Atividade da enzima nitrato redutase e formas de nitrogênio no cultivo de trigo em combinações de nitrogênio e potássio

Abstract

Wheat is one of the foods that guarantee world food security, being cultivated for millennia and adapted to different environmental conditions, so that proper fertilization management is one of the main factors for increasing productivity and grain quality. Thus, the objective was to evaluate the activity of the enzyme nitrate reductase, the productive, structural and morphological characteristics of BRS 394 wheat, cultivated with combinations of nitrogen and potassium doses in Cerrado Matogrossense soil under greenhouse conditions, using Red Latosol collected in a remaining agricultural area cultivated with wheat for 6 consecutive years. A randomized block design was used in a 5x5 factorial scheme, corresponding to five doses of nitrogen (0, 70, 140, 210 and 280 mg dm-3 ) and five doses of potassium (0, 50, 100, 150 and 200 mg dm-3 ), with four repetitions. The experiment was collected 80 days after sowing. The analyzed variables were phytometric and nutritional characteristics, productive components, biomass, nitrate reductase enzyme activity and forms of nitrogen in the soil. Data were submitted to analysis of variance and, when significant, to regression analysis at 5% probability of error using R and MINITAB software. The activity of the nitrate reductase enzyme was influenced only by the doses of nitrogen, with the dose of 95 mg dm-3 of nitrogen providing the best result for the enzymatic activity. The application of nitrogen doses between 152.67 and 163.53 mg dm-3 and potassium dose 191.50 mg dm-3 provided the best responses for the SPAD index of the wheat cultivar BRS 394. Dry mass of the aerial part, the nitrogen concentration and the protein content in the leaves, were influenced only by the doses of nitrogen that promoted increment of 39.26%, 66.18% and 67.32% respectively, between the lowest and highest dose. The increase in nitrogen doses positively influenced the concentrations of nitrate and ammonium in the soil, as well as the productive characteristics of the wheat crop, with the exception of the mass of 100 grains.