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Soil conservation in relation to maize productivity on sub-tropical red soils in Yunnan Province, China
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|Title: ||Soil conservation in relation to maize productivity on sub-tropical red soils in Yunnan Province, China|
|Advisors: ||Fullen, Michael A.|
Hocking, Trevor J.
Mitchell, David J.
|Publisher: ||University of Wolverhampton|
|Issue Date: ||2001 |
|Abstract: ||Agricultural land in China is being degraded, with soil erosion becoming an
increasing problem. In Yunnan Province, south-west China, there is a long history of
soil erosion due to soil type, climate, anthropogenic influence and because 95% of the
Province is mountainous. Population pressure and lack of flat land necessitate
cultivation of steep slopes. The Yunnan Government prohibits cultivation of slopes
>25°, however policy enforcement would result in food shortages in the Province, due
to a lack of suitable land <25°. Therefore, the most appropriate way to curb soil
erosion in Yunnan is to devise affordable agronomic means of reducing soil loss,
which do not decrease crop productivity on sloping land currently under cultivation.
At present, very little research has addressed these issues.
A research project, building on existing work from 1993-1996, was initiated in 1998.
The aim was to test the hypothesis that contour cultivation and contour cultivation
plus straw mulch decrease runoff and soil erosion rates on sloping land in Yunnan
Province under maize cultivation and to assess the impact of these conservation
measures on maize productivity and soil nutrient status. Thirty runoff plots, located on
three different slope angles (I 3°, II 10° and III 27°), in three groups of 10, were used
to examine three cropping treatments in a replicated plot design in 1998 and 1999.
Treatments were downslope cultivation (control), contour cultivation and contour
cultivation plus straw mulch. In addition, there was an unreplicated bare plot in each
group. Runoff and soil loss were measured on a storm-by-storm basis. Soil nutrient
status was measured at the beginning and end of each cropping season. Crop growth
parameters and soil physical properties were measured throughout the cropping
seasons (21/05–7/10 in 1998 and 22/05–2/10 in 1999).
In 1998, seasonal rainfall was 1024 mm, ~28% greater than the 30-year mean. Soil
loss was significantly reduced by contour cultivation on Slopes I and II. On Slope I,
downslope cultivation produced 3.07 t ha-1 soil loss and contour cultivation reduced
this by 81.4 %. On Slope II, downslope cultivation produced 19.11 t ha-1 and contour
cultivation reduced this by 58.0%. The addition of straw mulch gave a further, nonsignificant,
reduction on both slopes. On Slope III, downslope cultivation and contour
cultivation produced 6.92 and 6.29 t ha-1 of soil loss, respectively, with contour cultivation plus straw mulch having 99.4% less erosion than downslope cultivation. In
the much drier 1999 season, no treatment significantly reduced soil loss on Slope I.
Contour cultivation significantly reduced soil loss on Slopes II and III. On Slope II,
downslope and contour cultivation produced 11.52 t ha-1 of soil loss and contour
cultivation reduced this by 85.8%. On Slope III, downslope and contour cultivation
produced 8.62 and 0.23 t ha-1, respectively; a reduction of 97.3% by contour
cultivation. The addition of straw mulch did not further decrease soil loss.
Treatment effects on soil nutrient status varied between the two years. At the end of
the 1998 season, there was significantly higher soil available N under contour
cultivation plus straw mulch on all three slopes (Slopes I and II P <0.001, Slope III
P <0.05), an effect that was not found in 1999. At the end of the 1999 season, soil
available K was significantly (P <0.001) higher under contour cultivation plus straw
mulch on Slope III. In both years, contour cultivation plus straw mulch significantly
reduced soil temperature. However, this did not result in yield reductions in
comparison with the control. There was an increase in soil moisture content under
contour cultivation plus straw mulch during dry periods, which was particularly
noticeable in 1999. In 1998, there were no significant treatment effects on grain or
shoot yield. In 1999, on Slope II, contour cultivation plus straw mulch significantly
increased grain yield by 50.3% compared with the downslope treatment (P <0.05). In
1999, contour cultivation plus straw mulch also significantly increased leaf plus stem
yield on Slopes I and II by 12.4 and 36.8%, respectively. It is concluded that on ≤10° slopes, contour cultivation alone is a suitable soil
conservation measure. However, use of straw mulch would benefit soil moisture and
nutrient status and could, therefore, increase crop yield. On ≥27° slopes, it is
recommended that contour cultivation plus straw mulch be used as a soil conservation
measure to ensure maximum soil conservation, even in extreme rainfall conditions.|
|Type: ||Thesis or dissertation|
|Description: ||A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of
|Keywords: ||Soil erosion|
|Appears in Collections: ||E-Theses|
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