Words'nTone

The agricultural imagery is also present
The imagery of the parable of the Sower who sows is also analogous to the agricultural imagery developed in Isaiah 1-5.

    Your land is desolate,
       Your cities are burned with fire,
       Your fields--strangers are devouring them in your presence;
       It is desolation, as overthrown by strangers.
    The daughter of Zion is left like a shelter in a vineyard,
       Like a watchman’s hut in a cucumber field, like a besieged
           city (1:7-8).

    Surely you will be ashamed of the oaks which you have desired,
    And you will be embarrassed at the gardens which you
           have chosen.
    For you will be like an oak whose leaf fades away
       Or as a garden that has no water.
    The strong man will become tinder,
       His work also a spark.
    Thus they shall both burn together
       And there will be none to quench them (1:29-31).

    The LORD enters into judgment with the elders and princes
     of His people,
        “It is you who have devoured the vineyard;
       The plunder of the poor is in your houses.
    What do you mean by crushing My people
       And grinding the face of the poor?
       Declares the Lord GOD of hosts (3:14-15).

Additionally, the agricultural imagery of oaks (1:29-30; 2:13; cf. 6:13) and gardens (1:29-30) is associated with idolatry.  Idolatry is associated with the dissonance between the function of worship and the nation’s community life and their social responsibilities (1:12ff; 1:17; cf. 1:21).  Their idolatry created attitudes, as well as, religious and socio-economic structures (2:6-8; 2:20) and habits that discouraged or hindered them from their responsibilities toward the poor.  God’s description of this failing and His judgment (e.g., the Lord will have a day of reckoning, 2:12) throughout Isaiah 1-5 are expressed in or followed by agricultural images (e.g., 2:13f).

The parable of God’s vineyard
There is also a connection, rarely noticed, between Mark 4 and Isaiah 5.  In Isaiah, the parable of the vineyard is sandwiched between indictments (Isa 1-3) and the idolatry-taunt (Isa 6:9ff.).  The owner of the vineyard is Yahweh and it represents His people (vv 1-2).  The vineyard was expected to produce good grapes, but only produces worthless ones (v 2).  As a result, God foretells judgment for His vineyard similar to the imagery in Mark’s parable:

    I will lay it waste;
    It will not be pruned or hoed,
    But briars and thorns will come up
    I will also charge the clouds to rain no rain on it (v 6)

Then, as with the parable of the Sower, after the parable of the vineyard an explanation is offered (vv 7ff).  Amid the rebellion and idolatry is the continued charge that justice and righteousness is absent from God’s vineyard:

    For the vineyard of the LORD of hosts is the house of Israel
       And the men of Judah His delightful plant
       Thus He looked for justice, but behold, bloodshed;
       For righteousness, but behold, a cry of distress (5:7).

In summary, there is a corresponding pattern seen in both Isaiah 1-6 and Mark 3-4:

-Indictments against the leaders of Jerusalem / Isa 1-4 / Mk 3:22ff
-Agricultural parable of judgment / Isa 5:1-7 / Mk 4:1-8
-Explanation and
   idolatry-taunt/judgment / Isa 5:8ff; 6:9ff / Mk 4:10-13; 4:13-30

The rhetorical function of the parable continues the programmatic themes established by Mark at the opening of his Gospel.  The parable of the Sower who sows and its place in Mark’s Gospel narrative is analogous to the content of Isaiah 1-6.  The parable presents the realities of the inaugurated Gospel of the Kingdom, not how hearts need to change.  The spreading of the word, that is the Gospel of the Kingdom, is not limited to the religious realm or to individual salvation, but ought to include outcomes that Mark draws upon to give content to His Gospel, which include social righteousness that addresses the needs of the vulnerable and the poor.