Influence of Cultivar, Harvest Date, and Selected Weather Conditions on the Essential Oils Content in Inflorescences of Hemp Cannabis sativa L

Figures & data

Table 1. Mineral fertilization.

Year	Pure ingredient		Mineral fertilizer			Month of sowing	Depth	Method
	Type	kg·ha^−1	Percent	kg·ha^−1
2018	N	90	Ammonium nitrate 34%	265		April	10 cm	Cultivator
	P2 05	70	Superphosphate 40%	175		April	10 cm	Cultivator
	K20	122,5	Potassium salt 60%	204		April	10 cm	Cultivator
2019	N	90	Ammonium nitrate 34%	265		April	10 cm	Cultivator
	P205	70	Superphosphate 40%	175		April	10 cm	Cultivator
	K20	100	Potassium salt 60%	166,7		April	10 cm	Cultivator
2020	K2 0	120	Potassium salt 60%	200		April	10 cm	Cultivator
	N	90	Ammonium nitrate 34%	265		April	10 cm	Cultivator

Table 2. The course of hemp vegetation in the various years of the experiment.

Years	2018			2019			2020
Sowing date	5. 05			1. 05			6. 05
Cultivar*	1	2	3	1	2	3	1	2	3
Seedling emergence
Beginning	13. 05	14. 05	13. 05	8. 05	9. 05	8.05	12. 05	15. 05	14. 05
The number of days since sowing	7	8	7	7	8	7	6	9	8
Full emergence	17. 05	18. 05	17. 05	15.05	16. 05	15. 05	16. 05	20. 05	18. 05
The number of days since sowing	12	13	12	14	15	14	10	14	12
Flowering
Beginning	20.07	28. 07 1. 08	24. 07	20–22. 07	25. 07	22. 07	21. 07	1.08	25. 07
The number of days since sowing	76	84-88	80	80-82	85	82	76	87	80
End	20.08	5.09	28. 08	8.08	10. 08	22. 08	24. 08	2.09	26. 08
The number of days since sowing	107	123	115	99	101	113	110	118	112
Harvest
I date of harvest	16.08			07.08			12.08
II date of harvest	02.10			16.09			22.09
Length of the vegetation period
I date of harvest	103			97			97
II date of harvest	120			137			138

*Cultivars.

1-Białobrzeskie.

2-Zenit.

3-Zolotonowska.

Table 3. Average air temperatures for decades and individual months during the vegetation period.

Year/Month/ Decade		April			May			June			July			August			September
		I	II	III	I	II	III	I	II	III	I	II	III	I	II	III	I	II	III
2018		7.5	11.2	12.4	11	14.5	20.4	19.7	21	17.2	16.6	22.5	17.7	19.2	19.4	17.1	13.1	12.3	14.0
2019		6.4	7.26	11.4	12.6	13.8	14.9	20.0	15.5	18.6	18.9	18.5	20.8	19.7	18.6	16.1	17.9	10.2	10.3
2020		11.0	9.9	13.6	12.2	12.3	14.4	13.0	14.6	18.0	19.2	19.1	18.6	19.9	18.3	18.8	17.2	15.2	13.3
Mean month temperatures in a given year	2018	10.4			15.3			19.3			18.9			18.6			13.1
	2019	8.37			13.84			18.0			19.4			18.1			15.2
	2020	11.5			13.0			15.2			19.0			19.0			15.2
Mean perennial temp.	2000–2020	9.0			14.3			17.3			20.0			18.7			14.0

Table 4. Precipitation totals for decades and individual months during the vegetation period.

Year/Month/ Decade		April			May			June			July			August			September
		I	II	III	I	II	III	I	II	III	I	II	III	I	II	III	I	II	III
2018		0.0	2.5	3.5	11.0	35.5	6.0	5.0	8.0	52.5	47	8.9	56.3	2.0	4.0	55	6.0	5.0	3.5
2019		4.2	32.0	0.0	5.5	9.5	1.5	0.0	7.3	1.2	11.5	39.0	4.0	2.0	39.5	16.5	2.5	0.0	13.0
2020		0.0	0.0	2.5	3.0	5.0	50.8	16.5	31	37.1	27.0	33.0	26.0	2.0	14.0	10.0	8.0	13.5	17.0
Mean month in a given year	2018	6.0			52.5				65.5			112.2		61.0			14.5
	2019	36.2			15.5				8.5			54.5		58.0			15.5
	2020	2.5			56.8				84.6			86.0		26.0			38.5
Mean perennial	2000–2020	26.4			44.0				54.5			76.6		66.0			44.0

Table 5. Selyaninov hydrothermal coefficient for decades and individual months.

Year/Month/ Decade		April			May			June			July				August			September
		I	II	III	I	II	III	I	II	III	I		II	III	I	II	III	I	II	III
2018		0	0.2	0.2	1	2.4	0.2	0.2	0.3	3.0	2.8		0.3	2.8	0.1	0.2	3.2	0.4	0.4	0.2
2019		0.6	4.4	0	0.4	0.6	0.0	0	0.4	0.0	0.6		2.1	0.1	0.1	2.1	1.0	0.1	0	1.1
2020		0	0	0.1	0.2	0.4	3.5	1.2	2.1	2.0	1.4		1.7	1.2	0.1	0.7	0.5	0.4	0.8	1.1
Mean for month in a given year	2018	0.2			1.1				1.1			1.9			1.1			0.3
	2019	1.4			0.4				0.2			0.9			1.1			0.3
	2020	0.1			1.4				1.8			1.5			0.4			0.8
Mean perennial	2000–2020	1.0			1.0				1.1			1.2			1.2			1.0

Interpretation of the Selyaninov hydrothermal coefficient.

K > 1.5 excessive moisture content for all plants.

K = 1.0–1.5 sufficient moisture content

K = 0.5–1.0 insufficient moisture content

K < 0.5 moisture content lower than the requirements of most plants – drought.

Table 6. The forecrop, soil pH, and abundance in phosphorus, potassium, and magnesium.

Year	Forecrop		Abundance of soil components [mg/100 g]
			phosphorus (P2O5)	potassium (K2O)	magnesium (MgO)	pH
2018	2015	Onion	-	-	-	-
	2016	Onion	-	-	-	-
	2017	Winter wheat	18.4	4.5	3.2	-
	2018	-	-	-	-	7.9
2019	2016	Alfalfa	-	-	-	-
	2017	Alfalfa	11.6	16.9	2.0	-
	2018	Barley	-	-	-	-
	2019	-	-	-	-	6.5
2020	2017	Alfalfa	42.5	18.3	3.6	-
	2018	Alfalfa	-	-	-	-
	2019	Maize	-	-	-	-
	2020	-	-	-	-	8.1

Figure 1. Influence of a cultivar on the content of essential oils in the dry matter of hemp inflorescences.

Figure 2. Influence of cultivar and harvest date on the content of essential oils in the dry matter of hemp inflorescences.

Figure 3. Influence of the harvest date on the content of essential oils in the fresh mass of hemp inflorescences.

Table 7. Statistical characteristics of the content of essential oils in the dry matter of inflorescences of the studied hemp cultivars (Pętkowo 2018–2020).

Cultivar	MIN [%]	MAX [%]	Mean value [%]	Standard deviation	Coefficient of variation [%]
“Zenit”	0.1000	0.2350	0.1617	0.0471	29.12
“Zolotonoska 13”	0.2700	0.1850	0.2308	0.0361	15.64
“Białobrzeskie”	0.1350	0.2350	0.179	0.0401	22.35

Table 8. The statistical characteristics of the content of essential oils in the fresh matter of the inflorescences of the tested hemp cultivars (Pętkowo 2018–2020).

Cultivar	MIN [%]	MAX [%]	Mean [%]	Standard deviation	Coefficient of Variation [%]
“Zenit”	0.2250	0.3300	0.2733	0.0491	17.95
“Zolotonowska 13”	0.1850	0.2800	0.2375	0.0418	17.60
“Białobrzeskie”	0.1850	0.3300	0.2642	0.0652	24.69

Table 9. The correlation between the content of essential oils in dry matter and in fresh mass of inflorescences of the tested hemp cultivars and the average temperature during the vegetation period (Pętkowo 2018–2020).

Cultivar	Correlation coefficient (inflorescences)
	dry matter	fresh mass
“Zenit”	0.3218	−0.4830
“Zolotonowska 13”	−0.0324	−0.7958
“Białobrzeskie”	0.7928	0.2186

Table 10. Correlation between the content of essential oils in dry and fresh matter of the inflorescences of the tested hemp cultivars and the sum of precipitation during the growing season (Pętkowo 2018–2020).

Cultivar	Correlation coefficient (inflorescences)
	dry matter	fresh mass
“Zenit”	−0.6454	0.3202
“Zolotonowska 13”	0.3343	0.4549
“Białobrzeskie”	−0.5385	−0.0193