Influence of Density and Development Stage of Ryegrass on Glyphosate Effectiveness

FIPKE, M.V.; VIDAL, R.A.

doi:10.1590/S0100-83582019370100025

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Article • Planta daninha 37 • 2019 • https://doi.org/10.1590/S0100-83582019370100025 copy

Influence of Density and Development Stage of Ryegrass on Glyphosate Effectiveness

Influência da Densidade e Estádio de Desenvolvimento do Azevém na Eficácia de Glyphosate

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT :

Glyphosate is one of the main herbicides used to control ryegrass. The objective of this research was to evaluated whether the glyphosate dose-response curve is affected by density of ryegrass plants in two phenological growth stages. To attend this objective, two experiments were carried out in greenhouse (one with Lolium multiflorum and another with Lolium rigidum) and two under field conditions. In the greenhouse experiments, the experimental design was a completely randomized design in a factorial scheme, with factor A as plant density and factor B as glyphosate doses. In the field, two experiments were carried out in a randomized block design in a split-plot scheme. Plots consisted of glyphosate doses (0, 40, 80, 120, 160, 250, and 350 g ha-1), and the subplots consisted of three ryegrass densities (8 plants m-2, 140 plants m-2 with thinning before herbicide application, and 140 plants m-2 with thinning after herbicide application). In one experiment, glyphosate was sprayed at 28 days after emergence (DAE), whereas in another the application was carried out at 51 DAE. High-density ryegrass plants required a higher herbicide dose to obtain the same level of control of low-density plants. In addition to the density effect, an increased glyphosate dose was necessary for the late application to obtain the same level of control when compared to the initial application. Herbicide effectiveness was affected by population density and plant development stage.

Keywords:
Lolium multiflorum L.; Lolium rigidum; time of application; tolerance

Sociedade Brasileira da Ciência das Plantas Daninhas Departamento de Fitotecnia - DFT, Universidade Federal de Viçosa - UFV, 36570-000 - Viçosa-MG - Brasil, Tel./Fax::(+55 31) 3899-2611 - Viçosa - MG - Brazil
E-mail: rpdaninha@gmail.com

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[1] * Corresponding author: <marfipke@gmail.com>

Sp⁽¹⁾	DNS⁽²⁾	Equation parameters (SE)⁽³⁾		D₅₀ ⁽⁴⁾	R²	p⁽⁵⁾	Equation
Sp⁽¹⁾	DNS⁽²⁾	a	b	D₅₀ ⁽⁴⁾	R²	p⁽⁵⁾	Equation
Shoot dry mass
L. m.	Low	100.9(9.3)**	1.25(0.35)*	50.89	91.9	<0.01	$y = a / 1 + {(x / D_{50})}^{b}$
L. m.	High BA	100.0(2.1)**	1.50(0.12)*	35.63	99.6	<0.01	$y = a / 1 + {(x / D_{50})}^{b}$
L. m.	High AA	97.8(10.1)**	1.68(0.47)*	107.45	90.0	<0.01	$y = a / 1 + {(x / D_{50})}^{b}$
Shoot fresh mass
L. r.	Low	100.6(3.3)**	1.33(0.13)**	116.21	98.4	<0.01	$y = a / 1 + {(x / D_{50})}^{b}$
L. r.	High BA	107.0(17.1)**	1.31(0.63)^ns	109.46	68.9	<0.05	$y = a / 1 + {(x / D_{50})}^{b}$
L. r.	High WT	103.1(5.2)**	1.48(0.36)*	248.53	91.6	<0.01	$y = a / 1 + {(x / D_{50})}^{b}$

DAE⁽¹⁾	DNS⁽²⁾	Equation parameters (SE)⁽³⁾			D₅₀ ⁽⁴⁾	R²	p⁽⁵⁾	Equation
DAE⁽¹⁾	DNS⁽²⁾	a	b	c
Control
28	Low	89.8(3.9)**	10.6(2.9)*	97.3**	99.73	97.6	<0.01	$y = a / 1 + e x p (- (x - c) / b)$
28	High BA	75.0(6.8)**	20.7(9.1)^ns	108.1**	122.5	91.7	<0.01	$y = a / 1 + e x p (- (x - c) / b)$
28	High AA	93.2(25.2)**	73.8(32.5)^ns	197.6*	208.3	88.4	<0.01	$y = a / 1 + e x p (- (x - c) / b)$
51	Low	85.7(7.0)**	33.3(10.5)*	106.8**	118.1	93.2	<0.01	$y = a / 1 + e x p (- (x - c) / b)$
51	High BA	69.1(3.3)**	24.2(5.1)**	102.4**	122.6	97.4	<0.01	$y = a / 1 + e x p (- (x - c) / b)$
51	High AA	68.1(7.4)**	42.5(15.9)*	124.6**	208.4	90.7	<0.01	$y = a / 1 + e x p (- (x - c) / b)$
Plant size
28	Low	100.3(3.7)**	-0.25(0.05)**	0.001*	-	82.9	<0.05	$y = a + b * x + c * x^{2}$
28	High BA	92.5(4.5)**	-0.12(0.02)**	-	329.6	81.3	<0.01	$y = a + b * x$
28	High AA	100.3(4.2)**	0.43(0.11)*	-	-	92.9	<0.01	$y = a / 1 {(x / D_{50})}^{b}$
51	Low	101.3(5.8)**	0.74(0.19)*	-	-	89.17	<0.01	$y = a / 1 {(x / D_{50})}^{b}$
51	High BA	89.3(5.9)**	-0.12(0.03)*	-	-	70.0	<0.05	$y = a + b * x$
51	High AA	93.3(5.4)**	-0.25(0.07)^*	0.001*	-	71.57	<0.05	$y = a + b * x + c * x^{2}$
Shoot dry mass
28	Low	101.51(10.4)**	0.89(0.30)*	-	73.8	86.2	<0.01	$y = a / 1 {(x / D_{50})}^{b}$
28	High BA	102.54(7.41)**	1.24(0.27)^*	-	148.7	92.2	<0.01	$y = a / 1 {(x / D_{50})}^{b}$
28	High AA	102.43(8.27)**	1.15(0.27)*	-	112.7	91.4	<0.01	$y = a / 1 {(x / D_{50})}^{b}$
51	Low	103.73(7.25)**	1.60(0.37)*	-	177.9	92.2	<0.01	$y = a / 1 {(x / D_{50})}^{b}$
51	High BA	100.76(7.54)**	0.47(0.20)*	-	341.8	82.1	<0.05	$y = a / 1 {(x / D_{50})}^{b}$
51	High AA	99.78(5.57)**	0.73(0.15)**	-	168.9	93.4	<0.01	$y = a / 1 {(x / D_{50})}^{b}$