Koppert Natugro greenhouse trial at PlantResearch clearly demonstrates:

High tomato yield with 20 per cent less nitrogen is feasible

In a greenhouse trial during the first half of 2013 at PlantResearch in Made, The Netherlands, it was found that a high yield tomato cultivation is feasible with significantly reduced nitrogen levels with the Koppert Natugro system, which aims to improve the vitality and resilience of crops through the use of biostimulants and micro-organisms (such as Trianum-P). The total nitrogen level, both NH4+ and NO3-, was reduced by an average 18.9% when compared to the control treatment, with overall yield being unaffected.

‘The main focus of the trial was to underpin and support our product claims of the Natugro products when applied via a dripper system,’ says Katja Hora, responsible for the field development of microbials at Koppert Biological Systems. ‘We wanted to demonstrate the relation between the application of Natugro products, including Trianum-P, and nutrient efficiency with respect to crop yield and performance. The trial at PlantResearch fits Koppert’s efforts towards furthering sustainable crop management.’

The trial at PlantResearch was carried out in a 240 m2 greenhouse equipped with pipe rail heating 10 cm above the greenhouse floor, a low calorie heating tube at plant head level, and a CO2 dosage rate of 600-800 ppm, similar to standard Dutch greenhouse practice. The tomato variety used was ‘Komeett’, grafted on ‘Maxifort F1’ rootstock, both varieties from De Ruiter Seeds (Monsanto). ‘Komeett’ was chosen as it is a truss tomato with a high average growing speed and a high yield potential, whilst it also is one of the most planted commercial tomato varieties in the Netherlands.

The plants were grown on 1 meter Forteco Profit coco slabs with 4 plants per slab and one head per plant, divided over 12 gutters, each with a length of 9 meters. This accounts for 2.5 plants per square meter, which was kept constant during the whole trial. At the start of the trial it was decided to introduce two pepino mosaic virus varieties by means of vaccination, in order to reduce the risk of a mosaic virus infection later in the trial.

‘Fertigation is an important cost factor for a grower,’ explains Ron Galiart, senior researcher at PlantResearch. ‘In addition, over-fertigation may ultimately lead to spills into the environment, even from recirculation systems. Therefore reducing nitrogen levels without affecting overall yield , as achieved by the Koppert Natugro products ProFortum and ProTerrum, is beneficial on several levels.’

André Zwinkels, the trial's crop supervisor, confirms that the reduced nitrogen gift has had no effect on the crop: ‘This is partly because a good root system and healthy soil life improve the uptake of nutrients. As a result, the plant can get by with less nutrients. Also no limits have been exceeded, so there were no deficiency symptoms. This trial is an important first step in understanding the influence of soil life and fertilisers on processes within the plant.'

The results from the PlantResearch trial are further supported by a similar experience by the Dutch tomato grower Mark van der Werf of Greenco. The company has been utilizing the Natugro system for a number of years as an important part of the 'ready-to-eat' strategy for its Tommies brand. 'For the past year we have been giving the plant much less nitrogen and nitrate,’ Van der Werf says. ‘Plant sap measurements show that there are very high levels of free nitrogen in the plant and very low levels of nitrate. We have seen absolutely no negative effects in the crop. In fact, it seems to have a positive effect on the plant's susceptibility to diseases and pests. Although there is still much to be learned about the processes which take place in the plant and how these are connected with each other, we absolutely believe in the Natugro system. Something really does happen in the soil,’ he concludes.

‘Looking at the plant performance in this trial, as well as the nutrient feed and drain water analyses, we have to conclude that the plants were not under nitrogen limitation during most of the trial,’ adds Katja Hora. ‘All drain water values were according to the target values as set by the Research Station for Floriculture and Glasshouse Vegetables. The reduced nitrogen feed still had fair nitrate levels in the drain water, up to 13 mmol/l. Furthermore, the leaf nitrogen content was comparable in all treatments, in early March, late April and mid-June. It therefore looks fair to assume we can reduce the nitrogen levels even further, something we will look at in the near future.’

For more information:
Koppert Biological Systems

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