Impact of organic and inorganic amendments on saturated and unsaturated hydraulic conductivity of sandy soil under alfalfa plants

الملخص EN

A field experiment was conducted a sandy soil cultivated with alfalfa during the winter season of 2001/2002 at Ezbet Dawoud, Sinnoris district, El Fayoum Governorate.

This work aimed to identify the changes of saturated and unsaturted hydraulic conductivity as affected by the application of local organic compost and inorganic natural deposits of bentonite shale, as soil amendments, which were applied at foure levels (0, 1.0, 2.0 and 4.0 % w/w), thoroughly mixed with the uppermost 15 cm depth.

These treatments represent field application of 0, 10, 20 and 40 ton/fed.

The results obtained showed that, there was a dual relationship between pore size distribution and both total porosity and available water content as affected by the applied soil amendment levels, where drainable pores (3000-30 ?,) exhibited a gradual decrease vs an increase in each of total porosity and available water with increasing the applied amendment levels.

These findings were confirmed by a parallel decrease in the values of saturated (Ks) and unsaturated (K?) hydraulic conductivity in soil surface and apart in subsurface layers.

This trend could be ascribed to the physico-chemical action of both applied organic and inorganic colloidal particles that supported soil structure, throughout increasing both meso and micro-pores (9.0-0.2 ?).

In addition, soil matric potential increased as a result of increasing particles surface area, which have a higher ability to retain water, and in turn to increase water potential.

In general, results obtained indicated that the applied organic compost was surpassed the bentonite shale for improving the previous soil parameters, due to it decreased the loss of soil moisture and enhanced the water retention, and in turn increased the volumetric moisture content (?), which enhanced the continuity of water films between the soil particles.

The positive effect of the used amendments on improving the previous soil properties was partly extended for the untreated subsurface layers, with a superiority for bentonite, may be due to the relative mobility and migration of inorganic colloids from the uppermost layer to the subsoil one throughout the quickly drainable pores.

The promotive effects of the used amendments are also reflected on growth of the grown alfalfa plants (fresh weight), and in turn their dry matter yield for the three cuts.

Data showed a progressive increase in the studied plant parameters associated with increasing the amendment rates.

Consequently, of N, P and K content in alfalfa plants responded positively to all the tested treatments, with a superiority for organic compost.

This is due to organic constituents (humic and fulvic acids) have a relatively pronounced effect on the improved the physical, chemical and biological characteristics of sandy soils as well as being as a source of nutritional elements.