I have read in Howard Resh's Hydroponic Food Production that ideally the researcher would "take tissue analyses of the plant once a week, and in conjunction with these tests, nutrient solution analyses. The level of each essential element in the plant tissue and nutrient solution must be determined and correlated so that if needed, adjustments can be made in the nutrient solution."
He mentioned that this method is not economically feasible for most commercial growers. My question is, today, is this method of taking tissue analyses the best way to truly optimize plant health in a hydroponics system, and has anyone been using this method and can comment on it?
I am consulting hydroponic growers. We use more and more leaf juice analysis. It gives a better impression of the status of fertilizers in the plant than dry matter analysis of tissue. At this moment Nova Crop Control in Holland has the most experience with this analysis.
Groen Agro Control makes for their clients a calculation of the uptake by the plant based on drip, drain and tissue analysis. It give new insights.
The measurements by probes in the drain water are still done (ea Cleangrow, Horticoop). But not all the elements can be easily determined by probes.
@ S. Umar ·
which other nutrients can SPAD be standardised for. May you kindly provide the details.
Like other people said SPAD can tell you the chlorophyll levels and u can correlated with other factors like Chlorophyll a fluorescence as indicator of how healty it's the plant.
In hydroponic crop production, you are supplying the plants with a known nutrient mixture. You are deciding the electrical conductivity of the solution, so the ratio and concentration of minerals are known, hence the ppm of each is known The only way for minerals to lave the nutrient solution is by being absorbed into the plants. Therefore, the only way to determine and quantify the minerals being taken up by the plants is to send samples of the nutrient solution to the lab at regular time intervals so a composition analysis can be done. As the crop grows, your lab results will indicate the ppm of certain nutrients decreasing more than others, and these can be individually supplemented to avoid any deficiencies from occurring. Practically speaking, what growers do is replace the entire nutrient solution with fresh stock periodically to ensure the proper ratio of nutrients. It is cheap to monitor pH and EC, and sensors with dataloggers are readily available. However, it is expensive to monitor individual nutrient levels. I hope this was helpful, good luck!
I agree with Joseph, frequent recycling of nutrient solution will be ideal. Individual nutrient measurement is not practical at each time. Apart from measuring pH & EC, one should also keep an eye on DO (dissolved oxygen) levels, which is very crucial! low oxygen will create hypoxia condition results in root decay. Apparently block nutrients uptake even though present plenty in hydroponic solution.
SPAD may not provide whole range of nutrient assay. It is an indirect index of leaf N content. Pl refer our papers; Bindumadhava et al., 2003 and Sheshshayee, Bindumadhava et al., 2006 (Ann Applied Biology). Thanks.
I am in favour of Chidiac and Rao's proposal.
However if there is a need to for more accurate analysis for say the major nutrient NPK, then for N and K the use of ion selective electrode devices can prove highly convenient. As for P there are potable colorimetric cartridges/vial that can address this though it is well understood that the latter if applied at the required dose initially should not normally be an issue.
Tissue chemical analysis even though it is precise and accurate, it is expensive and is often a post-mortem assay convenient for future improvement/amendment addressing deficiencies in the existing production protocol.
SPAD and leaf sample methods stated above are very good but they could not provide real time measurement. you should try non destructive and non contact methods, which could provide real time data acquisitions. do a research on non destructive topics such as optical reflectance or florescence methods. i think you can find beautiful approaches.
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