Is there a list of all the agriculturally significant dates on the Jewish Calendar? A brief explanation of what happened on those days would also be great. For example, was Shavuot the beginning, middle, or end of the Harvesting?
1st of Tishre - The new year for animal tithes -- Animals born in one year do not combine with animals born the following year - Rambam, Hilchot Bechorot 7:6
10th of Tishre - Shofar was blown on the 10th of Tishre on a Yovel Year to signal the freeing of the slaves - Vayikra 25:9
15th of Tishre - Chag Ha'Asif -- Celebrating the ingathering of the crops -- see Shemot 23:16 -- Rashi on the verse: For during the entire summer, the grain dries out in the fields, and on the festival [of Succoth], they gather it into the house because of the rains [that are about to fall].
7th of Cheshvan - those living in Israel begin requesting rain by adding “Veten Tal U’Matar” to their Shmone Esre prayers.
17th of Cheshvan - If no rain has fallen by the 17th, a drought is feared and private ritual fasting begins. -- Source: Ta'anit 1:4
1st of Kislev - If no rain has fallen by the 1st, a drought is feared and public ritual fasting and special prayer begins. -- Source: Ta'anit 1:5
15th of Shevat - New Year for Trees (Rosh Hashanah 2a) - From here: Tradition teaches the new year for fruit begins on the fifteenth of Shevat, because most of the winter rains will have passed and the sap of the new growth has begun to flow: the dormant tree is waking from its winter sleep. A tree that blossoms before Tu B'Shevat is considered last year's produce; if it blossoms after Tu B'Shevat, it belongs to the new year.
1st of Adar - Declaration to get rid of forbidden agricultural mixtures. (Shekalim 1:1)
15th of Adar - Among other public services, agents of the court destroy forbidden mixtures. (Shekalim 1:1)
16th of Nissan - Omer offering. Barley grown in the previous year was now permitted to eat. -- commencement of barley harvest
6th of Sivan - Chag Habikurim. Earliest one could bring the First Fruits Offering (Mishna Bikurim 1:3). Two loaves of bread were offered in the Temple, and new wheat now became permitted to be used in sacrifices (Rashi Shemot 23:16)