The effect of nitrogen and phosphorus application on some enzymatic activities in soil containing wheat residues

Soil is one of the factors influencing the balance of the ecosystem and countless biological and biochemical processes take place in it. In all of these processes, enzymes act as catalysts. Their presence in different cycles of soil nutrients causes the release of elements needed by plants. Therefore, the measurement of some of these enzymes can be an important indicator and criterion for evaluating soil bioavailability and consequently ecosystem measurement. Therefore, in order to investigate the extent and effect of mineral nitrogen (ammonium nitrate) and mineral phosphorus (triple superphosphate) in soils to which wheat plant residues have been added, on the enzymatic activities of urease, invertase, cellulase, alkaline and acid phosphatase were performed by a factorial experiment in a completely randomized design with three replications in the laboratory. The purpose of this study was to investigate the effect of different levels of N and P and their interactions on some enzymatic activities of soil containing plant residues of wheat.

For the purpose of this study, different levels of inorganic nitrogen were: control, 10, 25, 50 and 75 mg Nitrogen per kg soil (N, N10, N25, N50 and N75) and different levels of phosphorus including: control, 15, 30 and 45 mg phosphorous per kg soil (P, P15, P30 and P45) into a P and N poor soil. The soil was added to this soil by 5 wt.% Of crushed wheat residue, transferred to FC moisture and incubated at laboratory (relatively constant) temperature for 6 months. At the end of the incubated, the activities of urease, invertase, cellulase and alkaline and acid phosphatase were measured.

The interaction of different levels of phosphorus and inorganic nitrogen on some enzymatic activities showed that urease enzyme was highest in P30N25, P30N50, P15N25, P30N10, P30N75 and P45N10 and lowest in control treatment. Urease activity in these treatments was about 2.3 times that of the control. The highest activity of invertase was observed in P15N10, P15N25, P15N50 and lowest in P30N75. The activity of this enzyme was about 21% higher in the treatments containing phosphorus 15 and nitrogen 10 (mg/kg soil) than in the treatments containing phosphorus 30 and nitrogen 75 (mg/kg soil). The highest cellulase activity was observed in P15N10, P15N25 and the lowest activity in P45N25. Alkaline phosphatase had the highest activity in P30N10, P15N10, P30N25, P15N25 and P30N50 and lowest in phosphorus 45 and inorganic nitrogen 75 (mg/kg soil). The enzyme activity in these treatments was about 1.2 times that of P45N75. Acid phosphatase activity was highest in P15N50 and P15N25 and lowest in phosphorus 45 and inorganic nitrogen 10 (mg/kg soil) and in phosphorus 45 and mineral nitrogen 75 (mg/kg soil), respectively.

In general, application of mineral fertilizers to soil containing wheat residues increased some of the enzymatic activities according to the results of experiments for maintaining soil fertility and also balance in the rate of decomposition and emission of greenhouse gases and enzyme activity. Inorganic fertilizers at low concentrations are recommended as the catalysts for the reaction. Therefore, farmers are advised not to remove plant residues from the soil after the end of the growing season, but to balance the residual decomposition rate by adding appropriate levels of mineral fertilizers to gradually improve plant nutrition and characteristics while gradually decomposing. Physically improve the soil as well.