Critical concentration and management of nitrogen fertilization in the establishment of Brachiaria hybrid Mavuno

Author(s)

Techio Pereira, Lilian Elgalise ^[1] ; de Sousa, Luan Jardim ^[1] ; Abaker Bertipaglia, Liandra Maria ^[2] ; Herling, Valdo Rodrigues ^[1] ; Bruno Tech, Adriano Rogerio ^[3]

Affiliation

^[1] Univ Sao Paulo, Dept Zootecnia ZAZ, Fac Zootecnia & Engn Alimentos FZEA, Pirassununga, SP - Brazil

^[2] Univ Brasil, Dept Prod Anim, Descalvado, SP - Brazil

^[3] Univ Sao Paulo, Dept Ciencias Basicas ZAB, Fac Zootecnia & Engn Alimentos FZEA, Pirassununga, SP - Brazil

• Document type: Journal article
• Source: REVISTA CIENCIA AGRONOMICA; v. 52, n. 4 2021.
• Web of Science Citations: 0

Abstract

The critical range of leaf nitrogen (%N-Leaf) concentration can be used to monitor the plant's nitrogen (N) status, being an essential tool to define strategic fertilization protocols, where the time and amounts of fertilizers are applied according to pasture's demand. The productivity parameters and two methods to determine N sufficiency - (i) the N nutrition index (NNI) and (ii) the normalized N sufficiency index (NSI) - were evaluated in Brachi aria hybrid Mavuno (Brachiaria spp. Syn. Urochloa spp.) along the regrowth cycles of the first growth season after seeding (establishment phase). The aims of the study were to estimate the critical %N-Leaf for Mavuno grass pastures through productivity parameters, considering the sampling of the youngest expanded leaf as reference. Fertilization rates were defined as follow: no-nitrogen (N0), 15 (N15), 30 (N30) and 45 (N45) kg ha(-1) of N and were applied after each cutting. The Falker chlorophyll index (FCI) was obtained from a portable chlorophyll meter Falker ClorofiLOG (R) CFL1030, and results were used to calculate the NSI. The regression analysis, on a regrowth cycle basis, provided the parameters to estimate the critical range of %N-Leaf and the fertilization rates to attain the maximum forage accumulation. Population density of tiller was the main response contributing to increasing leaf and stem mass, leaf area index and forage accumulation as N fertilization increased. The FCI and NSI were unable to capture differences in %N-Leaf but NNI was a suitable tool to detect N status in Mavuno grass. The critical %N-Leaf range varied from 2.75 to 3.07% and may be indicated to monitor pasture's N status. The strategic N fertilization protocol suggested for the growth season after seeding is to apply 42.0 to 46.7 kg ha(-1) of N at the first regrowth, 27.0 to 32.5 kg ha(-1) of N during the two following regrowth cycles, whereas at the end of the season (April to May regrowth) only 22.2 to 24.7 kg h(-1) of N would be enough to sustain a maximum growth. (AU)

• FAPESP's process: 20/00345-1 - Determination of nitrogen status in Mavuno pastures through image analysis using artificial neural networks (ANN)
• Grantee: Adriano Rogério Bruno Tech
• Support Opportunities: Regular Research Grants