Thermodynamics of greenhouse systems : a new approach leading to new proposals for sustainable production

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Greenhouse production systems produce in the Netherlands and Flanders economical important quantities of vegetables, fruit and ornamentals. Control of the crop environment has led to a high primary energy use (1500MJ/m²/year). This high primary energy use affects the economical and environmental sustainability. Research projects in the Netherlands and Flanders are launched to achieve sustainable greenhouse systems with high crop yields and low primary energy use. Until now, these projects didn’t result in the desired primary energy savings. On the contrary, the civil building industry succeeds by the passive house technology in a magnitude’s reduction for primary energy use. The primary energy saving research in greenhouse systems was mainly based on analysis of energy balances. However, the thermodynamic theory indicates that an analysis based on the concept of exergy (free energy) and energy is preferred. Such analysis could reveal possibilities for primary energy savings. The different processes and in/outputs of the greenhouse system are outlined. The appropriate equations for exergy calculations are developed. First, analyses are performed on the processes of transpiration and ventilation. Further, a total system assessment is performed. The exergy analysis indicates that primary energy saving in greenhouse systems could be the same as in the building industry, but adapted technologies need to be developed. The Institute for Agricultural and Fisheries Research (ILVO) will use this exergy analysis as a basis for the development of an exergy efficient greenhouse prototype (EXEkas).mp201

Manuel d'hygiène privée et d'hygiène scolaire á l'usage des écoles normales primaires

par E. Schreven

Multidimensional analysis of environmental impacts from potato agricultural production in the Peruvian Central Andes

Rain-fed potato systems, being the most important cash crop in the Peruvian Central Andes, play a key role in food security. Quantifying the environmental impacts and understanding their complex interactions is an important step towards an improvement of the technical sustainability of these systems. From 2005 until 2015, 58 potato field plots located on a transect of Mantaro Valley, Junín, Peru were investigated at field level during the rainy cropping seasons. All external inputs used for crop production were measured and registered on fortnightly basis. A life cycle assessment (LCA) was performed (per ton yield fresh weight) to assess the most important potential environmental impact categories (EICs). Due to the intrinsic variability of the production systems, a cluster analysis (k-means algorithm) and linear discriminant analysis (LDA) were implemented to group and evaluate the classification based on the EICs values. Furthermore, latent variables were obtained using exploratory factor analysis (EFA) to investigate the correlational structure of main biophysical inputs (kg ha-1) and EICs values (kg unit-eq. t-1). Similarly, data envelopment analysis (DEA) was used to quantify the relative environmental efficiency based on the EICs values (unit-eq. t-1, input) and the productivity level (kg ha-1, output). Overall LCA results showed considerable EICs values for acidification and eutrophication due to the inappropriate or sub-optimal use of fertilizer sources. Restricted use of machinery and low technology level caused low global warming potential and cumulative energy demand. Based on the cluster analysis, three groups were found mainly defined by the nature of the inputs and EICs values: inorganic, organic and mixed systems. LDA showed a good overall classification accuracy for the groups (98.3%), being cumulative energy demand the most important discriminant variable due to scarce machinery use. In addition, EFA proved that the first and second latent variables are correlated with an inorganic- and organic-oriented agriculture respectively, being the inorganic more associated with the EICs values. Environmental efficiency (from 0.04 to 0.61 on average) was linked to the quantity and source of the inputs, showing that potential environmental savings can be reached if more balanced input sources are used.status: publishe

Nitrogen and water use efficiency under rain-fed potato agriculture: an experimental study

status: publishe

Datasets of the environmental factors and management practices of the smallholder tomato production systems in the Colombian Andes

© 2019 The Author(s) Datasets presented here were employed in the main work “Understanding the heterogeneity of smallholder production systems in the Andean tropics – The case of Colombian tomato growers” Gil, et al., 2019. In this region, tomato crop is developed under two technological levels: low, carried out under open field (OF) conditions and, a high, by using greenhouses (GH). For OF, data belong to five municipalities of the Guanentá province (Santander department), while for GH, data belong to five municipalities of the Alto Ricaurte province (Boyacá department). The data presented here includes information on soil parental materials and climate variables (averages ± standard deviations) relevant from the agricultural point of view, which were calculated from historical climate series. Soils natural fertility data, obtained by sampling the production areas, are also presented. After filtering the data, 67 samples were obtained for OF and 70 for the GH. For GH, a dataset with the results of 38 soil samples taken inside greenhouses were paired with the results of samples taken outside these greenhouses in uncropped areas. In the case of these soil analyses, the data correspond to tables with the results reported by the laboratory for both, chemical and physical variables, for each location in which soil samples were taken. In this work, the main dataset is one that contains the inputs of fertilizers and water, and the corresponding yields of tomato production cycles managed by local growers. This information was collected through two data collection tools: surveys (SVY) to growers about these aspects in their last production cycle, and through detailed follow-ups of selected production cycles (FWU). For the OF, we collected data from 71 cycles through the surveys and 22 through the follow-ups, while for the GH, information from 138 to 38 tomato cycles was collected through surveys and follow-ups, respectively. A table with the results aggregated by tomato cycle is attached.status: publishe

Environmental savings in tomato production under optimal agrochemicals management: a modeling approach

The use of agrochemicals has been recognized as one of the main environmental burdens in agriculture. Actual management practices aggravate pollution issues due to overdosing and untimely applications, even more if farmers are reluctant to change their practices. The application of crop modeling coupled to environmental impact tools offers an alternative to analyze improved production scenarios. The objective of this study was to estimate the environmental savings due to optimized agrochemicals management for tomato production in Colombia. For this purpose, we calibrated a generic growth model for greenhouse tomatoes. The environmental performance of the current and optimized schemes was evaluated through a life-cycle assessment (LCA) approach. Data for current practices were collected through detailed follow-ups of 38 growing cycles. The optimized scenario was constructed by simulating crop growth based on the climate for each cycle. These scenarios also considered optimized nitrogen fertilization and restricted use of pesticides. All resource consumption and emissions referred to a functional unit of 1 t tomatoes with boundaries defined from raw material extraction to farm gate. The assessment considered the manufacture and emissions to water and soil of nitrogen fertilizers and pesticides. Average observed and simulated yield were 83.3 and 178.5 t ha-1, respectively. Most of the reductions due to the optimal strategy were above 90% for most of the impact categories. Under the actual production strategy, the manufacture of N fertilizers was the main contributor to the environmental impact for most categories. The impact of N field emissions was more relevant under the optimal model, since the shares of this component were 26.1, 74.7, and 95.1% for acidification potential, eutrophication potential, and global warming potential, respectively. The optimized scenario showed that there is huge room to improve Colombian tomato production technically and environmentally

Assessing the potato yield gap in the Peruvian Central Andes

The Peruvian Central Andes is a highly important area for potato production. Assessing the potato yield gap and the potential yield is an essential step towards sustainable crop intensification. Fifty-eight smallholder potato farmer's plots in total were monitored at field level during the 2005–2008 and 2010–2015 rainy cropping seasons. All the main crop management inputs were registered. Three field experiments (on-farm trials) established during the 2014–2017 rainy cropping seasons were used to calibrate (2014–2016) and validate (2016–2017) the SUBSTOR-potato model under potential conditions. Potential potato yield (Yp) was estimated for each individual field pilot plot (in kg ha−1) based on the calibrated and validated crop model. Yield gaps (Yg) were calculated as the difference between Yp and farmers' actual yield (Ya). A classification tree-based model predicting the potato gap quantiles was used to elucidate the main biophysical and crop management components inducing Yg. Performance of the SUBSTOR-potato model showed a close agreement of simulated crop biomass, tuber yield, and N-uptake (i.e. N-demand) with the measured data under potential conditions. Redefined index of agreement were 0.84 and 0.80 while the associated mean square error were 2232 and 916 kg tuber dry weight (DW) ha−1 for the calibration and validation, respectively. The mean farmers' actual DW yield was 7118 kg ha−1, however, a high variability due to heterogeneous biophysical conditions and crop management was found (from 710 to 18,885 kg DW ha−1). The potato Yg ranged from 0.1 to 95.8% of the potential yield (x¯ = 42.1%, x~ = 46.0%, σx = 28.14% and CV = 0.67), hence there is an important difference that needs to be reduced. The classification tree analysis showed that inorganic N is the main yield explaining factor. While large yield gaps (Fourth quantile) are induced by low Inorganic N (< 88 kg ha−1) and scarce Human Labour energy (< 4196 MJ ha−1), small yield gap (First quantile) is mainly attributed to high N-inputs (≥ 139 kg ha−1 inorganic and ≥ 154 kg ha−1 organic). Third and Second quantiles (mid potato yield gaps) were characterized by more intricate nutrient input use, being difficult to classify; the Third quantile was partially explained by Inorganic N (< 139 kg ha−1), while part of the Second quantile by Extractable soil phosphorus (< 7.3 mg kg−1) and Inorganic N (< 139 kg ha−1). This classification can be helpful to diagnose the main site-specific crop management and biophysical recommendations towards closing the potato yield gap. The analysis suggests that there is opportunity to enhance potato actual yields in the study zone. More rational amount of inputs together with best management practices might improve potato productivities. However, sustainable potato intensification should be complemented with the expected quantification of environmental burdens under the local socio-economic constraints.The Peruvian Central Andes is a highly important area for potato production. Assessing the potato yield gap and the potential yield is an essential step towards sustainable crop intensification. Fifty-eight smallholder potato farmer's plots in total were monitored at field level during the 2005–2008 and 2010–2015 rainy cropping seasons. All the main crop management inputs were registered. Three field experiments (on-farm trials) established during the 2014–2017 rainy cropping seasons were used to calibrate (2014–2016) and validate (2016–2017) the SUBSTOR-potato model under potential conditions. Potential potato yield (Yp) was estimated for each individual field pilot plot (in kg ha−1) based on the calibrated and validated crop model. Yield gaps (Yg) were calculated as the difference between Yp and farmers' actual yield (Ya). A classification tree-based model predicting the potato gap quantiles was used to elucidate the main biophysical and crop management components inducing Yg. Performance of the SUBSTOR-potato model showed a close agreement of simulated crop biomass, tuber yield, and N-uptake (i.e. N-demand) with the measured data under potential conditions. Redefined index of agreement were 0.84 and 0.80 while the associated mean square error were 2232 and 916 kg tuber dry weight (DW) ha−1 for the calibration and validation, respectively. The mean farmers' actual DW yield was 7118 kg ha−1, however, a high variability due to heterogeneous biophysical conditions and crop management was found (from 710 to 18,885 kg DW ha−1). The potato Yg ranged from 0.1 to 95.8% of the potential yield (x¯ = 42.1%, x~ = 46.0%, σx = 28.14% and CV = 0.67), hence there is an important difference that needs to be reduced. The classification tree analysis showed that inorganic N is the main yield explaining factor. While large yield gaps (Fourth quantile) are induced by low Inorganic N (< 88 kg ha−1) and scarce Human Labour energy (< 4196 MJ ha−1), small yield gap (First quantile) is mainly attributed to high N-inputs (≥ 139 kg ha−1 inorganic and ≥ 154 kg ha−1 organic). Third and Second quantiles (mid potato yield gaps) were characterized by more intricate nutrient input use, being difficult to classify; the Third quantile was partially explained by Inorganic N (< 139 kg ha−1), while part of the Second quantile by Extractable soil phosphorus (< 7.3 mg kg−1) and Inorganic N (< 139 kg ha−1). This classification can be helpful to diagnose the main site-specific crop management and biophysical recommendations towards closing the potato yield gap. The analysis suggests that there is opportunity to enhance potato actual yields in the study zone. More rational amount of inputs together with best management practices might improve potato productivities. However, sustainable potato intensification should be complemented with the expected quantification of environmental burdens under the local socio-economic constraints.status: Published onlin

Effect of water stress after flowering stage on tomato crop yield and soil water content in the semi-arid Peruvian coastline

To evaluate the effects of water stress on tomato at reproductive stages four irrigation treatments were established, based on the crop water requirements using the FAO methodology. At full flowering stage irrigation treatments were reduced in 50% until the end of harvesting season. T1 (150% to 75% of FAO ETc), T2 (100% to 50% of FAO ETc), T3 (75% to 33% of FAO ETc) and T4 (50% to 25% of FAO ETc). The experiment was laid out as a Latin square design with four treatments and four replicates. The soil in the experimental site is a loam with a depth of 70 cm and the following characteristics: saturation (SAT) 43%, field capacity (FC) 27% and wilting point (WP) 13%. Soil Volumetric water content at four depths (10, 20, 30 and 45 cm) was measured using a time domain reflectometry system (TDR) on the 3-hourly basis. Biometric destructive measurements were performed every 20 days to measure leaf area, dry mass production and nutrient content (NPK). Coverage images were taken on the weekly basis, resulting on a maximum coverage of 80%, 60%, 50% and 40% for T1, T2, T3 and T4 respectively. Tomato production was significantly affected by irrigation treatments. The highest yield was obtained with T1 (50.23 t ha-1), finding significant differences between this and T2, T3 and T4 yielding 25.98, 18.3 and 16.6 t ha-1 respectively. The three deficit treatments yielded below the national average yield (35 t ha-1), however for T1 produced 15 t.ha-1 additional yield, reducing water use in 90% compare to and average tomato farmer. In further research, we will use processed based mechanistic modelling to simulate the water transport dynamics under fertigation.cited By 0 document_type: Article source: Scopusstatus: publishe