Automation in Tree Fruit Production

Principles and Practice

Qin Zhang

• Publisher: CAB International
• Year: 2017
• Print ISBN: 9781780648507
• eBook ISBN: 9781780648521
• Topic: Technology & Engineering
• Subtopic: Agronomy
• Index: Technology & Engineering

The technology that allows automation in agriculture is rapidly developing and being applied to wide variety of key crops. This book focuses on automation in tree fruit crops worldwide. It covers topics such as automated tree fruit production systems, plant stress sensing and high-throughput phenotyping in precision horticulture, the economics of automation in tree fruit production, light interception sensing systems for canopy management, precision irrigation and water management, precision technologies for pest and disease management, opportunities for the application of robotics in tree fruit production, and the mechanical harvesting and handling of fruit crops.

1 Tree Fruit Production Automation

QIN ZHANG^*

Washington State University, Prosser, Washington, USA

^*[email protected]

1.1 Introduction

One solution for producing high-quality, high-yield fruit, with minimal dependence on seasonal human labor, is to create a means for automatous mechanized precision production in orchards. This involves three key technologies: agricultural automation; mechanization; and precision farming. Among them, mechanization and precision farming are at the core of a comprehensive system using automation technologies.

As one of the top-ranked engineering accomplishments of the 20th century, agricultural mechanization has made revolutionary changes in field crop production technology and made it possible to achieve high yields using minimal human labor to meet continuously growing needs for food, feed, fiber and fuel. To make machines operate efficiently, one feature of mechanized production is the uniformity of operation in a field. Even though tree fruit production is quite different from field crop production, many of the fundamental mechanization technologies for field crop production can be used directly or modified for use in tree fruit production. The uniformity of mechanized production increases efficiency at the expense of being able to respond to crop growth variabilities often caused by inter- or intra-field soil type, fertility and moisture variance.

Precision farming offers a management practice based on observing, measuring and responding to inter- and intra-field variability in crop growth, hoping to gain the highest possible either in yields or in economic returns or in both. The concept of performing field tasks precisely in response to crop growth is not new. Our ancestors exercised very small area-based, if not plant-based, precise farming practices in response to actual crop growth at the location for thousands of years in the past, manually. How to effectively integrate the capability of performing uniform operations with the need for responding to the natural variations in yield potential and/or crop growth is a new challenge to be solved by mechanized precision crop production.

Invented in the early 1980s in the USA, the concept of precision agriculture divides a large field into many small management zones, allowing performance of a field operation uniformly in a specific zone according to the yield potential or actual crop growth within that zone, resulting in responsive variable operations for the entire field. The core of this technology is a responsive farming management system based on observing, measuring and responding to inter- and intra-field variability in crops. This creative and innovative technology provided famers with a functional means to practice precise responsive field operations using uniformly implemented machines in large-scale mechanized precision crop production.

Crop growth usually varies both spatially and temporally in a field and mainstream farmers are trying to maximize their profits by spending money to perform their field operations only in the right place at the right time. Enabling farmers to perform their time-sensitive site-specific mechanized precision operations requires an effective tool to support farmers making operation decisions based on both spatial and temporal crop variabilities. Because crop growth is strongly correlated to soil properties, researchers at the University of Minnesota invented a method for making precise input recommendations for fertilizers and pH corrections for fixed grid areas in a field based on soil properties sampled from corresponding grids in the 1980s. Resulting from over 30 years of development since then, technology providers have introduced yield monitoring and soil-, plant- and pest-sensing technologies, combined with the advent of global positioning systems (GPS) technology, for acquiring critical data to uncover the variabilities in crops and/or soils, and display only the information needed to support decision making in the cab for the condition. Contributing to those accomplishments, the practice of precision crop farming has been gaining ground.

Although GPS and in-cab display technologies have played an important role in many precision farming systems, precision farming does not automatically happen when a GPS unit and an in-cab display are installed. It starts with farmers gaining a basic understanding of how they could more effectively manage their resource inputs in the field corresponding to soil types, field topography and hydrology, microclimates and crop stresses, and occurs over time as they adopt new tools and management strategies using detected and verified variance of yield-affecting factors within the fields to manage inputs precisely, enabling farmers to attain all promises of the technology by crunching massive data collected from their productions, as well as those similar to theirs, using big data technology to optimize their operations.

A few core technologies available today for precision crop production include GPS, soil sampling and remote sensing, yield monitoring and mapping, automated guidance and variable-rate input controls, and big data and decision making. Among those core technologies, some could be shared by many different applications other than precision crop production. For example, GPS is a critical element of modern information infrastructure, having numerous applications affecting almost every aspect of our life from car navigation to smartphone positioning, and boosts productivity across a wide swath of the global economy, including but not limited to farming, transportation, mining, mapping and surveying, package delivery and logistical supply-chain management. Big data and decision making are also in this category.

Some of those core technologies that are specifically developed for precision crop farming are yield monitoring and mapping, automated crop scouting, tractor guidance and variable rate (VR) input controls. Monitoring site-specific yields and recording the data using harvester-mounted yield-monitoring sensors is often the first step many farmers take in adopting precision farming technologies. Yield monitoring and mapping is the process specifically created for collecting georeferenced data on crop yield and characteristics, such as moisture content, while the crop is being harvested, and graphically presenting such data to show the intra-field variation in crop yield. Instantaneous yield monitors are currently available from various technology providers. Coupled with a GPS receiver, many of those yield monitors could provide spatial coordinates for collected yield data to generate yield maps automatically. Such data recorded in a yield map could be used to compare yield variations within a field from year to year, providing farmers with the necessary information to make decisions for effective site-specific precision management of their crops.

While the yield map could provide historic yield variations within a field, farmers often also need to know the actual crop growth conditions to make adequate precision operation decisions. Satellite-, aerial-, or tractor-based crop monitoring or scouting technologies provide farmers with the capability of obtaining adequate spatial and temporal resolution of field data for various precision agriculture applications. The availability of unmanned aerial systems (UAS) for agriculture could provide farmers with much more freedom to scout the crop, and allow them to collect field data many times during the season to support near real-time soil, crop and pest management.

Aimed at increasing efficiency of crop inputs utilization, reducing the adverse impact of over-application of inputs and maximizing production profitability, variable rate application (VRA) technology plays a key role in applying the right amount of crop inputs where and when it is needed, and forms one of the fundamental technologies specifically developed for precision crop production. VRA operation is, in general, implemented using mobile crop inputs application machinery: either a seeder, a sprayer/applicator, or an irrigator, equipped with a VR input control system to change the application rate in a site-specific application. A typical VR control system often consists of a differential GPS (DGPS) receiver, a prescription map of inputs, some VR control software, and actuating controllers to make it work. A broader definition of VRA could also include targeted applications that apply the inputs accurately where the target has been detected, either at the same rate or a varying rate.

1.2 Precision and Automated Production for Tree Fruit

Tree fruit production is a highly competitive agricultural industry worldwide with growers seeking more effective methods to manage their orchard operations precisely, and automatically if possible, to remain competitive in the international market.

In principle, the precision crop production technologies developed for field crops could be adapted to tree fruit production; and precision tree fruit production is precision farming applied to enhance orchard performance by optimizing fruit yield and quality while minimizing adverse environmental impacts. It can also be accomplished by observing, measuring and responding to local variability in tree crops or soils in the hope of getting the desired yield of high-quality fruit. While it may require some adjustments or improvements to make it more fitting to tree fruit production, many of the existing precision agriculture sensing technologies developed for field crop production, including GPS, meteorological and other environmental sensors, satellite and airborne remote sensing, and geographic information systems (GIS), could easily be adopted to detect or assess the variability of factors that could influence fruit yield and quality (such as soil, topography, microclimate, plant nutrients, and water and disease stress). However, a few special sensing methods for obtaining some critical crop information that is unique in the precise management of tree fruit may be required. One example is the growing interest in measuring the amount of photosynthetic energy being absorbed by tree canopies at different times of day to support more adequate precise pruning of the trees. Another example is the use of soil, or even leaf, moisture sensors to support more efficient variable-rate irrigation to supply the trees with just the right amount of water and/or fertilizer, depending on what a particular plant needs.

Due to the morphologic and cultivation differences between tree fruit crops and field crops, some implementations in tree fruit precision farming practices could be quite different from those commonly seen in field crop farming. For example, training, pruning and thinning are some of the special and important operations only seen in tree fruit farming, requiring accurate and precise location and removal of certain branches, twigs, blossoms and/or green fruit from the trees in a precision operation. Different from conventional precision operations for field crop farming, the data required to support those operations in tree fruit farming are physical locations, sizes and orientations of objects of interest rather than the spatial or temporal variabilities of soils and plants. Therefore, different types of sensing technologies from that for conventional precision field crop farming will be needed for tree fruit farming. Meanwhile, some other implementations in tree fruit farming could be fairly similar to those of precise field crop farming in process, but require different mechanisms to fit the morphologic and cultivation features of tree crops. A few examples include irrigation, fertilization and pesticide applications. Those operations often need equipment specially designed for orchard use to perform the required precision implementations.

While harvest is an essential operation for all crops, the unpredictable distribution of fruit on trees, uneven maturity of the fruit and the high quality requirement of fruit harvested for the fresh market make mechanical fruit harvest a unique operation in precision and automated production. It is necessary to have not only adequate sensing technologies for reliably and accurately detecting the locations, sizes or even orientations of fruit on a tree, and to precisely assess multiple parameters of the fruit to determine if it is ready to be harvested, but also to have devices capable of removing the ready-to-pick fruit from the trees gently without inducing much mechanical damage to the harvested fruit. Such complicated requirements make mechanical harvesting one of the most challenging tasks in precision and automated production of tree fruit.

1.3 Special Issues for Precision and Automated Production of Tree Fruit

In general, the goal for performing precision and automated tree fruit production is the same as for field crop production, i.e. to implement an effective and sustainable management practice based on observing, measuring and responding to inter- and intra-field variability in crop growth in the hope of gaining the highest possible levels in either yield or economic returns, or both. However, it requires addressing a few specific, special challenges in production. One specific challenge is that a fruit tree is a perennial woody plant, and in general has an almost permanent trunk with a growing branch/twig structure, which could be described as a four-dimensional (4D) structure (a specific 3D trunk for individual trees, plus variations between trees and between different years). Another major challenge is the different operations required for tree fruit production as described in the previous section; and the third is the high sensitivity of the plant and the fruit to mechanical interaction. All these challenges create significant reluctance among tree fruit producers to adopt mechanization and automation technologies developed for field crops, resulting in a low level of mechanization in tree fruit production today. Some crop-specific issues need to be addressed for tree fruit automation, and this book intends to provide an overview on such crop-specific issues.

The low level of mechanization makes tree fruit production rely heavily on a large, seasonal semi-skilled workforce to perform many of the field operations such as training, pruning, thinning and harvesting, especially for fresh market fruit, creating one of the most critical labor-related risks of not having enough of the right people at the right time to perform time-sensitive field operations. However, when trying to decide on whether or not to use automated machinery and new technology in an operation, the cost will involve more than just purchasing the equipment; it will also require an initial adjustment for workers to learn to use the new technology and equipment. Not all technologies are feasible for all growers. The adoption of automation technologies for tree fruit may need to start with a techno-economic analysis, including not only the initial purchasing cost, but also the operation and maintenance costs.

Sensing is always an essential element in agricultural automation. In orchard automation, sensors are used to measure the microclimate, quantify tree-absorbed sunlight, detect fruit location in tree canopies and monitor fruit development, in addition to measuring soil properties and various crop stresses. Therefore, it can be expected that more types of different sensors will be used to obtain such additional information required in implementing tree fruit automation. While measurement could be accomplished using various types of mobile scouting platforms, it is also possible to set up wireless sensor networks permanently during the crop lifespan, due to the perennial nature of tree fruit. Scouting based on UAS (Fig. 1.1) could provide some attractive advantages over other scouting methods in orchard automation, including but not limited to: the capability of being deployed at almost any time, not limited by field accessibility as for ground-based scouting platforms; carrying adequate sensor(s) flying over the orchard canopy at different altitudes to get georeferenced data at either fixed or variable resolutions even within one flight; and finding a stressed area in an orchard and then going straight to the area to get more detailed data from that area. One fundamental requirement for the successful performance of an orchard automation system is that its sensing system must be able to measure the data accurately.

Fig. 1.1. An example of an unmanned helicopter scouting a commercial apple orchard in the Pacific Northwest region of USA.

As in any automation system, effective orchard automation relies on the ability to make correct operation decisions. Similar to precision field crop production management, precision orchard management also aims to increase the efficiency of crop inputs utilization, reduce the adverse impact of over-application of inputs, and maximize production profitability through harvest of more and better fruit; and all the operation decisions should aim to achieve those goals. Due to necessary differences in comparison with field operations, making appropriate decisions for tree pruning and training, irrigation scheduling and pest, disease and plant nutrition management, as well as crop load management, are required to implement orchard automation processes effectively and profitably.

As high-efficiency orchard systems have been proven to produce hig...

Table of contents

• Cover
• Half Title
• Title
• Copyright
• Contents
• Contributors
• 1. Tree Fruit Production Automation
• 2. The Economics of Perennial Crops’ Production Automation
• 3. Sensing for Stress Detection and High-throughput Phenotyping in Precision Horticulture
• 4. Light Interception and Canopy Sensing for Tree Fruit Canopy Management
• 5. Precision Orchard Systems
• 6. Variable Rate Irrigation on Center Pivots
• 7. Precision Technologies for Pest and Disease Management
• 8. Precision Nutrient Management
• 9. Precise Crop Load Management
• 10. Mechanical Harvest and In-field Handling of Tree Fruit Crops
• 11. Opportunity of Robotics in Precision Horticulture
• Index
• Back Cover