Effect of Agricultural Exploitation on the Activity of Alkaline Phosphatase and Its Kinetic Properties in Some Soils

Abstract

In order to study the role of agricultural exploitation in the activity of alkaline phosphatase in the province of Diwaniyah, six sites that differ in some of their chemical, physical and biological properties were selected (Diwaniyah, Sunniya, Shamiya, Daghara, Afak and Al Budair). Three types of soils were chosen in each location, namely, orchard soil, field soil and jungle soil. The kinetic parameters of the enzymes maximum velocity (Vmax) and Michaelis constant (Km) were estimated in all study soils using increasing concentrations of the controlled substance. The results present that the highest efficacy of this enzyme is in the orchard soil of all sites except the location of the center Diwaniyah and Shamia. The average efficacy values ranged between (208.11 -234.95) μg P-Nitro phenol. g -1 soil. 1 hour -1 . The highest value of maximum velocity (Vmax) recorded at the field soil of Al-Shamia site (108.57) μg P-Nitro phenol. g -1 soil. 1 hour -1 . The lowest value recorded at the soil of a jungle field at the Sunniya location (49.62) μg P-nitro phenol. g -1 soil. 1 hour -1 . While the orchard soil of Al-Budair had the highest value of the Michaelis constant (Km) of (85.90) mM, the orchard soil of the Sunniya location had the lowest value (24.34) mM.

Influence of substrate concentration on kinetic parameters of alkaline phosphatase enzyme

“…1 hr -1 Al-Taweel, (2001). confirmed the variation in Vmax and Km values for Imidase enzyme among the ten studied soils, as the Km values of ranged between (2.56-44.19) mmol.…”

“…The Vmax values were between (12.88-446.68) μg-N NH4 gm -1 soil .2hr -1 , and found a difference in Vmax and Km values of the Amide enzyme in the rhizosphere soil of wheat and bean plants, the Vmax values were (205.88 and 216.59) Micrograms N -NH4 g -1 soil 2 hr -1 and Km values (10.78 and 9.86) mM, respectively, due to a difference in the nature of plant roots secretions, plus the difference in the numbers and types of microorganisms that secrete the enzyme. The high V max value indicates the high effectiveness of the enzyme in the soil and the difference in its sources and composition, resulting from the high amount of organic matter in the study soil and the nature of the types and numbers of microorganisms in forest soils, as well as the increase in the amount of root exudates and the type of clay minerals(Al Taweel, 2001).…”

Relationship among Soil Biophysicochemical Properties, Agricultural Practices and Climate Factors Influencing Soil Phosphatase Activity in Agricultural Land

“…Although ALP activity has been proposed as an early indicator of change in soil biological status [64], it does not show a strong association with specific soil bacterial community composition [66], suggesting that it may be less sensitive compared to other enzymatic activities such as urease or dehydrogenase [55]. Consequently, ALP activity may not be a reliable indicator of soil microbial abundance [67], plausibly due to the diverse sources of this enzyme originating from both microorganisms and microbial plant secretions [68]. A positive relationship between microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) has been demonstrated [62], and both are indicative of microbial biomass [63].…”

“…Our findings provide evidence of positive associations between APase activity and MBC, but also with microbial biomass P (MBP) and MBN (Figure 1, Table S3) Although ALP activity has been proposed as an early indicator of change in soil biologica status [64], it does not show a strong association with specific soil bacterial community composition [66], suggesting that it may be less sensitive compared to other enzymatic activities such as urease or dehydrogenase [55]. Consequently, ALP activity may not be a reliable indicator of soil microbial abundance [67], plausibly due to the diverse sources of this enzyme originating from both microorganisms and microbial plant secretions [68].…”