Genesis 4:11

And now because thou hast killed him, thou art cursed from the earth, which hath opened the mouth, and received the bloods of thy brother from thy hand.

CURSED ART THOU FROM THE GROUND — more than it has already been cursed on account of its sin. In this, too, it has further sinned in that it hath opened its mouth to take thy brother’s blood. Therefore, I impose upon it an additional curse: it shall not continue to give unto thee her strength. Thus the words of Rashi.
But this is not correct since here He did not curse the ground because of him as He did in the case of his father, rather He said that he be cursed through the ground. The explanation of the curse is that the earth shall not continue to give him its strength, and that he be a fugitive and a wanderer in it, and He further stated, “When thou tillest the ground with all your efforts to cultivate it properly by plowing and hoeing, and in all manner of service in the field and by properly sowing it, it shall not continue to give unto thee her strength. Instead, you will sow much and harvest little.” This then was the curse, in the same sense as in the verse: And I will curse your blessings. Thus He uttered the curse in connection with his occupation for he was a tiller of the ground, and so He cursed his work. This then is the sense of the expression, it shall not continue to give unto thee her strength, meaning, “It will no longer yield to you its full produce as it had done till now when you cultivated it.” And so did Rabbi Abraham ibn Ezra explain it.
It is possible that He also cursed him though the ground in that it should no longer yield its strength to him of its own accord; the fig-tree and the vine would not yield their strength in his estate, and the trees of the field would not yield him their fruit. Then He added, “Even when you work the ground by plowing and sowing, it will not continue to give you its strength as before.” Thus there were two curses relating to his occupation, and a third one — that he be a fugitive and a wanderer in the world. This means that his heart will not be at rest, and he will lack the tranquility to remain in one place on the earth; he will wander forever for the punishment of murderers is exile.
The expression in that it hath opened its mouth to take thy brother’s blood means: “You have killed your brother and covered his blood with the earth, and I will decree upon it that it uncover its blood, and she shall no more cover her slain for it will be punished together with all that is covered up in it, such as seed and plant.” This is the punishment for all blood-letting on the earth, even as it is written, For blood, it polluteth the land. The pollution of the land consists of a curse upon its produce, as it is written: When one came to a heap of twenty measures, there were but ten; when one came to the wine vat to draw out fifty press-measures, there were but twenty.

ארור אתה מן האדמה, cursed and deprived of the good the earth has to offer.

אשר פצתה את פיה, because it allowed itself to be used to cover up the killing of your brother. As a result, earth will no longer be free to provide the needs of your livelihood in the degree it did up until now. There was no need to spell out the penalty for the murderer. His punishment is part of the principle applying to the penalty for anyone causing willful damage, i.e. he will experience tit for tat as spelled out in Leviticus 24,19.

ועתה ארור אתה מן האדמה, the curse will be spelled out in the verse following, where G’d explains that Kayin will experience that the source of his curse is the very earth he had used to hide his crime. This earth would not continue to provide its strength for Kayin.

אשר פצתה את פיה, a reference to soaking up Hevel’s blood, [not as in the case of Korach being actively involved in swallowing Hevel. Ed.] We have a similar incident in Job 16,18 ארץ אל תכסי דמי, “Earth, do not cover my blood!” Also Ezekiel 24, 7-8 uses similar language, i.e. כי דמה היה על צחיח סלע שמתהו לא שפכתהו על הארץ לכסות עליו עפר, “For her blood remained within her, she placed it on a smooth rock. She did not pour it upon the ground to cover it with dust.”