Between 1953 and 1955 a series of field experiments have been carried out in Great Britain to assess the effect of sowing date on the extent and the rate of emergence of a number of varieties of maize.
The range of sowing dates was from late March till May. Records were kept of the soil temperatures, these will be reported later, and in certain experiments the water content of the soil was maintained at field capacity. In all experiments a northern flint variety and a southern dent variety were sown, in the first year only flint × dent hybrids were also grown.
There was an increase in final emergence with the later sowing dates. The northern flint varieties were superior to the southern dent varieties, while the flint × dent hybrids occupied an intermediate position. The lower final emergence of the southern dent variety was most marked at the earlier sowing dates.
Differences between varieties in the speed of emergence, taken as the number of days from sowing until half of the surviving seedlings had emerged, was observed at several centres. The open-pollinated varieties usually emerged more slowly than the flint × dent hybrids. There was a very marked difference between early- and late-sowing dates in speed of emergence.
It was possible in the second year to compare seed of high quality with that of low quality as determined by the ‘cold test’ of germination capacity. The lowquality seed gave greatly reduced final emergence, the experiments stressing the need for the adoption of a standard ‘cold test’ for maize seed, especially of that intended for sowing in north-western Europe.
The high final emergence of the northern flint varieties suggest that a gene source for resistance to soil pathogen attack is readily available. The possibilities in north-western Europe for expansion of growing grain maize would be greatly strengthened by development of varieties capable of growth at low temperatures. The experiments suggest that until such varieties are available little advantage in time of emergence will be gained by sowing maize before late April in Britain.
