Comparison of a Lightweight Experimental Shaker and an Orchard Tractor Mounted Trunk Shaker for Fresh Market Citrus Harvesting

[EN] A designed lightweight experimental shaker successfully used to collect ornamental oranges has been tested to harvest fresh market citrus. The aim of this study was to evaluate the removal efficiency and operational times of this experimental device compared to an orchard trunk shaker. Three different collecting systems were studied. 'Caracara' citrus trees were tested. Removal efficiency, vibration parameters, fruit and tree damages, and fruit quality were measured. A high-speed camera was used to record operational times and determine cumulative removal percentage over vibration time. The canvases on the ground reduced the severe fruit damages but were not useful to protect against light damages. The experimental shaker produced a higher percentage of slightly damaged oranges. No significant differences in removal efficiency were found between the two harvesting systems. However, removal efficiency using the experimental device could be reduced by 40 percent and working time increase by more than 50 percent when access to the main branches was difficult. In agreement with previous results, the curve representing the branch cumulative removal percentage in time followed a sigmoidal pattern. A model was built showing that during the first 5 s more than 50 percent of the fruits were detachedThis research has been fund by the European Agricultural Fund for Rural Development and cofounded by the Ministerio de Agricultura, Pesca y Alimentacion (project GO "Avances tecnologicos para la modernizacion y la sostenibilidad en la produccion de citricos CITRUSTECH").Ortiz Sánchez, MC.; Torregrosa, A.; Castro-García, S. (2021). Comparison of a Lightweight Experimental Shaker and an Orchard Tractor Mounted Trunk Shaker for Fresh Market Citrus Harvesting. Agriculture. 11(11):1-10. https://doi.org/10.3390/agriculture11111092110111

An ultra-low pressure pneumatic jamming impact device to non-destructively assess cherimoya firmness

[EN] The quality of cherimoya fruit is reduced by the rapid deterioration of firmness during ripening. Different methods have been developed for the measurement of firmness. The objective of this study was to use a developed impact prototype for the non-destructive assessment and prediction of cherimoya fruit firmness. The prototype has an ultra-low pressure pneumatic jamming rod used to copy the irregular fruit shape. A sample of 200 cherimoyas from Málaga (Spain) `Fino de Jete¿ were tested during 4 days. Every day all the fruits were non-destructively tested and a set of 15 were destructively tested. On the fourth day all the remaining fruits were also destructively tested. The prototype was capable of copying the irregularities of the fruit and non-destructively assessing the decrease in cherimoya firmness during ripening without causing damage. A high correlation was found between destructive firmness and non-destructive variables from the prototype. A PLS model was developed to relate destructive firmness from day 4 to non-destructive variables and diameter from day 3, with a R2 of 75.6 and a RMSECV of 0.9885. A calibration set confirmed the prediction with a R2 of 80.2 and a RMSEP of 0.0561. Firmness decay could be non-destructively predicted 24 h in advance using the variables extracted from the prototype device signal.Ortiz Sánchez, MC.; Blanes Campos, C.; Mellado, M. (2019). An ultra-low pressure pneumatic jamming impact device to non-destructively assess cherimoya firmness. Biosystems Engineering. 180:161-167. https://doi.org/10.1016/j.biosystemseng.2019.02.003S16116718

Evaluation of Citriculture Mechanisation Level in Valencia Region (Spain): Poll Results

[EN] The increase of the technology level of citrus production operations is required to improve production profitability and reduce production costs. In the framework of the project CITRUSTECH ("Technological advances for modernisation and sustainability in citrus production"), three different poll questionnaires were developed and conducted in the Valencia region to assess the citriculture mechanisation level. In total, 142 questionaries for small and medium-size plantations, 32 for cooperative technicians and 16 for large-size plantations were conducted. From a socioeconomic point of view, clear age and sex inequalities were found. From the technological point of view, relevant differences were found between plantation sizes. The role of the cooperative mechanisation services (custom cost) and other customer services was revealed, with a higher percentage of the area under cultivation at the expense of the small-size plantations. The use of some manual tools was confirmed in pruning, even in large-size orchards. In small-size orchards, the use of backpack sprayers was verified. Regarding farm machinery, besides tractors, hydro-pneumatic sprayers and agricultural shredders were employed. No farm machinery was used during harvesting operations, apart from transport equipment, due to the reduced plantation frames.This research has been funded by the European Agricultural Fund for Rural Development and cofounded by the Ministerio de Agricultura, Pesca y Alimentacion (project GO "Avances tecnologicos para la modernizacion y la sostenibilidad en la produccion de citricos CITRUSTECH").Ortiz Sánchez, MC.; Torregrosa, A.; Martínez, JM. (2022). Evaluation of Citriculture Mechanisation Level in Valencia Region (Spain): Poll Results. Agronomy. 12(6):1-6. https://doi.org/10.3390/agronomy120613661612

Mechanical properties of citrus and impact damage under different storage conditions

[EN] Mechanical handling of fresh-market citrus is restricted by damage susceptibility. The objective of this research study was to determine the effect of variety and storage conditions on the resistance of citrus to impact damage. Three citrus varieties, two of them in two different stages of maturity, were tested in two different experiments: a freedropping experiment and a physical properties experiment. Two relative humidity conditions and two temperature conditions were studied. In the physical properties test, puncture resistance and compression resistance were measured. Significant differences were found in the damage resistance of each of the varieties. Puncture resistance of the peel of postharvest citrus and whole-fruit compression resistance are related to storage temperature and relative humidity conditions. To increase citrus whole-fruit compression resistance and peel puncture resistance, low temperatures and high relative humidity should be used. Under suitable previous temperature and relative humidity conditions, citrus varieties such as ‘Valencia Late,’ with a high resistance to compression and low peel deformation, could be apt for aggressive mechanical handling.This study was funded by the Ministerio de Ciencia e Innovación (research project RTA2009-00118-C02-02) and FEDER.Ortiz Sánchez, MC.; Torregrosa, A. (2014). Mechanical properties of citrus and impact damage under different storage conditions. Transactions of the ASABE. 57(2):593-598. https://doi.org/10.13031/trans.57.10479S59359857

Mechanical Thinning of Mandarins with a Branch Shaker

[EN] Thinning is the process of removing some flowers or fruit to increase fruit size at harvest. In the Valencia region of Spain, the thinning operation for citrus fruit (Citreae) is performed for some mandarin varieties. This is always performed manually; however, this method is very expensive. The goal of this research study was to assess the mechanical thinning of mandarin ( Citrus reticulata) using a hand-held branch shaker. Different thinning treatments were conducted over a 3-year period. The gasoline-powered branch shaker was capable of detaching fruit four- to five-times faster than manual thinning. Final fruit size was significantly higher using manual and mechanical thinning compared with a no thinning treatment. Similar final fruit size was obtained with manual and mechanical thinning. However, no significant differences were found in final fruit yield by weight among no thinning, mechanical thinning, and manual thinning treatments. The use of a branch shaker could be recommended for thinning operations to increase efficiency, reduce labor costs, and obtain larger and higher-quality fruit.This work was supported by funding from the Instituto Nacional de Investigaciones Agrarias (INIA) and European FEDER (Project RTA2014-00025-C05-02). Fontestat provided the experimental fields.Ortiz Sánchez, MC.; Torregrosa, A.; Ortí García, E.; Balasch Parisi, S. (2020). Mechanical Thinning of Mandarins with a Branch Shaker. HortTechnology. 30(6):745-750. https://doi.org/10.21273/HORTTECH04451-20S74575030

Application of Electrical Bio-Impedance for the Evaluation of Strawberry Ripeness

"This is an Author's Accepted Manuscript of an article published in González-Araiza, José Raymundo, María Coral Ortiz-Sánchez, Francisco Miguel Vargas-Luna, and José Manuel Cabrera-Sixto. 2016. Application of Electrical Bio-Impedance for the Evaluation of Strawberry Ripeness. International Journal of Food Properties 20 (5). Informa UK Limited: 1044 50. doi:10.1080/10942912.2016.1199033, available online at: https://www.tandfonline.com/doi/full/10.1080/10942912.2016.1199033."[EN] Electrical bio-impedance measurements were conducted on local strawberry fruits. A non-destructive device was designed to obtain the impedance spectrum of the whole fruit. Four electrical variables were tested: low frequency resistor R0 (related to extracellular resistances), the high frequency resistor R∞ (related to intracellular resistances), and constant phase element (magnitude and phase, related to the membrane capacitances and heterogeneity, respectively). In parallel with the electrical bio-impedance measurement, color and firmness were correlated to the ripeness stage. The results indicated that the strawberries at the highest stage of ripeness had significantly lower constant phase element and R0 values.The authors would like to express their gratitude to Mr. and Mrs. Abraham from Irapuato, Mexico for providing the fruits, and to Mr. Juan Manuel Noriega from the University of Guanajuato for his technical support. The authors would like to thank the University of Guanajuato for the financial support.Gonzalez-Araiza, J.; Ortiz Sánchez, MC.; Vargas-Luna, F.; Cabrera-Sixto, J. (2017). Application of Electrical Bio-Impedance for the Evaluation of Strawberry Ripeness. International Journal of Food Properties. 20(5):1044-1050. https://doi.org/10.1080/10942912.2016.1199033S10441050205Cordenunsi, B. R., Nascimento, J. R. O., & Lajolo, F. M. (2003). Physico-chemical changes related to quality of five strawberry fruit cultivars during cool-storage. Food Chemistry, 83(2), 167-173. doi:10.1016/s0308-8146(03)00059-1Sacks, E. J., & Shaw, D. V. (1994). Optimum Allocation of Objective Color Measurements for Evaluating Fresh Strawberries. Journal of the American Society for Horticultural Science, 119(2), 330-334. doi:10.21273/jashs.119.2.330Harker, F. R., & Forbes, S. K. (1997). Ripening and development of chilling injury in persimmon fruit: An electrical impedance study. New Zealand Journal of Crop and Horticultural Science, 25(2), 149-157. doi:10.1080/01140671.1997.9514001Bauchot, A. D., Harker, F. R., & Arnold, W. M. (2000). The use of electrical impedance spectroscopy to assess the physiological condition of kiwifruit. Postharvest Biology and Technology, 18(1), 9-18. doi:10.1016/s0925-5214(99)00056-3Harker, F. R., & Maindonald, J. H. (1994). Ripening of Nectarine Fruit (Changes in the Cell Wall, Vacuole, and Membranes Detected Using Electrical Impedance Measurements). Plant Physiology, 106(1), 165-171. doi:10.1104/pp.106.1.165Fang, Q., Liu, X., & Cosic, I. (s. f.). Bioimpedance Study on Four Apple Varieties. 13th International Conference on Electrical Bioimpedance and the 8th Conference on Electrical Impedance Tomography, 114-117. doi:10.1007/978-3-540-73841-1_32Vozáry, E., & Benkó, P. (2010). Non-destructive determination of impedance spectrum of fruit flesh under the skin. Journal of Physics: Conference Series, 224, 012142. doi:10.1088/1742-6596/224/1/012142Harker, F. R., Elgar, H. J., Watkins, C. B., Jackson, P. J., & Hallett, I. C. (2000). Physical and mechanical changes in strawberry fruit after high carbon dioxide treatments. Postharvest Biology and Technology, 19(2), 139-146. doi:10.1016/s0925-5214(00)00090-9Juansah, J., Budiastra, I. W., Dahlan, K., & Seminar, K. B. (2014). Electrical Properties of Garut Citrus Fruits at Low Alternating Current Signal and its Correlation with Physicochemical Properties During Maturation. International Journal of Food Properties, 17(7), 1498-1517. doi:10.1080/10942912.2012.723233O’Toole, M. D., Marsh, L. A., Davidson, J. L., Tan, Y. M., Armitage, D. W., & Peyton, A. J. (2015). Non-contact multi-frequency magnetic induction spectroscopy system for industrial-scale bio-impedance measurement. Measurement Science and Technology, 26(3), 035102. doi:10.1088/0957-0233/26/3/035102Gore, C. M., White, J. O., Wachsman, E. D., & Thangadurai, V. (2014). Effect of composition and microstructure on electrical properties and CO2 stability of donor-doped, proton conducting BaCe1−(x+y)ZrxNbyO3. Journal of Materials Chemistry A, 2(7), 2363. doi:10.1039/c3ta12668

Yield and Economic Results of Dif-ferent Mechanical Pruning Strategies on "Navel Foyos" Oranges in the Mediterranean Area

[EN] Pruning is one of the most manpower-consuming agricultural operations in citrus production.Mechanical pruning can help to reduce pruning time and costs. In order to obtain the knowledge of its effects on the important orange variety ¿Navel Foyos¿, several pruning strategies that include manual pruning and various intensities of mechanical pruning were tested for three years. The results showed that in ¿Navel Foyos¿ oranges, the mechanical pruning strategies did not affect the yield nor the size of the fruit in comparison with manual pruning. In conclusion, mechanical strategies are a potential alternative to manual pruning because they reduce the time necessary to prune and the pruning costs, thereby maintaining or even increasing the yield.This research was funded by (1) the project "Application of new technologies for a comprehensive strategy of mechanized citrus harvesting (CITRUSREC)" funded by the Spanish National Institute for Agriculture and Food Research and Technology (INIA) and the Ministry of Economy, Industry and Competitiveness of Spain (project RTA2014-00025-C05-00), cofunded by the European Regional Development Fund (ERDF); (2) the project of the Operative Group "Technological advances for modernization and sustainability in citrus production. (GO CITRUSTECH)" cofunded by the Agricultural European of Rural Developing-EAFRD (80%) and the Ministry of Agriculture, Fisheries, and Food (20%); (3) the project "Engineering developments to ensure profitable, sustainable and competitive agriculture from farm to fork" cofinanced by the Valencian Institute of Agricultural Research (IVIA) and by the European Regional Development Fund (ERDF). G.M. was a beneficiary of a scholarship for training and specialization of the European Social Fund (ESF).Chueca, P.; Mateu, G.; Garcerá, C.; Fonte, A.; Ortiz Sánchez, MC.; Torregrosa, A. (2021). Yield and Economic Results of Dif-ferent Mechanical Pruning Strategies on "Navel Foyos" Oranges in the Mediterranean Area. Agriculture. 11(1):1-12. https://doi.org/10.3390/agriculture1101008211211

Preliminary evaluation of a blast sprayer controlled by pulse width modulated nozzles

[EN] Precision spraying relies on the response of the spraying equipment to the features of the targeted canopy. PWM technology manages the flow rate using a set of electronically actuated solenoid valves to regulate flow rate at the nozzle level. Previous studies have found that PWM systems may deliver incorrect flow rates. The objective of the present study was to characterize the performance of a commercial blast sprayer modified with pulse-width-modulated nozzles under laboratory conditions, as a preliminary step before its further field validation. Four different duty cycles (25 percent, 50 percent, 75 percent and 100 percent) and four different pressures (400 kPa, 500 kPa, 600 kPa and 700 kPa) were combined to experimentally measure the flow rate of each nozzle. Results showed that the PWM nozzles mounted in the commercial blast sprayer, under static conditions, were capable of modulating flow rate according to the duty cycle. However, the reduction of flow rates for the tested duty cycles according to pressure was lower than the percentage expected. A good linear relation was found between the pressure registered by the control system feedback sensor and the pressure measured by a reference conventional manometer located after the pump. High-speed video recordings confirmed the accurate opening and closing of the nozzles according to the duty cycle; however, substantial pressure variations were found at nozzle level. Further research to establish the general suitability of PWM systems for regulating nozzle flow rates in blast sprayers without modifying the system pressure still remains to be addressed.This research was funded by the Government of Spain through the project "Smart spraying for a sustainable vineyard and olive trees" PIVOS (PID2019-104289RB).Ortí García, E.; Cuenca, A.; Pérez Teruel, M.; Torregrosa, A.; Ortiz Sánchez, MC.; Rovira Más, F. (2022). Preliminary evaluation of a blast sprayer controlled by pulse width modulated nozzles. Sensors. 22(13):1-12. https://doi.org/10.3390/s22134924112221

A new internal quality index for mango and its predicción by external visible and near-infrared reflection spectroscopy

[EN] A non-destructive method based on external visible and near-infrared reflection spectroscopy for determining the internal quality of intact mango cv. ‘Osteen’ was investigated. An internal quality index, well correlated with the ripening index of the samples, was developed based on the combination of a biochemical property (total soluble solids) and physical properties (firmness and flesh colour) of mango samples. The diffuse reflectance spectra of the samples were recorded and used to predict the internal quality and the ripening index. These spectra were obtained using different spectroscopic external measurement sensors involving a spectrometer, capable of measuring in different spectral ranges (600– 1100 nm and 900–1750 nm), and also a spectrocolorimeter that measured in the visible range (400– 700 nm). Three regression models were developed by partial least squares to establish the relationship between spectra and indices. Good results in the prediction of internal quality of the samples were obtained using the full spectral range (Rp 2 = 0.833–0.879, RMSEP = 0.403–0.507 and RPD = 2.341–2.826) and some selected wavelengths (Rp 2 = 0.815–0.896, RMSEP = 0.403–0.537 and RPD = 2.060–2.905). The results obtained from this study revealed that external visible and near-infrared reflection spectroscopy can be used as a non-destructive method to determine the internal quality of mango cv. ‘Osteen’.This work was partially funded by the Conselleria d' Educació, Investigació, Cultura i Esport, Generalitat Valenciana, through the project AICO/2015/122 and by the INIA through the projects RTA2012-00062-C04-01, 02 and 03 with the support of FEDER funds. V. Cortés López thanks the Spanish MEC for the FPU grant (FPU13/04202).Cortés López, V.; Ortiz Sánchez, MC.; Aleixos Borrás, MN.; Blasco Ivars, J.; Cubero García, S.; Talens Oliag, P. (2016). A new internal quality index for mango and its predicción by external visible and near-infrared reflection spectroscopy. Postharvest Biology and Technology. (118):148-158. doi:10.1016/j.postharvbio. 2016.04.011S14815811

Optimised computer vision system for automatic pre-grading of citrus fruit in the field using a mobile platform

The mechanisation and automation of citrus harvesting is considered to be one of the best options to reduce production costs. Computer vision technology has been shown to be a useful tool for fresh fruit and vegetable inspection, and is currently used in post-harvest fruit and vegetable automated grading systems in packing houses. Although computer vision technology has been used in some harvesting robots, it is not commonly utilised in fruit grading during harvesting due to the difficulties involved in adapting it to field conditions. Carrying out fruit inspection before arrival at the packing lines could offer many advantages, such as having an accurate fruit assessment in order to decide among different fruit treatments or savings in the cost of transport and marketing non-commercial fruit. This work presents a computer vision system, mounted on a mobile platform where workers place the harvested fruits, that was specially designed for sorting fruit in the field. Due to the specific field conditions, an efficient and robust lighting system, very low-power image acquisition and processing hardware, and a reduced inspection chamber had to be developed. The equipment is capable of analysing fruit colour and size at a speed of eight fruits per second. The algorithms developed achieved prediction accuracy with an R-2 coefficient of 0.993 for size estimation and an R-2 coefficient of 0.918 for the colour index.This research work has been funded by the Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria de Espana (INIA) and the European FEDER funds (projects RTA2009-00118-C02-01 and RTA2009-00118-C02-02). The authors wish to thank the collaboration of the company Argiles Diseny i Fabricacio, S.L.Cubero García, S.; Aleixos Borrás, MN.; Albert Gil, FE.; Torregrosa, A.; Ortiz Sánchez, MC.; García Navarrete, OL.; Blasco Ivars, J. (2014). Optimised computer vision system for automatic pre-grading of citrus fruit in the field using a mobile platform. Precision Agriculture. 15(1):80-94. doi:10.1007/s11119-013-9324-7S8094151Baeten, J., Donné, K., Boedrij, S., Beckers, W., & Claesen, E. (2008). Autonomous fruit picking machine: A robotic apple harvester. Springer Tracts in Advanced Robotics, 42, 531–539.Blasco, J., Aleixos, N., Gómez-Sanchis, J., & Moltó, E. (2009a). Recognition and classification of external skin damage in citrus fruits using multispectral data and morphological features. Biosystems Engineering, 103, 137–145.Blasco, J., Aleixos, N., Roger, J. M., Rabatel, G., & Moltó, E. (2002). Robotic weed control using machine vision. Biosystems Engineering, 83(2), 149–157.Blasco, J., Cubero, S., Gómez-Sanchis, J., Mira, P., & Moltó, E. (2009b). Development of a machine for the automatic sorting of pomegranate (Punica granatum) arils based on computer vision. Journal of Food Engineering, 90, 27–34.Chong, V. K., Monta, M., Ninomiya, K., Kondo, N., Namba, K., Terasaki, E., et al. (2008). Development of mobile eggplant grading robot for dynamic in-field variability sensing––manufacture of robot and performance test. Engineering in Agriculture, Environment and Food, 1(2), 68–76.Coppock, G. E., & Jutras, P. J. (1960). Mechanizing citrus fruit harvesting. Transactions of the ASAE, 3(2), 130–132.Cubero, S., Aleixos, N., Moltó, E., Gómez-Sanchis, J., & Blasco, J. (2011). Advances in machine vision applications for automatic inspection and quality evaluation of fruits and vegetables. Food and Bioprocess Technology, 4(4), 487–504.Cubero, S., Moltó, E., Gutiérrez, A., Aleixos, N., García-Navarrete, O. L., Juste, F., et al. (2010). Real-time inspection of fruit on a mobile harvesting platform in field conditions using computer vision. Progress in Agricultural Engineering Science, 6, 1–16.DOGV. (2006). Diari Oficial de la Comunitat Valenciana, 5346, 30321–30328.Edan, Y., Rogozin, D., Flash, T., & Miles, G. E. (2000). Robotic melon harvesting. IEEE Transactions on Robotics and Automation, 16(6), 831–834.Ehsani, M. R., Grift, T. E., Maja, J. M., & Zhong, D. (2009). Two fruit counting techniques for citrus mechanical harvesting machinery. Computers and Electronics in Agriculture, 65(2), 186–191.Feng, G., Qixin, C., & Masateru, N. (2008). Fruit detachment and classification method for strawberry harvesting robot. International Journal of Advanced Robotic Systems, 5(1), 41–48.Gómez-Sanchis, J., Gómez-Chova, L., Aleixos, N., Camps-Valls, G., Montesinos-Herrero, C., Moltó, E., et al. (2008). Hyperspectral system for early detection of rottenness caused by Penicillium digitatum in mandarins. Journal of Food Engineering, 89(1), 80–86.HunterLab. (2008). Applications note, 8(9) http://www.hunterlab.com/appnotes/an08_96a.pdf . Accessed Nov 2012.Jiménez-Cuesta, M.J., Cuquerella, J., & Martínez-Jávega, J.M. (1981). Determination of a color index for citrus fruit degreening. In: Proceedings of the International Society of Citriculture, Tokyo (Japan), vol. 2 (pp. 750–753).Jutras, P.J., & Coppock, G.E. (1958). Mechanization of citrus fruit picking. Florida State Horticultural Society, 71, 201,204.Kohno, Y., Kondo, N., Iida, M., Kurita, M., Shiigi, T., Ogawa, Y., et al. (2011). Development of a mobile grading machine for citrus fruit. Engineering in Agriculture, Environment and Food, 4(1), 7–11.Kondo, N. (2009). Robotization in fruit grading system. Sensors and Instrumentation for Food Quality, 3, 81–87.Lee, W. S., & Slaughter, D. C. (2004). Recognition of partially occluded plant leaves using a modified Watershed algorithm. Transactions of the ASAE, 47, 1269–1280.Lee, W. S., Slaughter, D. C., & Giles, D. K. (1999). Robotic weed control system for tomatoes. Precision Agriculture, 1(1), 95–113.Li, Z., Li, P., & Liu, J. (2011). Physical and mechanical properties of tomato fruits as related to robot harvesting. Journal of Food Engineering, 103(2), 170–178.Lorente, D., Aleixos, N., Gómez-Sanchis, J., Cubero, S., García-Navarrete, O. L., & Blasco, J. (2012). Recent advances and applications of hyperspectral imaging for fruit and vegetable quality assessment. Food and Bioprocess Technology, 5(4), 1121–1142.Mazzetto, F., Calcante, A., Mena, A., & Vercesi, A. (2010). Integration of optical and analogue sensors for monitoring canopy health and vigour in precision viticulture. Precision Agriculture, 11(6), 636–649.McBratney, A., Whelan, B., Ancev, T., & Bouma, J. (2005). Future directions of precision agriculture. Precision Agriculture, 6(1), 7–23.Mizushima, A., & Lu, R. (2011). Cost benefits analysis of in-field presorting for the apple industry. Applied Engineering in Agriculture, 27(1), 33–40.Muscato, G., Prestifilippo, M., Abbate, N., & Rizzuto, I. (2005). A prototype of an orange picking robot: Past history and experimental results. Industrial Robot, 32(2), 128–138.Nieuwenhuizen, A. T., Hofstee, J. W., & van Henten, E. J. (2010). Adaptive detection of volunteer potato plants in sugar beet fields. Precision Agriculture, 11, 433–447.Official Journal of European Communities. (2001). 14.09.2001. pp. L244/12–L244/18. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2001:244:0012:0018:EN:PDF . Accessed May 2013.Ortiz, C., Blasco, J., Balasch, S., & Torregrosa, A. (2011). Shock absorbing surfaces for collecting fruit during the mechanical harvesting of citrus. Biosystems Engineering, 110, 2–9.Qiao, J., Sasao, A., Shibusawa, S., Kondo, N., & Morimoto, E. (2004). Mobile fruit grading robot (part1)––Development of a robotic system for grading sweet peppers. Journal of the Japanese Society of Agricultural Machinery (JSAM), 66(2), 113–122.Qiao, J., Sasao, A., Shibusawa, S., Kondo, N., & Morimoto, E. (2005). Mapping yield and quality using the mobile fruit grading robot. Biosystems Engineering, 90(2), 135–142.Ruiz-Altisent, M., Ortiz-Cañavate, J., & Valero, C. (2004). Fruit and vegetables harvesting systems. In: R. Dris and S. M. Jain (Eds.), Production practices and quality assessment of food crops, vol. 1: Preharvest practice (pp. 261–285). Dordrecht: Kluwer.Torregrosa, A., Gil, J., Ortiz, C., Ortí, E., & Martín, B. (2009). Mechanical harvesting of oranges and mandarins in Spain. Biosystems Engineering, 104(1), 18–24.Vidal, A., Talens, P., Prats-Montalbán, J. M., Cubero, S., Albert, F., & Blasco, J. (2012). In-line estimation of the standard colour index of citrus fruits using a computer vision system developed for a mobile platform. Food and Bioprocess Technology,. doi: 10.1007/s11947-012-1015-2