CRITICAL NITROGEN AND NUTRITIVE INDEX IN CENCHRUS PURPUREUS (SCHUMACH) MORRONE CULTIVARS

Abstract

Objective: to determine and compare the parameters of the nitrogen curve and the nutritive nitrogen index of cultivars of C. purpureus with and without nitrogen fertilization.

Design / methodology / approach: Five cultivars of C. purpureus were evaluated, with or without fertilization, the dose was 141-43-20. The grass was harvested every 21 days with production of dry matter (DM) and nitrogen (N). Growth rates and Critical Nitrogen (Nc) were obtained. The negative power equation was used with its parameters Nc and the Nitrogen Decrease Coefficient (Cd). The Nutritive Nitrogen Index (INN) was obtained with the Nc parameter of each curve, divided by the N content of the cultivar in each sampling. The data were analyzed with a completely randomized design in a factorial arrangement of 5 (cultivars) and 2 (with or without fertilization).

Results: The results of the cultivars show a Nc of 2.6 and a Cd of 0.65 fertilized and 1.14 of Nc and 0.68 of Cd without fertilization, in turn all of them supplemented the amount of N for their soil growth. The INN for the fertilized cultivars was 0.8 with classification of excess and sufficient for the first 56 days.

Limitations of the study / implications: The variables to determine the availability of water and the balance of N, soil-plant, would further expand the knowledge of these tools.

Findings / conclusions: the parameters obtained such as Nc and INN help us to determine the nutritional status of forages.