and finally, assessment of applicable working principles, to achieve a viable solution of the problem. This paper describes in detail the steps in the approach to achieve an efficient and inexpensive system acceptable to the farmers.

A leaf picking device for cucumbers was designed and evaluated. The picking device is manually operated but can be used as a picking tool for a robot. The device consisted of a picking rotor composed from knives and brushes, a motor and a vacuum cleaner. The performance of removal, cutting, torque and shredding was investigated in the laboratory experiments. In the greenhouse experiments, the performance of picking and cutting was investigated. The results were as follows: (1) the highest removal success rate was achieved at a rotation speed of 1000 min¿1, a rotor configuration of `two knives and two brushes¿ and an insertion speed of 50 mm s¿1; (2) in this mechanical setting, the percentage of the summation of the smooth cut surface of the leaf stalk and the smooth cut surface with small skin was 90%; (3) the required torque was 0.09¿0.96 N m and the average particle size of the shredded leaves was 7.3¿21.2 cm2; (4) the percentages of area of the dropped particles to the average area of leaves was 10¿16%; (5) the average execution time per leaf was 1.1¿2.3 s.

There is increased awareness of the environmental impacts of soil carbon (C) and nitrogen (N) losses through wind erosion, especially in areas heavily affected by dust storm erosion. This paper reviews the recent literature concerning dust storm-related soil erosion and its impact on soil C and N losses in northern China. The purpose of our study is to provide an overview of the area of erosion-affected soils and to estimate the magnitude of soil C and N losses from farmland affected by dust storm erosion. According to the second national soil erosion remote-sensing survey in 2000, the area affected by wind erosion was 1.91 million km 2 , accounting for 20% of the total land area in China. This area is expanding quickly as the incidence of heavy dust storms has greatly increased over the last five decades, mainly as a result of the intensification of soil cultivation. The economic and ecological damage caused by wind erosion is considerable. Heavily affected areas show a loss of nutrients and organic carbon in soils and the heavily degraded soils are much less productive. Compared with the non-degraded soil, the C and N contents in degraded soils have declined by 66% and 73%, respectively. The estimated annual losses per cm toplayer of soil C and N by dust storm erosion in northern China range from 53 to 1044 kg ha − 1 and 5 to 90 kg ha − 1 , respectively. Field studies suggest that soil losses by wind erosion can be reduced by up to 79% when farmers shift from conventional soil tillage methods to no-till. Thus shifting to no-till or reduced tillage systems is an effective practice for protecting soil and soil nutrients. Our study indicates that soil conservation measures along with improved soil fertility management measures should be promoted in dry-land farming areas of northern China. As erosion is a major mechanism of nutrient withdrawal in these areas, we plead for the development of accurate methods for its assessment and for the incorporation of erosion, as a nutrient output term, in nutrient budget studies.

Sweet pepper production is characterized by large fluctuations in fruit yield per week. Synchronization of yield patterns between nurseries in response to weather conditions leads to variations in market supply and affects price formation. In order to improve supply chain efficiency, auctions and wholesalers require nurseries to supply production forecasts several weeks in advance. At the nursery level, yield prediction is helpful for efficient labour planning. Because the dynamics of sweet pepper production are complex, growers find it difficult to understand and effectively control the production process. A model can be useful to assist growers in making efficient decisions with regard to crop and climate management. It is hypothesized that a phase-shift in the feedback-regulation of fruit set by growing fruits could be the cause of the periodic yield pattern observed in practice. This paper describes a dynamic model of sweet pepper production based on this principle. Model output was compared with measurements of sweet pepper production obtained from a commercial nursery. The calibrated model was able to simulate the measured data fairly well, in particular the yield fluctuations. These results are consistent with the hypothesis and serve as a promising starting point for further research aiming at a better understanding of the underlying processes and, consequently, model improvement.

The effect of hot air-drying on the essential oil constituents and yield in French and Russian tarragon (Artemisia dracunculus L.) leaves was studied. The tarragon leaves were dried at air temperatures ranging from 40 to 90 °C. The drying stopped when the moisture content of the samples reached 10% or for some of the treatments reached 7, 20 and 30%. The essential oil of the fresh and dried leaves was isolated by hydrodistillation and analysed by capillary gas chromatography and gas chromatography-mass spectrometry. The decrease of oil during the drying process was highest at 60 °C drying temperature. For French tarragon the decrease in the amount of oil was significantly lower at 90 °C. The effect of the relative humidity of the drying air at each temperature was not significant. The main compounds were estragole in French tarragon (69%) and sabinene in Russian tarragon (40%). The drying process changed the relative percentage of the constituents in the oil; for instance, the relative percentages of estragole decreased and sabinene increased in French tarragon

Two evaluation methods are introduced for expression of the quality of the thermal conditions in the animal-occupied zone (AOZ) in rooms for weaned piglets. One method uses only the AOZ temperature, while the other uses the kata-value (KV), which combines air velocity and temperature and indicates the heat loss to the environment. AOZ thermal conditions should be within the thermo-neutral zone (TNZ) of the piglets. The methods use two new numerical indicators, based on the duration and the magnitude of excess of AOZ thermal conditions outside the TNZ: one referring to the number of degree-hours (°Ch), and the other to the number of kata-value-hours (KVh) during a batch. The objective was to evaluate the two methods in a door-ventilated room for weaned piglets. In the experiment, temperature was measured in all ten pens of a room and air velocity in three pens during eight successive batches, together lasting about one year. Pens closer to the air inlet had higher temperatures and lower KV than pens in the back of the room. Momentary temperature difference between pens reached up to 7°C. During the first days of most batches, pen conditions in the back of the room were "too cold." At the end of most batches, pen conditions in the middle of the room were "too warm." The value of the two indicators varied per pen and per batch from 0 to 319°Ch (0 to 219 KVh) "too cold" and from 0 to 602°Ch (0 to 793 KVh) "too warm." For "too warm" conditions, there was a significant (P 0.96), but not for "too cold" conditions (R 2 > 0.48). Therefore, measuring air velocity in addition to temperature in the AOZ for recognition of "too cold" conditions had surplus value. Excluding outliers from one extremely warm batch, the maximum value of the indicator for "too warm" was 65°Ch. This indicator significantly affected the feed conversion ratio, which increased with 0.0024 kg/kg per °Ch, and daily growth and daily feed intake, which decreased with 0.0022 kg/animal and 0.0030 kg/animal, respectively, per °Ch. The methods presented are useful tools in the technical evaluation of climate systems and for a more optimal climate control in the AOZ.

Risk factors concerning both the pasture and housing seasons for interdigital dermatitis and heel-horn erosion (IDHE) were studied in dairy cows in a cross-sectional study in The Netherlands. The study population included 2326 cows (41 herds) and 2751 cows (46 herds) for the pasture and housing seasons, respectively. Of these animals, 545 (23%) showed serious lesions of IDHE (stages 2 and 3) at the end of the pasture season and 1269 (46%) during housing. Logistic regression of the pasture study indicated that increased parity, solid concrete floor, restricted grazing time, and herd trimming at long intervals were associated with an increased odds of IDHE, while dry cows and lactating cows within 30 days after calving as well as cows on a slatted floor with manure scraper, and grassland with mixed type of soil were associated with lower odds. In the housing study, odds of IDHE increased with parity, administering low- or medium-energy roughage, and introduction of dry cows into the lactating herd at >2 weeks before calving. The presence of long cubicles, knee-bumpers installed in cubicles as well as rearing calves and heifers within the dairy cows’ accommodation decreased the odds of IDHE.

Several claw shape measurements, horn hardness, and horn growth and wear were recorded monthly at 12 dairy farms to investigate the effect of floor type and changes in these traits over time. Herds were either housed on a slatted floor (SL), solid concrete floor (SC), grooved floor (GR), or on a straw yard (SY). Twenty cows per farm were selected and stratified by parity. Information on claw traits was recorded on right lateral hind claws between October 2002 and May 2003. In addition, lesion development of interdigital dermatitis and heel erosion (IDHE) and digital dermatitis (DD) was studied in both rear feet. No differences in claw traits were detected among groups on different floor types, with the exception of claw angle. Claw angles were smallest in cows on SY. Claws of cows on SC were steeper than those on SL and GR. The study provided no evidence that floor-related differences in claw lesions were related to differences in horn growth, wear, and resulting claw shape. Lesions of IDHE developed gradually over time and did not differ among flooring types. Cows in SY had the smallest lesion scores for DD, whereas cows on SL had significantly less DD than cows on SC and GR. Incidence of DD fluctuated over time. Development of different stages of DD was monitored in-depth. Both early and healed stages were rather changeable and often turned into other disease stages. Classical ulcerative lesions (stage M2) persisted for a long time, with 20% of the initially unaffected claws having active lesions of DD within 5 mo. The M2 lesions generally did not cure effectively after claw trimming, and frequent use of footbaths resulted in a poor prognosis for recovery.

Based on data from 10-year field experiments on residue/fertilizer management in the dryland farming region of northern China, Century model was used to simulate the site-specific ecosystem dynamics through adjustment of the model's parameters, and the applicability of the model to propose soil organic carbon (SOC) management temporally and spatially, in cases such as of tillage/residue/fertilization management options, was identified via scenario analysis.Results between simulations and actual measurements were in close agreement when appropriate applications of stover,manure and inorganic fertilizer were combined. Simulations of extreme C/N ratios with added organic materials tended to underestimate the measured effects. Scenarios of changed tillage methods, residue practices and fertilization options showed potential to maintain and enhance SOC in the long run, while increasing inorganic N slowed down the SOC turnover rate but did not create a net C sink without any organic C input. The Century model simulation showed a good relationship between annual C inputs to the soil and the rate of C sequestration in the top 20 cm layer and provided quantitative estimations of changes in parameters crucial for sustainable land use and management. Conservation tillage practices for sustainable land use should be integrated with residue management and appreciable organic and inorganic fertilizer application, adapted according to the local residue resource, soil fertility and production conditions. At least 50%residue return into the soil was needed annually for maintenance of SOC balance, and manure amendment was important for enhancement of SOC in small crop-livestock systems in which crop residue land application was limited

Explorative experiments were done to investigate the possibility that tomato plants infected by Botrytis cinerea have a different emission of volatile organic compounds (VOC) than healthy plants. This was done by headspace analysis of volatiles emitted by detached leaves of infected and healthy plants. Principal component analysis (PCA) of GC-FID chromatograms revealed clearly separated clusters between infected and control leaves and identification of an interesting compound. In further analysis by GC-MS, the significantly distinctive component (p≤0.05) was identified as the sesquiterpene α-copaene. In previous work on herbivore damage, α-copaene was not distinctive, which may suggest that α-copaene may be specifically associated to fungal infections in tomato.

Precompression stress is often used as a criterion for soil susceptibility to compaction. The objective of this study was to compare precompression stresses derived from different compression test methods and relate these values to measured stress and displacement during wheeling in the field. Precompression stress was measured at three depths at two sites on a Eutric Cambisol in Sweden using in situ plate sinkage test, and by compressing soil cores in the laboratory with sequential loading (oedometer) and at constant displacement speed, respectively. At the same sites, wheeling experiments were carried out where vertical soil displacement and vertical soil stress were measured simultaneously at three depths. No clear relationship between precompression stress and compression method was found. Precompression stress values derived from the oedometer and the in situ plate sinkage test did generally not differ from each other. Precompression stress derived from the constant speed test was either higher (site A, silty clay loam) or lower (site B, silty clay) compared to the other methods. Precompression stress did not work as a threshold value between reversible and irreversible deformation when precompression stress values derived from the different methods were compared with stress and displacement measured in the field during the wheeling experiment. Even when the observed stress was lower than the precompression stress, a residual displacement was observed. The study demonstrates that the precompression stress is not a sharp value but depends on the compression test method and its analysis, and that compression tests might not represent the soil behaviour in the field sufficiently. There is an urgent need to study soil behaviour in the field and link these experiments to soil mechanical (laboratory) tests.

Claw health was examined in an observational study on Dutch dairy farms with either a slatted floor (SL), slatted floor with manure scraper (SL-SCR), solid concrete floor (SCF), a straw yard (SY), or a zero-grazing feeding system (ZG). Hooves of cows' hind legs were examined for the presence and severity of claw disorders during hoof trimming events at the end of the pasture (P-study) and housing period (H-study). The number of cows in each study was 3078 (49 herds) and 3190 (47 herds), respectively. Due to a different hoof trimming strategy, data collected during both observation periods in SY herds (638 cows; 16 herds) were combined. Cows in straw yards (SY) had by far the lowest numbers of claw disorders. Over 80% of cows exposed to concrete flooring had at least one claw disorder at the time of observation, whereas on SY surfaces, this percentage was between 55 and 60. Cows on SL-SCR were less frequently affected by interdigital dermatitis/heel erosion (IDHE) and digital dermatitis (DD) than cows on SL (reference floor system). Little difference in claw health was found between SF and SL. The ZG cows were at higher risk (OR > 2) for most claw disorders in the P-study, whereas in the H-study, ZG cows showed less IDHE, sole hemorrhage, and sole ulcer. All herds on concrete flooring (SL, SL-SCR, SCF, ZG) were infected by DD, resulting in an average cow level prevalence of 30%. This indicates that the level of DD infection has increased considerably over the last 10 yr in The Netherlands.

A simple method was developed to estimate the fraction radiation intercepted by small eastern white cedar plants ( Thuja occidentalis 'Brabant'). The method, which describes the crop canopy as rows of cuboids, was compared with methods used for estimating radiation interception by crops with homogeneous canopies and crops grown in rows. The extinction coefficient k was determined at different plant arrangements and an average k-value of 0.48 ± 0.03 (R%sup2; = 0.89) was used in the calculations. Effects of changing plant characteristics and inter- and intra-row plant distances were explored. The fraction radiation intercepted that was estimated with the method for rows of cuboids was up to 20% and for row crops up to 8% lower than estimated with the method for homogeneous canopies at low plant densities and a LAI of 1. The fraction radiation intercepted by small plants of Thuja occidentalis 'Brabant' was best estimated by the simple method described in this paper

Uitleg van de doeleinden die men op Wageningen UR voor ogen heeft met het organiseren van een wedstrijd voor het ontwerpen van een nieuwe veldrobot

A protocol was developed and applied in a field survey to incorporate evaluation of herd welfare into the existing quality assurance program in Dutch dairy farming. Welfare was derived from the state of the biological needs of cows. Welfare targets and critical control points were selected according to HACCP principles, while restriction was to dairy herds with loose-cubicle housing (>90% of Dutch herds). The feasibility for measurement of the protocol was tested in a pilot study with 52 preselected, medium-sized herds for time needed for the observations (set at ~1 h to 2 h ), robustness of parameters (threshold of 80% true cases for repeated scores), and opinions from inspectors and farmers, which were variable but positive on average. The final protocol consisted of 16 animal-based and 14 environment-based parameters. From a random sample of 240 dairy herds (1% of Dutch farms), 164 herds (12,267 cows) with median herd size of 67 cows (SD=38) participated in the field survey, on a voluntary basis. The time needed for scoring averaged 78 min (SD=22) per herd. Animal-based parameters included leg disorders, normal and abnormal locomotion, external lesions, skin and teat problems, poor body condition, and fearfulness of the herd. Herd prevalence averaged highest for abnormal locomotion (43.8%), swollen hocks and knees (25.2%), dermatophytosis (24.2%), scabies (20.1%), and filthiness (17.4%). However, herd prevalence was lowest ( p Environment-based parameters included technical dimensions and stocking densities of the feeding gate and cubicles, availability of feed at the feeding gate, the floor of cubicles, and access to and hygiene of drinking water. The scores were analyzed on basis of statistical parameters and prevalence distribution, and were compared with existing technical Dutch recommendations, the ‘standard’. Deviations from the recommendations could partly be attributed to the age of the facilities. For most herds, the cubicle bed was a rubber mat (44%) or mattress (21%), whereas litter as bedding material was observed in 21% of herds; but there was no Dutch standard. For stocking rates of the feeding gate and cubicles, the results were variable. But for lactating cows, the average stocking rates of feeding gate (103.6%; SD=26.7) and cubicles (95.8%; SD=14.1) were close to standard (100%). Provision, hygiene, and access to drinking water were generally according to requirement (>96% of herds). Overall, our results indicate various directions for welfare improvement in practice, both at the individual farm and sector level.

International audience; Food production is highly dependent on regional yields of crops. Regional differences in grain yields could be due to fertilizer management and climate variability. Here, we analyze trends of grain yields in North China, Northeast China, East China, and Central and Southwest China from 1992 to 2012, using the Chinese statistical yearbooks. We estimate the major factors influencing yield by regression analysis. Results show that fertilizer indices were 40 % for Northeast China, 36 % for East China, 9 % for North China, and 6.8 % for Central and Southwest China. Soil indices were 67 % for Northeast China, 14 % for East China, 90 % for North China, and 6 % for Central and Southwest China. The indices of annual mean temperature were positive for Central and Southwest China (72 %) and East China (39 %), but negative for Northeast China (−15 %) and North China (−16 %). Soil factors explained 80 % of yield variation in North China. Annual mean temperature explained 80 % of yield variation in Central and Southwest China.

Cow preferences for one of two compartments with different floors were tested in a barn with two symmetrical, connected compartments, each intended for 16 cows. Compartments were identical except for the floor. One floor was grooved longitudinally to the feeding barrier and the other was slotted perpendicular to that barrier. Sixteen pregnant, lactating Holstein-Friesian cows were used. After 14 d of habituation, cow behavior was videotaped for 10 full 24-h d, spread over 22 d. Their daily time budget spent on different activities performed in both compartments was analyzed, as was their relocation and use of the concentrate dispenser in each compartment. On average, cows spent 120 min longer per day in the slotted floor compartment than in the grooved floor compartment, and performed all activities in the daily time budget significantly longer in this compartment. However, testing the preference of individuals revealed that, although five cows significantly preferred the slotted floor compartment, two cows significantly preferred the other compartment, and nine cows had no preference. On the slotted floor, cows ate longer at the feeding barrier and more often drank front-on to the water trough; on the grooved floor they more often drank standing parallel to the water trough. Thus, they seemed to prefer to stand parallel to the slots. Relocation of cows, indicated by index of movement, was not significantly different between the floors. Relocation seemed to be stimulated more by the presence of concentrate dispensers in both compartments than by floor profile. Although one floor type was not clearly preferred over the other, the findings and methods of this study have implications for design and implementation of future preference tests for testing husbandry systems and their components.

The effects of planting date (season) and plant density (32, 48 or 64 plants m-2) on growth of cut chrysanthemum (Chrysanthemum (Indicum group)) were investigated in six greenhouse experiments, applying the expolinear growth equation. Final plant fresh and dry mass and number of flowers per plant decreased with plant density and this decrease was larger in summer than in winter. Stem length hardly responded to plant density and total dry mass production per m2 linearly increased with plant density. Plant dry-matter content was not influenced by plant density. Plant dry-matter content, plant fresh and dry mass, number of flowers per plant, stem length and biomass production per m2 were all higher in summer than in winter. Final plant fresh mass (y; g) showed a linear relationship with cumulative incident photosynthetic active radiation (PAR) per plant (x; MJ plant-1) (y = 16.7x 28.0, R2 = 0.97). This relationship implies proportionality between incident light per plant and plant density (at the same final plant fresh mass), showing that plant density effects were primarily mediated through competition for light. Dry-mass production in time could be described accurately by the expolinear growth equation with three regression parameters: maximum relative growth rate (rm; assumed to be independent of plant density), maximum absolute growth rate (cm) and lost time (tb). rm was 2.4 times higher and cm was 4.1 times higher in summer than in winter and no effect of plant density on cm was observed, whereas to decreased linearly with increased plant density. Using these parameters and measured maximum leaf area index (LAI) for calculating dynamic growth patterns of LAI, resulted in large over- or under-estimations, except for summer-grown crops. When an extended expolinear growth function was fitted simultaneously on dry-mass production and LAI in time, accurate time curves for LAI were obtained, whereas dry-mass production was accurately described only for the summer crops. Only under rather constant radiation levels during a cultivation (summer), could accurate descriptions for both dry mass production and LAI increase in time be obtained. Light use efficiency (LUE), the slope of the linear relationship between crop growth and cumulative intercepted PAR, varied between 3.4 g MJ-1 in summer and 5.3 g MJ-1 in winter and LUE slightly increased with plant density.