Soil organic matter
Organic matter in soil was determined by the Walkley-Black procedure was described in Nelson and sommers (1996). In this method, 1.0g soil sample was treated with 10 mL of 1 N K2Cr2O7 and 20 mL of concentrated H2SO4. After adding of 200 ml distilled water upon cooling, the suspension was filtered and filtrate was titrated against 0.5 N FeSO4 solution using ortho-phenopthaline as indicator with appearance of maroon color as end point. A blank sample was run simultaneously. The amount organic matter was calculated from the number of moles of K2Cr2O7 utilized in the oxidation of organic C in soil.
Soil Texture
Soil texture was determined by Bouyoucos hydrometer method (1962). in brief, 50 g air-dry soil was dispersed 5 ml 10% sodium exametaphosphate solution in a mechanical dispersion for 5 min. After quantitative transfer of suspension to a 1 L Bouyoucos cylinder, filling the cylinder with distilled water to 1-L mark. After through mixing, care fully inserted a hydrometer in the suspension and took the hydromitrec reading after 40 sec for silt + clay and after two for clay. Also note the temperature of the suspension with each hydrometer readied and made necessary correction in hydro meter reading. Percent silt and clay were calculated from hydrometer while % sand was calculated by difference. Percent sand, silt and clay were used to determined soil textural classes on the USDA soil textural triangle.
Extractible P and K in soil
The extractible P and K in soil were also measured in the AB-DTPA extract (Soltanpor and Schwab, 1977). Potash was read on read Flame photometer, while P on spectrophotometer at 880nm after proper color development. The concentration of extractible P and K were calculated from the regression equation develop from reading their respective standards.
Extractible Micronutrient in soil
The concentration of extractible micronutrient Zn in soil was determined by the AB-DTPA extraction procedure (Soltanpor and Schwab, 1977). In this method, 10g soil sample was shaken with 20 ml AB-DTPA extract in an open Erlenmeyer flask for 15 min. After filtering, extract was read for Zn on an atomic absorbtion spectro meter (Perkin Elmer analyst 200, USA).
Respective leaves from each treatment plot were collected after ashing for the required qualitative and quantitative determination of spinach.
