Four soil samples were collected from the surface layer of some cultivated and uncultivated calcareous soils located in the areas of Wadi El-Assiut and its interference zone with the Nile valley at Assiut to evaluate the application effects of certain organic materials on some chemical properties and the available Ca and P of these soils. The organic materials included 1) humic acid (HA) 2) vinasse (V) 3) clover straw (CS) and 4) ethyllyene diamine tetra acetic acid (EDTA). They were applied to the soil samples at levels of 2.5 and 5.0%. Soil samples treated with organic materials as well as the controls were moistened to the field capacity and then incubated at 24±2ºC for different time periods (30, 60 and 120 days).
The EC of studied soils significantly increased with the addition of the studied organic materials and with increasing the addition level. It also increased with the time of incubation until 60 days but then decreased after 120 days of incubation. The soil pH increased with adding both humic acid and EDTA compared to the control. However, the application of vinasse and clover straw to all studied soils at both application levels showed a reduction in the soil pH. The CaCO3 content of the organic material treated soils decreased with increasing both the application level of each organic material and the incubation time. Most organic material treated soils showed decreases in CaCO3 in the order of CS > HA ≈ EDTA ≈ Vinasse.
The available Ca of the studied soils increased with adding the investigated organic materials as well as their application level, except using CS. EDTA as a synthetic chelating agent gave the highest amounts of the available calcium in all studied soils. The increases in the soil available Ca induced by addition of the investigated organic materials showed the order of Vinasse> HA> EDTA> CS in all soils.All organic materials resulted in significant increases in the available P of all studied soils compared to the control treatment. In most cases, the available P of the studied soils treated with the investigated organic materials increased with increasing the incubation time up to 30 days and then, decreased in the last two incubation periods (60 and 120 days). Highest levels of available P were observed in the treated A and B (cultivated) soils. However, relatively low available P levels were found in the treated C and D (uncultivated) soils. The increases in the soil available P induced by addition of the investigated organic materials, generally, decreased in the order of the Vinasse > HA > CS > EDTA.