Diazotrophic endophytes: progress and prospects for nitrogen fixation in monocots

Spatial variability of plant growth has been a major problem for plant physiologists, agronomists, agro-foresters and soil scientists comparing or modelling treatment effects on acid sandy soils in the Sahel. While aerial photographs from aeroplanes or satellite images may provide valuable information for the surveying of large areas, their use for individual small experiments or farmers' fields has been limited due to high costs, restricted availability, and unsatisfactory resolution. As a simple alternative, a commercially available Zeppelin-type balloon, dragged on a rope by a camel, was fitted with an standard 35 mm camera and a remote control system. Flight altitude varied from 20 m to 500 m above ground. A ground-based camera mounted vertically on a tripod was used to center the Zeppelin over the target area. The high-resolution true colour negatives and colour infrared slides obtained by this device were used to unravel the history of farmers' management strategies for maintaining soil productivity, to monitor treatment effects and crop growth variability in an on-station experiment, and to visualize light absorption by photosynthesis in crops and trees. Such non-destructively collected data may serve as quick but reliable references for ground measurements in a wide range of experiments with loosely-spaced crops, bushes, and trees. ei]B E Clothier