1. Second part of precision farming Crop sensing by reflectance – Greenseeker Measuring fluorescence and photosynthesis – Yara N-tester Using Vegetation index – NDVI or WDVI or NDRE (Reliable yes or no) Basics of crop Sensing – Remote or near sensing or taking pictures !!

2. VI

3. Height above crop

5. Wavelenght of light Red 650-780 Orange 585-650 Yellow 575-585 Green 490-575 Blue 420-490 Violet 380-420 UV < 380 NIR > 780

6. colourspectrum

7. Light response

8. Absorption by plastiden

9. Chlorofyl

10. Questions Why looks a leaf of a crop green or purple(red) What do measure when you use sensors: 1.Reflection of light of an certain wavelength 2.Fotosynthesis activity 3.Both 1 + 2 When the UAV is being used how is this sensor working. 1 to 3 or just making pictures (RGB-red/green/blue)

11. What do we see and pigment abs

12. Photosystem…fluorescentie

13. What can be done by sensing Crop sensing (NIR) – Irrigation (soil sensor or Water watch; energy) – Nutrition – Crop protection Biomass sensing (UV) Soil sensing (Gamma Ỵ-radiation)

14. Precision circle

15. potato planting

16. Plantdensity When you want to harvest potatoes for consuming (eating) or processing (chips) In case of cultivation of seed potato variable planting (4 % more yield by change density 10 %) What is the best density – Smaller than 75 cm – Closer than 30 cm How do you translate density of a potatocrop – Seedpotato/m2 or stems/m2

17. Normal

18. Density between wheels In case of seedpotato variation in density seems to have some effect.

19. Close planting In a situation when lutum is changing usefull 10 % more plants where lutum is 10 % lower

20. Plantdensity in the shade Zones: I = 40 %; II = 60 % en III = 80 en IV = 100 Shade less dense ??

21. Shade or Far red

22. Reaction in stem elongation

23. Shade versus light How important is light for crop growth Fotosynthese depends of light LAD and yield is lineair Lack of water and/or light causes shortage of tubers and that is why the influence of light is less important. Especially when tuber set takes place the need of water is high.

24. Digistaat Injection of highly concentrated (pig) manure with N and K (no P !!) and looks like KAS Better is injection because otherwise you get NH3 into the air.

25. Side dress N rate in potato Crop reflectance to determine sidedress N ! WDVI is related to N-uptake (calibration) Instead of collecting petioles (Nitrate, BSO) Neither taking soil samples (ALTIC) BUT: Reflectance may be caused by other factor than N, such as: Drought, water logging, disease, genotype, insect damage, nematode, soil structure, other nutrients and weeds !!

26. Side dress P, K in potato ? Crop sensing for P shortage can be done Potasium as no relationship with sensing and it seems that N/K-ratios can be measured. Modelling with photosynthesis-light-curve if hyper - or ultraspectral bands are being used.

27. Nutrient deficiencies

28. Sucros

29. Measuring is knowing What do you decide – Improve bad spots – Speeding up yield (SUSY) on good spots When side dressing for N is only 30 – 50 kg – Is this usefull when sensing gives this advice? When you know that the NBI for the efficiency of nitrogen is not more than 50 %; what is the use of sensing…