Vermicompost, Phosphorous Nano-Fertiliser and Humic Acid: Their Effect on the Activity of Inorganic Pyrophosphatase Enzyme and its Thermodynamic Parameters

Abstract

A field experiment was conducted during the autumn season of 2020 in one of the fields of Afak district - Al-Diwaniyah governorate / Iraq to investigate the effect of vermicompost, phosphorous nano-fertiliser and humic acid on the activity of inorganic pyrophosphatase enzyme and its thermodynamic parameters at the flowering and full maturity stages of maize. Randomized Complete Blocks Design was used at three replications. The experimental treatments were 14 treatments, including the control treatment and these treatments consisted of Vermicompost, Humic acid and Phosphorus and Nano-Fertiliser. The results showed that the V treatment had the highest means of inorganic pyrophosphatase enzyme activity (152.5 and 186.9 μg PO4-3-P g-1 soil 5h-1) and the lowest means of Ea (10.34 and 4.72 Kj mole-1) and Q10 (1.162-1.123 and 1.071-1.054) at the flowering and full maturity stages, respectively. The nP2 treatment achieved the highest means of inorganic pyrophosphatase enzyme activity (71.6 and 55.9 μg PO4-3- P g-1 soil 5h-1) at the flowering and full maturity stages, respectively, and the lowest means of Ea (3.54 Kj mole-1) and Q10 (1.053-1.041) at the full maturity stage only. Further, the H1 treatment gave the highest means of inorganic pyrophosphatase enzyme activity (64.5 and 75.9 μg P-nitrophenol g-1 soil 1h-1) and the lowest means of Ea (8.31 and 3.17 Kj mole-1) and Q10 (1.128-1.097 and 1.043-1.033) at flowering and full maturity stages, respectively. Also, the VnP1 and VH1 treatments gave the highest means of inorganic pyrophosphatase enzyme activity (159.0 and 222.3 μg PO4-3-P g-1 soil 5h-1) for both treatments at flowering and maturity stages, respectively, while the H1nP1 and Vnp1 treatments gave the lowest means of Ea (3.72 and 1.59 Kj mole-1) and Q10 (1.056-1.043 and 1.023-1.018) for both treatments at flowering and maturity stages, respectively.