Spatial and temporal variability of soil moisture in non-flooded landscape units in Namibian Zambezi region

Abstract

Climate variability will continue to impact the spatial and temporal variability of soil moisture in different landscapes across the world; and in turn the variability may affect crop production. Non-flood areas in the Namibian Kwalala Landscape of Zambezi (NKLOZ) region are generally relegated to second place, as somewhat marginal for the successful production of major crops such as maize (Zea mays L.). Even when flood water has receded, non-flooded areas which get affected during floods, are still avoided for crop production. This is because residual moisture following the rainy season, is suspected to fall far short of the longer growing duration of maize, to the extent that farmers are too apprehensive to grow maize in such areas. The objective of this study was to determine the effect of seasonal rainfall on spatial and temporal variability of soil moisture within the Namibian Kwalala Landscape of Zambezi (NKLOZ) ecology, and the extent to which soil moisture status and soil temperature patterns (STEPs) characterise soil type (STP) productive potential. Three sensors were setup up at 20, 40 and 60 cm landscape of the NKLOZ, after digging a one-metre trench at each site. Soil moisture and temperature data were retrieved and monitored using Decagon DataTrac 3 software. ANOVA multiple regressions were used to analyse the effects of soil depth, rainfall, and soil temperature on soil moisture. Seasonal rainfall in the NKLOZ during the growing period between October and April (2012-2015) significantly (P < 0.05) and positively affected soil moisture, both in time and space, in recharging soil moisture to sufficiently meet maize crop water requirements in the region. Although it appeared like high amounts of soil moisture sufficiency were as a result of the events of seasonal rainfall received during the growing period, anything received between mid-January and Mid-March was still below the historical minimum and maximum decadal; and in any case late for early planted maize crop. Average soil moisture data indicated for loamy soil (8.30), sandy loam (14.30) and sand at the respective sites suggested a large rainfall season-soil texture interaction. Such an interaction should inform the prudence of production of maize from the point of view of a smart or robust crop system growing planning and management.

Key words: Decagon sensors, residual moisture, Zea mays