Hydroponic farming: Stick to GAP and keep consumers happy

lettuce; hydroponic

Vegetable farmers, including those using hydroponic systems, have to adhere to Good Agricultural Practice (GAP) if they want to market produce successfully to concerned consumers.

Good Agricultural Practice (or GAP) could be briefly defined as a concept that focuses on sustainable agriculture, set out in a range of standards that describe specific requirements.

The 3 pillars of GAP could be said to be:
• concerns related to food safety, such as chemical inputs, and food diseases;
• environmental aspects such as pollution, wastes, protection of natural resources; and
• social accountability/worker welfare, legal and ethical aspects.

What does GAP entail?


There is a greater need for transparency. Consumers want to know that there are ways to trace produce right back to the origin (production area) should any concerns arise. This will ensure that producers are accountable for their practices.


Records of activities must be kept in an orderly manner so that they can be used to support facts related to the production of a specific crop. This is not an exhaustive list, but it should include procedures, such as: risk assessments (pollution, health and safety, and hygiene, and so on), application records; planting/sowing records; records of meetings; and residue testing.

Varieties and rootstock

The thought process behind variety and/or rootstock selection must be clear. Aspects such as resistance to/tolerance of certain pests have to be considered as well as propagation material quality. Planting and providing GMOs (genetically modified organisms) should be agreed on in
advance with customers and local legislation must always be observed.

Site history and management

Areas where new developments are to be undertaken must be assessed for risks before preparation starts. Aspect, water availability, surrounding areas (whether these are cropped or potentially environmentally sensitive) and soil types, are only some of the considerations to be incorporated in the planning process.

Soil and substrate management

In the case of hydroponics it should be defined, for example, how substrates are sterilised; once again, local legislation has to be observed. Conventional farmers could consider erosion here.

Fertiliser use

Fertiliser must be applied at the most appropriate time to prevent leaching into underground water sources. The composition of the fertiliser must be known and farmers should also consider factors such as heavy metals. Equipment used to apply fertiliser must be calibrated to ensure accuracy.


In many instances, taking a water sample at least annually is recommended in order to understand the quality of irrigation water to be used on crops. The crop could indicate which type of test should be done, but chemical and micro-biological tests are the ones most commonly conducted. The most effective irrigation methods should be considered and, if viable, when they should be implemented.

Crop protection

This is one of the most important aspects of GAP. The use of chemicals must always be justified and – in all cases – should be applied as instructed in the chemical’s registration, and given on the label. Integrated Pest Management practices should also be considered; these could include regular scouting and orchard monitoring as well as biological control methods, such as the use of beneficial insects or predators.

Produce must also be sent for analysis to an accredited lab to verify that no maximum allowable chemical residue limits have been breached. Spray or chemical application equipment should be well-maintained and calibrated regularly.


Harvesting hygiene is important and has to be handled according to the risk attached to the product. Harvesting practices are different for different crops. Practices should, therefore, reflect the appropriate protocols.

Produce handling

This is mainly aimed at a packing facility, if there is one on site. There are a number of due diligence requirements through related standards. These usually take into account post-harvest treatments and the staff responsible for packing produce. This is based on GMP (Good Manufacturing Practice) and food safety standards, such as HACCP (Hazzard Analysis and Critical Control Points).

Waste and pollution

Waste and pollution outputs have to be identified and managed in an appropriate manner. Waste could include packaging, graded-out produce, empty pesticide containers and orchard waste. Pollution would include diesel and oil storage areas, chemical stores, liquid fertiliser tanks, and so on.

Worker health, safety and welfare

I’m sure we’ve all heard some gruesome stories of farm accidents. By considering Good Agricultural Practice, we are isolating ways to prevent their occurrence. This can be done by identifying risk areas and then developing a plan to manage the risks. The plan could amongst others include appropriate training and putting up warning signs. Worker welfare should also be addressed and local legislation observed.

Environmental issues

Ways of maintaining and managing an ever-decreasing natural habitat should be considered. Without a healthy natural environment, farming would not be sustainable. Water sources, landscape and wildlife features in surrounding areas should be conserved and form part of an integrated farm management system.

Why is GAP important?

Many consumer concerns will be addressed proactively if the farmer implements or adopts the GAP standards set by the various organisations and retailers. Some customers may require their supply base to undergo certification to a standard (and could vary from customer to customer) and could create market access independent of the size of the farming business.

A number of available standards stipulate criteria in terms of which audits in farming businesses (second party or third party) take place.

Some industry standards currently available include (although this is not a complete list):
• Farm level – GlobalGAP, Tesco’s Nurture, Field to Fork, LEAF, etc.
• Farm and/or packhouse/processing level – BRC, HACCP, IFS, ISO22000, PPC, Hygiene, etc.
• Social/Welfare level – SA8000, ETI, GRASP, Fair Trade, etc.

In most cases, the customer will be able to point potential suppliers in the direction of the standards important to them; or the business could start to adopt certain “base standards” as starting point and later adopt “bolt on standards”.

One thing that should be understood when implementing GAP standards is that usually a standard will not overrule local legislation or the legislation of the countries where trade is intended. The standards’ criteria will, in most cases, support local legislation or (in the absence thereof) define at least an absolute minimum.

This article is a brief overview and the considerations mentioned may vary from site to site. Please consider this only as a skeleton guideline of GAP.

  • This article was written by Jurie van Wyk and first appeared in Farming SA.


share this