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Plant population influences niger seed yield in the northern Great Plains.

NIGER is an annual oilseed crop cultivated in Ethiopia and India in rotation with cereals and pulses. Niger originated in Ethiopia (Baagoe, 1974) and may have been taken to India by Ethiopian immigrants around the third millennium BC (Doggett, 1987). The Indian cultivars are distinctly different from the Ethiopian cultivars, with Ethiopian niger being taller, later maturing, and higher yielding than Indian niger (Getinet and Sharma, 1996). Currently, the entire USA usage of niger, approximately 30 000 t annually, is imported from India, Ethiopia, and Myanmar (Quinn and Myers, 2002). In the USA the niger seed, commonly referred to as thistle seed, is mainly used as bird food, especially for finches (Carduelis spp.).

Niger is a dicotyledonous herb with epigeal emergence and pale green to brownish hypocotyls and cotyledons (Seegeler, 1983). The crop is usually produced on poor, coarse-textured soils (Chavan, 1961) and it has shown limited response to N and P fertilizer. Weiss (2000) reported niger requires moderate temperatures, and that above 30[degrees]C the rate of growth and flowering are adversely affected and maturity is accelerated. Niger seeding rates vary from 5 to 10 kg [ha.sup.-1] in Ethiopia and from 5 to 8 kg [ha.sup.-1] in India (Getinet and Sharma, 1996). Weiss (2000) suggested seeding rates between 6 and 12 kg [ha.sup.-1]. The niger plant is moderately to well branched depending on the plant population. Leaves are 100 to 200 mm long and 30 to 50 mm wide. Both Ethiopian and Indian cultivars exhibit short-day responses to day length and both have an indeterminate growth habit (Getinet and Sharma, 1996). The niger flower is yellow and the heads are 15 to 50 mm in diameter with 5- to 20-mm long ray florets. For seed set, the plants depend on cross-pollination as they are mostly self-incompatible (Sujatha, 1993). Bees and other insects are the major aids in pollination (Ramachandran and Menon, 1979) and are required for seed set (Weiss, 2000). Flowering of an individual head takes about 8 d. One-thousand-seed weight is from 3 to 5 g (Weiss, 2000), with about 40 seeds per head (Seegeler, 1983).

Niger seed (achenes) in major production areas are used for human food and for edible oil extraction (Seegeler, 1983). The seed contains about 400 g [kg.sup.-1] oil (Getinet and Sharma. 1996) but varies from 250 to 450 g [kg.sup.-1] for unimproved types, and 500 to 600 g [kg.sup.-1] in niger selections (Weiss, 2000). Yields of recommended Indian cultivars averaged 467 kg [ha.sup.-1] (Getinet and Sharma, 1996) and 392 to 448 kg [ha.sup.-1] (Purseglove, 1979). Vegetative growth generally increases in niger when >30 kg [ha.sup.-1] N is applied. Higher N levels may cause lodging, which will negatively impact seed yield (Getinet and Sharma, 1996). Niger can tolerate high rainfall during the vegetative phase (Weiss, 2000), and in Ethiopia the crop can be grown on waterlogged soils where most other crops and oilseeds fail to grow, but rainfall at physiological maturity may lead to seed shattering (Getinet and Sharma, 1996). Salunkhe and Desai (1986) stated that during harvest, 25% of the seed could be lost due to shattering, even though niger is typically hand harvested. Shorter cultivars, 0.5 m in stature (Purseglove, 1979), with less branching, more uniform flowering, increased seeds per head, and little or no shattering would improve harvest efficiency as well as seed yield, especially when mechanically combined (Weiss, 2000).

In a planting date study near Rosemount, MN, niger only flowered before frost in one of three years (Robinson, 1986). In a multisite evaluation of planting dates in North Dakota, Diaz (1993) found that niger produced little or no seed and concluded that the genotypes tested did not have potential in North Dakota. In both states, the cultivars planted were not adapted to the relatively short growing season in the northern plains. Niger was evaluated in Canada as a potential oilseed crop but was not considered profitable (Weiss, 2000). Researchers in Indiana, Illinois, and Missouri evaluated 16 niger accessions in 2001, and several accessions flowered and matured similar to a commercial field that yielded 480 kg [ha.sup.-1] (Quinn and Myers, 2002).

In recent years, a private plant breeder in Minnesota has developed an early maturing cultivar named EarlyBird. Members of a niger growers cooperative in northwest Minnesota have grown this variety on limited acreage since 1998. Herbicide research was conducted on niger in Minnesota during the 2000 growing season (Holen et al., 2000), resulting in special-use clearance labels in Minnesota in 2001, and Minnesota and North Dakota in 2002.

The Minnesota niger producers were offered a contract that recommended a seeding rate of approximately 1.5 kg [ha.sup.-1], a seeding rate sometimes recommended in India. We hypothesized that seeding rates reported from countries with mainly nonmechanized farming systems might not be best suited to the mechanized farming operations in North America. The objective of this experiment was to determine the effect of seeding rate on yield, plant height, and test weight of EarlyBird niger, when grown in the northcentral USA, and to establish a recommended seeding rate for this cultivar and locale.

MATERIALS AND METHODS

The study was conducted in seven environments (location by year combinations): Red Lake Falls (47[degrees]93' N, 96[degrees]38' W) and Kennedy (48[degrees]75' N, 96[degrees]96' W), MN, in 2000 and 2001 [RLF00, RLF01, Ken00, and Ken01]; and Carrington (47[degrees]30' N, 99[degrees]08' W), Landgon (48[degrees]46' N, 98[degrees]20, W), and Prosper (47[degrees]00' N, 97[degrees]07' W), ND, in 2001 [Car01, Lan01, and Pro01]. At Red Lake Falls, the soil is a Foxhome loam (sandy-skeletal over loamy, mixed, superactive, frigid Oxyaquic Hapludolls); at Kennedy the soil is a Northcote clay (very fine, smectitc, frigid Typic Epiaquerts); at Carrington the soils are a complex of Heimdal loam (coarse-loamy, mixed, superactive, frigid Calcic Hapludolls) and Emrick loam (coarse-loamy, mixed. superactive, frigid Pachic Hapludolls); at Langdon the soil is a Svea loam (fine-loamy, mixed, superactive, frigid Pachic Hapludolls); and at Prosper the soils are mostly a Perella silty-clay loam (fine-silty, mixed, superactive, frigid Typic Endoaquolls) and a Bearden silt loam (fine-silty, mixed, superactive, frigid Aeric Calciaquolls). The RLF00, RLF01, Ken00, and Ken01 environments were located on producers' fields, which were fertilized for commercial canola (Brassica rapa L.) production (Table 1). Precipitation and temperature records were obtained from the North Dakota Agricultural Weather Network (NDAWN) and Northwest Research and Outreach Center (Crookston, MN).

The experimental design was a randomized complete block with four replicates. In 2000, eight seeding rates (0.56, 1.12, 1.68, 2.24, 2.80, 3.36, 6.72, and 10.1 kg [ha.sup.-1]) were evaluated at two Minnesota locations (RFL and Ken). In 2001, these same eight seeding rates plus two higher rates (13.44 and 16.80 kg [ha.sup.-1]) were evaluated on different fields at the same two Minnesota locations as well as at three North Dakota locations (Car, Lan, and Pro). Plot size was approximately 1.2 m by 6.7 m at all locations. Chemical weed control was preplant incorporation of trifluralin at 0.84 kg a.i. [ha.sup.-1]. The RLF01 environment was treated against Tarnished plant bugs [Lygus lineolaris (Palisot de Beauvois)] with permethrin [(3-Phenoxyphenyl)methyl(+ or -])cis-trans 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate]. Previous crop, row spacing, fertilizer application, and seeding, swathing, and harvest dates are reported in Table 1.

EarlyBird niger seed came from one source each year. In 2000, the 1000-seed weight was 3.08 g and the germination rate was 80%. In 2001, the 1000-seed weight was 3.26 g and the germination rate was 90%. Seeds were sown in the spring when soils were considered warm and dry enough for seed germination and emergence (Table 1). Supplemental weed control was done by hand weeding. Plant stand counts were taken approximately 5 wk after planting from three 0.19-[m.sup.2] quadrates. In 2001, plant height was measured at full bloom. Naturally occurring insects pollinated the flowers at all locations. At Lan01, days after planting when 10% of the plants were flowering was recorded. At RLF01, the percentage bloom was determined 73 d after planting, when approximately 50% of the blooms were visible for the seeding rate of 6.72 kg [ha.sup.-1]. Sclerotinia [Sclerotinia sclerotiorum (Lib.) de Bary] wilt scores were taken in each environment where the disease was evident. At Lan01, 30 plants per plot were monitored for white mold by evaluating the main stem. If a branch had white mold and the main stem did not, it was not recorded as infected. At Car01, three plants per plot in six of the 10 seeding rates were evaluated at swathing for aboveground biomass, head weight, and number of heads per plant. Also at Car01, seed oil content was determined for each plot by a nuclear magnetic resonance spectrometer (MARAN 5, Universal Systems Inc., Solon, OH).

In the fall, plots were swathed and later harvested with a small plot combine (Table 1). Yield was determined after cleaning the samples. Test weight was determined at all environments except for the low-yielding environments Ken00 and Pro01, where there was not enough seed available for an accurate determination.

Ken00 was seeded relatively late, as the topsoil was dry because of limited rainfall in May (Table 2). Both RLF00 and Ken00 were extremely wet in June of 2000, with water standing in the plots at RLF00 for several days. At Pro01, above-average rainfall in May 2001 delayed seeding. At all locations in 2001, rainfall in July was substantially above the long-term 30-yr average. After the wet July, rainfall was below normal in August and September at all environments. The total seasonal rainfall at all environments was at or above the 30-yr avg (Table 2). In 2001, minimum temperatures where higher than the long-term minimum temperature average.

Because percentage germination and seed size differed slightly between the two years, seeding rates in kg ha t were converted to pure live seed seeding rates and reported in seeds [m.sup.-2]. Plant stand, plant height, yield, and test weight data were analyzed with mixed-model analysis of variance assuming environments and replications within environments were random effects. Graphics were produced with the R statistical system (Ihaka and Gentleman, 1996). Models were fit by the NLME package for R (Pinheiro and Bates, 2000). The models could also be fit by the SAS mixed-models procedure Proc Mixed (Littell et al., 1996). Let i index the environment number, j the replication within the environment, and k the level of the seeding rate s. The largest model we considered was of the form:

[1] [y.sub.ij] = ([[beta].sub.0] + [b.sub.0i] + [b.sub.0ij)+ ([[beta].sub.1] + [b.sub.1i]) [x.sub.k] + ([[beta].sub.2] + [b.sub.2i]) [x.sup.2.sub.k] + [e.sub.ijk]

The [beta]'s are fixed effect parameters giving the average fitted curve, and the b's are random effects for environments and replications. According to this model, each environment has its own fitted quadratic curve, and each replication within an environment has a fitted curve with the same shape but potentially with a different intercept. We assumed that all the random effects for environment were normally distributed, with an unstructured covariance matrix. The random effect for replication was also assumed normally distributed, independent of the environment random effects, and these were also independent of the errors [e.sub.ijs]. In all, this model has three fixed-effect parameters and five random effect variance parameters and three random effect correlation parameters. We used restricted maximum likelihood fitting (Pinheiro and Bates, 2000).

We obtained fitted curves for each of the seven environments based on best linear unbiased predictors (BLUPs) given by the fixed effects added to the best estimates of the random effects for each environment, but without the random effects for each replication within an environment. With these curves, we computed the estimated seeding rate and plant stand that gave the maximum and 90% of the maximum yield at each environment and across all environments.

Standard LSD values were reported for flowering, head weight, heads per plant, and aboveground biomass data that was collected in only one or two environments (SAS Institute, 1985).

RESULTS

Plant Stand vs. Seeding Rate

The relationship for model [1] between y = plant stand and x = pure live seed seeding rate is summarized in Fig. 1. For this analysis, the quadratic terms in model [1] for both the fixed effect [[beta].sub.2] and for the random effect [b.sub.2i] were unnecessary (approximate t = -0.822, P = 0.41). As shown in Fig. 1, a linear fit for each environment was adequate, but a separate random slope was required for each environment (likelihood ratio test = 212.68, df = 2, P < 0.001). The slopes varied between 0.21 and 0.69 (Table 3), suggesting that in these seven environments the number of plants established for each pure live seed planted was between about 0.21 and 0.69. Overall, for the seven environments we observed 0.46 established plants for each pure live seed planted. Relatively poor plant stands were observed at Ken00, Lan01, and Ken01, where <40% of the pure live seed sown produced viable plants. At all environments, the CVs for plant population were relatively large (Table 3), which may be a reflection of difficulty of seedling survival due to the small and variable mass of the individual seed, which averaged 3.17 mg.

[FIGURE 1 OMITTED]

Niger Yield vs. Seeding Rate

Confidence intervals for parameter estimates in model [1] across seven environments for the relationship between y = niger yield and x = pure live seed seeding rate are presented in Table 4, where random effect size was summarized by a standard deviation rather than a variance. The fitted model based on the fixed effects is the best estimate of the response to pure live seed seeding rate in future environments. The large values for the estimated standard deviations for the variance components for [b.sub.0i], [b.sub.0ij], and for [e.sub.ijk] summarize the large variability in data both between environments and between replications within environments. The relatively smaller estimates of standard deviations for the linear and quadratic terms suggest that although the fitted curves differ from environment to environment, the variation in these curves is relatively small compared with the variation between environments.

Figure 2 shows curves of niger yield and seeding rate for each of the seven environments. Two fitted lines are shown in each graph. The solid line gives the fitted values based on fixed effects alone, while the dashed lines show the BLUP when both fixed effects and random environmental effects are included. The reasonable fit of the random effects and the poor fit of the fixed effects alone highlights the high between-environment variation. In two of the environments, Car01 and RLF01, the fitted curves were either flat or the quadratic provided a minimum rather than a maximum. We interpret this to mean that for these environments, no trend was visible given the large variation present. For the other five environments, the BLUP curves have approximately the same maximum value. At RLF01, the environment where the overall grain yield was the greatest, the observation that seeding rate had no influence on yield may have been a result of relatively good plant establishment, especially at the lower seeding rates (Table 3).

[FIGURE 2 OMITTED]

Given the fixed effect estimates in Table 4 and the BLUP estimates of the fitted curve in each environment, we computed the estimated seeding rate that gave the maximum yield and 90% of maximum yield (Table 5). The estimated seeding rate that gave the greatest yield was 284 pure live seeds [m.sup.-2] (or a seeding rate of approximately 10 kg seed [ha.sup.-1]) across all environments, and ranged from 251 to 308 pure live seeds [m.sup.-2] at RLF01 and Lan01, respectively. The seeding rate resulting in 90% of maximum yield was 127 pure live seeds [m.sup.-2] (or a seeding rate in the range of 5 to 7 kg seed [ha.sup.-1]) across all environments, and ranged from 113 to 169 pure live seeds [m.sup.-2] at Ken01 and Pro01, respectively.

The higher-yielding environments (RLF00, RLF01, Lan01) were seeded around the middle of May, earlier than the other environments. At Lan01, finches were observed around the trial from flowering to harvest, and they may have reduced seed yield at that location. The lower-yielding environments Ken00 and Pro01 were seeded on 30 May and 9 June, respectively (Table 1 and Fig. 3).

[FIGURE 3 OMITTED]

Niger Yield vs. Plant Stand

We repeated the analysis with y = niger yield as the response, but with x = plant stand as the predictor in place of seeding rate. The results for plant stand were essentially the same as for seeding rate (Table 5 and Fig. 3): the estimated plant stand that gave the greatest yield was 157 plants [m.sup.-2] (or a seeding rate of approximately 10 kg seed [ha.sup.-1]) across all environments, and ranged from 140 to 186 plants [m.sup.-2] at RLF01 and Pro01 respectively. The plant stand resulting in 90% of maximum yield was 72 plants [m.sup.-2] (or a seeding rate in the range of 5 to 7 kg ha 1) across all environments, and ranged from 56 to 107 plants [m.sup.-2] at Ken01 and Pro01, respectively.

Test Weight vs. Seeding Rate

We used model [1] to compare y = test weight to x = pure live seed seeding rate for five of the seven environments for which test weights were taken (all but Ken01 and Pro01), but omitting the quadratic terms in both the fixed and random effects (Fig. 4). We found no effect due to pure live seed seeding rate (P = 0.34), but significant random effects for both environments and for replications within environments (P < 0.0001 for both). The mean test weight across the five environments was estimated to be 469 kg [m.sup.-3] with 95% confidence interval from 396 kg [m.sup.-3] to 542 kg [m.sup.-3]. Test weight was the lightest at Ken01, averaging 323 kg [m.sup.-3]. The crop was not fully mature at Ken01 when the plants were swathed after a killing frost. This likely explains the lower test weight at Ken01 (Fig. 4).

[FIGURE 4 OMITTED]

Plant Height vs. Seeding Rate

An identical analysis, with data summarized in Fig. 5, of y = plant height found no effect due to seeding rate, but significant environment and replication effects. The estimated mean height across the five environments was 1.12 m with 95% confidence interval from 0.90 m to 1.35 m. Plant height was the shortest at Ken01, averaging 0.83 m and the tallest at Pro01 and Lan01, averaging approximately 1.38 m. The tallest niger plants were at Pro01 and Lan01 (Fig. 5), yet Pro01 had lower yields relative to most other locations and the highest average plant stand.

[FIGURE 5 OMITTED]

Agronomic Characteristics

Increasing the seeding rate reduced the heads per plant and reduced the days to flowering (Table 6). Visual observation at the end of the season indicated that plants in plots with higher seeding rates matured a few days before the lower seeding rates and that higher seeding rates were more uniformly maturing. Plants at the lowest seeding rate had more heads per plant and higher aboveground biomass than the other seeding rates evaluated; however, individual head weights did not differ among seeding rates (Table 6). At Car01, the mean oil content of the niger was 318 g [kg.sup.-1] and there were no significant differences among the seeding rates (data not shown).

Disease Observations

Sclerotinia scores where taken at three of seven environments where infection levels were greatest (data not shown). At Lan01, 30% of the plants showed some Sclerotinia symptoms. Levels of the disease at RLF01 and Car01 were substantially lower, and virtually no Sclerotinia was observed at the other environments. There were no significant differences between seeding rates in the incidence of Sclerotinia at any environment.

DISCUSSION

Previous research in North Dakota by Berti and Schneiter (1992) showed an average niger yield of 118 kg [ha.sup.-1] across seven environments. Niger research was not continued because of these low yields, and the researchers concluded that earlier-maturing cultivars were essential before niger could be considered for commercial production in the state. Robinson (1986) in Minnesota came to the same conclusion. EarlyBird, the variety we evaluated in this study, is an earlier-maturing variety than those previous researchers had evaluated. Our research showed mean yield across the seven environments was 355 kg [ha.sup.-1], with mean yields at RLF00 and RLF01 of 535 and 580 kg [ha.sup.-1], respectively. These values are comparable with production yields of 392 to 448 kg [ha.sup.-1] in regions where niger is commonly grown (Purseglove, 1979).

Maximum yields across all environments corresponded to a seeding rate of 284 seeds [m.sup.-2] and a plant stand of 157 plants [m.sup.-2], or approximately 10.0 kg seed [ha.sup.-1], whereas 90% of the maximum yields corresponded to a seeding rate of 127 seeds [m.sup.-2] and a plant stand of 72 plants [m.sup.-2], or the planting of slightly under 6.7 kg seed [ha.sup.-1] (Table 5). Niger yield necessary to offset seed cost is equal to seed cost in dollars [kg.sup.-1] times seeding rate in kg [ha.sup.-1] divided by niger grain value in dollars [kg.sup.-1]. On the basis of a seed cost of $3.30 [kg.sup.-1] and a selling price of $0.66 [kg.sup.-1], the yield increase necessary to offset seed cost would be 14, 17, 34, 51, 67, and 84 kg [ha.sup.-1] for seeding rates corresponding to 2.80, 3.36, 6.72, 10.08, 13.44, and 16.80 kg seed [ha.sup.-1], respectively. With this information and our model for the best estimate of yield response to seeding rate (Table 4), the most economical seeding rate was approximately 6.7 kg [ha.sup.-1]. The niger plant yield response was elastic across seeding rates. At the lowest seeding rate the plants branched and produced many flowers (Table 6), however, flowers did not mature uniformly. Increasing the seeding rate resulted in more plants with fewer flowers per plant, which was also observed by Patil and Patil (1981), and the plants began flowering a few days earlier than for the low seeding rates (Table 6). All plots in this study were kept weed free, with hand weeding necessary for weeds that were not controlled by trifluralin. There was more labor required to keep the low seeding rate plots weeded than the higher seeding rate plots. On commercial fields it would be important to have a quick soil cover and uniform maturing of the crop. In our study, a seeding rate of at least 6.72 kg [ha.sup.-1], which corresponded to approximately 180 pure live seeds [m.sup.-2] or 90 plants [m.sup.-2], fulfilled both of these requirements. This seeding rate is consistent with rates reported by Getinet and Sharma (1996) and Weiss (2000). Patil and Patil (1981) reported that 50, 33, 25, and 22 plants [m.sup.-2] produced significantly higher yields of 29, 23, 20, and 13%, respectively, over the lower plant density of 17 plants [m.sup.-2]. Sclerotinia in niger was reported in North Dakota (Diaz, 1993). Berti and Schneiter (1992) reported that dry root rot and wilting of niger plants was observed at Fargo and Prosper, ND, and Breckenridge, MN. The researchers attributed the disease to Fusarium spp. In our study, Sclerotinia was observed only at RLF01, Car01, and Lan01. In some instances, especially at Lan01, the disease caused the entire infected plant to wilt, resulting in zero seed production. Although in this study there were no significant differences between seeding rates in the incidence of Sclerotinia at any environment, the highest seeding rates provided very thick plant stands, which may be conducive for disease development.

Niger sold in the USA for bird feed is imported. There is an opportunity to sell locally produced niger as a replacement for imported niger. This research indicates that EarlyBird niger can be grown in the northern Great Plains. For commercial production of niger to be profitable enough to compete with other crops grown in the region, profits from niger would have to be comparable. According to one economic analysis, niger yield of 347 and 419 kg [ha.sup.-1] would be required to break even, assuming a selling price of $0.88 and $0.66 [kg.sup.-1], respectively, and yield above 550 kg [ha.sup.-1] would make niger competitive with other crops grown in the region (S. Metzger, 2001, personal communication). In contrast, Quinn and Myers (2002) estimated a niger yield of 1120 kg [ha.sup.-1] would be required for niger to compete with Midwest corn and soybean production.

Abbreviations: BLUP, best linear unbiased predictor; Car01, Carrington, ND, in 2001: Ken00, Kennedy, MN, in 2000; Ken01, Kennedy, MN, in 2001; Lan01, Landgon, ND, in 2001; Pro01, Prosper, ND, in 2001: RLF00. Red Lake Falls, MN, in 2000; RLF01, Red Lake Falls, MN, in 2001.
Table 1. Previous crop, fertilizer applied, and dates of planting,
swathing, and harvesting of niger in a seeding rate trial conducted
in seven environments: at Red Lake Falls, MN (RLF) and Kennedy,
MN (Ken) in 2000 and 2001; and at Carrington, ND (Car); Langdon
(Lan), ND; and Prosper, ND (Pro) in 2001.

                                    RLF00      Ken00      RLF01

Previous crop                       Wheat      Wheat      Wheat
Niger row width, m                   0.152      0.152      0.152
Soil available N, kg [ha.sup.-1]    13         43         27
Soil available P, kg [ha.sup.-1]     9          9         13
Soil available K, kg [ha.sup.-1]   452        448        694
N applied, kg [ha.sup.-1]          155        112        112
P applied, kg [ha.sup.-1]           47         50         17
K applied, kg [ha.sup.-1]            0          0          0
Plant date                         11 May     30 May     12 May
Swath date                         14 Sept.   21 Sept.   24 Sept.
Harvest date                        3 Oct.     3 Oct.     9 Oct.

                                    Ken01          Car01

Previous crop                       Wheat       Oats
Niger row width, m                   0.152      0.178
Soil available N, kg [ha.sup.-1]    37         77
Soil available P, kg [ha.sup.-1]    11          4
Soil available K, kg [ha.sup.-1]   784        890
N applied, kg [ha.sup.-1]          101         45
P applied, kg [ha.sup.-1]           36          0
K applied, kg [ha.sup.-1]            0          0
Plant date                         29 May     25 May
Swath date                         27 Sept.   31 Aug-11 Sept.
Harvest date                       17 Oct.    26 Sept.

                                    Lan01      Pro01

Previous crop                       Wheat      Wheat
Niger row width, m                   0.152      0.152
Soil available N, kg [ha.sup.-1]    68        176
Soil available P, kg [ha.sup.-1]     8        128
Soil available K, kg [ha.sup.-1]   347        941
N applied, kg [ha.sup.-1]           83          0
P applied, kg [ha.sup.-1]          116          0
K applied, kg [ha.sup.-1]            0          0
Plant date                         16 May      9 June
Swath date                         10 Sept.   27 Sept.
Harvest date                       27 Sept.    9 Oct.

Table 2. Growing season climatic conditions for the niger
seeding rate study at seven environments in
the northern Great Plains.

                        RLF00         Ken00       RLF01       Ken01

                                         [degrees]C

Average high
    temperature
  May                20 (17)         20 (19)     21 (17)     19 (19)
                       ([dagger])
  June               23 (23)         22 (24)     24 (23)     23 (24)
  July               27 (27)         27 (28)     28 (27)     27 (28)
  August             27 (27)         26 (27)     28 (27)     27 (27)
  September          21 (19)         19 (20)     21 (19)     21 (20)

Average low
    temperature
  May                 6 (7)           4 (5)       7 (7)       7 (5)
  June               11 (12)          9 (11)     12 (12)     11 (11)
  July               14 (14)         13 (13)     15 (14)     14 (13)
  August             13 (14)         12 (13)     13 (14)     12 (13)
  September           6 (7)           5 (6)       8 (7)       6 (6)

                                             mm

Average
    precipitation
  May                28 (69)         21 (60)     71 (69)     82 (60)
  June              145 (89)        128 (84)     30 (89)     58 (84)
  July               82 (76)         42 (72)    169 (76)    191 (72)
  August             35 (72)        153 (65)     64 (72)     30 (65)
  September          41 (58)         29 (54)     65 (58)     22 (54)
  Total             331 (364)       373 (335)   399 (364)   383 (335)

                      Car01       Lan01       Pro01

                                [degrees]C

Average high
    temperature
  May                20 (19)     19 (18)     21 (20)

  June               23 (24)     22 (23)     25 (25)
  July               27 (27)     26 (25)     28 (29)
  August             28 (26)     26 (25)     28 (27)
  September          21 (20)     20 (19)     22 (21)

Average low
    temperature
  May                 7 (5)       6 (4)       8 (7)
  June               11 (10)     11 (10)     13 (12)
  July               14 (13)     14 (12)     16 (15)
  August             13 (11)     13 (10)     14 (14)
  September           7 (5)       7 (5)       8 (8)

                                   mm

Average
    precipitation
  May                54 (56)     56 (57)     97 (62)
  June              122 (88)    117 (74)     62 (72)
  July              151 (70)    100 (78)    144 (69)
  August             29 (51)     23 (65)     52 (62)
  September          20 (44)     18 (47)     50 (51)
  Total             376 (309)   314 (321)   405 (316)

([dagger]) Values in parentheses are the long-term 30-yr averages.

Table 3. Niger early season plant stand for the niger seeding rate
study at seven environments in the northern Great Plains, and the
estimated intercept and slope for the regression of plant stand
(plants [m.sup.-2]) on pure live seed seeding rate (seeds [m.sup.-2]).

                 Seeding rate

Seeding rate     2000   2001    RLF00     Ken00     RLF01

                     seeds
kg [ha.sup.-1]    [m.sup.-2]         plants [m.sup.-2]

0.56               15     16    13         4        16
1.12               29     32    21         5        24
1.68               44     46    28         9        33
2.24               58     62    35        13        45
2.80               73     77    44        12        55
3.36               87     93    57        15        65
6.72              175    186    80        45       107
10.08             262    279   118        50       169
13.44             --     372     --        --      196
16.80             --     465     --        --      267
  CV, %                         15.8      50.5      14.4
  Intercept                      5.267     0.296     6.135
  Slope                          0.440     0.211     0.547

                                                           7-Env.
Seeding rate                                             ([dagger])
                  Ken01     Car01     Lan01     Pro01       avg.

kg [ha.sup.-1]                   plants [m.sup.-2]

0.56               8         7         3        13         9
1.12              14        18        10        19        16
1.68              20        24        13        31        23
2.24              27        27        20        54        31
2.80              39        40        20        55        38
3.36              41        55        39        71        49
6.72              67       122        68       141        90
10.08             96       149       132       223       134
13.44            136       205       136       261       187
16.80            174       263       179       313       239
  CV, %           19.2      25.6      19.6      15.9      18.4
  Intercept        2.923     3.094     1.000     6.060     3.540
  Slope            0.360     0.555     0.391     0.690     0.460

([dagger]) The two highest seeding rates were
only evaluated at five environments.

Table 4. Confidence intervals for all the parameters, fixed and
random effects, in the model describing the response of niger
yield (kg [ha.sup.-1]) to pure live seed seeding rate (seeds
[m.sup.-2]) across seven environments.

                            Lower
                            ([dagger])   Estimate    Upper

                                      (kg [ha.sup.-1])

Fixed effect coefficient
    estimates
  Intercept                 155.23       287.82      420.41
  Seeding rate                0.1625       0.9888      1.775
  Seeding rate (2)           -0.00338     -0.00174    -0.0001016
Random effect standard
    deviations
  Level: Environment
    Intercept                93.98       171.43      312.69
    Seeding rate              0.600        1.032       1.775
    Seeding rate (2)          0.0010       0.0020      0.0038
  Level: Replicate in
      environment
    Intercept                53.53        75.89      107.62
    Within-group standard
      deviation              79.47        87.17       95.61

([dagger]) Approximate 95% confidence.

Table 5. Best linear unbiased predictor of the niger pure live
seed seeding rate and plant stand with maximum and 90% of
maximum yield, by environment and across all environments.

                         Seeding Rate               Plant Stand

                                 Estimated                 Estimated
                  Estimated         90%        Estimated      90%
Environment        maximum      of maximum      maximum    of maximum

                        seeds [m.sup.-2]          plants [m.sup.-2]

RLF00                261            138           146          79
RLF01                251       NA ([dagger])      140          NA
Ken00                281            185           152          98
Ken01                283            113           168          56
Car01            NE ([double        NE            NE           NE
                   dagger])
Lan01                308            143           159          72
Pro01                290            169           186         107
Across all
  environments       284            127           157          72

([dagger]) NA = Not applicable (for RLF01, the estimated value was <0).

([double dagger]) NE = No estimate available (for Car01, the quadratic
equation provided a minimum rather than a maximum).

Table 6. Niger percentage bloom at Red Lake Falls in 2001 (RLF01),
days to flower at Langdon in 2001 (Lan01), and heads per plant,
aboveground biomass, and head weight at Carrington in 2001 (Car01).

                   RLF01         Lan01        Car01

                   Bloom      Days to 10%   Heads per
Seeding rate     ([dagger])    flowering      plant

kg [ha.sup.-1]       %
0.56                14           68            182
1.12                24           68             -
1.68                28           67             -
2.24                25           67             -
2.80                31           67             -
3.36                35           66           67
6.72                53           65           36
10.08               55           65           30
13.44               69           64           20
16.80               68           64           20
  Mean              40.0         66.1         59.1
  CV, %             18.0          1.3         76.2
  LSD(0.05)         10.4          1.2         68

                                 P > F

  Seeding rate     0.0001       0.0001       0.0009
    effect

                                  Car01

                    Aboveground         Head
                      biomass          weight
Seeding rate     ([double dagger])   ([section])

kg [ha.sup.-1]      g per plant      g per head
0.56                    183             0.084
1.12                     -                -
1.68                     -                -
2.24                     -                -
2.80                     -                -
3.36                   71               0.079
6.72                   17               0.086
10.08                  21               0.074
13.44                  12               0.070
16.80                  12               0.070
  Mean                 53.3             0.077
  CV, %                72.8            21.0
  LSD(0.05)            58                NS

                                P > F

  Seeding rate        0.0001           0.5853
    effect

([dagger]) Percentage bloom 73 days after planting.

([double dagger]) Aboveground biomass does not include head weight.

([section]) Head weight includes seeds plus receptacle.


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H. J. Kandel, P. M. Porter, * B. L. Johnson, R. A. Henson, B. K. Hanson, S. Weisberg, and D. G. LeGare

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Title Annotation:Crop Ecology, Management & Quality
Author:Kandel, H.J.; Porter, P.M.; Johnson, B.L.; Henson, R.A.; Hanson, B.K.; Weisberg, S.; LeGare, D.G.
Publication:Crop Science
Date:Jan 1, 2004
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