Potassium fertilizer applied by different methods in the zucchini crop

Fernandes, Carlos N. V.; Azevedo, Benito M. de; Camargo, Débora C.; Dias, Chrislene N.; Rebouças Neto, Mario de O.; Costa, Fellype R. B.

doi:10.1590/1807-1929/agriambi.v20n7p643-648

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SOIL, WATER AND PLANT MANAGEMENT • Rev. bras. eng. agríc. ambient. 20 (7) • July 2016 • https://doi.org/10.1590/1807-1929/agriambi.v20n7p643-648 copy

Potassium fertilizer applied by different methods in the zucchini crop

Adubação potássica aplicada por diferentes métodos na cultura da abobrinha

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Aiming to evaluate the effect of potassium (K) doses applied by the conventional method and fertigation in zucchini (Cucurbita pepo L.), a field experiment was conducted in Fortaleza, CE, Brazil. The statistical design was a randomized block, with four replicates, in a 4 x 2 factorial scheme, which corresponded to four doses of K (0, 75, 150 and 300 kg K₂O ha^-1) and two fertilization methods (conventional and fertigation). The analyzed variables were: fruit mass (FM), number of fruits (NF), fruit length (FL), fruit diameter (FD), pulp thickness (PT), soluble solids (SS), yield (Y), water use efficiency (WUE) and potassium use efficiency (KUE), besides an economic analysis using the net present value (NPV), internal rate of return (IRR) and payback period (PP). K doses influenced FM, FD, PT and Y, which increased linearly, with the highest value estimated at 36,828 kg ha^-1 for the highest K dose (300 kg K₂O ha^-1). This dose was also responsible for the largest WUE, 92 kg ha^-1 mm^-1. KUE showed quadratic behavior and the dose of 174 kg K₂O ha^-1 led to its maximum value (87.41 kg ha^-1 (kg K₂O ha^-1)-1). All treatments were economically viable, and the most profitable months were May, April, December and November.

Key words:
Cucurbita pepo L.; KCl; fertigation

Month	Air temperature (ºC)	Relative air humidity (%)	Wind speed (m s^-1)	Rainfall	EToPM
Month	Air temperature (ºC)	Relative air humidity (%)	Wind speed (m s^-1)	(mm)
September	27.1	64	4.4	16.7	5.96
October	27.5	75	4.5	10.1	6.08
November	27.5	68	4.3	5.7	5.76
Mean	27.4	69	4.4	10.83	5.93

SV	DF	Mean square
SV	DF	FM	NF	FL	FD	PT	SS	Y
Methods (M)	1	27,632^ns ns Not significant by F test;	0.32^ns ns Not significant by F test;	7.58^ns ns Not significant by F test;	80.31^ns ns Not significant by F test;	1.61^ns ns Not significant by F test;	0.04^ns ns Not significant by F test;	3,952,315^ns ns Not significant by F test;
Doses (D)	3	120,472^ Significant at 0.01 by F test;	0.31^ns ns Not significant by F test;	7.36^ns ns Not significant by F test;	129.42^* * Significant at 0.05 by F test;	14.26^* * Significant at 0.05 by F test;	0.08^ns ns Not significant by F test;	345,773,901^ Significant at 0.01 by F test;
M x D	3	5,684^ns ns Not significant by F test;	0.05^ns ns Not significant by F test;	1.09^ns ns Not significant by F test;	19.46^ns ns Not significant by F test;	0.86^ns ns Not significant by F test;	0.007^ns ns Not significant by F test;	7,781,600^ns ns Not significant by F test;
Blocks	3	43,258^ Significant at 0.01 by F test;	0.42^ns ns Not significant by F test;	8.83^ns ns Not significant by F test;	120.11^* * Significant at 0.05 by F test;	14.14^* * Significant at 0.05 by F test;	0.05^ns ns Not significant by F test;	253,096,491^ Significant at 0.01 by F test;
Residual	21	8,618	0.14	3.21	28.45	2.94	0.08	26,167,827
Total	31	-	-	-	-	-	-	-
CV%	-	12.49	16.94	7.54	7.02	12.27	8.62	18.02

Treatment	Dose of K₂O (kg ha^-1)	Yield (kg ha^-1)	Indicators
Treatment	Dose of K₂O (kg ha^-1)	Yield (kg ha^-1)	NPV (R$)	IRR (%)	PP (years)
T0	000	21,814	039,036.30	34.65	3.61
T50%	075	25,567	060,689.59	50.17	3.20
T100%	150	29,321	082,342.89	65.52	2.87
T200%	300	36,828	125,649.48	95.90	2.38

Month	Price (R$)	NPV (R$)
Month	Price (R$)	0	75	150	300
January		21,393.70	40,011.24	58,628.79	95,863.87
February	0.70	-24,918.10	-14,269.41	-3,620.72	17,676.66
March	0.95	2,648.45	18,040.50	33,432.56	64,216.67
April	1.38	50,062.92	73,613.56	97,164.20	144,265.48
May	0.46	58,884.21	83,952.73	109,021.25	159,158.28
June	1.00	8,161.76	24,502.49	40,843.21	73,524.67
July	0.67	-28,226.09	-18,146.60	-8,067.11	12,091.86
August	0.65	-30,431.41	-20,731.40	-11,031.38	8,368.66
September	0.53	-43,663.36	-36,240.15	-28,816.95	-13,970.54
October	0.82	-11,686.16	1,239.35	14,164.85	40,015.87
November	1.28	39,036.30	60,689.59	82,342.89	125,649.48
December	1.33	44,549.61	67,151.57	89,753.54	134,957.48

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[1] newdmar@gmail.com (Corresponding author)

Chemical analysis
P (mg dm^-3)	6.00
K⁺ (cmol_c dm^-3)	0.11
Na⁺ (cmol_c dm^-3)	0.06
Ca²⁺ (cmol_c dm^-3)	1.70
Mg²⁺ (cmol_c dm^-3)	1.20
H⁺+Al³⁺(cmol_c dm^-3)	1.65
Al³⁺ (cmol_c dm^-3)	0.10
pH	5.60
EC (dS m^-1)	0.20
Physical analysis
Fine sand (g kg^-1)	386
Coarse sand (g kg^-1)	405
Silt (g kg^-1)	96
Clay (g kg^-1)	113
Textural class	Sandy loam
Soil bulk density (kg dm^-3)	1.43
Soil particle density (kg dm^-3)	2.57
Field capacity (g 100g^-1)	7.52
Permanent wilting point (g 100g^-1)	4.52