1. Ki Savo opens with the parsha of bikkurim, the mitzvah to bring the first fruits to the beis hamikdash, followed by the parsha of viduy ma'asros, the mitzvah to declare after a a three year cycle that all terumos and ma'asros have been properly distributed and disposed of (see Seforno who explains why this declaration is called viduy). The parsha then continues, "Hayom hazeh Hashem metzavecha la'asos es hachukim ha'eileh v'es hamishpatim..." (26:16). Rashi comments that this pasuk is a bracha: just like on this day -- hayom hazeh -- you have fulfilled the mitzvah of bikkurim, so too next year you should be zocheh to fulfill the mitzvah again. If that's what the pasuk means, then shouldn't it appear immediately after the parsha of bikkuim, not here, after the parsha of viduy ma'asros?
In a biographical sketch of Rashi I was reading the author noted that while there seems to be a consensus as to the date of Rashi's death, there is some ambiguity as to when he was born. The reason why is simple -- news of the great Rashi's death reverberated around the Jewish world and made headlines; news of his birth was of interest only to family and friends, as at that point in time he was not yet the great Rashi! The Torah here is giving us a similar message. The bikkurim are not just the "reishis," the first of fruits to be harvested, but they are the first steps of a process of treating one's crops, one's income, as something that is a gift from Hashem, not the natural result of "kochi v'otzem yadi." It's only after the farmer finishes the cycle and has distributed terumos and ma'asros properly that "igla'i milsa l'mafre'a" that the gift of bikkurim was one of significance that merits bracha.
2. The parsha of bikkum contains a mitzvah for the farmer of, "V'samachta b'chol hatov asher nasan lecha Hashem Elokecha u'beisecha.." (26:11) I am willing to assume that the farmer this mitzvah is directed to is not a total Litvak -- mistama he is overjoyed at seeing his crops finally bear fruit; he doesn't need a pasuk in chumash to tell him to be happy. Why does the Torah need to command the farmer to be happy?
A few possibilities:
1. The Torah commands a specific type of simcha, one that comes along with a recognition that the crops are, "...Nasan lecha HASHEM ELOKECHA," gifts from Hashem, not merely the product of the farmer's own hard work.
2. The mitzvah comes to teach us the midah of histapkus (see Tiferes Shlomo). There will always be another farmer that has nicer fruit, that has a nicer basket, etc. Nonetheless, be happy with what is given to you, "Asher nasan... LECHA."
3. Along similar lines, it's possible that the farmer has a great crop of olives, but the grapes that year were not so good, or vica versa -- seldom does everything go right in sync. The Torah is telling us to look at the bigger picture and be happy, 'B"CHOL hatov" -- don't nitpick on the details and use them as an excuse to complain.
4. Finally, as the end of the pasuk indicates, don't be selfish with simcha. Spread it to "Beisecha.. halevi.. v'ha'ger..."