The conflict of human versus in Arrow of God relates to the Igbos’ involvement in agriculture, and forms a central part of the plot about changing colonial control. Because they are particularly dependent on yams, they have developed religious rituals intended to help them ensure a good harvest. The conversion of many people to Christianity, along with the British political repression of Igbo leaders, including incarceration, interferes with the rituals.

The primary development of this theme involves Ezeulu’s inability to eat ritual yams each month, and related insistence of delaying an important festival for the new yams. The human attempts to intervene with the natural process so that the crops will crow well and harvest will be successful, are thus interrupted. The British co-opt the indigenous ritual, replacing it with a festival dedicated to Christ, and encourage the harvest to proceed, thereby pressuring the Igbo people to convert just so they can eat.

I just answered this question, so if you look on the right side of this answer under "Top Tags in Arrow of God", you'll see a list. If you click on "man vs society", you'll get the answer to your question. That question asked about two conflicts in the novel, man vs. nature and man vs. society.