Spectral analysis of coffee, maize and wheat production in Kenya

Spectral methods are applied to coffee, maize, and wheat production series. Coffee and wheat spectra reveal two cycles each. For coffee, most spectral power is concentrated at a frequency corresponding to a 2.4 year cycle. A second coffee cycle has a period of about 4.6 years. Similarly, wheat has 5 year and 2.9 year cycles. Maize has one cycle lasting for a period of 2.8 years.