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Abstract

The relationship of soil wetness to soil strength in Red Ferrosols was compared between fields of well structured
to degraded soil structure. Soil structure was assessed using a visual rating. Soil resistance measurements were taken over a range of soil wetness, using a recording penetrometer. Readings were taken as the soil dried by evapotranspiration after both irrigation and rainfall events. The influence of soil wetness on penetration resistance was greater on fields with degraded structure than on well-structured fields. In fields with degraded structure, the wetter the soil, the smaller were the penetration resistance values. Field soil structure score was negatively correlated with the slope of the line relating soil wetness and penetration resistance at 150–300mm depth. The structurally degraded fields had a highly significant relationship between penetration resistance and soil wetness at 150–300mm depth. In well-structured fields, variations in soil wetness had less effect on
penetration resistance. These results indicate that visual assessment can be used with confidence to assess Ferrosol structure. The implications for soil management are that fields with degraded soil structure have greater resistance to root growth at drier moisture contents than well-structured fields. Consequently, farmers need to keep degraded soils wetter with more frequent irrigation
than well-structured soils, to ensure optimum plant growth.

Item Type:	Article
Authors/Creators:	Cotching, WE and Belbin, K
Keywords:	penetration resistance, visual scorecard, root growth, irrigation.
Journal or Publication Title:	Australian Journal of Soil Research
Publisher:	CSIRO
ISSN:	0004-9573
DOI / ID Number:	10.1071/SR06113
Additional Information:	Copyright © 2007 CSIRO
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