American Journal of Plant Sciences, 2016, 7, 201-217
`Published Online January 2016 in SciRes. http://www.scirp.org/journal/ajps
`http://dx.doi.org/10.4236/ajps.2016.71021
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`Effects of Planting Date on Winter Canola
`Growth and Yield in the Southwestern U.S.
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`Sultan H. Begna, Sangamesh V. Angadi
`New Mexico State University, Agricultural Science Center, Clovis, NM, USA
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`Received 4 December 2015; accepted 25 January 2016; published 28 January 2016
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`Copyright © 2016 by authors and Scientific Research Publishing Inc.
`This work is licensed under the Creative Commons Attribution International License (CC BY).
`http://creativecommons.org/licenses/by/4.0/
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`Abstract
`Canola (Brassica napus L.) has potential to become alternative cash crop (healthy oil for human
`and meals for animal uses) with tremendous rotational benefits in the Southwestern U.S., a region
`dominated by cereal-fallow cropping systems. However, information on optimum planting date for
`its successful production is limited. Field experiments were conducted in 2011-12 and 2012-13
`seasons under irrigation condition to study the response of canola growth and yield to planting
`dates at Clovis, NM. Three planting dates (mid-September, late-September and early-October) and
`four canola varieties (early flowering: DKW41-10 and DKW46-15; medium flowering: Riley and
`Wichita) are studied. Fall plant stand density is significantly higher for early-October than mid-
`and late-September plantings. However, a ratio of fall to spring plant stand density indicates a
`greater reduction in spring plant stand density with early-October (25%) and mid-September
`(19%) than late-September (7%). Vegetative (by 13 days) and flowering (by 7 days) duration
`phases are significantly shortened with delay in planting. The decline in aboveground dry matter
`(DM) due to delayed planting resulted in significant seed yield reduction in both 2011-12 (26%)
`and in 2012-13 (8%) when early-October and mid-September plantings were compared. There
`was a positive relationship between final DM and canola seed yield, accounting for 84 and 34%
`variation for 2011-12 and 2012-13 seasons, respectively with the 2011-12 environmental condi-
`tions being conducive for genetically controlled variation in DM production to be more apparent
`and strong in explaining the variation in seed yield among varieties. Medium-flowering varieties
`produced higher DM (9741 vs. 8371 Kg∙ha−1) and seed yield (2785 vs. 2035 Kg∙ha−1) than ear-
`ly-flowering varieties. In addition to seed yield, DM can be used as an indirect selection criterion
`for seed yield in variety selection and appropriate planting dates including a guarantee for high
`crop residues (~75% of the total aboveground biomass) production to make canola a potential al-
`ternative cash and rotational break crop in the Southwestern U.S.
`Keywords
`Alternative Potential Crop, Planting Dates, Yield, Diversity, Southwestern U.S.
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`How to cite this paper: Begna, S.H. and Angadi, S.V. (2016) Effects of Planting Date on Winter Canola Growth and Yield in
`the Southwestern U.S. American Journal of Plant Sciences, 7, 201-217. http://dx.doi.org/10.4236/ajps.2016.71021
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`1. Introduction
`Canola has become the second largest oil crop after soybean in the world in just two decades [1] [2]. Recent
`rapid increase in production is associated with increases in demand for oil (as healthy oil for human use) and
`meal for animal feed [3]. USA’s share of the world canola production was still small (spring and winter canola
`combined with 0.655 and 1.002 million tons in 2008 and in 2013, respectively) but had increased substantially.
`Canola’s benefits as a good break/rotational crop are also another factor for the increase in canola production in
`a region with cereal-fallow or continuous cereal based cropping systems [4]-[8]. Grower’s interest in winter ca-
`nola in the Southern Great Plains of the USA is increasing in part to the benefits mentioned above and the crop’s
`good fit to the growing conditions and cropping systems of the region. Winter canola production area has in-
`creased from about 20,000 in 2009 to over 73,000 ha in 2012 in the Southern Great Plains [8]. Moreover, the
`value of canola’s meal after oil extraction from seed crushing is potential protein rich animals feed for the large
`dairy and beef industries that exist in west Texas and eastern New Mexico. Thus, there is a market for growers
`to sell their seeds to a crushing company easily since seed crushing plants are available in the region. However,
`there is limited information on optimum planting date for winter canola in this region, the Southwestern U.S. in
`particular.
`Planting date is one of the most important and manageable agronomic practices that affect growth, dry matter
`production, quality and yield of crops [9]-[16]. With other plant growth affecting factors being unlimiting, early
`planting has been generally found to improve crop growth and yield compared to late planting of both spring
`and winter type crops. Unlike spring crops, winter crops have to overwinter and appropriate planting date is
`even more crucial for the crops to establish well in the fall and overwinter and resume growth in spring and
`make economical yield. Finding winter survival canola varieties for the region has been a challenge but progress
`has been made by breeders of both public and private organizations with the development of varieties that are
`winter tolerant and yields comparable to other winter canola growing areas of the world [8]. New Mexico, as
`part of the Southwestern U.S., is one of the states where the national winter canola variety test is being con-
`ducted and its winter survival and yield potentials being documented [17].
`The planting window for canola in the Southern Great Plains is wide ranging from mid-August to mid-Octo-
`ber. Planting too early can lead to large plants resulting in excessive water and nutrient use while too late plant-
`ing can produce small plants that are prone to winter kill [15] [16]. For canola seed to emerge and have two un-
`folded leaves, it will require about 218-324 growing degree days [18] which can be achieved with even early-
`October planting in the Southwestern U.S. Unlike spring crops, however, good emergence in winter crops is not
`a guarantee for final good plant stand since final plant stand is determined by spring not by fall plant stand, and
`this in turn can be affected by weather and cultural practices including planting date. It was reported that later
`planting date (October 15) for canola in Kansas produced higher fall plant stand than mid-August, early-, mid-
`and late-September plantings in one of two years studies. In this study, spring plant stand was reported to be not
`different among the earlier planting dates, however later planting dates (late-September and mid-October) de-
`spite having higher fall plant stand, plants did not survive the winter [15]. A study done in China showed that
`winter extreme low temperatures resulting from late plantings (passed early-October) damaged established ca-
`nola leading to significant yield reduction [16]. A study done in Australia on canola and mustard showed that a
`yield potential of early planting over later planting if plants of early plantings are not affected by spring frost
`damage during flowering and grain filling [13]. Generally, vegetative growth and maturation periods are af-
`fected by planting date leading to dry matter production and yield difference between early and late planting
`dates.
`Several researchers have reported a positive relationship between dry matter production (both at flowering
`and maturity) and seed yield of many crops including canola, with the higher the dry matter the higher the seed
`yield which, in turn, can be affected by planting dates [9]-[14] [16] [19] [20]. A biomass of 5000 Kg∙ha−1 at
`flowering has been suggested for canola as maximum enough for maximum yield with little yield advantage for
`crops with higher levels of biomass [21] [22]. However, several studies done in different parts of the world
`showed an increase in seed yield with an increase with biomass both at flowering and maturity [13] [16] [20]
`[23]. A study done in Australia [19] using measured data and a simulation model reported a 3% to 9% canola
`seed yield reduction per week of planting date delay for the high and low rain regions, respectively. A study
`done in China using method mentioned above reported a yield penalty due to delayed planting (passed ear-
`ly-October) by as much as 20% [16]. A study done in Kansas showed that seed yield reduction by 18% with
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`mid-September and mid-August compared to early-September plantings. The Kansas research, canola planted
`after September 15 did not consistently survive winter resulting in no seed production [15]. In the Southeastern
`U.S. where winter is milder than the above mentioned regions, canola seed yield was significantly reduced with
`mid- and late-October planting compared to early-October planting [24]. On the other hand, oil content was re-
`ported to be positively related to harvest index and seed size and negatively to temperature conditions post-an-
`thesis [13] [16]. The economy of winter oilseed rape cultivation is determined primarily by the achievable seed
`yield and less by oil content [25]. The biological yield of winter oilseed rape is the product of growth rate, dura-
`tion of vegetative period, and seed filling [26] [27] which, in turn, can be affected by genetic, environmental,
`agronomic factors and the interaction between them [28]-[31]. Planting date is one of the most important and
`manageable agronomic factors that can affect crop production including canola. However, there is limited in-
`formation on optimum planting date for successful winter canola production and hence an increase in production
`areas in the Southwestern U.S. The objective of this study was to investigate the response of growth and yield of
`canola to planting dates under Southwestern U.S. growing conditions.
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`2. Materials and Methods
`2.1. Experimental Site and Design
`The study was conducted during the 2011-12 and 2012-13 growing seasons at the New Mexico State University
`Agricultural Science Center at Clovis (34.60˚N, 103.22˚W, elevation 1331 m). Soil type was Olton clay loam
`(Fine, mixed, superactive, thermic aridic paleustolls). Soil test resulted in 29.1 ppm N, 32.8 ppm P and 606 ppm
`K with pH of 7.5 and organic matter of 1.4% in 2011-12 and 28.9 ppm N, 16.7 ppm P and 456 ppm with pH of
`7.5 and organic matter of 1.9% in 2012-13 growing seasons. Fertilizer was pre-plant soil incorporated (100.8-0-
`39.2-15.9 and 78.4-0-28.0-12.7 Kg∙ha−1 N-P2O5-K2O-S for 2011 and 2012, respectively) based on soil test re-
`sults. The previous crop for both growing seasons was corn. In both years, herbicide Treflan (trifluralin) at the
`rate of 2.4 L∙ha−1 was soil incorporated before planting for weed control. Hand-hoeing was also done as needed.
`Insecticide Intrepid (methoaxyfenozide and propylene glycol) at16.8 L∙ha−1 and Corgan (chlorantraniliprole) at
`350 mL∙ha−1 were applied in spring to control insects, diamondback moth (Plutella xylostella) in particular in
`2011-12 season. In 2012-13 season insecticides mixture of Dimethoate at 1.4 L∙ha−1 and Acephoate, and Lan-
`nate (methomyl) at 4.2 L∙ha−1 targeting flee beetle (Phyllotreta spp.) in particular and a mixture of Baythroid
`(beta-Cyfluthrin and cyclohexanone) at 196 mL∙ha−1, and Prevathon (chlorantraniliprole) at 980 mL∙ha−1 target-
`ing harlequin bugs (Murgantia histrionica), flee beetle, lygus bugs (Lygus spp.) and moth larvae in fall and Tri-
`max (imidacloprid) at 350 mL∙ha−1 targeting false chinch bugs (Nysius raphanus), green peach aphid (Myzus
`persicae), cabbage aphid (Brevicoryne brassicae) and harlequins in particular were applied in late spring and a
`mixture of Dimethoate at 1.4 L∙ha−1, Brigade (bifenthrin) at 420 mL∙ha−1 and Brinstar at 5.6 L∙ha−1 targeting
`harlequins, lygus bugs was applied in June of 2012-13 growing season. The application rates of herbicide and
`insecticides were determined based on the recommendation for weed and insect control indicated in the Great
`Plains canola production handbook.
`In both years, canola was planted into a conventionally tilled seedbed under sprinkler irrigations. The row
`spacing was 0.15 m with a plot having 11 rows. Plot size was 9.14 by 1.68 m. Canola was planted with a plot
`drill (Model 3P600, Great Plains Drill) at seeding rate of 6.7 Kg∙ha−1 in both years and this is within the recom-
`mended seeding rate for canola production in this region. The experimental design was a randomized complete
`block with split plot arrangement replicated four times. The main plots had three planting dates (September 19
`as mid-September, September 28 as late-September and October 7 as early-October). The subplots were 4 cano-
`la varieties (early flowering/maturing: DKW 41-10, DKW 46-15 and medium flowering/maturing: Riley and
`Wichita). The canola varieties were selected based on yield potential, flowering/maturity groups and seed avail-
`ability. The early flowering/maturing (open pollinated and Roundup Ready) varieties were from Monsanto while
`the medium flowering/maturing (open pollinated) varieties were from Kansas State University.
`Growing season weather data were collected from a National Weather Service station located at the Agricul-
`tural Science Center at Clovis. Sprinkler irrigations were applied as needed throughout the growing season and
`more so from the time the crop started regrowth in spring (Figure 1). In April and early May of 2012-13 crops
`were irrigated more to encourage more regrowth so that the damage caused by the unusual repeated freeze oc-
`curred that year could be compensated. Precipitation was not adequate in both growing seasons (with total pre-
`cipitation from planting to final harvest was only 215 and 193 mm for 2011-12 and 2012-13 growing seasons,
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`Figure 1. Daily minimum, mean and maximum temperature and daily irrigation and
`precipitation during 2011-12 and 2012-13 growing seasons.
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`respectively) resulting in 453.4 and 518.2 mm of irrigation water used in 2011-12 and 2012-13 seasons, respec-
`tively. Irrigation was terminated on May 26 and June 14, respectively, in 2011-12 and 2012-13 growing seasons.
`Daily irrigation and precipitation amounts along with daily minimum, maximum and mean temperature are pre-
`sented in Figure 1.
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`2.2. Data Collection
`Plots were assessed for fall and spring plant stand 2 rows of 1 meter taken from the center rows and converted
`into plant stand m−2. A fall to spring plant stand ratio was also calculated which is a good indicator of winter
`survival. When there was 50% of the plants in the plot with 1 flower or more the date was noted as bloom date.
`In 2012 the bloom date occurred between March 24 through April 4, 2012 and while in 2013 because of cooler
`temperatures it occurred between April 4 through 21, 2013. In 2013 there was a repeated freeze (Figure 1) re-
`sulting in plant parts being damaged including flower parts, buds and small pods leading to a regrowth and
`re-bloom of plants. In the 2012-13 season, beside the above parameters, vegetative growth was assessed on
`samples harvested 2.5 cm aboveground within 0.25 m2 area of each plots three times during the growing season.
`All plant samples were bagged and dried to a constant weight at 65˚C to calculate the aboveground dry matter.
`Final harvest at 2.5 cm aboveground within 2 m2 of each plots were done on June 18 and July 2 for 2012 and
`2013 seasons, respectively. Bagged plants samples were dried to a constant weight at 65˚C. Once total weight of
`each sample was recorded, samples were threshed with a plot combine (Model Elite Plot 2001, Wintersteiger,
`Ried, Austria) and seed were collected and weighed. Harvest index, the ratio of grain to total biomass (grain plus
`aboveground dry matter) was calculated for each plot. Seed oil content was also determined on seed samples
`sent to the Brassica Breeding and Research Lab at the University of Idaho and this also allowed calculation of
`oil yield (Oil yield, seed yield multiplied by seed oil content).
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`2.3. Statistical Analysis
`Statistical analyses were performed using SAS PROC MIXED procedures in SAS 9.3 [32] to detect if differ-
`ences existed between planting dates and varieties and their interactions with year. Significance was considered
`at p < 0.05 and protected LSD was obtained using the PDIFF statement in the LSMEANS option within SAS
`PROC MIXED to decide where differences occurred within significant interactions [33]. Regression functions
`were also fitted to the data and planting date of each growing season.
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`3. Results and Discussion
`3.1. Environmental Conditions
`The distribution of precipitation during the experimental periods varied between the years. Precipitation re-
`ceived during crop establishment and early plant growth stage (September through November) in the 2011-12
`season (5 rain events with only one above 10 mm) was lower than the 2012-13 season (8 rain events with three
`above 10 mm). The opposite occurred during the later plant growth stage, especially during the month of March,
`April and May the time the crop is most active with flowering and podding process (9 rain events with two
`above 10 mm and 4 rain events with all below 10 mm, for the 2011-12 and 2012-13 seasons, respectively)
`(Figure 1). The number of rain events and amounts during seed filling in 2011-12 and 2012-13 seasons were
`similar (8 and 6 rain events for 2011-12 and 2012-13 seasons, respectively with 2 of them above 10 mm) and the
`growing period in both seasons can be considered as dry since the benefit from such rainfall events to the plants
`was limited. Total precipitation amount received during the 2011-12 (215 mm) and the 2012-13 (193 mm)
`growing seasons were similar (a difference of only 22 mm) but still not enough to grow a crop with only preci-
`pitation. Thus, this study was done under limited irrigation and 104 and 137 mm of irrigation water was applied
`for 2011-12 and 2012-13 growing seasons, respectively, during the early growth stage “emergence through ro-
`seate” (September through November). Irrigation amount applied during the latter active part of the growing
`seasons (flowering and seed filling periods) were 279 and 32 mm in 2011-12 and 241 and 89 mm in 2012-13
`seasons (Figure 1).
`Temperature pattern during the crop cycle varied between the 2011-12 and 2012-13 seasons. Daily tempera-
`ture ranged from −8°C to 34°C (early growth stage), from −9°C (12 minimum temperature events with below 0°C)
`to 27°C (beginning of regrowth to beginning of flowering), from −8°C (6 minimum temperature events with be-
`low 0°C, flowering and podding stages) to 34°C (with 37 maximum temperature events above 21°C), ranged
`from 9°C to 37°C (with 32 maximum temperature events above 21°C and this is during the whole seed filling pe-
`riod) in 2011-12 season. Whereas in 2012-13 season, daily temperature ranged from −11°C to 32°C (early
`growth stage), from −12°C (26 minimum temperature events with below 0°C) to 28°C (beginning of regrowth to
`beginning of flowering), from −9°C (12 minimum temperature events with below 0°C, flowering and podding
`stages) to 34°C (with 44 maximum temperature events above 21°C), from 9°C to 39°C (with 30 maximum tem-
`perature events above 21°C during the whole seed filling period) in 2012-13 season. As seen with the above
`minimum temperature events, the 2012-13 season was a lot colder than the 2011-12 season during early growth,
`flowering and pod formation stages leading to longer time requirement for plants to reach those different stages
`including maturity (Table 1). The extreme and potentially yield limiting weather that occurred in 2012-13 sea-
`son during flowering and early podding stages resulted in the loss of plant parts including flowers, buds and
`small pods. This, in turn, resulted in plants investing some of the resources for regrowth which otherwise could
`have been used for more pods and hence more seeds and possibly more yield.
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`3.2. Crop Establishment and Plant Stand
`Canola establishment and subsequent fall plant stand density were good for all of the three planting dates
`(mid-September, late-September and early-October) in both 2011-12 and 2012-13 seasons. This was expected
`since the growing conditions including moisture through irrigation was favorable for the crop to establish well.
`Although the crop established well, as expected plants of late planting date were much smaller when winter ar-
`rived reflecting the shorter time and accumulated degree days resulting from the delay in planting. There was a
`significant year x planting date interaction effect (p < 0.0001) on fall plant stand density. The highest fall plant
`stand density was recorded for early-October (133 plants∙m−2) and mid-September (128 plants∙m−2) plantings in
`2011-12 and mid-September planting in 2012-13 (127 plants∙m−2) seasons. Groups with second and third for fall
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`Table 1. Fall and spring plant stand and their ratio of four canola varieties under three planting dates in 2011-12 and 2012-13
`seasons.
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`Planting dates
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`Mid-Sept.
`Late-Sept.
`Early-Oct.
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`LSD (0.05)
`
`DKW4110
`DKW4615
`RILEY
`WICHITA
`
`LSD (0.05)
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`Source of variation
`
`2011-12
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`2012-13
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`2011-12
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`2012-13
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`Fall plant stand (numbers∙m−2)
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`Spring plant stand (numbers∙m−2)
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`2 yrs avg
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`Fall to spring plant stand ratio
`
`10
`
`105a
`128
`133
`
`119
`129
`102
`115
`
`10
`
`
`
`127
`87
`115
`
`
`
`
`
`
`
`
`
`
`92
`111
`102
`
`121
`106
`84
`95
`
`
`
`12
`
`8
`
`109
`90
`102
`
`98
`124
`85
`95
`
`
`
`1.19
`1.07
`1.25
`
`0.10
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`
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`
`
`
`
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`
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`
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`
`
`
`
`
`
`
`
`
`
`0.1239
`
`0.7943
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`0.0208
`Year (Y)
`0.0148
`
`0.9326
`
`0.0155
`Planting date (PD)
`0.0862
`
`0.0129
`
`<0.0001
`Y x PD
`0.5430
`
`<0.0001
`
`0.0008
`Variety (V)
`0.1713
`
`0.0014
`
`0.0905
`Y x V
`0.5943
`
`0.6893
`
`0.1857
`PD x V
`0.9305
`
`0.7765
`
`0.8347
`Y x PD x V
`aNumber within row x column groups differing by the values less than the LSD value were not different according to LSD (p > 0.05).
`
`plant stand density were early-October and early-September planting dates of 2012-13 and 2011-12 seasons, re-
`spectively (Table 1). The lowest fall plant stand density (87 plants∙m−2) was recorded for late-September plant-
`ing date in 2012-13 seasons. Plants of the first two planting dates (especially mid-September) in both seasons
`were more vigorous than the early-October planting. This result in part agrees with the results of research on
`canola planted in October 15 in Kansas produced higher fall plant stand than mid-August, early-September,
`mid-September and late-September plantings in one of 2 years studies [15].
`There were year and variety one-way significant effects on fall plant stand density. Greater fall plant stand
`density, averaged over planting dates and varieties, was recorded in 2011-12 (122 plants∙m−2) compared to the
`2012-13 season (110 plants∙m−2) perhaps a reflection of the slightly conducive warmer temperature occurred in
`2011-12 (mean daily temperature ranging from 11˚C to 23˚C) than in the 2012-13 season (mean daily tempera-
`ture ranging from 5˚C to 23˚C) (Figure 1). There was significant difference between canola varieties for fall
`plant stand density (Table 1). Early flowering/maturing DKW46-15 and DKW41-10 varieties gave 129 and 119
`plants∙m−2, respectively, followed by Wichita with 115 plants∙m−2 and the lowest plant stand density recording
`was for Riley with 102 plants∙m−2 reflecting their genetic makeup with the early flowering/maturing variety in
`general producing more plant stand than the medium flowering/maturing ones.
`Plots were also assessed for spring plant stand density, and a significant year x planting date interactions ef-
`fect (p < 0.0129) was detected for this variable. Within the interaction effects in spring plant stand density, the
`highest spring plant stand was recorded for late-September planting of 2011-12 (111 plants∙m−2) and mid-Sep-
`tember planting of 2012-13 (109 plants∙m−2) seasons, followed by a secondary group that included early-October
`planting of both seasons (102 plants∙m−2) and the lowest plant stand density was recorded for late-September
`planting of 2012-13 season (90 plants∙m−2). A ratio of fall to spring plant stand density which is a good indicator
`of winter survival was also assessed and only planting date had significant effect on this variable (Table 1). The
`reduction in plant stand density ratio was 19 and 25% for mid-September and early-October, respectively while
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`that of the late-September planting date had only 7% reduction in plant stand density ratio. This, perhaps, sug-
`gests that plant sizes of late-September planting to be less damaged by winter kill than the mid-September (big-
`ger plants) and early-October (small plants) planting dates. Planting too early could lead to large plants resulting
`in excessive water and nutrient use, while planting too late on the other hand could produce small plants that are
`prone to winter kills [15] [16]. Too big of a plant from early planting and too small of a plant from late planting
`suggests a requirement of an optimum planting date for appropriate stage and plant size for better winter surviv-
`al by the canola crop. As with fall plant stand density, the highest spring plant stand density was recorded for
`early flowering/maturing DKW41-10 and DKW 46-15 varieties (111 plants∙m−2, averaged over varieties), fol-
`lowed by medium flowering/maturing Wichita and Riley varieties (90 plants∙m−2, averaged over varieties). Early
`flowering/maturing variety had higher spring plant stand density than the medium flowering/maturing varieties
`which was also seen in fall plant stand density perhaps reflecting their overall genetic difference. Even though
`there was a reduction in spring plant stand density due to planting dates reflected in the ratio ranging from 7 to
`25%, final spring plant stand recorded in this study are more than the spring optimum stand density (80 to 150
`and 60 to 80 plants∙m−2, for fall and spring stand density) reported in Europe [26] reflecting the milder winter
`and growing conditions of Southwestern US compared to the one in Europe. A study done in Kansas showed
`that spring plant stands of canola were not different among the earlier planting dates (mid-August, late-August
`and early-September) while later planting dates (late-September and mid-October) despite having higher fall
`plant stand, plants did not survive the winter and hence zero spring plant stand which can be linked to the grow-
`ing conditions of the study area which was also rainfed while our study was under irrigation [15].
`Given canola’s ability to compensate for lower plant densities by producing larger leaf area, enhanced
`branching and increased number of pods per plant, average yield can be achieved over a wide range of plant
`densities (8 - 90 plants∙m−2; [21]; 20 - 80 plants∙m−2; [34]). It was also reported that a plant stand density ranging
`from 34 to 64 plants∙m−2 (with similar seed yield 4800 and 4100 Kg∙ha−1) [5] for winter canola varieties planted
`from March through April in Australia. And these were considered as acceptable commercial levels (>30
`plants∙m−2) to produce economical yield. Spring plant stand is more critical than fall plant stand density since
`yield is being determined by final spring plant stand not fall plant stand. Canola is also one of the crops reported
`to be capable of producing close to maximum yields with stand reductions by more than 50% [35]. Since this
`was a study with irrigation, winter canola varieties tested here germinated and grew well in the fall and survived
`the winter well, and produced economical yield from all planting dates although there was a reduction in spring
`plant stand density.
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`3.3. Crop Phenology
`There were a significant year x planting date and year x variety interaction effects on the time and degree days
`required for the plants to reach flower initiation, 50% flowering, end of flowering, seed filling duration and ma-
`turation (Table 2 and Table 3). The number of days required for plants to reach flower initiation (174 to 187 vs.
`184 to 195 days), 50% flowering (179 to 192 vs. 191 to 204 days) and end of flowering (224 to 242 vs. 233 to
`252 days) were significantly lower in the 2011-12 than in the 2012-13 seasons. The difference between the two
`seasons in number of days to reach these stages by the plants were also reflected in the accumulated GDD (for
`example 1153 to 1218 vs. 1259 to 1322 GDD were required to 50% flowering , for 2011-12 and 2012-13 sea-
`sons, respectively, Table 3). Minimum temperatures during rosette and beginning of regrowth have been linked
`to prolonging plant stages including stem elongation and flower initiation in winter crops [13] [16] [19] [20] [36]
`[37]. Twelve minimum temperature events below 0˚C during beginning of regrowth to beginning of flowering
`occurred in 2011-12 season while 26 minimum temperature events with below 0˚C occurred in 2012-13 seasons
`(Figure 1). Number of days and accumulated GDD requirements for plants to initiate flowering, 50% flowering
`and end of flowering were significantly affected by planting date in both seasons (Table 2 and Table 3). The
`number of days required for the above mentioned plant stages were reduced with delay in planting (for example,
`174 vs. 187 days for early-October and mid-September, respectively in 2011-12 season and 184 vs. 195 days in
`2012-13 seasons were required for plants to reach 50% flowering) while more degree days being accumulated
`with delayed planting (Table 2 and Table 3). The shortening of plant growth period such as reaching 50% flo-
`wering with delayed planting date has been reported before for many crops including canola, safflower, wheat
`[13] [16] [20] [38]) which can lead to the faster phenological development resulting from more accumulated
`growing degree days.
`
`
`
`207
`
`CSIRO Exhibit 1015
`
`

`

`S. H. Begna, S. V. Angadi
`
`
`Table 2. Growing degree days required from planting to start of flowering, 50% flowering and end of flowering and seed
`filling duration of four canola varieties under three planting dates in 2011-12 and 2012-13 seasons.
`
`2012-13
`2011-12
`Start of flowering
`
`1080a
`1099
`1158
`1112
`
`1081
`1123
`1121
`1124
`1112
`
`6.2
`
`5.9
`
`1176
`1210
`1251
`1212
`
`1183
`1230
`1210
`1226
`1212
`
`2012-13
`2011-12
`2012-13
`2011-12
`End of flowering
`50% flowering
`Growing degree days from planting
`1259
`1933
`1290
`1933
`1322
`1933
`1290
`1933
`
`2189
`2191
`2189
`2190
`
`1153
`1186
`1218
`1186
`
`1130
`1198
`1205
`1209
`1186
`
`6.2
`
`5.8
`
`1240
`1297
`1302
`1322
`1290
`
`1933
`1933
`1933
`1933
`1933
`
`1.3
`
`1.4
`
`2191
`2189
`2189
`2189
`2190
`
`
`
`Planting dates
`Mid-Sept.
`Late-Sept.
`Early-Oct.
`Mean
`LSD (0.05)
`DKW4110
`DKW4615
`RILEY
`WICHITA
`Mean
`LSD (0.05)
`
`
`
`
`
`
`
`Source of variation
`<0.0001
`
`<0.0001
`
`<0.0001
`
`<0.0001
`Year (Y)
`0.3966
`
`0.3966
`
`<0.0001
`
`<0.0001
`Planting date (PD)
`0.3966
`
`0.3966
`
`0.9269
`
`0.0403
`Y x PD
`0.4000
`
`0.4000
`
`<0.0001
`
`<0.001
`Variety (V)
`0.4000
`
`0.4000
`
`0.0066
`
`0.0383
`Y x V
`0.4350
`
`0.4350
`
`<0.0001
`
`0.1659
`PD x V
`0.4350
`
`0.4350
`
`0.0770
`
`0.3709
`Y x PD x V
`aNumber within row x column groups differing by the values less than the LSD value were not different according to LSD (p > 0.05).
`
`Table 3. Number of days required from planting to start of flowering, 50% flowering and end of flowering and seed filling
`duration of four canola varieties under three planting dates in 2011-12 and 2012-13 seasons.
`
`2012-13
`2011-12
`Seed filling duration
`
`692
`692
`692
`692
`
`692
`692
`692
`692
`692
`
`1.3
`
`1.4
`
`754
`753
`754
`754
`
`753
`753
`753
`753
`753
`
`
`
`
`
`
`
`
`
`
`2012-13
`2011-12
`Seed filling duration
`
`2012-13
`2011-12
`Start of Flowering
`
`187a
`180
`174
`180
`
`178
`181
`181
`181
`180
`
`195
`192
`184
`190
`
`187
`193
`190
`192
`191
`
`2012-13
`2011-12
`2012-13
`2011-12
`End of flowering
`50% flowering
`Number of days from planting
`204
`242
`200
`233
`191
`224
`198
`233
`
`252
`245
`233
`243
`
`192
`185
`179
`185
`
`182
`186
`187
`187
`186
`
`
`
`233
`233