RADIATION USE EFFICIENCY AND OPTICAL PROPERTIES OF THE PEANUT CROP

Abstract

An experiment was conducted with peanut (Arachis hypogaea L.), cv. IAC-TATU-ST, in Botucatu, São Paulo State, Brazil; in the period from 11 February through 03 June 2001. In all plant development stages, the photosynthetically active radiation (PAR), the incident PAR, the reflected PAR, and the transmitted PAR were monitored, as well as the growth and the weekly phytomass production and the accumulated chemical energy in the roots, stems, leaves, fruits and seeds. The objective of the study was to determine the radiation extinction coefficient (k), the radiation use efficiency (RUE), the radiation conversion efficiency (RCE), and the crop harvest index (HI). The results showed that k has been equal to 0.66. Peanuts, at the final stage, intercepted 628 MJ m-² and absorbed 592 MJ m-² of the PAR, accumulating 803 g m-² of dry matter and storing 14.8 MJ m-² of chemical energy with RUE equal to 1.28 g MJ-¹ and RCE equal to 2.5%. The observed yield was 4.4 t ha-¹ of peanut in pods, corresponding to 3.3 t ha-¹ of peanut seeds. The HI was equal to 0.58 MJ MJ-¹, in energy basis, and 0.41 g g-¹ in dry matter basis.

KEY-WORDS: Growth analysis; leaf area index; light interception.