Diurnal course of light interception by a groundnut crop grown in association with maize

Abstract

Maize and groundnut crops were grown in pure and mixed cultures in adjacent plots in the FTC farm at Homabay, Kenya. Measurements of diurnal light interception, leaf diffusive resistances (r1), water potential and leaf temperature on both groundnut intercrop and sole crop were carried out on 3 consecutive days. Characteristics related to nitrogen fixation were also estimated. The canopy of the groundnut intercrop intercepted low irradiance at all times in contrast to the sole groundnut crop. Between 1100 and 1500 h the groundnut intercrop received about 11% and 41% of the available photosynthetic photon flux density (PPFD) and total radiation, respectively. In general, both adaxial and abaxial r1 values were lower at midday when irradiance was maximal than at 0800 or 1800 h. The r1 data together with high values of leaf (ψω) (∼−0.30 MPa) suggest the absence of midday closure of stomata in both pure and mixed groundnut crops. The degree of nodulation was higher in monocrops than intercrops although their N2 fixation capacities did not vary with cropping system. It is suggested that the low yields of legume intercrops reported heretofore are mainly due to the selective absorption of the active wavelengths of PAR by the tall cereal crops.