INFLUENCE OF SOIL PHOSPHORUS ON ENZYME ACTIVITY, RYEGRASS YIELD AND EXTRACTABLE PHOSPHATE

Q. U. Khan, T.H. Flower* and Sanaullah**

Department of Soil and Environmental Sciences, Gomal University, Dera Ismail Khan, Pakistan
*Department of Analytical and Environmental Chemistry, University of Glasgow, U.K.
**Agriculture Research Institute, Dera Ismail Khan, Pakistan
Corresponding author. E-mail: qudrat_baloch@yahoo.com

ABSTRACT

To investigate the effect of soil Phosphate on enzymatic activity and plant availability under controlled conditions, five Scottish soil series viz. Dreghorn, Darvel, Caprington, Dunlop and Midelney having different physico – chemical characteristics were studied. The experiment was laid out in a Latin square design, with two blocks, with and without ryegrass. The enzymic activities showed a significant difference in all the soils except Dreghorn soil for alkaline phosphatases and phosphodiesterase. The enzyme activities generally increased in grassed soils as compared to non grassed soil with the variable differences to original soils. The yield of roots and tops of ryegrass and P uptake was significantly different amongst the different soils. The highest yield of tops was recorded 4.36 and 4.07 g pot-1 in Darvel and Midelney soil series respectively. The dry matter yield of roots was significantly highest in Darvel soil. The total P uptake by the leaves and roots also showed a significant difference between the soils. The highest P concentration of 0.276 and 0.209 % P in leaves and roots was found in Midelney soil. Positive correlation (r = 0.7955) was recorded between the dry matter yield and P uptake by the ryegrass. The soil phosphate extracted by using different extractants also showed significant differences amongst the soils before planting and after harvesting. The acetic acid extractant in grassed pot was lower which suggest that 0.5 M acetic acid is a good measure of P utilized by the grass.
Key words: Phosphate, Ryegrass, Phosphatases Enzymes, Phosphate uptake.