Answer
The long period of wet weather is causing problems in the soil by washing away nitrogen from the soil and/or by disrupting the growth of root nodules which provide nitrogen needed for chlorophyll synthesis. The disruption could be due to water building up in the soil, causing anoxia.
Work Step by Step
Review Concepts 37.3 and 37.1 on soil structure and the role of water in it as well as the value of root nodules for legumes such as peanuts.