This breaking open of the earth is one of the signs of Allah (swt). It paves the way for the growing of the plant and its emergence into the air. If we were to look at a plant, we would find that it is made up of thin sprouts or leaves. Albeit this, it is able to break open the earth and emerge from it. We might even notice that there are some traces of soil left behind on the small leaves! This phenomenon does not happen except due to the power of Allah (swt) and His Guardianship over His Creation. It may even be that He lays down in this seed of His Power.
Furthermore, the breaking open of the earth is necessary for the fertility of the soil and it is suitable for agriculture. For that, you might see farmers ploughing the soil many times because, ploughing the soil will turn it over and allow air to penetrate into the outer layer, thus making it crumbly. It also exposes it to the sun rays. Hence, when rain falls, the earth will break open and with the permission of its Creator, it is now the turn of the plant to carry out its job.