On the ground – US Virgin Islands

On the ground – US Virgin Islands

Walter Lawrenz

A senior manager at Ichthys Aquaponics has been in the US Virgin Islands for the past few months to assist a client in getting the farm up in production. He has shared some of the key highlights…

As with any commercial farming operation, it is vital to know where the produce is going before the harvest date, and ideally even before the seeds are planted. This form of planning allows ample time to ensure that we are growing the right crop for the client, and at the same time, allows us to plan more efficiently regarding the volumes we should be planting.

At the farm here, we have had to constantly refine our production cycle due to the high demand from the client and the short turnaround time. What we have discovered is that we yield bigger, better lettuce heads at about 30 days rather than 25, but at the same time that anything more than 33 days the risk of bolting increases dramatically. To give an example, we are supplying 300 cases of lettuce each week, the minimum is 10 heads in a case. Some heads are smaller than others, so in the beginning we had an average of 18 heads in a case to ensure we deliver a good amount of product. This translated to around 5400 heads. That meant that we needed to prepare and seed around 50 trays (about 6000 seeds), and still take care of all the harvesting and packing of that high volume on a weekly basis.

Over the last few weeks, by allowing the heads to grow bigger, we are able to reduce that to around 3600 heads, or 30 trays of seeds. This delivers the same result, but bigger and more consistent sized heads and at the same time reduces the harvesting and packing workload. This same principle is being applied to the 100 cases of Kale and Pak Choi we supply each week.

Spring Onion Seedlings
Spring Onion
Spring Onion at 3 weeks

We are fortunate to have an offtake agreement so we know exactly what is expected each week by the client and we can work towards that. Planning becomes a critical management tool for this size operation.

Head of lettuce
Produce ready to ship
Pak Choi

Part of this includes the process management. It all starts with the sowing of the seeds, if this is delayed, the knock on effect is detrimental to the end product. A lettuce production cycle on the farm would look something like this;

Sowing, transplanting 13 days later, harvest 30 days later. That means that we go from the date of seeding to having a packed product in 43 days. Within this production cycle, we can plan for different types of crops, some of which have repeat harvests such as basil, chives and coriander. Each of these have a slightly different production cycle. So understanding this and planning for it becomes one of the most important aspects of farming on a commercial scale. We are incredibly fortunate to be in a warm tropical climate. Average minimum temperatures are around 22deg and maximums up to 35deg. This does pose risks from diseases and pests, but by ensuring that there are strict rules and checks in place, it can be managed easily.

We have 6 green houses, with a conservative total capacity for around 26500 leafy plants and 1250 fruiting plants. We currently run the operation with 8 full time greenhouse staff, 1 manager and an administrative assistant. We have implemented daily greenhouse reports which help to keep potential problems from arising. These reports give daily information of important factors like pH, temperature, ammonia, nitrite, nitrate, fish health, plant health and any pest issues.

A full water quality analysis is carried out twice a week for each greenhouse. We also manage all our own pest control in house, making sure that we comply with all requirements and legislation. Due to the favourable climate, we are incredibly vulnerable to pests like armyworms, aphids and whiteflies.

One of our most important control factors remains our spray program that has been developed with the assistance of Dr Dreeves at UVI. This is executed twice a week in a preventative manner.

Another of the key focus areas is the constant system maintenance and cleaning that needs to take place in the greenhouses. By ensuring that aquaculture filters are maintained on a weekly basis, we have been able to effectively manage our water quality without resorting to extreme measures such as adding extra nitrifying bacteria to buffer high ammonia levels. With the warmer water, dissolved oxygen also plays a key role in fish and plant health.

By ensuring that we have sufficient aeration in the water, we are able to provide the best possible environment for the fish and plants to grow optimally. In order to achieve this, all our airlines consist of a diffuser tube which is more effective at dissolving air into the water at a much lower pressure than an air stone would be able to.

Managing the pH has posed a challenge for us, however, incredibly, the natural process of nitrification has again proved our biggest ally. Our water source is at a pH of 7.8 – 8, which is very high, and naturally this would drive the overall system pH up well above our target of 6.5. Although we have needed to add some acid to buffer down, it is remarkable to watch how the natural process of nitrification helps to drive the pH down. Some nutrients such as iron only become available to the plant in a certain pH range, hence pH management becomes very important on such a large scale.

Overall, the experience has been incredibly rewarding and I have learned a lot about what aquaponics can be in a much warmer climate, as well as what the potential of a 365 day growing season can yield. I must add that without the team at the farm, the farm will not be successful. Each individual knows exactly what is expected of them and they are incredibly passionate about what they do. We all work hard together and they have learned to understand the importance of sticking to the processes and now, the results speak for themselves.

Collard Greens
Lettuce at 2 weeks
Fish health inspection

Leave a Reply

Your email address will not be published. Required fields are marked *