Abstract:

The present research was conducted to assess the effects of vermicompost (VC) treatments under different soil moisture contents on consistency limits of sandy-clay-loam (SCL) soils in which lettuce (Lactuca sativa var. crispa) was cultivated in a greenhouse. Liquid limit (LL), plastic limit (PL), plasticity index (PI), consistency index (Ic) and clay activity (A) values were investigated. Three different VC doses (0, 2.5 and 5% w/w) were applied at 3 different soil moisture contents (100% FC-field capacity, 50% FC and 25% FC). Experiments were conducted in 3 replications over 27 experimental plots (3×3x3). Increasing LL and PL values were observed with increasing VC doses. The greatest LL (46.6%) and PL (37.7%) values were obtained from the 5% VC treatment under high soil moisture content (100%FC) and the lowest LL (35.0%) and PL (23.0%) were obtained from the control treatment under low soil moisture content (25%FC). LL had significant correlations with VC (0.848**), PL (0.904**), PI (0.565**), Ic (0.668**) and A (0.548**). Ic had significant correlations with VC (0.815**), PL (0.417*) and PI (0.740**). As compared to the control treatments, Ic values increased by 13.0% and 21.9% respectively with 2.5% and 5% VC treatments. Ic values were greater than 0.75. Therefore, it was observed that the sandy-clay-loam soils could be cultivated without any structural deformations at FC or higher moisture contents with vermicompost application. Moisture content upper limits for optimal tillage without any structural destructions were suggested as 26.8%, 34.9% and 36.9% for 0%VC, 2.5%VC and 5%VC treatments, respectively. Present findings indicated that VC treatments extended the range of moisture for workability.

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