Effects of watering interval, planting depth and soil crusting on ermegence and seedling establishment of sorghum (sorghum bicolor (L.) moench)
Date
2011-03-25
Authors
Ntlou, Napo Khotso Emmanuel
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Abstract
A study was conducted in the glasshouse to investigate the effects of soil type,
watering interval, planting depth, and crust formation on emergence and seedling
establishment of sorghum. Three separate pot experiments were conducted
using three soil types and sorghum as a test crop. Various treatment
combinations of soil type/watering interval, soil type/planting depth and soil
type/water drop size delivered from a rainfall simulator were evaluated.
Following the addition of water through the rainfall simulator, soil samples were
prepared into thin sections that were examined under a microscope to determine
the impact of water drops on the soil. Sorghum emergence, shoot height and
shoot dry matter, and crust strengths of the soils were measured. Sorghum
emergence was measured for 15 days while shoot height and shoot dry weight
were measured at 28 days after planting.
Watering intervals had no significant effect on seedling emergence. Increasing
watering interval from 2 days to 8 days reduced shoot height and shoot dry
weight on all three soils. Shoot height and shoot dry weight from clay loam soil
was significantly (P<0.01) higher than from both the sand soil and the sandy
loam soil. The effect of planting depth on seedling emergence was highly
significant (P<0.01). The seedling emergence percentage at 15 days after
planting (DAP) was significantly higher at the shallower planting depth of 3 cm
(98%) than at the depths of 6 cm (64%) and 9 cm (13%).
Shoot height and shoot dry mass were significantly (P<0.01) reduced when
seeds were planted any deeper than 3 cm. The effect of crusting on emergence
and seedling establishment varied significantly (P<0.01) with soil type. Seedling
emergence was 83% from sandy loam, 81% in sand and with the least from clay
loam (52%) at 15 DAP. The crust strength varied with soil type, clay loam (3.5
kg.cm"2), sandy loam (1.54 kg.cm"2) and sand (0.9 kg.cm"2). The crust strength
was negatively and significantly (P<0.01) correlated with seedling emergence (r =
-0.61**), shoot height (r= -0.72**), and shoot dry weight (r= -0.61**) across soil
types. Microscopic examinations of soil thin sections revealed that soil crusts in
clay loam and sand were thicker (1 mm) than in sandy loam (0.2 mm). This
investigation has shown that planting shallower (3 cm) and avoiding soil crusting
especially in clay loam can lead to improved sorghum emergence and better
stand in the field.
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Keywords
Sorghum-Irrigation , Soil permeability