ABSTRACT
Question from Mr. P.E. Rijtema to Mr. A.L.M. van Wijk
Crop development stage and crop development may differ considerably when the speed of crop development is strongly dependent on soil and air temperature in the early stage of growth. This is in particular true for the development of potatoes, maize and beans. I really have my doubts whether this system can be applied to years with deviating temperature in May, as for instance was the case in 1964, when average May temperature was about 3°C higher than normal, resulting in a growth explosion of the potato crop. On the other hand high temperatures can reduce the length of the growing season considerably as is for instance well known for tulips. A short period of high temperatures early June may shorten the vegetation period by about 10 days, giving a reduction in production of about 1500 kg/ha. How do you determine harvesting time in your simulation because it may differ from year to year? In my opinion the approach of early crop development and temperature sum as shown by Mr. Aslyng will be better, since it is dependent on temperature conditions and time instead of time alone.
