Guidelines for construction of netting systems now available
Posted on: 18 May 2023
“The purpose of the Guidelines document is to make all parties aware of the different aspects and decisions that need to be addressed before selecting the relevant netting structure.” This is the view of Wouter Visser of FORE, a multi-disciplinary engineering firm specialising in engineering applications in the agricultural environment that played a major role in drafting The Best Practice Guideline for the Construction of Agricultural Netting Structures. The document, which has just been released, was commissioned by KAL Group and industry partners, and provides producers with useful guidelines for erecting netting structures in the fruit industry.
“The document also serves to confirm the responsibility of the various parties involved and to clarify who is responsible for the design, choice of materials, installation methods and the other actions involved,” said Stephan van Rensburg of ProPlast Nett.
He explained that a number of organisations in the industry embarked on a collaborative initiative to establish the Fruit Industry Netting Infrastructure Guidelines and Standards (FINIGAS). The objective of the FINIGAS investigation was to identify specific netting structure considerations that should be taken into account when erecting a netting structure, i.e. establishing guidelines and standards for industry best practice and risk mitigation. This led to the compilation of the Guidelines document.
PURPOSE OF DOCUMENT
The Guidelines document’s stated purpose is to assist in the design, construction, and quality control of agricultural netting systems to ensure that the owner receives the correct product for the desired purpose whilst reducing the potential risks related to structural failure and/or consequential damage to the crop and loss of crop yield.
Hannes Smit, senior manager of procurement at KAL Group, explained that the document should be used by producers as a guideline to ensure that the quotation they receive incorporates the minimum requirements of a netting structure.
“They should inform themselves of existing material standards for products used in agricultural netting structures, recommended practice and procedures, possible pitfalls, contractual responsibilities and obligations, and the importance of ongoing maintenance of the structure,” he said.
“It is correct to assume that the document is not binding to the various parties, and KAL Group will only register a contractor on our supplier list if he has agreed to follow these guidelines. In other words, we will not finance the construction work on behalf of the customer if it is not done according to the standards set out in the Guidelines document," Hannes reiterated.
BENEFITS TO END-USERS
Hannes emphasised that the main value of this document is to alert the prospective customer that the netting construction industry is currently still unregulated and that the process incorporates many aspects and dangers to be taken into consideration before one can safely construct this very expensive asset on a farm, with the expectation for it to last and protect crops against the elements. After all, the producer’s livelihood ultimately depends on it.
“Agricultural producers should not think about these guidelines as the alpha and the omega. Due to the huge variations in environment, soil type, topography, structural requirements, and crop diversity, there simply isn’t a one-size-fits-all solution, but at least it provides a very good guideline of the basic requirements that should be considered and applied when putting up such a structure.”
Prof. Paul Cronje, Portfolio Manager: Citriculture at Citrus Research International, agreed that the purpose of the Guidelines document is to assist producers who want to construct shade netting in fruit orchards with detailed information for them to be able to make complex decisions regarding the physical installation of these structures.
“The document did not focus on the nets themselves but concentrated on the structure over which the nets are fixed. The focus was on factors influencing the design, i.e. wind and soil conditions, as well as the materials used in the structure. It also addresses quality management during construction and continued maintenance.
“The value of this document is that it is the first document with independent information regarding the components and netting structures over fruit orchards which is approved by the agricultural engineering association (SAIAE). Following these guidelines can prevent serious mistakes and save costs for producers,” he said.
“Although there are design examples in the document that could lead the designer to incorporate certain design features, the Best Practice document is not a design handbook. Designs should always be managed by someone who is suitably qualified. In my experience with failed netting structures, in many cases the failure could have been avoided by following certain guidelines if all aspects regarding the erecting of nets were taken into consideration and thought-through decisions were taken,” Wouter said.
According to Wouter, the document provides uninformed users with enough information to enable them to ask the right questions. It also provides guidelines regarding the processes that should be followed for agricultural producers to reach the right conclusions and the best options for their specific needs.
SEPARATE CONTRACT NECESSARY
“Producers should note that the agreement with the contractors stipulating their participation is a separate document. There are no aspects in the Guidelines document that is binding on the customer, the contractor or the materials provided – these should all be included in detail in a separate agreement. The Guidelines document provides a description of the typical roles and responsibilities of all parties involved. Compiling a list of responsibilities along with a list of actions required and who is responsible for each one, ensures that all aspects of the process are addressed,” he made clear.
Wouter says the Guidelines document addresses the decision-making framework for all aspects pertaining to the construction of the netting system. It first considers the role of the weather, including rain, hail, sand and snow, and then it mentions soil conditions. These aspects determine the foundation needs of the structure. Recommendations can then be made in terms of cable thickness, pole diameters, and the size of anchors and anchor cables.
Because the nets are erected in dynamic soil conditions, a section of the document also refers to the lifespan of the structure. It is important to remember that although the document addresses all aspects of the construction, specific calculations about the structural components and forces affecting the structures should still be made.
PREVENT EXPENSIVE MISTAKES
Constructing netting systems is similar to building other infrastructure on a farm. Engineers are needed to design barns, consultants need to assist with the choice of pesticides, irrigation designers and dam engineers are necessary to manage water. All these activities have guidelines and best practises to be followed. Without guidelines, it is hard to determine if the design meets the requirements while the producer cannot determine if his needs were addressed if there is nothing to measure it against.
Because the average producer’s strength lies in agricultural activities and not building structures of this magnitude, they often are out of their depth where netting structures are concerned. With clear guidelines, the producer has access to a standard with which the proposal presented can be evaluated and measured against particular needs. With these guidelines, producers will be able to ensure that quality is not sacrificed to save costs.
Best Practice Guideline for the Construction of Agricultural Netting Structures.