Effect of Some Natural and Organic Soil Amendments on Improving Some Clayey Soil Properties and its Productivity

A field experiment was conducted on old agricultural land in the Nile alluvial clayey at Gemaiza Agric. Exp. Station, Egypt, located between Latitude 30° 58′ 56′′ N Longitude 30° 57′ 8′′ E during winter growing season of 2010/11. This study aimed conducted to improve some physical and chemical properties as induced by the natural zeiolite and gypsum applied in combination with seaweed extract as well as availability of essential nutrients and their positively effects on plant growth, nutritional status and yield of onion (Alluim cepa L. Giza 20) as well as yield and its components. The obtained results revealed that all the applied treatments increased the total aggregates, as found in the descending order of zeiolite + seaweed extract ≥ gypsum + seaweed extract > zeolite ≥ gypsum> seaweed extract. Regarding soil aggregates hierarchy, the obtained data clearly showed that soil aggregates of 1.00 and 1.0-0.50 mm recorded the highest values at the treatments of (seaweed extract+ zeiolite) and seaweed extract+gypsum for all soil depths vs a pronounced decrease in soil micro-aggregates of <0.25 mm without any clear trend. Soil bulk density values, were significantly decreased in top soil (0-15cm) as well as in subsurface layer (15-30cm) as a result of the applied treatments, with a descending order of seaweed extract + zeiolite > seaweed extract + gypsum > zeiolite > gypsum > seaweed extract> control. Soil porosity and available water showed an increase with a maximum value at the treatment of (seaweed+ zeolite and seaweed extract+ gypsum ) for all soil depths, with relative decrease percentages of 76.6, 14.6 and 12.9 % for seaweed extract +zeolite treatment for soil depths at 0-15, 15-3 0 and 30-40 cm, respectively. The represented data cleared that soluble salts as indicated by ECe and SAR decreased as a result of applied seaweed extract. Also, the CEC showed pronounced increases with all the treated soil. In general, the magnitude of soil available nutrient contents showed a positive response towards the soils treated by (seaweed extract, seaweed extract + zeolite and seaweed extract+ gypsum), which was surpassed the other applied treatments. Nutrient contents in onion bulb, showed progressive increase, since they found to be reached their maximum values at the combined treatments of (seaweed extract+ zeiolite and seaweed extract+ gypsum). Statistically, different tested treatments (seaweed, zeiolite, gypsym, seaweed extract+zeolite and seaweed extract + gypsum) significantly increased bulb yield (as fresh and dry weights) with no significant differences between seaweed extract+ zeiolite and seaweed extract+gypsum. The applied treatment showed the highest increases for total bulbs as a fresh or dry weight, where their increase reached 29.68 and 94.97% over the control treatment. Economical aspects indicated that the highest net benefit values were incorporated with seaweed extract and seaweed extract+ gypsum treatments followed by seaweed extract, seaweed extract + gypsum shell, seaweed extract+ zeiolite , gypsum and zeiolite, where they recorded 4554, 4350, 4023, 3886 and 3314 LE fed, respectively. The lowest value was always incorporated with the control treatment (2461 LE fed).