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

Pereira, Lilian Elgalise Techio; Sousa, Luan Jardim de; Bertipaglia, Liandra Maria Abaker; Herling, Valdo Rodrigues; Tech, Adriano Rogério Bruno

doi:10.5935/1806-6690.20210052

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Scientific Article • Rev. Ciênc. Agron. 52 (4) • 2021 • https://doi.org/10.5935/1806-6690.20210052 copy

Critical concentration and management of nitrogen fertilization in the establishment of Brachiaria hybrid Mavuno[¹ 1 Pesquisa financiada pela Fundação de Amparo à Pesquisa do Estado de São Paulo/FAPESP (Processo nº. 2020/00345-1) ]

Concentração crítica e manejo da adubação nitrogenada no estabelecimento de Brachiaria híbrida Mavuno

Authorship SCIMAGO INSTITUTIONS RANKINGS

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 Brachiaria 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® 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 ha^-1 of N would be enough to sustain a maximum growth.

Key words:
Brachiaria spp; Best management practices; Nitrogen sufficiency; Tropical pastures

Canopy parameters²	Regrowth cycles (RC)				F_value¹ 1 Anova Fvalue for the effect of regrowth cycle,
Canopy parameters²	Jan/Feb	Feb/Mar	Mar/Apr	Apr/May	F_value¹ 1 Anova Fvalue for the effect of regrowth cycle,
Sward height	58.0±0.42 A	44.7±0.40 B	42.9±1.12 B	38.9±0.55 C	310.33^ P < 0.0001.
%DM	26.2±0.37 C	25.1±0.37 C	27.8±0.37 B	32.1±0.39 A	57.97^ P < 0.0001.
FAc	6154±228.3 A	4017±218.8 B	4026±218.8 B	3087±218.8 C	33.29^ P < 0.0001.
Leaf mass	3696±197.0 A	2524±48.9 B	2530±131.2 B	1998±133.2 C	21.59^ P < 0.0001.
Stem mass	2462±109.9 A	1494±94.8 B	1496±94.8 B	1089±94.8 C	26.96^ P < 0.0001.
TPD	543±29.6 C	790±29.6 B	831±29.6 B	1034±29.6 A	46.25^ P < 0.0001.
TW	2.83±0.030 A	2.53±0.027 C	2.69±0.027 B	2.59±0.027 C	29.93^ P < 0.0001.
SLA	62.5±2.60 A	54.5±2.49AB	58.3±2.49 AB	49.0±2.49 B	5.13^* * P < 0.05 and
LAI	2.22±0.110 A	1.36±0.101 B	1.82±0.101 A	0.96±0.101 C	32.29^ P < 0.0001.
ChloT	35.5±1.01 C	47.5±1.01 A	42.8±1.01 B	40.0±1.01 B	25.26^ P < 0.0001.

Canopy parameters² 2 Sward height, in cm; Dry matter (%DM) content, in %; Forage accumulation (FAc), in kg ha-1 DM; Leaf and Stem mass, in kg ha-1 DM; Tiller population density (TPD), in tiller m-2; Tiller weight (TW), in g tiller-1; Specific leaf area (SLA), in cm2 g-1; Leaf area index (LAI); ChloT represents the Falker chlorophyll index for total chlorophyll (Falker ClorofiLOG®, Model CFL1030). R2 represent the determination coefficient of the regression models	Fertilization rates (FR)				SEM	F_Value¹ 1 Anova Fvalue for the effect of fertilization rates, nsnon-significant effect	Descriptive statistics of regression models³
	N0	N15	N30	N45	SEM		Descriptive statistics of regression models³
Sward height	46.0	46.0	45.9	46.6	± 0.68	0.32^ns	Ŷ= 46.1
%DM	28.2	27.8	27.2	27.4	± 0.37	1.38^ns	Ŷ= 27.5
FAc	3,123	4,392	5,246	4,523	± 218.8	16.25^ P < 0.0001.	Quadratic, F_Value=8.23^* * P < 0.05 and ; R²=21.5
Leaf mass	1,952	2,696	3,228	2,870	± 163.9	10.75^* * P < 0.05 and	Quadratic, F_Value=9.14^* * P < 0.05 and ; R²=23.1
Stem mass	1,170	1,696	1,930	1,744	± 94.74	13.54^ P < 0.0001.	Quadratic, F_Value=7.04^* * P < 0.05 and ; R²=19.5
TPD	682	727	851	938	± 29.6	15.56^ P < 0.0001.	Linear, F_Value=11.98^* * P < 0.05 and ; R²=16.2 ^,Value
TW	2.66	2.65	2.67	2.66	± 0.026	0.02^ns	Ŷ= 2.65
SLA	56.8	55.5	56.1	56.0	± 2.49	0.04^ns	Ŷ= 56.0
LAI	1.22	1.63	1.89	1.63	± 0.105	10.90^ P < 0.0001.	Quadratic, F_Value=3.98^ P < 0.0001. ; R²=15.4
ChloT	40.9	39.6	41.8	43.4	± 1.01	2.48^ns	Ŷ= 41.4

Parameters ofN status³	Regrowth cycles (RC)				SEM²	F_Value¹	Descriptive statistics of regression models⁴
Parameters ofN status³	Jan/Feb	Feb/Mar	Mar/Apr	Apr/May	SEM²	F_Value¹	Descriptive statistics of regression models⁴
%N_Leaf	2.82 AB	3.02 A	2.99 A	2.75 B	± 0.056	5.38^* * P < 0.05 and	-
NNI	1.45 A	1.34 A	1.33 A	1.10 B	± 0.033	18.87^ P < 0.0001.	-
NSI	0.95 A	0.98 A	0.96 A	0.94 A	± 0.018	0.84^ns	-
	Fertilization rates (FR)
	N0	N15	N30	N45
%N_Leaf	2.70	2.88	2.90	3.10	± 0.056	8.35^* * P < 0.05 and	Linear F_Value=13.18^* * P < 0.05 and , R2=18.5
NNI	1.09	1.31	1.40	1.42	± 0.033	20.07^ P < 0.0001.	Quadratic F_Value=12.67^ P < 0.0001. , R2=30.4
NSI	0.93	0.93	0.96	1.00	± 0.023	3.41^ns	Ŷ= 0.96

Fertilization rates (FR)		Regrowth cycles (RC)
	Jan/Feb	Feb/Mar	Mar/Apr	Apr/May
		Forage accumulation (FAc, in kg ha^-1 of DM)
N0	4472.1	2772.5	2984.3	2261.3
N15	5898.6	4105.8	4307.2	3255.9
N30	7367.0	4973.7	4401.2	4244.0
N45	7438.6	4216.1	4409.7	2587.1
Parameters of the regression equations $\hat{Y} = FAc$
c	4403.2 (±672.94)	2714.5 (±267.85)	3041.4 (±398.13)	2129.4 (±461.30)
b	135.5 (±72.04)	139.2 (±28.68)	94.9 (±42.62)	145.7 (±49.38)
a	-1.45 (±1.53)	-2.32 (±0.61)	-1.46 (±0.91)	-2.95 (±1.05)
R²	0.49	0.71	0.39	0.40
¹F _value	6.23^* * P < 0.05 and **P < 0.0001.	16.18^* * P < 0.05 and **P < 0.0001.	4.16^* * P < 0.05 and **P < 0.0001.	4.35^* * P < 0.05 and **P < 0.0001.
²FAc at P _Max	7566.9	4802.5	4582.3	3927.9
²FR at P _Max	46.7	30.0	32.5	24.7
³FR at P _90%	42.0	27.0	29.2	22.2

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Critical concentration and management of nitrogen fertilization in the establishment of Brachiaria hybrid Mavuno[1 1 Pesquisa financiada pela Fundação de Amparo à Pesquisa do Estado de São Paulo/FAPESP (Processo nº. 2020/00345-1) ]

Concentração crítica e manejo da adubação nitrogenada no estabelecimento de Brachiaria híbrida Mavuno

ABSTRACT

Critical concentration and management of nitrogen fertilization in the establishment of Brachiaria hybrid Mavuno[¹ 1 Pesquisa financiada pela Fundação de Amparo à Pesquisa do Estado de São Paulo/FAPESP (Processo nº. 2020/00345-1) ]