no other land is like it

When Avraham administered an oath to Eliezer not to take a Canaanite girl for Yitzhak, he referred to Hashem as אֱלֹקי הַשָּׁמַיִם וֵאלֹקי הָאָרֶץ (24:3): 

 וְאַשְׁבִּיעֲךָ בַּה׳ אֱלֹקי הַשָּׁמַיִם וֵאלֹקי הָאָרֶץ אֲשֶׁר לֹא תִקַּח אִשָּׁה לִבְנִי מִבְּנוֹת הַכְּנַעֲנִי אֲשֶׁר אָנֹכִי יוֹשֵׁב בְּקִרְבּוֹ

However, just a few pesukim later, Avraham told Eliezer that Hashem אֱלֹקי הַשָּׁמַיִם will send an angel to guide him (24:7).  

ה׳ אֱלֹקי הַשָּׁמַיִם אֲשֶׁר לְקָחַנִי מִבֵּית אָבִי וּמֵאֶרֶץ מוֹלַדְתִּי וַאֲשֶׁר דִּבֶּר לִי וַאֲשֶׁר נִשְׁבַּע לִי לֵאמֹר לְזַרְעֲךָ אֶתֵּן אֶת הָאָרֶץ הַזֹּאת הוּא יִשְׁלַח מַלְאָכוֹ לְפָנֶיךָ וְלָקַחְתָּ אִשָּׁה לִבְנִי מִשָּׁם

Why here does Avraham omit any reference to Hashem as אלֹקי הָאָרֶץ and only refer to him as ה׳ אֱלֹקי הַשָּׁמַיִם? 

R' Moshe Avigdor Amiel answers that in the first pasuk Avraham is speaking about taking a wife for Yitzchak.  In this second pasuk Avraham is speaking about his having left his homeland to go to Eretz Yisrael.  Avraham is telling us that if you want to know why he left home, you won't find the answer if you look at the land, if you focus on אלֹקי הָאָרֶץ.  There are other countries that have more natural resources, that have the benefit of not being surrounded by hostile neighbors, where life might be easier or more economically rewarding.  You can only understand our love of the land through the lens of ה׳ אֱלֹקי הַשָּׁמַיִם.  What Eretz Yisrael has more than any other place is a direct pipeline to connect to Hashem.

The Kuzari makes a similar point (II:9-10):

אָמַר הֶחָבֵר: כֵּן הַכָּבוֹד: נִיצוֹץ אוֹר אֱלֹקי מוֹעִיל אֵצֶל עַמּוֹ וּבְאַרְצוֹ. 

  אָמַר הַכּוּזָרִי: מַאֲמָרְךָ "אֵצֶל עַמּוֹ" כְּבָר הִתְבָּאֵר לִי, אֲבָל מַאֲמָרְךָ, "וּבְאַרְצוֹ" קָשֶׁה לִי לְקַבְּלוֹ. 

 אָמַר הֶחָבֵר: אַל יִקְשֶׁה בְעֵינֶיךָ שֶׁתִּתְיַחֵד אֶרֶץ בְּדָבָר מִכָּל הָאֲרָצוֹת, וְאַתָּה רוֹאֶה מָקוֹם שֶׁמַּצְלִיחַ בּוֹ צֶמַח מִבִּלְתִּי צֶמַח, וּמוֹצָא מִבַּלְעֲדֵי מוֹצָא, וְחַיָּה מִבַּלְעֲדֵי חַיָּה, וּמִתְיַחֲדִים יוֹשְׁבָיו בְּצוּרוֹת וּמִדּוֹת מִבַּלְעֲדֵי זוּלָתָם – בְּמִצּוּעַ הַמֶּזֶג. וְהִנֵּה עַל פִּי הַמֶּזֶג תִּהְיֶה שְׁלֵמוּת הַנֶּפֶשׁ וְחֶסְרוֹנָהּ.

It's understood that plants, minerals, animals, thrive in the environment best suited for them.  If you want champagne, you need grapes from a specific region in France.  If you want to raise a giraffe, you should move to the African plains.  The same is true of ruchniyus, of the connection to ה׳ אֱלֹקי הַשָּׁמַיִם.  You need the proper environment for it to flourish, and that environment is Eretz Yisrael.   

The Kuzari there goes on to discuss nevuah and he writes that prophecy takes place only in and for Eretz Yisrael: אָמַר הֶחָבֵר: כָּל מִי שֶׁנִּתְנַבֵּא לֹא נִתְנַבֵּא כִּי אִם בָּהּ אוֹ בַעֲבוּרָהּ

This, I think, helps explain a seeming redundancy in the pasuk.  Avraham refers to Hashem  וַאֲשֶׁר דִּבֶּר לִי וַאֲשֶׁר נִשְׁבַּע לִי.  If the point is that Hashem promised Eretz Yisrael to him, then just referring to the shevu'a should suffice.  What is this אֲשֶׁר דִּבֶּר לִי?  (See Meshech Chochma, Seforno)  What Avraham I think is saying is that only in Eretz Yisrael can Hashem speak to him.  Only Eretz Yisrael has the "climate" which is suited for conversing with G-d.