Energy and Biomass Yield of Industrial Hemp (Cannabis sativa L.) as Influenced by Seeding Rate and Harvest Time in Polish Agro-Climatic Conditions

Figures & data

Figure 1. Combustion parameters of hemp whole plants material. (a) Heat of combustion over combustion time (HOC). (b) Emission of CO₂ (black line) and CO (red line) over combustion time. (c) Heat release rate (HRR) (black line) and Mass loss rate (MLR) (red line) over combustion time. Please note double axes presentation in (a) and (b).

Table 1. Total yield and energy efficiency of whole plants at 18% humidity depending on the amount of sowing and harvest time.

Sowing density [kg · ha^−1]	Time of harvesting
	I		II		III
	Total yield [t · ha^−1]	Energy efficiency [GJ · ha^−1]	Total yield[t · ha^−1]	Energy efficiency [GJ · ha^−1]	Total yield [t · ha^−1]		Energy efficiency [GJ · ha^−1]
5	10,02^cd	188.58^cd	13.26^a	249.45^a	12.15^ab	228.63^ab
10	10.82^bcd	203.47^bcd	13.39^a	252.02^a	12.64^a	237.72^a
15	10.20^cd	192.02^cd	13.69^a	257.49^a	12.39^a	233.11^a
20	9.24^d	173.90^d	12.62^a	237.53^a	12.00^ab	225.87^ab
30	12.82^a	241.23^a	14.65^a	275.56^a	12.29^a	231.19^a
40	11.92^ab	224,29^ab	13.69^a	257.65^a	11.92^ab	224.26^ab
50	11.04^bc	207.74^bc	13.61^a	255.97^a	11.88^ab	223.54^ab
60	11.61^abc	218.46^abc	12.90^a	242.73^a	9.87^b	185.68^b
LSD	1,64	30.84	3,31	62.29	2,35	44.26

Different small case letters (a, b, c, d) indicate significant differences among treatment means according to Fisher’s LSD test (p < .05).

Table 2. Yield and energy efficiency of straw at 18% humidity depending on the amount of sowing and the time of harvest.

Sowing density [kg · ha^−1]	Time of harvesting
	I		II		III
	Straw yield [t · ha^−1]	Energy efficiency [GJ · ha^−1]	Total yield [t · ha^−1]	Energy efficiency [GJ · ha^−1]	Straw yield [t · ha^−1]	Energy efficiency [GJ · ha^−1]
5	8.34^cd	149.36^cd	9.62^a	172.22^a	8.17^a	146.40^a
10	9.09^bcd	162.72^bcd	10.03^a	179.50^a	8.83^a	158.02^a
15	8.64^bcd	154.66^bcd	10.57^a	189.29^a	8.58^a	153.67^a
20	7.66^d	137.21^d	9.46^a	169.32^a	8.00^a	143.22^a
30	11.09^a	198.67^a	11.5^a	205.88^a	9.23^a	165.22^a
40	10.42^ab	186.47^ab	11.03^a	197.37^a	8.98^a	160.72^a
50	9.72^abc	174.01^abc	11.04^a	197.57^a	9.00^a	161.14^a
60	10.15^ab	181.76^ab	10.45^a	187.13^a	7.62^a	136.33^a
LSD	1.79	32.14	2.79	50.02	1.77	31.65

Different small case letters (a, b, c, d) indicate significant differences among treatment means according to Fisher’s LSD test (p < .05).

Table 3. Yield and energy efficiency of hemp panicles at 18% humidity depending on the sowing amount and harvest date.

Sowing density [kg · ha^−1]	Time of harvesting
	I		II		III
	Panicle yield [kg · ha^−1]	Energy efficiency [GJ · ha^−1]	Panicle yield [kg · ha^−1]	Energy efficiency [GJ · ha^−1]	Panicle yield [t · ha^−1]	Energy efficiency [GJ · ha^−1]
5	1.67^ab	33.19^ab	3.41^a	67.53^a	3.88^a	76.87^a
10	1.71^a	33.83^a	3.20^ab	63.48^ab	3.70^ab	73.28^ab
15	1.54^ab	30.58^ab	3.00^abc	59.57^abc	3.72^ab	73.76^ab
20	1.36^ab	27.04^ab	2.84^abc	56.32^abc	3.80^a	75.25^a
30	1.70^a	33.79^a	3.04^abc	60.20^abc	3.01^bc	59.66^bc
40	1.46^ab	28.92^ab	2.57^bc	51.07^bc	2.89^cd	57.39^cd
50	1.28^b	25.35^b	2.48^bc	49.24^bc	2.79^cd	55.41^cd
60	1.39^ab	27.54^ab	2.35^c	46.60^c	2.21^d	43.70^d
LSD	0.41	8.23	0.81	15.98	0.71	14.12

Different small case letters (a, b, c, d) indicate significant differences among treatment means according to Fisher’s LSD test (p < .05).

Figure 2. Energy efficiency of (a) whole plants, (b) hemp straw, and (c) hemp panicles obtained on three harvest dates: (I) beginning of panicle formation; (II) full flowering; (III) the end of seed setting. Different small case letters (a-c) indicate significant differences between harvest term means according to Fisher’s LSD test (p < .05). Red stars represent the mean values and red vertical lines standard deviations (SD). Dots of different colors represent results obtained from individual plots of different sowing rates as indicated in the legend.

Figure 3. Share of panicles in the total hemp energy efficiency to the whole plants energy efficiency. Ellipses show grouping and dots represent results from individual plots from three harvest dates: (I) beginning of panicle formation; (II) full flowering; and (III) the end of seed setting.