What does your garden need?
With the Growers Toolbox you see straight away how much water your crop needs, which growth stage it is in and which smart devices suit you. No form, no waiting.
No form. Instant answer.
It used to mean getting in touch and waiting for a callback. Now you pick your type of crop and see instantly how much water it needs, which growth stage it is in and which smart devices fit. Simple for the allotment, advanced for the experts.
Calculate your water needs in 30 seconds
Allotment or rose nursery, greenhouse or open ground: tell us briefly what you grow and the toolbox instantly works out your water needs, watering schedule, reservoir size and the recommended Zigbee set. Switch between simple and advanced with a single tap.
Water needs change with each growth stage
A young plant drinks the least, a plant in flower and setting fruit drinks the most, and a ripening plant less again. Click a stage and see what happens. Flip the switch to advanced for the BBCH codes, crop coefficients and growth models.
Sources and scientific basis
Advanced mode uses recognised, peer-reviewed methods, not rules of thumb. Below you’ll find the primary source for each step of the calculation. In science, only what can be traced counts, so you can look up every equation and table value.
The water requirement follows the FAO standard: crop evapotranspiration ETc = ETo × Kc, with reference evapotranspiration calculated by Penman-Monteith and, for the Netherlands, by the KNMI’s Makkink standard. The soil water balance (TAW, RAW, watering interval) comes from the same FAO-56 guideline. Salinity follows the Maas and Hoffman model, and the temperature sum follows McMaster and Wilhelm. For growing under glass we draw on the work of Stanghellini.
- Allen, R.G., Pereira, L.S., Raes, D. & Smith, M. (1998). Crop evapotranspiration: guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper 56. FAO, Rome. fao.org/4/x0490e. Source for ETo (Eq. 6), Kc correction (Eq. 62/65), TAW/RAW (Eq. 82/83) and Table 19/22.
- Penman, H.L. (1948). Natural evaporation from open water, bare soil and grass. Proceedings of the Royal Society A, 193, 120-145. doi:10.1098/rspa.1948.0037
- Monteith, J.L. (1965). Evaporation and environment. Symposia of the Society for Experimental Biology, 19, 205-234.
- Makkink, G.F. (1957). Testing the Penman formula by means of lysimeters. Journal of the Institution of Water Engineers, 11, 277-288.
- De Bruin, H.A.R. (1987). From Penman to Makkink. In: Hooghart, J.C. (ed.), Evaporation and Weather, CHO-TNO Proceedings 39, 5-31. Introduces the KNMI constant c = 0.65.
- Hooghart, J.C. & Lablans, W.N. (eds.) (1988). Van Penman naar Makkink; een nieuwe berekeningswijze voor de klimatologische verdampingsgetallen. CHO-TNO Rapporten en Nota’s 19 (also KNMI TR-111), The Hague.
- Maas, E.V. & Hoffman, G.J. (1977). Crop salt tolerance: current assessment. Journal of the Irrigation and Drainage Division (ASCE), 103(IR2), 115-134. doi:10.1061/JRCEA4.0001137
- McMaster, G.S. & Wilhelm, W.W. (1997). Growing degree-days: one equation, two interpretations. Agricultural and Forest Meteorology, 87(4), 291-300. doi:10.1016/S0168-1923(97)00027-0
- Meier, U. (ed.) (2001). Growth stages of mono- and dicotyledonous plants. BBCH Monograph, 2nd edition. Federal Biological Research Centre for Agriculture and Forestry (BBA), Germany. Open access (2018): doi:10.5073/20180906-074619
- Steduto, P., Hsiao, T.C., Raes, D. & Fereres, E. (2009). AquaCrop, the FAO crop model to simulate yield response to water: I. Concepts and underlying principles. Agronomy Journal, 101(3), 426-437. doi:10.2134/agronj2008.0139s
- Allen, R.G. & Pereira, L.S. (2009). Estimating crop coefficients from fraction of ground cover and height. Irrigation Science, 28(1), 17-34. doi:10.1007/s00271-009-0182-z
- Stanghellini, C. (1987). Transpiration of greenhouse crops: an aid to climate management. PhD thesis, Wageningen Agricultural University. doi:10.18174/202121
- Katsoulas, N. & Stanghellini, C. (2019). Modelling crop transpiration in greenhouses: different models for different applications. Agronomy, 9(7), 392. doi:10.3390/agronomy9070392
- Ayers, R.S. & Westcot, D.W. (1985). Water quality for agriculture. FAO Irrigation and Drainage Paper 29 Rev.1, Rome. Reproduces the salt tolerance table of Maas and Hoffman.
What is the Growers Toolbox?
A set of practical tools that answer growing questions instantly, starting with a water-needs calculator. No form to fill in, just an answer.
How does the water calculator work?
You enter a few details about your plot and it estimates your water needs in about 30 seconds, adjusted for the growth stage your crop is in.
Why does water need change with growth stage?
Plants use water differently as they develop, so the calculator factors in the stage to give a more realistic figure than a fixed amount.
Is the advice based on real science?
Yes. The calculations are based on recognised scientific sources, all listed on this page.
Do I need an account to use the tools?
No. The tools give you an instant answer, with no sign-up. For live data from your own site, see sensors.
Can FairGrow do this automatically?
Yes. With your own sensors, FairGrow tracks conditions live and keeps advising you as things change. See how it works.