Predicting the Best Time to Apply Nitrogen to Grassland in Spring

A great number of experiments with varying dates of N application to grassland showed that the most suitable time of applying spring N in tbe Netberlaods varies, as a result of weather conditions, from year to year from mid‐February to mid‐April. In such experiments the best time of spring N application, which needs to be known in advance, can only be determined after the grass bas been harvested and weighed. The results of these experiments supported the opinion that the best application date coincides with the banging of grass growth. However, at that time it was not possible clearly to define the begimiing of grass growth. When in 1959 a measuring disc was put into use the beginning of grass growth could be precisely determined and it was then found that the beginning of grass growth was closely correlated to a certain accumulated temperature from 1 Jan. from which the date of the beginning of grass growth can be predicted. This date is the most suitable one for applying spring N to grassland.