With cultivation so closely intertwined with the Internet and with the advent of crop and climate sensors, big data is becoming available to the greenhouse horticulture sector. Big data consists of huge collections of information that growers can use to optimise operational aspects such as crop growth and energy consumption. A consortium of companies and organisations is working on the calculation models and algorithms that should make a comprehensive management program possible. “Think of it like a satellite navigation system (satnav): the grower enters a target and the program guides them there.”
“Imagine you’re a tomato grower. Wouldn’t it be great if you could manage your yields, quality and harvesting times even more accurately than you do at present. What buttons should you press to achieve that? That’s what we’re working towards,” says Simon van Mourik, Assistant Professor at the Farm Technology Group at Wageningen University & Research in the Netherlands, where he works on intelligent agri-systems based on precision technology and data streams.
Van Mourik has teamed up with energy specialists AgroEnergy to lay the foundation for a joint research project. The university, the energy partner for greenhouse horticulture and a number of companies and organisations were recently awarded funding for this project, which is entitled “Energy saving in greenhouse crop production by flexible management” and goes by the working title “FlexCrop”. The research project will start in a crop of artificially lit tomatoes next summer. The consortium also includes the Dutch growers’ organisation LTO Glaskracht and the companies B-Mex, LetsGrow.com and Delphy.
Developing a management program based on big data is no small matter. A period of four years has therefore been allowed for FlexCrop. There are a lot of requirements to be met. First of all, the program must be able to adjust for temporary fluctuations, just as a satnav recommends an alternative route for the driver if there is congestion ahead. “This dynamic must be built in. So the program must steer dynamically. In terms of climate and energy consumption, for example, that can be done by adjusting the settings hour by hour based on the most recent data,” says van Mourik.
Analyse and interpret
All the relevant cultivation factors must be built in. For example, B-Mex is looking at forecasts from changed settings. Take the CO2 dosage. What happens if the grower increases the concentration of CO2? What would that cost? And what would it deliver in terms of crop growth or extra kilograms of product? Based on the measurements and calculations, the program must be able to recommend the best and most cost-effective CO2 dose for the crop.
Van Mourik: “Next Generation Growing has already taught us that a crop is very flexible. With even more information about this, we can develop an algorithm that optimises the settings accordingly. That calls for models that predict the consequences of a particular action or situation. These models do already exist but they are not yet perfect. The challenge is to analyse and interpret the enormous volume of data in the right way.”
Two PhD students are helping with the research. One is working on knowledge of crop physiology and the other is working on an algorithm that utilises the flexibility of the crop. “In this project, the trick will be to make the best use of all the partners’ expertise,” the Dutch scientist says.
For growers, the datasets on which the management information system is based are invisible. Will they have the courage to trust the advice? Van Mourik thinks so. “Look at the satnav. You don’t know how it works but you still follow the instructions and you do what the screen on the dashboard tells you to. ‘After 300 metres, turn left’ – and you really do turn left after 300 metres. And that gets you where you need to go.”
Intertwined with business aspects
One example of where big data can take us is BiedOptimaal from AgroEnergy. This program calculates the optimum APX bid for the next day based on extensive data sets and prediction models. More than 130 growers are already using it every day. There’s a lot to be got out of the energy market for the grower, AgroEnergy product developer Peter Goudswaard explains. “Energy is an important part of the cost price and energy prices can fluctuate strongly on the APS and the intraday market. With the right APX bid and by adjusting for intraday, you can use the program to make significant savings in energy costs and time.”
At the moment the company is working on a series of additional solutions designed to help growers with everyday issues. There’s no shortage of examples. Goudswaard: “Is it worth switching on the lights or would it be better to leave them switched off? What would it cost you in the first scenario, and what would you save in the second? And what does the crop do when the lights are on or off? What extra yields could you get, and what costs would be involved? The program doesn’t approach the cost factor of energy in isolation and is becoming more and more closely intertwined with many areas of production, climate and day-to-day operational aspects. We are working with a number of partners on this.”
Support for decision-making
Goudswaard’s colleague Bram van Rens is a data scientist at the Delft-based energy specialists: “The yield has to come from cultivation, whereas climate is a cost factor. It takes time if the cultivation manager and the energy manager keep having to meet because the cultivation manager wants to switch on the lights to boost growth and yields while the energy manager wants to feed energy back into the grid because prices are good at that point. Their objectives differ, but cultivation and energy are both factors in the company’s bottom line: they have to go hand-in-hand.”
Big data makes it possible to provide advice that will highlight the optimum, van Rens believes. “With systems that support decision-making we can make things easier for the grower. As sensors and the Internet of Things produce more and more information and data, there is an increasing need for this.”
Less to the daily market, higher mid price
The Dutch company HortiKey is working on other applications based on big data. The company’s latest innovation is the Plantalyzer, which has been developed for tomatoes to begin with.
The autonomous measuring system photographs the colour of the tomatoes on a scale from 1 to 12. The measurements are then used to produce a forecast of the harvest in kilograms two weeks in advance. This is very handy. After all, if the grower knows that in two weeks’ time he will be producing more than he is contracted to deliver to the customer, his sales staff can start looking for alternative outlets. General Manager Andreas Hofland: “Otherwise they have to get rid of the surplus on the daily market, where prices almost always put pressure on their mid price. With this system, you can reduce the normal margin of error in production planning by around ten percent.”
When all is said and done, the measuring system is a sales tool, Hofland says. But it is a little more than that, because it also highlights production differences and can detect colour variations. “If some trusses are ripening differently from the others, this tells the crop manager that there has been a problem there. If he is able to find out exactly what that is, that mistake can be avoided in the future – even if it was only a leaking window. This is a way for inquisitive growers to get their hands on a wealth of new information.” The company mainly specialises in applications for large fruiting vegetable nurseries. That’s a strategic choice, because these nurseries are becoming larger and larger the world over, and yet it is becoming harder to find good crop managers and the risks (in other words, errors in cultivation or production) still have to be eliminated.
The trick with big data is to recognise patterns in the enormous streams of data and convert them into information that can be applied to the grower’s day-to-day practice. Various parties in the greenhouse horticulture sector are working hard on this. A consortium is developing a management information system based on big data, for example, and one company is focusing on yield forecasts that helps growers manage production and sales even more precisely.
Text and images: Jos Bezemer.
When several of the sweet pepper plants at Zwingrow in Honselersdijk (Westland, the Netherlands) were found to be growing more slowly than the rest, the nursery decided to have an uptake analysis performed. An uptake analysis gives the grower a detailed picture of the actual uptake of nutrients by the plant. After all, as field researcher Ruud Kaarsemaker says, the drainage and drip values often don’t give a clear enough picture on their own.
It was in May that Zwingrow saw the first signs that the crop was ‘unhappy’. Cultivation manager Bart van der Valk noticed several plants across the crop that were not growing as vigorously as the others. They were wilting under high solar radiation and had brown, thickened roots. These plants were less dense, thinner and shorter than the others, prompting the growers to look into what could be going wrong. Were the systems still working properly or had something gone wrong with the nutrient tank schedules or the watering strategy? The grower couldn’t quite put his finger on it and called in Groen Agro Control of Delfgauw to help.
This research organisation was already sampling the nursery’s irrigation and drainage water on a weekly basis and, after visiting the site and talking to the growers, they recommended an uptake analysis. The analysis was carried out retrospectively to obtain a picture of the development of the nutrient uptake that led to the imbalance in the crop.
A glance at the graphs illustrates what this analysis is about. The lines show the calculated uptake of all main and trace elements per week. The results are based on the concentrations in the irrigation and drainage water, the drainage percentage, watering volumes and a calculated estimate of the dry matter produced based on the amount of light and the CO2 concentration achieved. Another line in the graphs indicates the concentrations in the slab. Comparing the crop uptake with the slab concentrations and the ratios of the various nutrients provides additional information on the crop’s nutrient status.
The Zwingrow values showed that overall nutritional uptake was already very low in early April. Kaarsemaker: “When uptake is low, it is especially important to ensure the nutrients are properly balanced. But these sweet pepper plants were taking up much less potassium than other cations at the time. Potassium is important for opening and closing the stomata: if the stomata don’t close properly, the plants can wilt. Potassium is also needed for transporting sugars. A potassium deficiency can therefore result in insufficient transport of sugars to the root system.”
Iron, boron and zinc deficiency
The analysis also revealed that the values of at least three nutrients were well outside the desirable bandwidth. “The graphs show a distinct boron, iron and zinc deficiency. Low uptake of these nutrients fits in well with the picture of a weak plant. An iron deficiency will cause the young leaves at the top of the plant to turn yellow, a zinc deficiency causes yellow discoloration between the veins, and low boron uptake results in distorted, brittle leaves, weak plants and a brittle crop.”
The sweet pepper growers were surprised. These trace elements were present in the drainage water in sufficient quantities and in the right proportions during the period analysed. And you wouldn’t expect there to be an uptake deficiency if the parameters are correct. “Clearly the plants were not being stimulated enough to take up the nutrients,” cultivation manager Bart van der Valk says. So he significantly increased the irrigation volume – by 50% – but to his surprise, he found that the drainage values remained the same. That made it clear that something else was going on. Van de Valk also realised that from then on, he would need to start looking at the drainage and drip values from a different perspective. Uptake analysis has been a permanent fixture at this nursery ever since.
Combination of factors
Kaarsemaker: “As we know, the conditions for optimum growth are complex and a healthy plant is the sum of various factors. Nutrition is just one of those. We don’t yet fully understand what effect all the elements the sweet pepper needs have, but we can spot anomalies in the uptake pattern. What led to these phenomena at this nursery were most likely a combination of high plant load, too little watering and imbalanced nutrition. We could probably have avoided some of the problems by optimising our plant nutrition in good time. It’s so important to keep a constant eye on nutrient uptake.”
This realisation is gradually taking root among greenhouse growers as they discover that this analysis method allows them to steer their crops more precisely. The result: better quality, higher production, more vigorous plants and possibly even savings on fertilisers and water discharge. Kaarsemaker is seeing growing demand for the calculation tool, particularly among tomato and sweet pepper growers. They have a good understanding of their water flows and can therefore make excellent use of the analysis data.
A lot is already known about tomatoes, and for the past year Groen Agro Control has been working more intensively with sweet peppers, a slower crop. The more data they can collect, including from new varieties, the more accurately the results can be interpreted. After all, all the information about the growth phases and plant stages of each crop type is used. That makes an uptake analysis in ornamentals a particular challenge, Kaarsemaker says. “We are doing them with plants such as rose and gerbera. Growers of these flowers often grow several different varieties and have plants of various ages in the same part of the greenhouse. That makes things complicated.”
The adjusted nutrient strategy at Zwingrow is working. The cultivation manager was concerned that the weaker plants may have been permanently damaged, but even they have been visibly improving. More importantly, no new problems have arisen: the healthy plants are staying healthy. So the damage caused by the imbalance has remained limited. From now on, the grower will be allowing enough time to check the uptake graphs once a week and is hoping that this will avoid any problems in the future. However, he realises that not everyone is falling over themselves to get hold of a tool like this. It costs money and it’s also difficult to prove that it will help increase yields.
Kaarsemaker is also coming up against resistance. “Nurseries prefer to stick to the traditional method. They sample the drip and drainage water and decide how much to fertilise based on the target values in the slab. That’s fine as long as everything stays ‘average’, in other words if the plant and root system are healthy and the climate is right. But as soon as a plant starts taking up less for whatever reason, an imbalance can occur. An uptake analysis enables you to keep on top of things and intervene as soon as there is the slightest anomaly. That way you can prevent problems from escalating.”
An uptake analysis gives growers an accurate picture of which elements the plant is actually taking up, enabling them to fine tune the nutrient solution to the plant’s needs. The values from drip and drainage samples alone are sometimes not enough, as sweet pepper nursery Zwingrow discovered. The calculation tool highlights even the smallest anomaly and prompts the grower to take action in good time.
Text: Jojanneke Rodenburg. Images: Jos Bezemer.
Building a high-tech greenhouse is one thing, but working with it is a whole different ball game. Nurseries in countries with no horticultural tradition often need high-frequency advice. Remote monitoring makes that a whole lot easier. A new system developed in recent years is an interesting option for remote management or benchmarking.
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