Shading: a traditional method of microclimate manipulation.

Microclimate management and manipulation are among the methods which have traditionally been employed on small plots in low-input agriculture. Methods employed by smallholders to shade soil, seedlings, plants and crops to protect them from environmental stresses and to improve their yield capacity are described. Specific examples collected from Tanzanian practice, including maize, millet, wheat, potatoes and sunflowers grown under trees, are described as evidence of the use of shading methods in traditional farming. (Abstract retrieved from CAB Abstracts by CABI’s permission

An extension approach to close the gap between suppliers and users of agrometeorological services in the South-Western Free State of South Africa

Agrometeorological information, advisories and services remains one of the major hindrances toward productive agriculture. Well researched and scientifically proven information is inaccessible to most potential farmers whether commercial, resource poor or subsistence. A noticeable gap exists between information developers or suppliers and end-users such as farmers. This paper is aimed at discussing the existing gaps and practical solutions toward the enhancement of proper information dissemination. In workshops organised by the Agricultural Research Council in partnership with the University of the Free State on the training of extension agents the following was discovered: the interviewed extension agents indicated that 13% had good background on the application of agrometeorological information and 87% had no skill. About 80% followed the daily weather forecast. But 86% of the participants could not differentiate between short term forecast, seasonal and long-term predictions. The need for intensive training of extension agents on agrometeorological information, advisories and services was emphasised, since such information is the integral part of agricultural decision-making toward sustainable agricultural productivity and food security.Keywords: Extension Approach, Agrometeorology, Advisories, south-western Free Stat

Scientific research in Africa in the 21st century, in need of a change of approach

The mangrove habitat exhibits many unique physical features, one of the most important of which is a salinity gradient. Photosynthetic rates, as measured by leaf stomatal conductance and leaf chlorophyll fluorescence induction, were tested as indicators of salinity stress in seedlings of the red mangrove, Rhizophora mangle, grown under five different salinity levels: 0, 15, 30, 45, and 60 parts per thousand. Photosynthetic gas exchange (measured by stomatal conductance), as well as the light reaction of photosynthesis (measured by chlorophyll fluorescence) were found to decrease as salinity increased. The use of leaf stomatal conductance and chlorophyll fluorescence as a measure of photosynthesis allowed a rapid and reliable quantification of the known stressor, salinity, in seedlings of R. mangle. These non-destructive in-vivo techniques were found to be rapid and reliable for monitoring photosynthetic stress, an important physiological parameter determining survival and growth of mangrove plants. These techniques should be considered in forestry management and mangrove restoration projects to assess plant condition

Wind reduction patterns around isolated biomass for wind erosion control in a desertified area of Central Sudan

The aim of this study was to assess the effectiveness of sparse vegetation, feature common in arid zone, to reduce wind force (velocity) and hence protect the surface and regions downwind from drifting sand and their consequences. Respectively 4 (with heights h of 4, 3.2, 2 and 1.66 m), 2 (with h of 3 and 2.5 m) and 3 (with h of 1.04, 0.9 and 0.8 m ) well established single biomass configurations of Leptadenia pyrotechnica trees, Prosopis juliflora trees and Panicum turgidum grass, were selected in the field. Solar powered cup anemometer wind measurements with a data logger system were taken at heights of 0.25 and 0.5 h, at distances 0.5 and 1 h, at four sides of the tree in the prevailing wind direction and perpendicular to it, and additionally at 2, 4 and 6 h windward and leeward. The protection effectiveness of the biomass was calculated as a wind reduction ratio and in terms of objects protection, which was evaluated using the dimensionless protection index (É). The study showed that windward protection provided by Leptadenia and Prosopis at level 0.25h and distance 0.5 h was similar, w ith a wind reduction ratio R0.8, while Panicum showed comparably higher R-values. Even at the 0.5 h level, Panicum showed an R of 0.65 at 0.5 h distance. Leew ard, at 0.25 h level differences were small, R increasing from 0.6/0.7 to 0.8/1 with distance, Leptadenia protecting best. At higher level (0.5 h) at distances 0.5 and 1 h Prosopis gave better protection than the other two at distances 0.5, 1 and 2 h. The research is an exam ple of simple experimental work under difficult environmental conditions in Africa. It was part of studies in which additional attention was paid to quantification aspects under such conditions as well as to the problems it helped solve in the African societies concerned as agrometeorological service

Multi-point temperature measuring equipment for crop environment, with some results on horizontal homogeneity in a maize crop. 1. Field results.

The use of temperature measurements above, below and within plant stands in physiological and ecological studies is briefly reviewed and the choice of sensor and protection from radiation effects in measuring temperatures within a maize crop are discussed. The horizontal homogeneity of temperature was investigated. Measurements in 1973 and 1974 showed the greatest horizontal temperature difference at 1.8 m above ground level due to an increase in leaf area density just above the height where the crop became closed and air flow was reduced; at lower levels temperature differences increased as turbulence was reduced, and differences in soil surface conditions influenced temperature measurement. The need for a large number of measuring points in the lower parts of the canopy is emphasized. (Abstract retrieved from CAB Abstracts by CABI’s permission

Multi-point temperature measuring equipment for crop environment, with some results on horizontal homogeneity in a maize crop. 2. Equipment used.

Details regarding equipment used in obtaining field data on crop environment temp. published earlier [see FCA 30, 5292] are reported. Pt resistance mounting and error analysis, calibration of these resistances and data logger requirements and modifications are dealt with. Equipment details regarding the actual collection of accurately scanned field temp. are discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission