Canopy Row Research Articles

Intelligent Sprayer Spray Rates Optimization to Efficiently Apply Chemicals in Modern Apple Orchards

Highlights Intelligent sprayers require crop canopy-specific base spray rate (SR) adjustments. SRs can be estimated by Tree Row Volume (TRV) and Unit Canopy Row (UCR) methods. This study formulated TRV and UCR based SRs for modern apple orchard canopies. Field trials evaluated spray deposition and coverage variations for these rates. TRV and UCR based treatments had comparable spray performance to the grower-adapted application rate. Abstract. The efficiency of air-assisted sprayer-based chemical applications in horticultural crops is dependent on several factors, including that of the application rate as the amount of liquid per ground area (L ha-1 or gal acre-1 [GPA]). In contrast to the conventional GPA-based application rates, recently developed intelligent and precision sprayers use the input spray rate (SR) as the amount of liquid volume (L) required to spray one cubic meter of crop canopy (L m-3 or ounces per cubic foot). This input rate ranges between 0.06 and 0.13 L m-3 depending on the architecture and canopy size. However, the exact value of input SR is decided based on grower experience and manufacturer recommendation and can often be a broad estimation. Therefore, this study was conducted to explore methods that could be used to have a precise estimate of the input SR related to the canopy being sprayed for optimal spray applications. Tree row volume (TRV) and unit canopy row (UCR) methods were used to estimate input SRs and the sprayer field efficiency was evaluated in a vertical fruiting wall-trained commercial apple orchard, typical in the State of Washington, USA. Field spray trials were conducted in the full canopy growth stage, spraying a mix of fluorescent tracer dye of 2 g L-1 concentration at a calibration speed of 1.50 m s-1. Spray deposition and coverage were evaluated in replicated field trials using deposit samplers (mylar cards and screen) and water-sensitive papers, respectively. Test results demonstrated that both TRV (SR: 0.09 L m-3) and UCR (SR: 0.10 L m-3) were effective methods to calculate the spray rates since their spray deposition and coverage were comparable to that of the grower-adapted application rate (935 L ha-1). While the spray rates calculated by both methods provided better application efficiency, an SR of 0.09 L m-3 calculated by the TRV method would be preferable in spray applications of fully foliated fruiting wall-trained apple trees as it sprayed less liquid. Although the TRV method could potentially be applicable for estimating SR with an adjustment factor to compensate for the pruning level, crop-specific further evaluations are suggested for different canopy training systems. Keywords: Intelligent sprayer, Modern orchard systems, Spray rate, Tree row volume, Unit canopy row.

Assessing the Potential of Fully Polarimetric Mono- and Bistatic SAR Acquisitions in L-Band for Crop and Soil Monitoring

Theoretical studies have shown that the use of simultaneous mono- and bistatic synthetic aperture radar (SAR) data could be beneficial to agriculture and soil moisture monitoring. This study makes use of extensive ground-truth measurements and synchronous high-resolution fully polarimetric mono- and bistatic airborne SAR data in L-band to assess and compare the sensitivity of mono- and multistatic systems to the maize canopy row structure and biophysical variables, as well as to soil moisture and surface roughness in both vegetated and bare fields. The effect of the row structure of maize crops is assessed through the impact of the orientation of the planting rows relative to the sensor beam on microwave scattering measurements. The results of this analysis suggest that the row orientation of maize crops has a significant influence on both mono- and bistatic scattering measurements in both copolarizations, and especially, in HH, while the cross polarizations are not affected. Furthermore, the study also shows through a linear regression analysis that bistatic data, even with a very small bistatic baseline, can provide valuable additional information for maize crop biophysical variable retrieval, which however does not appear to be the case for soil moisture retrieval over bare soils.

Dynamic evaluation of airflow stream generated by a reverse system of an axial fan sprayer using 3D-ultrasonic anemometers. Effect of canopy structure

Air assisted sprayers are currently used for the applications of plant protection products in fruit trees and vineyards. However, the use of these equipment carries a high environmental risk, mainly owing to the generation of airborne spray drift in the lower boundary layer above crop canopy. Hence, many tests are currently focused on investigating several factors that affect the efficiency of the spray process, in which air assistance and air behaviour are two of the most difficult parameters to evaluate. This present work proposes a first approach on the characterization of the airflow generated by an orchard sprayer equipped with an axial fan and an air reverse system in the outlet plane of the air, while circulated through two artificial rows of canopy representing vineyard trellis, using 3D-ultrasonic anemometers to measure the experimental data. A first series of static field tests measured the air velocity at different heights on both sides of the sprayer and at both sides of every row of artificial canopy and evaluated the effect of the canopy on the sprayer airflow passing through. A second set of experiments were carried out with the sprayer moving at 4.1 km h−1 between canopy rows to simulate the normal spray process. Finally, velocity vectors and turbulent intensities were calculated. The resistance of the vegetation was also characterized by using a drag coefficient, both when the sprayer was stationary and moving. The results between the static and dynamic tests were compared. Although there were similarities between the two tests, the results indicated that when the equipment moves along the canopy rows, the axial fan asymmetry on air velocities is more noticeable and turbulence intensity increased. In addition, the vegetation received direct airflow at different times. This could affect the trajectory of the droplets. On the other hand, the resistance of the vegetation on each side was similar. The air reverse system could be affecting the airflow direction to the driving direction. Ultrasonic anemometers were successful in characterizing sprayer fan airflows but it is necessary to continue working on the descriptive analysis of the airflow in other planes different from the air outlet only and with other vineyard systems.

The Planar Cordon – new planting systems concepts to improve light utilisation and physiological function to increase apple orchard yield potential

Contemporary high density apple orchards, although very productive in historical terms, are yield-limited at 100-120 t ha(-1) because their maximum fractional utilisation of sunlight is only circa 60% of total seasonally-available radiation. Previous research in New Zealand proposed a theoretical potential productivity of 169 t ha(-1) for late-season cultivars if orchard light interception of 90% could be achieved. A major constraint to improving light interception by planting systems is the allocation of space between rows. Any increase in light utilisation will require closer rows and/or inclined canopies. New planting systems to increase light interception by reducing inter-row distances, whilst achieving adequate within-canopy irradiance for high quality fruit, are being studied in New Zealand. Rows spaced at 1.5 to 2 m apart require new tree forms with narrow planar canopies for both eco-physiological and practical reasons. Tree architecture comprises two opposing, not-quite horizontal cordon leaders along the row, each subtending five vertical non-branched fruiting stems, 30 cm apart, to create narrow planar trees, 3 m long, less than 0.5 m wide, and with an anticipated height of 3-3.5 m. Four cultivars in a first prototype, planted at 1667 (2 m inter-row) and 2222 (1.5 m inter-row) trees ha(-1) yielded from 9 to 29 t ha-1 in their second year. Fractional light interception of 2- and 3-year-old plantings characterised young-tree planar cordon canopy row spacing effects, in comparison with a same-aged 1.5×3.5 m tall spindle system. Productivity traits from 3-year-old systems planted at 1.5 and 2 m row spacing and between vertical and narrow vee planar canopy variants of two-year-old planting systems indicate productivity gains over the three-dimensional tall spindle canopy configuration. In additional to light interception, these results also indicate that growth processes regulating the allocation fate of annual growth resources are important factors determining the productivity potential of apple orchards. Evidence for plasticity of resource partitioning into fruit development in response to different manipulations of tree architecture are drawn from our studies of new planar cordon systems and with conventional tall spindle planting systems.

Thermal analysis of greenhouses installed under semi arid climate

The greenhouse design as well as the cover material properties in particular may strongly impact the greenhouse energy. To study the effect of these parameters, three typical unheated greenhouses equipped with rows of canopy were considered. Experiments were launched to establish the boundary conditions and validate the model. Two parametric studies were carried out: for the nocturnal period when the energy performance of each type of greenhouse was investigated, and for the diurnal period, when the sun path was simulated taking into account the type of the cover, its spectral optical and thermal properties. Results indicate that for the nocturnal period, the ambient air temperature in the tunnel and vertical wall greenhouse was relatively homogenous and warmer compared with the temperature distribution in the Venlo greenhouse. The plastic greenhouse, especially the tunnel one had better performances concerning the homogenization of the climate and the thermal energy storage. Concerning the diurnal period, and for both plastic greenhouses equipped with fully opened side vents, the air located between the rows of canopy and ground surfaces remained very slow, not exceeding 0.2 ms-1; for the Venlo glasshouse, the recirculation loop situated above the crop improved the air mixing and induced a good homogenization. Results indicate that the cover material with highest absorptivity, deteriorated the natural ventilation, increasing the air temperature by convection, and reduced the available Photosynthetically Active Radiation.

Numerical prediction of thermal environment and energy consumption of three different greenhouses under hot and semi-arid climate

The evaluation of the thermal performance of a greenhouse requires an understanding of the energy exchanges between its components. In recent years, Computational Fluid Dynamics (CFD) proved to be efficient to predict the microclimate inside greenhouses, but few CFD works analyzed hot and arid climatic conditions. The aim of the present study is to investigate the impact of such specific conditions prevailing in the southern Mediterranean basin considering three different unheated greenhouses equipped with rows of canopy (tunnel, Venlo and plastic vertical wall greenhouse). 2D simulations were conducted in order to estimate the influence of the greenhouse geometry and cover material on the energy balance, focusing in particular on the heat losses. To establish the boundary conditions and validate the model, experiments were launched inside the greenhouses. Simulations were conducted for two contrasted conditions: the nocturnal period when the energy performance of each type of greenhouse was investigated, and the diurnal period for which a solar day was simulated taking account of natural ventilation. A good agreement was found with experiments concerning the temperature profiles and the energy losses. The predicted stable flow patterns slightly differed from one greenhouse to another for each condition: during the night they all disclosed two convective loops sweeping the floor, rising along the middle of the greenhouse, cooling down along the roof and moving down along the sidewalls of the greenhouse, while during the day flow patterns were strongly impacted by the vent openings. The obtained values (temperature and velocity) were coherent with results found in the literature for different greenhouse types and sizes. The developed tool offers potential applications in research on greenhouse climate to assess different cover material performances. It could also be used to investigate the energy consumption and partition for different greenhouse shapes, different crop densities different growth stages.

Effect of the greenhouse design on the thermal behavior and microclimate distribution in greenhouses installed under semi‐arid climate

AbstractGreenhouse design and cover material properties may strongly impact greenhouse energy. To study the effect of these parameters, three typical unheated agricultural buildings equipped with rows of canopy were considered, and two‐dimensional simulations were conducted using the discrete ordinate model for simulating radiative transfers. Experiments were conducted to establish the boundary conditions and to validate the model. Two parametric studies were carried out: one for the nocturnal period when the energy performance of each type of greenhouse was investigated, and one for the diurnal period, when the sun path was simulated taking into account the type of the cover, its spectral optical and thermal properties. Results indicate that for the diurnal period, and for both plastic greenhouses equipped with fully opened side vents, the air located between the rows of canopy and ground surfaces remained very slow, not exceeding 0.2 m/s; for the Venlo glasshouse, the recirculation loop situated above the crop improved the air mixing and induced a good homogenization. Results also indicate that the cover material with the highest absorptivity, deteriorated the natural ventilation, increasing the air temperature by convection, enhancing local air temperature favoring the development of a secondary recirculation, and reduced the available photosynthetically active radiation. Concerning the nocturnal period, the ambient air temperature in the tunnel and in the vertical wall of the greenhouse was relatively homogenous and warmer than the temperature in the Venlo greenhouse. During the nocturnal period, the plastic greenhouse (in particular the one with the tunnel) performed better in regard to the homogenization of the climate and thermal energy storage.

Dosage Adjustment for Pesticide Application in Vineyards

Traditional pesticide application in grapevines causes large losses to the air and the ground, particularly in early to mid-season applications. Traditional application rates do not differ much according to the season. Canopy size varies as growers choose different row widths, varieties, and trellis designs; however, pesticide labels for vineyard sprays persist in using ground area based application rates. That is why dosage adjustments according to the canopy characteristics have been developed. In the trial described in this article, three adjustment methods, unit canopy row (UCR) (Australia), DOSAVIA (Spain and U.S.), and leaf wall area (LWA) (Germany and Belgium) are compared with traditional American application rates. This article presents the methodology and results of the study. In total, three trials were completed. Results demonstrated that at the early growth stage, deposits with the DOSAVIA and LWA methods were not significantly different from that of the traditional method, and deposits were not different from each other among DOSAVIA, LWA, and UCR (application rates were 327, 281, 234, and 187 L ha-1 for the traditional, LWA, DOSAVIA, and UCR methods, respectively). Concerning the uniformity of distribution, UCR achieved the best results in the early growth stage, followed by LWA. At the middle growth stage, LWA and the traditional method achieved similar results, while deposits using DOSAVIA and UCR were not significantly different. At the middle growth stage, the application rate was increased to 700 L ha-1 for the traditional method and to 560, 327, and 374 L ha-1, respectively, for LWA, DOSAVIA, and UCR. The application rate was increased significantly according to the hugely changed canopy size. The LWA method achieved the best results in terms of deposits and uniformity of distribution. At the late growth stage, the traditional method achieved the highest deposits, while LWA and DOSAVIA achieved similar deposits. The lowest deposits in the canopy occurred with DOSAVIA and UCR. The results showed a high potential for reducing application rates using alternative methods compared with the traditional method. This article discusses only the deposits and coverage rate. In the next few years, biological efficacy trials are planned to confirm the advantages of the selected dosage adjustment methods.

Modeling Thermal Stratification in Fan-Ventilated Greenhouses

A two-dimensional thermal model was developed to investigate the thermal stratification in fan-ventilated greenhouses. Model inputs include outside weather (air temperature, humidity, and solar radiation), geometric parameters of crop rows and leaf area index, greenhouse ground and roof temperatures, ventilation rate, and operation of evaporative cooling pads. Comparing predictions with observed data indicated that the air temperature and relative humidity were modeled at acceptable accuracies, with air temperature underpredicted by 1.3C and relative humidity overpredicted by 9%, on average for a planted greenhouse. For an unplanted greenhouse, the air temperature was predicted with an absolute error of 0.7C, while for relative humidity the absolute error was 3%. Vertical temperature variation, defined as maximum temperature minus minimum temperature at approximately the central location of greenhouse, was predicted with an absolute error of 0.1C and a relative absolute error of 10% for the planted greenhouse, while for an unplanted greenhouse it was 0.6C for the absolute error and 12% for the relative absolute error. Simulations with the model suggest that increasing ventilation rate reduced the vertical temperature gradient. Increased ventilation reduced air temperature more at the top than the bottom of the greenhouse. Greater air temperature variation was produced when using evaporative pad cooling than not. Air temperature was reduced more at the bottom than at the top with evaporative pad cooling. The presence of a canopy altered the vertical air temperature distribution and reduced the temperature variation. A sample simulation showed that on a typical summer day at Raleigh, North Carolina, the presence of a canopy row with a height of 1.75 m occupying 69% of the ground area reduced the air temperature variation from 11.5C to 1.8C in a fan-ventilated greenhouse operating with a ventilation rate of 0.087 m3 m-2 s-1 and using evaporative pad cooling. The peak air temperature generally occurred at the top of canopy or somewhat below the canopy top. This finding may have some significance in establishing the location of temperature control sensors in future control systems.

DEPOSITION ANALYSIS OF SEVERAL APPLICATION VOLUMES OF PESTICIDES ADAPTED TO THE GROWTH OF A GREENHOUSE TOMATO CROP

For the calculation of the pesticide-application volume in a greenhouse tomato crop, four spray tests have been made in different states of crop growth. For this, the spray tests were conducted sequentially with three application volumes for each growth stage. The tracers used were tartrazine, indigo carmine, and patent blue. For the characterization of crop canopy, the evolution of its growth were studied, measuring LAI (Leaf Area Index), which ranged from 0.68 and 3.16 m·m, and the geometric parameters that define the volume of the vegetation, in order to calculate the TRV (Tree Row Volume) and UCR (Unit Canopy Row). The tests were made with a vertical boom sprayer equipped with a variable number of flat fan nozzles, depending on the height of the crop. LAI was used to calculate the theoretical application volume applying the method of the optimal coverage, spraying the theoretically optimal amount, in addition to 33 % more and 33% less. The deposition was measured at three heights and four depths in the canopy, with four replications per treatment. From the results, the standardized depositions were calculated, based on the amount of tracers per surface ground unit, in addition to identifying the most suitable application volume, based on the standardized deposition and the degree of its uniformity in the canopy. The TRV values calculated were related to those of the application volume that better standardized deposition offered obtaining a regression model with a R of 0.9.

Effects of Irrigation on Wine Grape Growth and Fruit Quality

Field studies were conducted to determine the effect of three drip irrigation regimes on grapevine growth, juice and wine quality, soil moisture, cold hardiness of bud and cane tissues and soluble sugar content of cortical cane tissues of Vitis vinifera, Linnaeus `Cabernet Sauvignon'. This study was developed to help provide some irrigation management strategies that would improve fruit quality and reduce excessive vigor. Irrigation treatments of 192, 96, and 48 L (51, 25, and 13 gal) per vine per week were initiated at bud break until veraison (initiation of berry color) and then reduced by 25% through harvest. Significant differences of fruit weight per vine, crop load, soil moisture, average berry and cluster weight, shoot length and pruning weight per meter of canopy row were observed among treatments. Juice and wine compositions and wine color were also significantly different; however, cold hardiness and soluble sugar contents did not differ between treatments.

Fruit tree and vine sprayer calibration based on canopy size and length of row: unit canopy row method

A sprayer calibration method for fruit trees and vines, based on height and width of canopy, and row length is presented. Using a unit canopy 1 m high × 1 m wide × 100 m of row length as the basis for calibration, means that area and row spacings are not required as parameters in the formulae. The whole approach is based on just one simple formula, which adjusts water volume to canopy size. Since the method adjusts spray volume and chemical dose more accurately without changing the average dose obtained on foliage, there are no changes in the information required for the registration of agricultural chemicals. The technique can be used with existing label information. However, for concentrate spraying recommendations, we propose that the industry work towards pesticide labels that provide chemical rates/100 m of unit canopy, and that rates/ha be deleted. The need for adjustments for canopy density, canopy type and sprayer type are also discussed. The method appears simpler and easier to understand than current tree-row-volume methods based on m 3 of canopy/ha, which have not been widely adopted.