Seeding rate in soybean according to the soil apparent electrical conductivity

MOURA, SUZANY S.; FRANÇA, LUIZ T.; PEREIRA, VITOR S.; TEODORO, PAULO EDUARDO; BAIO, FÁBIO H.R.

doi:10.1590/0001-3765202020181112

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AGRARIAN SCIENCES • An. Acad. Bras. Ciênc. 92 (suppl 1) • 2020 • https://doi.org/10.1590/0001-3765202020181112 copy

Seeding rate in soybean according to the soil apparent electrical conductivity

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This work aimed to study different seeding rates in soybean, at management zones determined by the mapping of the soil apparent electrical conductivity (ECa) and its relationships with plant phenology and grain yield (GY). The experiment consisted of a completely randomized design, with six replications. The plant population ranged between 311,000, 360,000, and 422,000 plants ha^-1, and the fixed population (360,000 plants ha^-1). The management zone with the least yield potential, received the highest seed population. The management zone with the highest plant vigor potential, received the lowest seed population. The variables plant height, Normalized Difference Vegetation Index (NDVI) at 50, 66, and 92 days after emergence (DAE), one hundred-grain weight, and GY were analyzed. ECa maps can be used to decide the seed population of the soybean. The decision strategy of increasing 20% of the seed soybean population on the smaller ECa map zones, and decreasing 20% seed population on higher ECa zones was effective and resulted in similar GY, even with the negative pressure of the high resistance of penetration (RP) values in some zones. GY map variability was influenced by ECa 0-0.2 m, by NDVI at 92 DAE and by RP 0.4-0.6 m soil layer.

Key words
seed population; precision agriculture; vegetation index; soil mechanical resistance to penetration

pH	H+Al	Ca	Mg	Al	CEC	B	Cu	Fe	Mn		Zn	K		P	OM	Clay	V	m
	cmolc dm^-3						g dm^-3			%
4.41	7.2	1.8	0.3	0.4	9.4	0.5	0.9	75.5	9.0		3.9	62.5		15.6	23. 6	456. 7	23.6	16.3

	Model	Nugget Effect (Co)	Sill (Co+C)	Range (m)	SD	r
NDVI 50 DAE	Exponential	0.0012	0.0018	35.28	0.35	0.67
NDVI 66 DAE	Exponential	0.0004	0.0006	22.04	0.36	0.43
NDVI 92 DAE	Exponential	0.0005	0.0026	12.25	0.81	0.85
ECa 0.0-0.2 m	Spherical	0.4382	1.5111	64.70	0.71	0.87
ECa 0.2-0.4 m	Exponential	0.0000	3.8100	21.27	1.00	0.46
ECa 0.4-0.6 m	Exponential	0.3574	1.0212	24.91	0.65	0.57
RP 0.0-0.2 m	Spherical	0.0000	5.2901	53.31	1.00	0.53
RP 0.2-0.4 m	Exponential	1.3984	3.6800	68.29	0.62	0.95
RP 0.4-0.6 m	Exponential	0.0000	1.9228	49.97	1.00	0.47
Yield	Exponential	0.0000	3.8105	24.91	1.00	0.45

Variable		F calculated values			Overall mean	CV (%)
Variable		Fixed seeding rate (FSD)	Variable seeding rate (VSR)	FSR vs. VSR	Overall mean	CV (%)
NDVI	50 DAE	1.84^ns	1.24^ns	0.18^ns	0.89	1.39
	66 DAE	0.38^ns	0.05^ns	0.29^ns	0.89	1.59
	92 DAE	0.95^ns	0.95^ns	5.71*	0.70	4.19
ECa (mS m^-1)	0.0-0.2 m	2.46^ns	2.55^ns	37.28*	5.48	4.10
	0.2-0.4 m	9.36^ns	3.11^ns	10.25*	4.11	7.11
	0.4-0.6 m	8.18^ns	0.71^ns	2.73^ns	3.25	12.72
RP (kPa)	0.0-0.2 m	0.82^ns	0.10^ns	2.85^ns	3040.24	12.20
	0.2-0.4 m	0.80^ns	2.09^ns	20.78*	2631.97	7.45
	0.4-0.6 m	1.81^ns	4.55^ns	27.91*	1851.65	7.82
PH (m)	46 DAE	2.24^ns	0.13^ns	2.22^ns	0.64	5.79
	50 DAE	0.04^ns	0.41^ns	0.29^ns	0.80	8.73
	66 DAE	4.14^ns	5.21^ns	1.25^ns	0.83	6.66
	92 DAE	0.30^ns	0.23^ns	0.36^ns	0.88	4.68
100GW (g)		2.21^ns	3.51^ns	1.18^ns	15.24	2.72
GY (kg ha^-1)		2.32^ns	1.71^ns	0.94^ns	3941.34	13.56

	Moran´s index				Relative deviation coefficient (RDC %)
	index	z-score	p-value	class	Yield	ECa	RP	ND 50	ND 66	ND 92
Yield	0.9874	11.1	<0.0001	clustered	0.0	4.0	7.1	7.9	8.9	5.5
ECa	0.9518	10.7	<0.0001	clustered	4.0	0.0	6.2	6.4	6.8	4.7
RP	0.9376	10.6	<0.0001	clustered	7.1	6.2	0.0	5.0	5.4	5.4
ND 50	0.2705	3.1	<0.0016	clustered	7.9	6.4	5.0	0.0	1.0	7.8
ND 66	0.2317	2.8	<0.0052	clustered	8.9	6.8	5.4	1.0	0.0	8.3
ND 92	0.5388	6.1	<0.0001	clustered	5.5	4.7	5.4	7.8	8.3	0.0

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[1] Correspondence to: Paulo Eduardo Teodoro E-mail: eduteodoro@hotmail.com