Troubleshooting for DNA extraction from soil sample (DNeasy powersoil pro kit, QIAGEN)

Greetings, this is a graduated student trying to extract DNA from soil sample, using DNeasy powersoil pro kit. However, there is a problem. Although I followed all of protocols without any change or mistake, yield of DNA (A260/A280) is low and graph is also not clear, which means DNA isn't extracted well.

Is there any tips or solutions for the problem?