Baird, J.M.

Shirtliffe, S.J.

Walley, F.L.

English

University of Saskatchewan Research Archive

 Optimizing productivity in organic farming systems through variation of seeding density for field peas and lentils   Julia M. Baird1, Fran L. Walley1 and Steven J. Shirtliffe2 1Dept. of Soil Science, University of Saskatchewan, Saskatoon, SK., julia.baird@usask.ca; 2Dept. of Plant Sciences, University of Saskatchewan, Saskatoon, SK  Introduction  Seeding rates for organic pulse production have not been established and organic producers must rely on seeding rates determined for conventional production.  These rates may not be optimal given that weed management strategies for organic production rely heavily on the competitive ability of the crop for weed suppression.  Objective  To determine the optimal seeding rates for organic field peas and lentils considering a number of factors including crop yield and weed suppression.  Materials and Methods  Randomized complete block trials were conducted during the 2005 growing season and will continue in 2006 near Vonda and Delisle, SK on certified organic farmland.  Both sites have been cropped continuously for at least three years.  Separate experiments were conducted for lentil and pea.  Seeding rates ranged from 10 to 250 plants m-2 for peas and 15 to 375 plants m-2 for lentils (Table 1).  Green manure ploughdown and summerfallow treatments were included for each crop.  In-crop harrowing was conducted approximately one month after planting.  Weed counts and identification were performed after in-crop harrowing.  Weed biomass was collected prior to the green manure ploughdown and at physiological maturity.  Crop biomass was collected simultaneously, and an additional sampling time occurred at final harvest.  Seed yield and harvest index were determined by threshing the crop biomass collected at final harvest (Table 2).  Results and Discussion  Both crops showed a general trend of decreasing weed biomass with increasing seeding density (Fig. 1).  Preliminary data indicate that increased lentil seeding density increased crop biomass at all rates, whereas field pea crop biomass reached a maximum at an intermediate seeding rate around 97 plants m-2 in Delisle but continued to increase in Vonda. Pea seed yields reached 1550 kg ha-1 (23 bu ac-1) in Delisle, while Vonda yielded up to 1840 kg ha-1 (27.3 bu ac-1) (Table 2).  The recommended seeding rate for conventional field pea production in western Canada is 88 plants m-2 (Saskatchewan Pulse Growers, 2000), which closely corresponds to our findings. Lentil seed yield increased up to 1150 kg ha-1 (17 bu ac-1) at the highest density in Delisle, while Vonda showed a seed yield of 1962 kg ha-1 (29 bu ac-1) at the highest plant density (Table 2) with comparable crop plant populations between sites.  The current recommended seeding rate for conventional lentils in western Canada is 130 plants m-2   Table 1.  Actual and target seeding rates for organic lentils and field peas in 2005  Target rates Actual mean densities  Both sites Delisle Vonda   plants m-2 bu. acre-1 plants m-2 plants m-2  Lentil   15 0.15† 9 14   38 0.37 25 36   94 0.91 75 78   235 2.27 179 168   375 3.63 254 234          Field pea        10 0.31 6 5   25 0.78 13 10   62 1.95 36 31   156 4.90 85 91   250 7.85 124 145  †Lentil seeding rates in bu. acre-1 were calculated from the Saskatchewan Seed Growers Association Seed Guide (2006).    (Saskatchewan Pulse Growers, 2000).  Our findings are similar to those of Ball et al. (1997) in herbicide-free trials as well as a mechanical weed control study conducted by Paolini et al (2003) where increased lentil seeding rates were recommended.  Based on the data collected in 2005, organic producers may benefit from increased yields and some reduction in weed biomass by increasing lentil seeding rates.  Seed cost may limit the degree by which seeding rates may be increased.  Further investigation will address possible differences between treatments on the nutrient and available water status of the soil for both crops.  Table 2.  Mean yield and harvest index for organic field peas and lentils in 2005               Harvest Index Seed yield seed: seed + straw -------------kg ha-1------------ ------------bu ac-1-----------                     Target seeding rate Delisle Vonda Delisle Vonda Delisle Vonda Lentil        15 0.45 0.46 263 530 3.86 7.77  38 0.39 0.47 346 758 5.07 11.12  94 0.40 0.45 492 1226 7.22 17.98  235 0.40 0.43 1033 1695 15.15 24.86  375 0.37 0.44 1160 1963 17.01 28.79         Field pea        10 0.53 0.51 151 416 2.21 6.10  25 0.50 0.50 546 698 8.01 10.24  62 0.51 0.51 1170 1065 17.16 15.62  156 0.49 0.49 1453 1739 21.31 25.51  250 0.47 0.45 1574 1873 23.09 27.47                                   Figure 1.  Crop and weed biomass dry weight at physiological maturity for sites at Delisle and Vonda for field peas (left) and lentils (right).  Dashed lines indicate biomass yield at recommended conventional seeding rates (Saskatchewan Pulse Growers, 2000). Vonda Lentils01000200030004000500060000 50 100 150 200 250 300Crop density (104) ha-1WeedsCropVonda Peas01000200030004000500060000 50 100 150Crop density (104) ha-1WeedsCropDelisle Peas0100020003000400050000 50 100 150Plant biomass kg ha-1WeedsCropDelisle Lentils0100020003000400050000 50 100 150 200 250 300Plant biomass kg ha-1WeedsCrop Summary  Seeding rate recommendations for conventional lentils may be too low for organic production when growers anticipate significant weed pressure; however, conventional seeding rates for field peas may also be appropriate for organic production.  References  Ball, D.A., Ogg, A.G. Jr. and P.M. Chevalier. 1997. The influence of seeding rate on weed control in small-red lentil (Lens culinaris). Weed Science. 45(2):296-300. Paolini, R., Colla, G., Saccardo, F. and E. Campiglia. 2003. The influence of crop plant density on the efficacy of mechanical and reduced-rate chemical weed control in lentil (Lens culinaris Medik.) Ital. J. Agron. 7(2):85-94. Saskatchewan Pulse Growers. 2000. Pulse Production Manual. 2nd Ed. Saskatoon, SK.  

Optimizing productivity in organic farming systems through variation of seeding density for field peas and lentils

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Optimizing productivity in organic farming systems through variation of seeding density for field peas and lentils

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