Maize response to in-field rainwater harvesting on the Fort Hare/Oakleaf ecotope
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Date
2007-05
Authors
Joseph, Lesoetsa Frans
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
The majority of rural households in the Eastern Cape Province struggle to meet basic
needs especially in terms of household food security. Recent studies done in the
Province indicate that agriculture contributes little to solve this problem especially in
the villages around Alice. Despite poverty, most households rely on purchasing food
from urban markets instead of producing food themselves. Crops are usually
produced under dryland conditions by using mouldboard plough (conventional
tillage) as the primary cultivation method. Research on clayey soils in semi-arid
ecotopes showed that in-field rainwater harvesting technique (IR'WH) has potential to
increase maize grain yield by up to 50% compared to conventional tillage (CON). The
question was whether IRWH will also perform better than CON in the Alice district
using Fort Hare/Oakleaf as a benchmark ecotope.
The main aims of this study were to characterize important climate, soil properties and
soil processes related to maize production on the selected ecotope and to compare the
influence of IR WH treatments and CON on; (i) maize grain yield (ii) soil water balance
components and (iii) crop-water related efficiencies. The ecotope was characterized in
detail with respect to slope, long-term climate and soil characteristics. Long-term (27
years) climate data was used to analyze climate parameters which are related to maize
production. A profile pit was dug next to the experimental plot and the soil was described
in detail and classified using the South African Classification System. To compare the
influence of IRWH treatments and CON on maize grain yield, a fully randomized
complete block design experiment was used in 2004/05 and 2005/06 growing seasons.
The three treatments viz. IRWH (with mulch), IRWH (without mulch) and CON were
replicated three times. Maize cultivar PAN 6480 was planted at a population of 22 000
plants ha-¹. Since planting was done by hand, 32.5 g of fertilizer mixture 3:2:3 (22) +
0.5% Zn was applied per hole to supply 60 kg N ha-¹, 40 kg P ha-I and 60 kg K ha-¹.
Evapotranspiration was calculated by using the soil water balance equation which
depended on rainfall (measured with rain gauge), drainage (by comparing soil water
measurements with drained upper limit), runoff (calculated) and change in soil water
content (measured with neutron water meter). Grain yield was measured and crop-water
related efficiencies were calculated. The results were used to compare maize response to
three different treatments in terms of grain yield, soil water balance components and
crop-water related efficiencies.
The long-term climate data indicates that the ecotope qualifies as semi-arid due to
high evaporative demand (1611 mm) and low rainfall (583 mm). The soil was
classified as an Oakleaf form of the Ritchie family. The mean grain yield indicates
that IRWH (with mulch) and IRWH (without mulch) produced 25 and 19% more grain
than CON, respectively. The grain yield ranged from 2066 to 4373 kg ha-¹ over the
two seasons. IRWH treatments had higher ET than CON at the end of both seasons.
The low Es at the end of both growing seasons for CON was ascribed to the higher exfield
runoff that decreased the available water for evaporation considerably. Cropwater
related efficiencies' results followed the same trend as grain yield. It can be
concluded that Fort Hare/Oakleaf ecotope is suitable for in-field rainwater technique
due to its climate and soil properties. IR WH treatments were compared to CON and
as hypothesized IR WH treatments performed better than CON in terms of to grain
yield and crop-water related efficiencies. Mulch application increased grain yield by
25% compared to CON, while IRWH (without mulch) increased grain yield by 19%
compared to CON Results showed that IRWH technique was able to harvest and
store more rainwater than the CON due to the total stoppage of ex-field runoff.
Description
Keywords
Corn -- Water requirements -- South Africa -- Fort Hare, Water harvesting -- South Africa -- Fort Hare, Rain and rainfall -- South Africa -- Fort Hare, Dissertation (M.Sc.Agric. (Soil, Crop and Climate Sciences))--University of the Free State, 2007