Alfalfa seed production studies in Michigan

An experiment was begun in 1928 to study the influence of artificial tripping upon alfalfa seed production under Michigan conditions. The experiment was enlarged in 1929 to include the influences of such atmospheric factors as temperature, relative humidity and calculated moisture content upon pod and seed production. In 1928, 45.1% of the flowers artificially, tripped produced pods, while 15.8% of those allowed to develop normally set pods. The pods from flowers artificially tripped and those from flowers allowed to develop normally contained 1.53 and 1.78 seeds per pod, respectively. At mid-day a greater percentage of the flowers produced pods than at either 9:00 or 5:00 o'clock, indicating that conditions are more favorable at that time to tripping and to those processes influencing the setting of pods. In 1929, 56.1% of the flowers artificially tripped produced seed pods, while 12.2% of those allowed to develop normally, set pods. The average number of seeds per pod was 2.35 for the artificially, tripped flowers and 1.99 for those allowed to develop normally. Pod production by the artificially tripped flowers varied materially-according to the time of day when the flowers were tripped. On the average the percentage of pods increased as the day advanced until 11:00 o'clock, decreased until 3:00 o'clock, and then increased again. Attempts to correlate atmospheric factors, such as temperature, relative humidity, and calculated moisture content, with the setting of pods failed to give any strong relationships. However, the consistent negative trend of the correlation values obtained between either relative humidity or calculated moisture and pod production tends to indicate that, as these atmospheric factors decrease, conditions become more favorable to those conditions favoring tripping and the setting of pods. The data presented prove conclusively that lack of tripping was one of the chief factors limiting alfalfa seed production in Michigan during 1928-29.