Kilayim is not similar to Shekalim, Pesach and Chagigah because it

is not a public Mitzvah with a fixed time but rather a private duty which varies according to when every individual's produce has grown enough to be forbidden because of Kilayim. Therefore people are wont to be lazy in uprooting the Kilayim and consequently, it logically follows that an announcement is required about this even though there is no source for this from a verse.

HAGO'OS HaBACH #4 is certainly not suggesting that Beis Din must proclaim every year that one should build a Succah, since this is a public Mitzvah with a fixed time which therefore does not usually require announcement as we learnt above. Rather BACH asserts that the Gemara cites the verse in Nechemia because the word "Yashmiu" is used there, which refers to announcement and this proves that the word "Mashmi'in" used by the Mishnah also means announcement. The reason that proclamation was necessary in the time of Nechemia was because they had only then just rediscovered the Sefer Torah which taught them that one dwells in a Succah in the seventh month. without the proclamation the people would have forgotten about the Mitzvah. However in subsequent years it was not necessary to proclaim about Succos.

BEHATZLOCHO RABAH,

D Bloom