One of the principles of energy friendly greenhouse cultivation, is the (scarce) light being optimally converted into assimilates, preferentially in the product to be harvested. The only way available now to determine whether nutrients and assimilates are in the 'right place', is by taking leaf samples and having those analyzed in a laboratory. This project is about a measuring method based on hyper-spectral cameras measuring light in the range of 400 to 1700 nm. Possibly, this enables wireless monitoring of the status of the crops, and based on this information the greenhouse climate can be controlled (dosing CO2, lighting on or off) or other growth measures (removing leaves, pruning) can be taken.
Destructive measurements in tomato
For this research, use was made of an existing tomato growth with five varieties. Treatments have been introduced to make sure the sugar levels and dry substance percentages in fruits and leaves are different, and to make differences in the nutrient content in the leaves. These leaves were then subjected to measurements with hyper-spectral cameras. The leaves and fruits were then used for destructive measurements of sugar, starch, nutrients, percentage in dry substance, and chlorophyll content in different laboratories. For every leaf and fruit, the spectral images and the lab measurements were combined, and it was determined to what degree the images gave a good correlation with the various content substances.
Good correlation
The results show that the hyper-spectral images correlate well with the sugar content in the leaves. There are also good correlations with the dry substance content and the pigment content (chlorophyll and carotids) in the leaf. There was a fair correlation between the images and starch content, total of nitrogen, and calcium. The content of a number of other nutrients turned out not to be predictable with the hyper-spectral camera. All these results show that hyper-spectral cameras are very useful in the greenhouse horticulture to determine the status and quality of fruits during the growth, without damaging the crops. The next step would be to determine whether hyper-spectral cameras can also be used in the regular growth to determine the content of substances, in such a way that the grower can use the information to control the crop growth.
This research is financed by Kas als Energiebron, the innovation and action program of the ministry of Agriculture, Nature, and Food quality, and LTO Glaskracht Nederland.
Click here for the complete research report (Dutch).
Source: Kas als Energiebron