Monitoring Crop Evapotranspiration and Crop Coefficients over an Almond and Pistachio Orchard Throughout Remote Sensing

In California, water is a perennial concern. As competition for water resources increases due to growth in population, California’s tree nut farmers are committed to improving the efficiency of water used for food production. There is an imminent need to have reliable methods that provide information about the temporal and spatial variability of crop water requirements, which allow farmers to make irrigation decisions at field scale. This study focuses on estimating the actual evapotranspiration and crop coefficients of an almond and pistachio orchard located in Central Valley (California) during an entire growing season by combining a simple crop evapotranspiration model with remote sensing data. A dataset of the vegetation index NDVI derived from Landsat-8 was used to facilitate the estimation of the basal crop coefficient (Kcb), or potential crop water use. The soil water evaporation coefficient (Ke) was measured from microlysimeters. The water stress coefficient (Ks) was derived from airborne remotely sensed canopy thermal-based methods, using seasonal regressions between the crop water stress index (CWSI) and stem water potential (Ψstem). These regressions were statistically-significant for both crops, indicating clear seasonal differences in pistachios, but not in almonds. In almonds, the estimated maximum Kcb values ranged between 1.05 to 0.90, while for pistachios, it ranged between 0.89 to 0.80. The model indicated a difference of 97 mm in transpiration over the season between both crops. Soil evaporation accounted for an average of 16% and 13% of the total actual evapotranspiration for almonds and pistachios, respectively. Verification of the model-based daily crop evapotranspiration estimates was done using eddy-covariance and surface renewal data collected in the same orchards, yielding an R2 ≥ 0.7 and average root mean square errors (RMSE) of 0.74 and 0.91 mm·day−1 for almond and pistachio, respectively. It is concluded that the combination of crop evapotranspiration models with remotely-sensed data is helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions

Integral olive harvesting systems: characterization, adjustment and improvements

La presente tesis doctoral aborda el estudio conjunto de la recolección mecanizada y la poda del olivo para mejorar el uso de las cosechadoras, actuales y en desarrollo, por medio de la adaptación del árbol y el diseño de la plantación. Se han considerado tres de las principales tipologías de cultivo del olivo presentes en España: tradicional, intensivo y superintensivo. Las adaptaciones del árbol a la máquina se han centrado en el olivar tradicional, ya que apenas se realizan nuevas plantaciones de esta tipología de cultivo, mientras que, el diseño de plantación se ha estudiado para el olivar superintensivo, En caso del olivar intensivo se han tenido en cuenta ambos factores. Para determinar la influencia del diseño de plantación sobre el funcionamiento de las cosechadoras de olivar se ha desarrollado un sistema de seguimiento remoto y una metodología de análisis de tiempos, junto con un monitor de rendimiento. Estos desarrollos han permitido la obtención y análisis de un gran volumen de datos para tres cosechadoras comerciales de olivar. En cuanto a la adaptación del árbol a las cosechadoras, se ha estudiado la distribución de la producción de aceite en la copa del árbol, tanto en calidad como en cantidad, para establecer las zonas prioritarias donde debe actuar un sistema de recolección mecanizada. Además, se han establecido tres tratamientos de poda para evaluar la adaptación del olivar tradicional a la recolección con cosechadoras, tanto actuales como en desarrollo. La caracterización de la estructura del árbol se ha completado con una metodología para evaluar la porosidad de copa basada en la radiación transmitida. Finalmente, a nivel de fruto se ha determinado el efecto que genera la aplicación de esfuerzos torsores en el pedúnculo del fruto, de cara a mejorar el porcentaje de derribo que podría obtenerse con una cosechadora en futuros desarrollos. Actualmente, el olivar superintensivo cuenta con un sistema de cosecha muy eficiente y con una alta capacidad de trabajo, aunque sensible a distintos parámetros de diseño de la plantación como son el ancho de calle de servicio o la longitud de línea de árboles. Al igual que el olivar superintensivo, las explotaciones intensivas requieren una adaptación del árbol a la cosechadora, mientras que el sistema de derribo se diseña para obtener una mayor eficiencia en aquellas zonas de la copa de mayor interés, como la zona exterior y superior del árbol. Del mismo modo, el olivar tradicional requiere una adaptación importante de la estructura del árbol para mejorar la eficiencia de la cosechadora. La adaptación de la estructura del árbol no ha influido en la producción de frutos en el periodo estudiado. Sin embargo, en algunos casos se ha producido una reducción de la producción de frutos en zonas de la copa que son difícilmente accesibles para algunos sistemas de derribo, como ocurre con la producción de las ramas interiores. Todo ello, a pesar de que la aplicación de diferentes tratamientos de poda si ha generado diferencias en la porosidad de la copa y, por lo tanto, en la radiación transmitida. Por último, se ha determinado que es recomendable generar giros superiores a 180º en los frutos para facilitar su desprendimiento, variando los resultados en función de la variedad.This doctoral thesis addresses the related studies of mechanised olive harvesting and pruning of olive trees, in order to improve their use by present and developing harvesters, through the adaptation of the tree and the layout of the orchard. In the research, the three main orchard categories currently in use in Spain have been considered: traditional, intensive and super high density olive orchards. On one hand, the adaptation of the tree to the harvester by pruning has been focused in traditional orchards, since very few new orchards are planted in this way. On the other hand, orchard layout was mainly considered for super high density orchards: whilst for intensive orchards, both factors were studied. A remote tracking system, a time elements methodology and a yield monitor were developed for the study of olive harvesters. Using these devices, a large data set from three olive harvesters was gathered and analysed. This data set was used to assess the influence of orchard layout on harvesting performance. Regarding the adaption of the tree to the harvesting system, the distribution of olive oil yield in the tree canopy has been studied – regarding quality as much as quantity – in order to establish a system to increase harvesting efficiency. Furthermore, three pruning treatments were tested, in order to evaluate the adaptation of traditional olive trees to different harvesting systems. A methodology for the measurement of olive tree crown porosity was developed and tested, based on radiation transmittance, in order to describe olive tree structure. Finally, the effects of twisting forces on fruit stalks were assessed in order to improve harvesting efficiency for further harvester developments. Currently, super high density olive orchards have an efficient and highly effective harvesting system, although this is influenced by orchard layout, mainly alley width and row length. The adaptation of trees to the harvester is required by both super high density and intensive olive orchards. Furthermore, the fruit detachment system should be designed to obtain high harvesting efficiency in those canopy areas which are more productive to harvest, such as the outer canopy and upper canopy. In the same way, traditional olive trees require important adaptations in order to increase harvesting efficiency, although it was found that debris production is not related to pruning treatments. Tree pruning did not influence the total fruit yield, although in some cases, fruit distribution has been modified by pruning, reducing yield within the inner canopy, which is more difficult to reach with some harvesting systems. Despite this, crown porosity and thus radiation transmittance were affected by pruning treatment. Finally, it was found that it is advisable to apply stalk twisting angles over 180 º in order to improve fruit detachment process although different cultivar behaviour was observed

Microclimate modification to improve productivity of ‘Carmen®-Hass’ avocado orchards using shadenet under subtropical conditions of Limpopo Province, South Africa.

Master of Agriculture in Agrometeorology. University of KwaZulu-Natal, Pietermaritzburg 2016.The agricultural environment is a complex and dynamic system. Microclimate, the crop, biosphere, and management practices interact to determine the best yield production. South Africa is a water-scarce country, with high variability in annual rainfall. Thus, water quality and quantity are major limiting factors in agriculture. Hence, shadenetting can be used to modify the orchard microclimate to make the environment more conducive for fruit production. The South African avocado industry is export-oriented, so there is a commercial need to optimise the exportable percentage of avocado fruit. Sunburn, wind and hail damage and small fruit size as a result of water stress are the major cull factors for the industry. It is believed that shadenetting, with changes in management practices, can counter these limiting factors. There is no literature on growing avocado fruit under shadenetting. Therefore, the aim of the research was to determine the effects of a 20% white shadenet on ‘Carmen®-Hass’ avocado orchards and productivity. The long term objective is to improve avocado fruit quality and profitability in the Mooketsi Valley, Limpopo province, South Africa, a subtropical environment by reducing abiotic stress, particularly, solar irradiance, heat and wind. The trial was conducted at Goedgelegen Estate in the Mooketsi Valley on ‘Carmen®-Hass’ trees planted in 2007/8 season. A 1-ha shadenet structure (6 m high) was used, with 20% white shadenet over the roof and 40% green shadenet on the sides. Air and canopy temperature, relative humidity, wind speed, solar irradiance and leaf wetness duration (LWD) and sap flow were monitored at a sub-hourly rate. Evapotranspiration was calculated from the above mentioned parameters. Irrigation was monitored five times per week using tensiometers at 300- and 600-mm soil depths. The comparison between open and shadenet leaf areas showed that leaves in the open treatment were reduced as a result of the abiotic stress. Fruit water content under the shadenet compared to the open was greater, such enabled fruit under the shadenet to reach maturity two weeks earlier when compared with open treatment. Air and canopy temperature and relative humidity were slightly reduced under the shadenet, with the greatest difference occurring during the flowering period in mid-winter. The modification in air temperature and relative humidity was beneficial for bee activity and pollination in 2015 compared to the 2014 season. ‘Carmen®-Hass’ flowers in mid-winter when temperature conditions are not conducive for pollination. Canopy temperature was also reduced under shadenetting compared to the open treatment. The reduction was due to differences in tree density and the role that shadenetting plays. The infrared thermometer measurements were uniform with dense canopies compared to sparse tree canopies. The midday incoming solar irradiance was reduced by 18% under the shadenet compared to the open treatment. Calm conditions were experienced under the shadenet. Hence, windspeed was reduced to negligible levels. Also, the shadenet resist air flow to a certain height compared to the open treatment. LWD was extended by 12% under shadenet. An infestation of the insect pest citrus leaf roller (Archips occidentalis) caused severe damage to the fruit during the 2014/15 season due to the high plant density used. Significant results were that evapotranspiration was reduced by 14 and 29% less water was applied under the shadenet to maintain an adequate soil water content compared to the open treatment. Fruit reached minimum maturity two weeks earlier under shadenet compared to the open treatment. Fruit quality and pack-out were improved under the shadenet due to reduction in sunburn, wind damage and small fruit. But poor yields were experienced during the 2014 season due to poor bee activity, pollination and fruit size distribution were reduced under the shadenet compared to the open treatment. But following the improved bee activity in 2015, the 2016 normal season yield is likely to be improved under the shadenet than in the open treatment. Data collected in the Mooketsi Valley showed that 20% white shadenet has modified the microclimate and improved fruit quality. The water use under the shadenet was improved compared to the open treatment. But a thorough investigation on bee management under shadenet is required to optimise pollination in order to obtain greater yields under the shadenet

Monitoring crop evapotranspiration and crop coefficients over an almond and pistachio orchard throughout remote sensing

In California, water is a perennial concern. As competition for water resources increases due to growth in population, California’s tree nut farmers are committed to improving the efficiency of water used for food production. There is an imminent need to have reliable methods that provide information about the temporal and spatial variability of crop water requirements, which allow farmers to make irrigation decisions at field scale. This study focuses on estimating the actual evapotranspiration and crop coefficients of an almond and pistachio orchard located in Central Valley (California) during an entire growing season by combining a simple crop evapotranspiration model with remote sensing data. A dataset of the vegetation index NDVI derived from Landsat-8 was used to facilitate the estimation of the basal crop coefficient (Kcb), or potential crop water use. The soil water evaporation coefficient (Ke) was measured from microlysimeters. The water stress coefficient (Ks) was derived from airborne remotely sensed canopy thermal-based methods, using seasonal regressions between the crop water stress index (CWSI) and stem water potential (Ψstem). These regressions were statistically-significant for both crops, indicating clear seasonal differences in pistachios, but not in almonds. In almonds, the estimated maximum Kcb values ranged between 1.05 to 0.90, while for pistachios, it ranged between 0.89 to 0.80. The model indicated a difference of 97 mm in transpiration over the season between both crops. Soil evaporation accounted for an average of 16% and 13% of the total actual evapotranspiration for almonds and pistachios, respectively. Verification of the model-based daily crop evapotranspiration estimates was done using eddy-covariance and surface renewal data collected in the same orchards, yielding an R2 ≥ 0.7 and average root mean square errors (RMSE) of 0.74 and 0.91 mm·day−1 for almond and pistachio, respectively. It is concluded that the combination of crop evapotranspiration models with remotely-sensed data is helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions.info:eu-repo/semantics/publishedVersio

Feature Papers in Horticulturae Ⅱ

Horticultural research has been undergoing fundamental changes to improve crop plants as a result of the emergence of new biochemical and molecular techniques. In addition, integration of new technologies with the desire to develop more sustainable production systems has also spurred production level research. The highlighted Feature Papers here reflect the diversity of the types of research performed on horticultural plant species, spanning basic to applied studies, production systems, and postharvest studies, in addition to highlighting some critical issues facing horticultural plant species

Modelled agroforestry outputs at field and farm scale to support biophysical and environmental assessments

This report, comprising Deliverable 6.17, in the AGFORWARD project brings together examples of modelled outputs at field and farm scale to support the biophysical, social, and environmental assessment of the innovations selected from work-packages 2 to 5.N/

The partitioning of evapotranspiration in apple orchards from planting until full-bearing age and implications for water resources management

Philosophiae Doctor - PhDOrchard evapotranspiration (ET) is a complex flux which has been the subject of many studies. It often includes transpiration from the trees, cover crops and weeds, evaporation from the soil, mulches, and other orchard artefacts. Studies of evapotranspiration in orchards often quantify tree water use and soil evaporation, treating the water use from the understorey vegetation on the orchard floor as negligible. Therefore, there is a paucity of information; first about the water use of cover crops in general, and secondly about the contribution of cover crops to whole orchard ET. This information is important, especially in semi-arid regions like South Africa where water resources are already under great strain and the situation is predicted to worsen in future due to climate change

Agricultural Meteorology and Climatology

Agricultural Meteorology and Climatology is an introductory textbook for meteorology and climatology courses at faculties of agriculture and for agrometeorology and agroclimatology courses at faculties whose curricula include these subjects. Additionally, this book may be a useful source of information for practicing agronomists and all those interested in different aspects of weather and climate impacts on agriculture. In times when scientific knowledge and practical experience increase exponentially, it is not a simple matter to prepare a textbook. Therefore we decided not to constrain Agricultural Meteorology and Climatology by its binding pages. Only a part of it is a conventional textbook. The other part includes numerical examples (easy-to-edit worksheets) and recommended additional reading available on-line in digital form. To keep the reader's attention, the book is divided into three sections: Basics, Applications and Agrometeorological Measurements with Numerical Examples