Effect of Polyacrylamide and Organic Matter on Three Structure Stability Indices in Two Fine and Medium Textured Soils Under Various Wetting and Drying Cycles

Document Type : Research Paper

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Abstract

Several quantitative stability indices including wet aggregate stability (WAS), mean weight diameter under fast wetting (MWDf) and dispersible clay (DC) have been employed to evaluate soil structure stability. Polyacrylamide (PAM) and organic matter as soil conditioners are vastly used to improve soil structure. This project was carried out to study the effects of PAM and organic matter on aggregate stability of two sandy loam and clay loam soils. It was conducted in pot under greenhouse conditions with applying anionic PAM at three rates (0, 10, 30 mg kg-1), organic matter to form decomposed animal manure < 0.5 mm at two rates (0 and 5 % by weight) and cycles of wetting and drying at five rates (1, 3, 5, 10, 15) with moisture contents ranged from FC to about 1/2 FC. The pots were kept at 22 – 250C under laboratory condition. The experiment was conducted as a factorial based on randomized complete block design with three replications. Indices of WAS, MWDf and DC were measured after 1, 3, 5, 10 and 15 wetting and drying cycles in three replicates. Results showed that with 5 % OM and 30 mg kg-1 PAM , WAS increased about 3.28 times in sandy loam and nearly to 2.4 times in clay loam soil. The climax effect of PAM on WAS in sandy loam occurred after 3 cycles of wetting and drying and thereafter it gradually declined to about half. In the clay loam soil both WAS and MWDf  steadily increased up to 15 cycles and never decreased. The effect of PAM on DC at both rates of PAM application was the reverse of WAS and MWDf. As an organic amendment, PAM appeared to have great ability in improving structure stability in both soils. 

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Water and Soil Science
Volume 22, Issue 4 - Serial Number 4
February 2012
Pages 161-172

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