Late Seeding (6/9/11)
A crop planted this late in the season will germinate rapidly as the soil and air temperatures have increased. The most critical factor will be the growing season temperatures. The number of days with 90 degree temperatures and above in June, July and August is very important. Above average temperatures early in the season are beneficial but can be detrimental during flowering of the crop. Increasing the seeding rate slightly, as the season advances, would be a good strategy as there is less time left for crops to compensate for adverse growing conditions. If seeding the crop gets very late there is a potential danger that the crop will not mature before the fall frost. NDSU recommendations to seed or replant some of our broadleaf crops are given in the table 1.
If earlier maturing soybean varieties are available producers may consider switching maturities at this time. The approximate number of days from emergence to maturity of various crops sown in a normal season are buckwheat 70 days, flax 85 to 92 days, pinto beans 80 to 84 days, soybean 110-120 days and sunflower 105-110 days.
Average temperatures drop about 10 degrees from the middle of August until the middle of September. The day length during the middle of September is about three hours less than the longest day. A growing crop makes less progress to maturity in one day during the middle of September than in the middle of August. A crop seeded late may take twice as many fall days toward maturity compared with a crop seeded at the normal time. For instance, while there may only be four or five days difference in maturity between flax varieties when planted at the optimum time the difference may be 10 or more days when sown late.
Hans Kandel - Extension Agronomist Broadleaf Crops