Citrus trees are used as ornamental plants in several Spanish cities. They give a nice color to the streets and a nice scent in the flowering stage, but when the fruits fall, they dirty the roads and pavements, and can cause accidents; this is the reason why gardeners must detach and collect the fruits. This task is being done manually, but it is quite inefficient and expensive. In this study, three types of machines have been used to mechanize this task: a trunk shaker with umbrella, a trunk shaker hitched to an orchard tractor, and an experimental smaller sized shaker that can be attached to small and pedestrian tractors. The shaking patterns used by each equipment, detachment percentages, mobility constraints, and tree damage have been measured, and reduction costs have been estimated. After three years of study, the system has been fully accepted by both gardeners and citizens.

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.

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.

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 detached.

The profitability of fresh citrus crops outlines the possibility of using mechanical systems to reduce the high cost of the manual harvesting operation. In this line, an experimental light shaker with low frequency and high amplitude and a hydraulic arm was developed. This device had been successfully used for harvesting ornamental citrus trees. In previous studies, it was proven that the removal percentage was adequate, but the percentage of slightly damaged fruit increased compared to a traditional fruit trunk shaker. Visualizing the fruit movements in high-speed video recording images during harvesting, a higher impact level was observed due to the higher amplitude. The aim of this study was to analyze the fruit movement during the vibration with the experimental shaker compared to the movement when vibrating with an orchard tractor mounted trunk shaker related to the increase of slightly damaged fruit when using the experimental shaker. Fruit movement parameters (fruit distance, fruit displacement, speed and acceleration) when using the two harvesting systems (experimental shaker and trunk shaker) were compared analyzing the high-speed video recordings. Results showed that the higher vibration amplitude produced a maximum distance experienced by the fruits (maximum displacement of 0.135 m with the experimental shaker compared to 0.078 m with the trunk shaker) that could cause a higher damage level (74% of slightly damaged fruits using the experiemntal shaker compared to 14% using the trunk shaker).

The flowrate control of spraying systems with pulse-width-modulated solenoid valves is currently being implemented for precision herbicide application in commodity crops, but solutions for fruit trees set in orchards that require higher pressures are mostly in the development stage. A reason for this has been the higher flowrate and pressure requirements of blast sprayers used for dense canopies typical of high value crops. In the present study, the duty cycles preset by an operator were compared to the actual ones estimated from measuring flowrates. A new developed air-assisted orchard sprayer with shelf hollow disc-cone nozzles was studied, such that flowrates and pressures were registered by a computer for different duty cycles commanded by an operator from 10% to 100% in intervals of 10%. In addition to sensor data, visual assessment was carried out via high-speed video images. The results showed that preset duty cycles were always more than 10% lower than the actual DC estimated from measured flowrates. The effective operational range of the duty cycles went from 20% to 80%. In general, the deviations in transitional periods were higher for lower duty cycles, being difficult to determine the real reduction in flowrate during the transition periods. A correction model has been proposed to adjust the preset duty cycles to make sure that the necessary spray flowrate is released as precisely commanded by prescription maps. Further research will be needed to verify the proper implementation of the developed correction model in field applications.