Seeding rate and row spacing effect on weed competition, yield and quality of hemp in the Parkland region of Saskatchewan

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1 SHORT COMMUNICATION Seeding rate and row spacing effect on weed competition, yield and quality of hemp in the Parkland region of Saskatchewan C. L. Vera 1, S. M. Woods 2, and J. P. Raney 3 Can. J. Plant Sci. Downloaded from by on 01/19/18 1 Agriculture and Agri-Food Canada, Melfort Research Farm, P.O. Box 1240, Melfort, Saskatchewan, Canada S0E 1A0 ( verac@agr.gc.ca); 2 Agriculture and Agri-Food Canada, Cereal Research Centre, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9; and 3 Agriculture and Agri-Food Canada, Saskatoon Research Centre, 107 Science Place, Saskatoon, Saskatchewan, Canada S7N 0X2. Received 19 September 2005, accepted 30 January Vera, C. L., Woods, S. M. and Raney, J. P Seeding rate and row spacing effect on weed competition, yield and quality of hemp in the Parkland region Saskatchewan. Can. J. Plant Sci. 86: Field experiments were conducted on a Black Chernozem silty loam soil at Melfort, Saskatchewan, Canada, from 2000 to 2002, to determine the effect of seeding rate and row spacing on weed competition, as well as on seed, shoot biomass production and seed quality attributes of industrial hemp (Cannabis sativa L. Fasamo and Finola ). Increasing seeding rate from 20 to 60 or 80 kg ha 1 decreased weed density in all years (average of 33%) and reduced weed size (34%) in It also increased hemp plant density, biomass and seed yield (average of 174, 23 and 34%, respectively). Seed weight and protein were not affected by seeding rates, but seed oil content increased 1% in one year, when seeding rate increased from 20 to 60 kg ha 1. Row spacing (18 and 36 cm) had little or no definite effect on most of the parameters studied. Key words: Biomass, cultivar, hemp, protein content, oil content, organic farming, row spacing, seeding rate, weed competition Vera, C. L., Woods, S. M. et Raney, J. P Incidence de la densité des semis et de l écartement des rangs sur la concurrence des adventices, le rendement et la qualité du chanvre dans la région des prairies-parcs de la Saskatchewan. Can. J. Plant Sci. 86: De 2000 à 2002, à Melfort (Saskatchewan, Canada), les auteurs ont procédé à des essais sur un loam limoneux de type tchernoziom noir dans le but de préciser les effets de l écartement des rangs sur la concurrence des mauvaises herbes, mais aussi sur la production de semences, la biomasse des pousses et la qualité des graines du chanvre industriel (Cannabis sativa L. cv. Fasamo et Finola). Quand la densité des semis passe de 20 à 60 ou à 80 kg par hectare, la densité de peuplement des adventices diminue tous les ans (d en moyenne 33 %) au même titre que la taille des plants (de 34 %). On observe également une augmentation de la densité du peuplement, de la biomasse et du rendement grainier du chanvre (moyennes de 174 %, de 23 % et de 34 %, respectivement). Le poids et la teneur en protéines des semences ne sont pas affectés par la densité des semis, mais la concentration d huile dans les graines s est accrue de 1 % une année, quand la densité des semis est passée de 20 à 60 kg par hectare. L écartement des rangs (18 ou 36 cm) n a aucune incidence définie, ou très peu, sur la plupart des paramètres examinés. Mots clés: Biomasse, cultivar, chanvre, teneur en protéines, teneur en huile, agriculture biologique, écartement des rangs, densité des semis, concurrence des mauvaises herbes There has been renewed interest in the production of nontraditional crops in Canada; crop diversification has become important to farmers seeking better net returns. One such crop is industrial hemp (Cannabis sativa L.). It was seeded on a total licensed area of nearly 9,700 ha in 2005, with 97% of this located in western Canada. Although industrial hemp is considered a fiber crop in many countries of the world, in western Canada it is presently grown mainly for seed production, because of the lack of fiber processing facilities in this region. Hemp seed contains close to 30% oil, with a fatty acid composition that has sparked interest in the international nutraceutical industry. A substantial proportion of the hemp crop in western Canada is presently grown under organic conditions, as most of its seed production is destined for the preparation of nutraceuticals and other health products for human consumption (Vera and Hanks 2004). Besides, organically produced hemp seed generates premium prices to producers. 911 There are economic and health reasons for reducing the use of pesticides in crop production (Nazarko et al. 2005). Reducing the effect of weed infestation through cultural practices is of particular importance in hemp production, in both organic and conventional systems, as there are no herbicides presently registered to control weeds in this crop. Enhancing crop competitive ability to reduce weed density is an important ecologically based weed management strategy (Anderson 2003). The practice of increasing crop plant density by using higher seeding rates associated with narrower row spacing can lead to earlier canopy closure, thus shading weeds in their early developmental stages. Hemp, especially taller fiber cultivars, competes well with weeds, as its quick initial growth allows it to outgrow and shade invading weeds (Ranalli 1999). It has been rec- Abbreviations: CV, cultivar; RS, row spacing; SR, seeding rate

2 Can. J. Plant Sci. Downloaded from by on 01/19/ CANADIAN JOURNAL OF PLANT SCIENCE ommended that seeding rates in hemp be higher for fiber production than for seed production (Baxter et al. 1998; Ranalli 1999), because fiber content and quality improve with increasing plant density. However, high plant densities (>90 plants m 2 ) in hemp have also resulted in death of adult plants due to intraspecific competition (van der Werf et al. 1995). Oilseed hemp cultivars are usually shorter, earlier maturing and perhaps less competitive with weeds than fiber cultivars, and may benefit from the use of higher plant densities. As with most new crops, there is limited agronomic information for optimum production of hemp in western Canada. The purpose of this study was to determine the effects of seeding rate and row spacing on the competitiveness of hemp against weeds, as well as on hemp biomass and seed yield and quality. The study was conducted at Agriculture and Agri-Food Canada, Melfort Research Farm, Melfort, Saskatchewan, in 2000, 2001 and Soil type was a Black Chernozem (Udic Haploborolls), with silty loam texture, ph 6.4 and 8.2% organic matter. Mean annual precipitation for the area is 413 mm, with about 60% occurring in the growing season (May August). The area has 93 frost-free days and 1517 growing-degree days (>5 C). The experimental design was a randomized complete block, with four replications. Treatments consisted of a factorial arrangement of two cultivars (Fasamo and Finola), four seeding rates (20, 40, 60 and 80 kg ha 1 ) and two row spacings (18 and 36 cm). Just the first three seeding rates were used in The experiment was seeded into cultivated stubble land, using a double-disk plot seeder, with 2.5 cm seeding depth. Seeding dates were 2000 Jun. 01, 2001 May 22 and 2002 May 28. Each plot consisted of four or seven rows (18- and 36-cm row spacing, respectively) and 4.2-m row length. Soil analysis was in the range of kg ha 1 NO 3 -N (0 30 cm soil depth), kg ha 1 P (0 15 cm soil depth) and kg ha 1 K (0 15 cm soil depth) for the study period. Recommended rates of kg N ha 1 and kg P ha 1 were applied each year. The nitrogen was broadcast shortly after emergence and the phosphorus was applied with the seed. At early seed formation, leaf and inflorescence plant samples were taken for THC (Delta 9-tetrahydrocannabinol) analysis (Meatherall Consulting, Winnipeg, MB), from a hemp cultivar experiment at the same site as the present study. The hemp cultivars Fasamo and Finola contained <0.06% THC every year of this study, well below Health Canada maximum acceptable THC content of 0.3%. Weed plant samples were collected from one (2000) or two (2001 and 2002) random 0.25 m 2 areas per plot on 2000 Aug. 08, 2001 Jul. 31 and 2002 Aug. 01. These samples were put in plastic bags and stored at 17 C, to be sorted by species, counted, dried (40 C for 24 h) and weighed. Hemp plant height was determined near maturity, with a single measurement per plot. At maturity, plants from all rows in each plot were cut (Finola: 2000 Sep. 20, 2001 Aug. 30 and 2002 Sep. 16; Fasamo: 2000 Oct. 02, 2001 Sep. 11 and 2002 Sep. 23) near soil level using a single row binder, put in cloth bags, and dried outdoors. The field-dried plant samples were then weighed for biomass determination and threshed with a plot combine. Seed samples were further dried (40 C for 24 h), cleaned and weighed for seed yield and other determinations. Seed weight was determined by weighing a sample of 500 seeds from each plot. Seed oil and protein contents were determined in 2000 and Seed oil content (dry matter basis) was measured using 25 g of dry (40 C, 48 h) whole seed sample per plot, using an Oxford continuous-wave, low-resolution nuclear magnetic resonance (NMR) instrument. Protein content of 0.5 g of dry (105 C, 3 h) whole seed per plot was calculated from nitrogen determinations by combustion analysis (LECO FP- 528), using a nitrogen to protein conversion factor of Hemp plant density was determined after harvest in 2001 and 2002, by counting the number of plants (stubble) in two 1.0- (2001) or 0.7- (2002) m 2 quadrants per plot. Analysis of variance was carried out on each year s data separately. A full factorial model was fitted to the data using the SAS procedure GLM (SAS Institute, Inc. 2004). A linear contrast was used to test for upward or downward trends in the effect of seeding rate. To stabilize the variances, crop height, crop biomass, seed yield, seed protein, weed density and weed size were log transformed, and crop density was square root transformed before analysis. Precipitation for the May September growing season was above normal in 2000 (124%) and below normal in 2001 (37%). In 2002, it was below normal for most of the growing season (64% for May through July), but heavy rains in August brought the total to near normal (102%). Drought was particularly severe in 2002, as spring soil moisture was low and precipitation in May was only 11% of normal. The main weed species present in the experimental areas each year were: stinkweed (Thlaspi arvense L.), with 60% of weed counts in 2000, 12% in 2001 and 52% in 2002; shepherd s purse [Capsella bursa-pastoris (L.) Medic.], with 16% in 2000 and 29% in 2001; cleavers (Galium aparine L.), with 7% in 2000 and 46% in 2001; wild buckwheat (Polygonum convolvulus L.), with 6% in 2000 and 5% in 2001; redroot pigweed (Amaranthus retroflexus L.), with 11% in 2002; lamb s quarters (Chenopodium album L.), with 5% in 2002, and wild oat (Avena fatua L.), with 4% in There were also volunteer wheat (Triticum aestivum L.) and canola (Brassica napus L.) plants in 2001, with 32 and 4%, respectively. Weed density was affected by cultivar (CV) and seeding rate (SR) in all years, and by row spacing (RS) in 2000 and 2002 (Table 1). Fasamo plots had more weeds than those of Finola every year, even though Fasamo plants were taller (46%) than those of Finola (Table 2). However, Finola had higher plant density than Fasamo in 2000 (visual observation), and in 2002 (57%), which could explain the higher weed population in Fasamo plots in these 2 yr. Increasing the seeding rate from 20 to 60 kg ha 1 in 2000, and from 20 to 80 kg ha 1 in 2001 and 2002, decreased weed density by 26, 33 and 41% in each year, respectively. The wider row spacing (36 cm) resulted in higher weed density in 2000, but the reverse was true in Weed size was affected by CV in 2000 and 2001, by SR in 2000, and by the interaction CV RS in 2002 (Table 1). Fasamo had larger weeds than Finola in both 2000 and 2001

3 VERA ET AL. WEED COMPETITION IN HEMP 913 Can. J. Plant Sci. Downloaded from by on 01/19/18 Table 1. F values and error mean squares from analysis of variance of seeding rate and row spacing effects on weed competition, and on whole plant and seed characteristics of two hemp cultivars grown at Melfort, Saskatchewan, in 2000, 2001 and 2002 Weed Weed Plant Plant Crop Seed Seed Seed Seed density z size y height z density y, x biomass z yield z weight protein z, x Oil x Source of variation df (plants m 2 ) (g plant 1 ) (cm) (plants m 2 ) (kg ha 1 ) (kg ha 1 ) (mg seed 1 ) (%) (%) 2000 Cultivar (CV) ** ** ** ** ** ** ** Seeding rate (SR) ** 4.95 * ** 4.23 * * SR Linear ** 9.86 ** ** 7.94 ** * CV SR ** Row spacing (RS) * CV RS SR RS * CV SR RS ** Error mean square Cultivar (CV) * ** ** ** ** ** ** Seeding rate (SR) ** ** 4.18 * 2.95 * SR Linear ** * ** ** 8.49 ** CV SR Row spacing (RS) * CV RS SR RS CV SR RS Error mean square Cultivar (CV) ** ** ** ** ** ** Seeding rate (SR) ** ** ** ** 0.22 SR Linear ** ** ** ** 0.34 CV SR * Row spacing (RS) * CV RS ** * SR RS CV SR RS Error mean square z Plant height, crop biomass, seed yield, seed protein, weed density and weed biomass data were log transformed before analysis. y Plant density data were square root transformed before analysis. x Plant density was not determined in 2000, and seed protein and seed oil were not determined in ** F value significant at P 0.05, P 0.01, respectively. (Table 2). In 2002, Finola had smaller weeds at the narrower row spacing, while weed size in Fasamo was not affected by row spacing. Weed size was decreased by 34% in 2000 by increasing the seeding rate from 20 to 60 kg ha 1. Because most oilseed hemp in western Canada is produced organically, the use of high seeding rates as a means of reducing weed interference could be worth considering. Crop height was affected by CV in all years (Table 1). Fasamo was 39, 40 and 58% taller than Finola in 2000, 2001 and 2002, respectively (Table 2). A significant linear contrast in 2001 indicated that the average crop height decreased (8%) as seeding rate increased from 20 to 80 kg ha 1 that year. Crop density was measured in 2001 and It was affected by SR in both years, and CV and the interaction CV RS in 2002 (Table 1). Crop density increased as seeding rate increased, in both years (Table 2). In 2002, Fasamo had 36% fewer plants than Finola, probably because of poor emergence. The difference in plant density between the two cultivars was greater at 36 cm row spacing (44%) than at 18 cm (28%). Crop biomass was affected by CV and SR in all years, and by the interaction CV RS in 2002 (Table 1). Fasamo produced more biomass than Finola in 2000 and 2001, but the reverse occurred in 2002 (Table 2). Biomass increased by 21, 20 and 29% respectively, as seeding rate increased from 20 to 60 (2000) or 80 kg ha 1 (2001 and 2002). In 2002, Fasamo had less biomass than Finola at the lowest seeding rate (20 kg ha 1 ), but the two cultivars had similar biomass at the highest seeding rate (80 kg ha 1 ), which indicated a rate of biomass increase for Fasamo that was almost three times as large as that of Finola (17.5 vs. 5.9 kg ha 1 of biomass increase per kg ha 1 of seeding rate increase, respectively). Seed yield was affected by CV and SR in all years (Table 1). Finola had higher seed yield than Fasamo, and the seed yield of both cultivars increased as seeding rate increased from 20 to 60 kg ha 1 in 2000 or from 20 to 80 kg ha 1 in 2001 and 2002 (Table 2). Seed weight was affected by CV in 2001 and 2002, and by the interactions CV SR and CV SR RS in 2000 (Table 1). Finola had larger (16%) seeds in 2001, but small-

4 914 CANADIAN JOURNAL OF PLANT SCIENCE Can. J. Plant Sci. Downloaded from by on 01/19/18 Table 2. Response of two hemp cultivars to three or four seeding rates and two row spacings at Melfort, Saskatchewan, in 2000, 2001 and 2002 Weed Weed Crop Crop Crop Seed Seed Seed Seed density z size z height z Density y, x biomass z yield z weight Protein z, x Oil x Year Factors (plants m 2 ) (g plant 1 ) (cm) (plants m 2 ) (kg ha 1 ) (kg ha 1 ) (mg seed 1 ) (%) (%) 2000 Cultivar Fasamo Finola Significance ** ** ** ** ** NS ** ** Seeding rate 20 w Significance ** ** NS ** ** NS NS * Row spacing 18 w Significance * NS NS NS NS NS NS NS 2001 Cultivar Fasamo Finola Significance * ** ** NS ** ** ** NS ** Seeding rate Significance ** NS * ** ** ** NS NS NS Row spacing Significance NS NS NS NS NS NS NS NS * 2002 Cultivar Fasamo Finola Significance ** NS ** ** ** ** ** Seeding rate Significance ** NS NS ** ** ** NS Row spacing Significance * NS NS NS NS NS NS z Weed density, weed biomass, crop height, crop biomass, seed yield and seed protein values are back-transformed least square means of log data. y Crop density values are back-transformed least square means of square root data. x Crop density was not determined in 2000, and seed protein and seed oil were not determined in w Seeding rate and row spacing units are in kg ha 1 and cm, respectively. *, ** F value for main effect or linear contrast (seeding rate) significant at P 0.05, P 0.01, respectively. NS, non significant. er (4%) seeds than Fasamo in 2002 (Table 2). The significant interactions of 2000 were erratic and hard to explain. Seed protein was only affected by CV in 2000 (Table 1). Finola had higher seed protein content than Fasamo in that year (Table 2). Seed oil was affected by CV in both 2000 and 2001, by SR in 2000 and by RS in 2001 (Table 1). Finola had higher oil content that Fasamo in both years (Table 2). Increasing seeding rates from 20 to 60 kg ha 1 resulted in higher seed oil content in The narrower row spacing (18 cm) resulted in higher seed oil content in In summary, increasing seeding rate of oilseed hemp from 20 to 60 or 80 kg ha 1 reduced weed density and size, and increased crop biomass and seed yield. It also improved seed oil content in one year, but had no effect on seed protein. Row spacing, on the other hand, had no definite effect on weed density and did not affect most other measured parameters. The results suggest that in western Canada, a seeding rate higher than the recommended 20 kg ha 1 for hemp seed production in Ontario (Baxter at al. 1998) may be an important tool to reduce weed infestation without the use of herbicides. The economics of increasing seeding rates and their effects on biomass and seed production in hemp should be considered before adopting high seeding rates as a standard practice for this crop in western Canada. We gratefully acknowledge the Saskatchewan Hemp Association and the Agriculture and Agri-Food Canada Matching Investment Initiative (MII) for financial assistance. We also recognize Glenn Moskal, Colleen Nielsen, Ken McJuray, Sheldon Stobbs, Dawnne Campbell and Gerald Serblowski for technical support, and Drs. Hugh Beckie and Sukhdev Malhi for internal review of the manuscript. Anderson, R An ecological approach to strengthen weed management in the semiarid great plains. Adv. Agron. 80: Baxter W. J., Scheifele, G. and Dragla, P Hemp production. Ontario Ministry of Food, Agriculture and Rural Affairs, Info sheet, Chatham, ON. Nazarko, O. M., Van Acker, R. C. and Entz, M. H Strategies for herbicide use reduction in field crops in Canada: A review. Can. J. Plant Sci. 85:

5 Can. J. Plant Sci. Downloaded from by on 01/19/18 VERA ET AL. WEED COMPETITION IN HEMP 915 Ranalli, P Agronomical and physiological advances in hemp crops. Pages in P. Ranalli, ed. Advances in hemp research. Food Products Press, An Imprint of The Haworth Press Inc. New York, NY. SAS Institute, Inc Online documentation for SAS, Version 8. [Online] Available: onlinedoc/index.html [2005 Jun. 30]. Van der Werf, H. M. G., Wijlhuizen, M. and Schutter, J. A. A Plant density affects yield and quality of fibre hemp (Cannabis sativa L.). Field Crop Res. 40: Vera, C. L. and Hanks, A Hemp production in western Canada. J. Indust. Hemp 9:

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