Narrow row spacing and high plant population to short height castor genotypes in two cropping seasons

Industrial Crops and Products 35 (2012) 244–249

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Narrow row spacing and high plant population to short height castor genotypes in two cropping seasons Rogério P. Soratto ∗ , Genivaldo D. Souza-Schlick, Adalton M. Fernandes, Mauricio D. Zanotto, Carlos A.C. Crusciol São Paulo State University (UNESP), College of Agricultural Sciences, Department of Crop Science, P.O. Box 237, 18603-970 Botucatu, SP, Brazil

a r t i c l e

i n f o

Article history: Received 4 April 2011 Received in revised form 3 June 2011 Accepted 6 July 2011 Available online 2 August 2011 Keywords: Ricinus communis Oilseed crop Spatial plant distribution Yield components Oil content

a b s t r a c t Castor plant (Ricinus communis L.) produces a very important oil for chemical and biofuel industries. However, doubts remain about what the best plant arrangement is to obtain the maximum yield of seeds and oil from short height castor genotypes cultivated in higher plant population. This study evaluated two castor genotypes (FCA-PB and IAC 2028) in 5 plant arrangements (row spacing × in-row spacing): 0.90 m × 0.44 m (traditional), 0.90 m × 0.20 m, 0.75 m × 0.24 m, 0.60 × 0.30 m, and 0.45 m × 0.40 m, in spring–summer and fall–winter cropping seasons in Botucatu, São Paulo State, southeastern Brazil. The traditional plant arrangement comprised an initial plant population of 25,000 plants ha−1 , while the others comprised 55,000 plants ha−1 . The IAC 2028 genotype presented the greatest plant height, first raceme insertion height, basal stem diameter, number of fruits per raceme and 100 seed weight; however, seed yield and seed oil content were equal between genotypes. Wider stems and higher number of racemes per plant and fruits per raceme were observed with a 0.90 m × 0.44 m plant arrangement, but due to the lowest plant population (25,000 plants ha−1 ) in this plant arrangement, the higher values of the yield components mentioned above did not result in higher yield. The higher plant population (55,000 plants ha−1 ) by narrower row spacings (0.45 or 0.60 m) combination produced a higher castor seed yield. The effect of plant arrangement was more intense in the spring–summer cropping season. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Castor (Ricinus communis L.) is an oilseed, found in tropical regions, and whose greatest producers are India, China and Brazil (Faostat, 2009; Lima et al., 2011). Castor seeds have high oil content (40–60%) compared to sunflower (Helianthus annuus L.) (38–48%), soybean [Glycine max (L.) Merr.] (18–19%), and cotton (Gossypium hirsutum L.) (15–19%) (Kittock and Williams, 1970; Severino et al., 2006b; Nass et al., 2007; Baldwin and Cossar, 2009). Castor oil has been used mainly in the chemical industry (Barnes et al., 2009; Severino et al., 2010), where it has numerous applications. Recently, it has also been used to produce biodiesel in several countries (Baldwin and Cossar, 2009), including Brazil (Nass et al., 2007; Hall et al., 2009). In Brazil, castor is predominantly cultivated in wide row spacings (>1.50 m), and cultivars have a long vegetative cycle and uneven maturation that requires manual harvest. Castor became an attractive option for crop rotation with soybean, corn, and cotton in the spring–summer cropping season (main harvest) because of

∗ Corresponding author. Tel.: +55 14 3811 7161; fax: +55 14 3811 7102. E-mail address: [email protected] (R.P. Soratto). 0926-6690/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2011.07.006

new genotypes with high yield potential, a short growing cycle and even maturation, non-shattering fruit, high oil content, resistance to pests and diseases, short stature, and adapted to combine harvest were developed (Freire et al., 2007; Savy Filho et al., 2007). Due to a relatively high drought tolerance (Babita et al., 2010), castor is considered an attractive option for growth in fall–winter cropping season (out-of-season harvest) in which the viability of other crops, such as corn and sunflowers, can be impaired by drought (Savy Filho, 2005; Silva et al., 2010). For any crop, it is essential to know the optimal combination between row spacing and in-row plant density, i.e., the best plant arrangement, to economically maximize the production (Henderson et al., 2000; Bedane et al., 2009). Adjusting the plant arrangement is a simplest technology with low cost but significant influence on yield (Severino et al., 2006a,c; Bizinoto et al., 2010). The interception of light by plants greatly influences crop yield when other environmental factors are favorable (Loomis and Amthor, 1999). Narrow row spacing also increases light interception because it provides a better spatial distribution of plants (Flénet et al., 1996; Severino et al., 2006a,c). However, the appropriate plant arrangement depends on characteristics of the genotype such as height, growth habit and plant architecture (Bezerra et al., 2009), as well as environmental conditions and management (Severino et al., 2006a,c; Bizinoto et al., 2010).

R.P. Soratto et al. / Industrial Crops and Products 35 (2012) 244–249 Table 1 Monthly rain, average monthly temperatures in Botucatu, São Paulo State, Brazil, during spring–summer and fall–winter cropping seasons in 2007–2008 and 2008–2009 agricultural years. Month

Spring–summer November December January February March April Fall–winter March April May June July August September

Monthly rain (mm)

Average temperature (◦ C)

2007–2008

2008–2009

2007–2008

2008–2009

177 181 279 95 61 103

69 137 332 142 112 87

22.0 23.3 22.5 23.5 23.1 21.6

22.1 22.7 22.4 24.0 24.1 21.6

61 103 116 31 0 81 27

112 87 63 103 144 89 151

18.3 17.9 19.2 19.9 19.2 18.3 17.9

20.0 16.1 17.8 19.1 20.7 20.0 16.1

Studies on plant arrangement have been done for castor crops (Canecchio Filho, 1954; Rocha et al., 1964; Severino et al., 2006a,c; Bizinoto et al., 2010; Carvalho et al., 2010); however, these studies were made with medium/high height cultivars and wide row spacing (>0.90 m) in which plant population was below 25,000 plants ha−1 . In the United States, Kittock and Williams (1970) found that with 1.02 m row spacing, the ideal plant population for short height castor was 58,000 plants ha−1 under irrigation conditions, and 30,000 plants ha−1 , in nonirrigated areas. But it is unclear whether narrower row spacing could provide higher seed yield of castor genotypes in a high plant population. Thus, it is necessary to establish the best plant arrangement to reach maximum seed yield of short height castor genotypes cropped in the main harvest as well as for out-of-season harvest. This study aimed to evaluate the influence of narrower row spacing and high plant population on growth and yield of two castor genotypes sowed in spring–summer and fall–winter cropping seasons. 2. Materials and methods Field experiments were carried out during spring–summer (main harvest) and fall–winter (out-of-season harvest) cropping seasons in 2007–2008 and 2008–2009 agricultural years (Table 1),

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in Botucatu, São Paulo State, in southeastern Brazil (48◦ 23 W; 22◦ 51 S; 740 m above sea level). The soil was a sandy clay loam, kaolinitic, thermic Typic Haplorthox (Oxisol). At the beginning of each experiment, the chemical characteristics of the topsoil (0–0.20 m) were determined according to Raij et al. (2001) (Table 2). Data on rainfall and temperature are presented in Table 1. The experiments were arranged in a randomized block design with split-plots and 4 replications. Plots consisted of two genotypes: FCA-PB and IAC 2028. Subplots consisted of five plant arrangements (row spacing × in-row spacing): 0.90 m × 0.44 m (traditional), 0.90 m × 0.20 m, 0.75 m × 0.24 m, 0.60 m × 0.30 m, and 0.45 m × 0.40 m. The traditional plant arrangement, that present 0.90 m row spacing and 0.44 m spacing between plants within a row, comprised an initial plant population of 25,000 plants ha−1 , while the others comprised 55,000 plants ha−1 (Table 3). Each plot was 5 m long and had ten rows when the row spacing was 0.45 m and 6 rows when the row spacing was 0.60 m, 0.75 m or 0.90 m. Only central lines were considered for evaluation, and 0.5 m at the end of each plant row and one row on each side of the experimental unit were not considered. FCA-PB genotype, developed in the improvement program of the College of Agricultural Sciences - São Paulo State University (UNESP), has a short height (1.40–1.80 m), indehiscent fruits, susceptibility to gray mold [Botryotinia ricini (G.H. Godfrey) Whetzel], an oil content greater than 47% and short cycle (130–150 days). IAC 2028 is a cultivar developed by The Agronomic Institute of Campinas (IAC), and is well adapted to edaphoclimatic conditions of São Paulo State, is short (1.50–1.80 m), has indehiscent fruits, a moderate susceptibility to gray mold, an oil content of around 47% and a short growing cycle (150–180 days) (Savy Filho et al., 2007). Two weeks prior to sowing, the area was sprayed with 1.44 kg a.i. ha−1 of glyphosate [N-(phosphonomethyl)glycine]. Experiments were cropped in a no-tillage system. Mineral fertilizer was applied in a dose of 150 kg ha−1 of NPK 08–28–16. Sowing was performed with an excessive number of seeds, allowing for a thinning at 10 days after emergence (DAE) to reach the plant population of each treatment. Sowing and seedling emergence dates are presented in Table 4. Topdressing fertilization was performed with 60 kg of N (ammonium sulfate) ha−1 , 30 DAE. Weeding was done by hand. At the beginning of flowering, fungicides were sprayed to preventive control of gray mold. In the 2007–2008 spring–summer cropping season, iprodione [3-(3,5dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidineat 0.5 g i.a. ha−1 , procymidone carboxamide] [N-(3,5-dichlorophenyl)-1,2-dimethyl-1,2-

Table 2 Topsoil (0–20 cm) chemical characteristics at the beginning of the experiments. Cropping season

pH (CaCl2 )

O.M. (g dm−3 )

P(resin) (mg dm−3 )

H + Al

K −3

2007–2008 spring–summer 2008 fall–winter 2008–2009 spring–summer 2009 fall–winter a b

5.3 5.0 4.3 5.6

36 38 38 40

37 39 14 26

(mmolc dm

)

46 51 67 29

2.8 4.1 3.3 2.6

Ca

Mg

CECa

BSb (%)

41 31 36 43

15 09 15 22

105 95 122 97

56 46 45 70

Cation exchange capacity. Base saturation.

Table 3 Row spacing, spacing between plants within row, within row plant density and initial plant population in each plant arrangement treatment. Plant arrangement

Row spacing (m)

Spacing between plants within row (m)

Within row plant density (plants m−1 )

0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m

0.90 0.90 0.75 0.60 0.45

0.44 0.20 0.24 0.30 0.40

2.25 4.95 4.13 3.30 2.48

Initial plant population (plants ha−1 ) 25,000 55,000 55,000 55,000 55,000

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Table 4 Sowing and seedling emergence dates and number of days since emergence to first raceme flowering and harvesting of castor genotypes. Cropping season

2007–2008 spring–summer 2008 fall–winter 2008–2009 spring–summer 2009 fall–winter

Sowing

Emergence

09 November 2007 08 March 2008 21 November 2008 10 March 2009

Flowering (day)

21 November 2007 18 March 2008 03 December 2008 20 March 2009

Cyclopropanedicarboximide] at 0.5 kg i.a. ha−1 , and epoxiconazole {rel-1-[[(2R,3S)-3-(2-chlorophenyl)-2-(4were used fluorophenyl)oxiranyl]methyl]-1H-1,2,4-triazole} at 0.020 kg i.a. ha−1 plus pyraclostrobin {carbamic acid, [2,[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl]phenyl] methoxy-, methyl ester} at 0.053 kg i.a. ha−1 . In the 2008–2009 spring–summer, 2 sprayings were done with procymidone at 0.5 kg do i.a. ha−1 . In the 2008 fall–winter, plants were sprayed with procymidone (0.5 kg ha−1 ) three times and with iprodione (0.5 kg ha−1 ) once. In the 2009 fall–winter 4 sprayings were done with 0.5 kg ha−1 of procymidone. The number of days since emergence to flowering and harvesting of each genotype are presented in Table 4. At harvest, data were collected on: plant surviving rate, plant height (distance from soil to the highest point of the plant), first raceme insertion height (distance between soil and the point of raceme insertion), basal stem diameter (in the first internode of plant), number of racemes per plant, number of fruits per raceme, number of seeds per fruit, 100 seed weight, and seed yield (13% humidity). After harvest, seeds were oven dried at 70 ◦ C for 24 h and oil content was measured by nuclear magnetic resonance. Experimental data were analyzed separately by cropping season (spring–summer and fall–winter). Genotypes and plant arrangements were considered fixed, and year and replication were considered random factors. Data for each cropping season were subjected to ANOVA using SISVAR (Ferreira, 2008) and means were separated using Tukey’s test at 0.05 probability level. Correlation coefficients were calculated across both genotypes and five plant

Harvesting (day)

FCA-PB

IAC 2028

FCA-PB

IAC 2028

42 42 40 59

62 70 50 71

147 153 138 185

155 173 148 188

arrangements using STATISTICA, version 6 (Statsoft, 1995), to determine the relationships between plant parameters. 3. Results and discussion The plant surviving rate was influenced only by plant arrangements in the spring–summer cropping season (Table 5). In plant arrangements with a higher plant population (55,000 plants ha−1 ), plant survival was lower. Rocha et al. (1964) also found higher castor plant mortality in a higher plant population, or more specifically, in higher plant density within a row. In fall–winter cropping seasons, the final stands were close to the initially established plant population, indicating that, regardless of the plant arrangement, plant mortality throughout the cycle was low. Cox and Cherney (2011) studied soybean growth and yield as affected by row spacing and sowing density and found no differences in the final stand among tested row spacings, and attributed this to a similar plant mortality rate. Higher mortality of plants in the spring–summer cropping season was probably due to higher rainfall during crop development (December and January) (Table 1), which could have favored Fusarium wilt [Fusarium oxyporum f. sp. ricini (Wr.) Snyd & Hans] occurrence (Araújo et al., 2007), after thinning of plants. Plants of IAC 2028 genotype were taller than FCA-PB in spring–summer cropping seasons, but plant height was not affected by plant arrangements (Table 5). In the fall–winter cropping season, there was significant genotype × plant arrangement interaction for plant height (Table 5). Plants of FCA-PB genotype were taller in conditions with higher plant density within a row compared to the widest (0.90 m × 0.44 m) and 0.60 m × 0.30 m plant arrangements

Table 5 Plant surviving rate, plant height, first raceme insertion height, basal stem diameter and number of racemes per plant of castor as affected by genotypes and plant arrangement in spring–summer and fall–winter cropping seasons across two agricultural years at Botucatu, São Paulo State, Brazil. Variation sources Spring–summer Genotype (G) FCA-PB IAC 2028 Plant arrangement (P) 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m Interaction G × P (Pr > F) Fall–winter Genotype (G) FCA-PB IAC 2028 Plant arrangement (P) 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m Interaction G × P (Pr > F)

Plant surviving (%)

Plant height (m)

First raceme height (m)

Basal stem diameter (mm)

Racemes plant−1

85.8a 87.3a

1.56b 1.84a

0.61b 0.79a

23.7b 27.4a

4.2a 2.3b

94.7a 85.9b 84.6b 85.1b 86.8b 0.726

1.73a 1.76a 1.69a 1.67a 1.66a 0.221

0.69a 0.70a 0.70a 0.71a 0.69a 0.890

29.2a 25.3b 23.7b 25.1b 24.6b 0.087

4.2a 2.8b 3.1b 3.1b 3.1b 0.083

97.6a 99.4a

1.11 1.33

0.40b 0.61a

18.9b 22.9a

2.3a 1.5b

100.0a 97.1a 99.3a 98.2a 98.9a 0.145

1.21 1.26 1.22 1.19 1.22 <0.001

0.45b 0.54a 0.51ab 0.51ab 0.52a 0.636

23.6a 20.1b 20.3b 20.0b 20.3b 0.063

2.6a 1.6b 1.8b 1.7b 1.7b 0.204

Values in column, within each factor (genotype and plant arrangement) and cropping season, followed by the same letter are not significantly different at p ≤ 0.05 according to Tukey’s test.

R.P. Soratto et al. / Industrial Crops and Products 35 (2012) 244–249 Table 6 Genotype × plant arrangement interaction for plant height in fall–winter cropping season across two agricultural years at Botucatu, São Paulo State, Brazil. Plant arrangement

Plant height (m) – Fall–winter 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m

Genotype FCA-PB

IAC 2028

1.06bcB 1.22aA 1.14abB 1.01cB 1.14abB

1.37aA 1.30aA 1.30aA 1.38aA 1.29aA

Values followed by same lower case letter in the columns and upper case letter in the rows, within each year and variable, are not significantly different at p ≤ 0.05 according to Tukey’s test.

(Table 6). The IAC 2028 plant height was not affected by plant arrangements. In general, IAC 2028 genotype plants were taller than FCA-PB in fall–winter as well. The height of insertion of the first raceme was higher in the genotype IAC 2028 than in the FCA-PB in both cropping seasons (Table 5). The greatest first raceme insertion height in IAC 2028 is a result of the greatest plant height of this genotype because a positive correlation between plant height and height of insertion of the first raceme was verified (r = 0.72, p < 0.001 in spring–summer and r = 0.81, p < 0.001 in fall–winter). In spring–summer cropping season, the height of insertion of the first raceme was not affected by plant arrangement; however, in fall–winter cropping season, 0.45 m × 0.40 m and 0.90 m × 0.20 m plant arrangements, provided taller insertions of the first raceme than treatment with the lowest plant population (0.90 m × 0.44 m). Kittock and Williams (1970) and Bizinoto et al. (2010) also observed taller insertion of the first raceme in higher plant density. In both cropping seasons, IAC 2028 genotype presented greater values of basal stem diameter than FCA-PB, and in plant arrangements with a higher plant population (55,000 plants ha−1 ), the basal stem diameter was lower than in the widest plant arrangement (0.90 m × 0.44 m), showing that castor plants increased basal stem diameter when grown in a lower plant population (Table 5), due to greater growth space availability and lower competition among plants within a row (Bedane et al., 2009), which makes

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plants accumulate higher amounts of photoassimilates in stems (Carvalho et al., 2010). In addition, plant arrangement alteration affects the amount of intercepted light, causes a greater light absorption in the red spectrum (R), and a higher reflection in the far red (FR). In plants that receive more reflected FR, i.e., higher ER/R relation, there is lengthening and thinning of the stem (Kasperbauer and Karlen, 1994). Kittock and Williams (1970), Severino et al. (2006c) and Bizinoto et al. (2010) also observed a reduction in stem diameter of castor plants when there was a plant population increase because the number of plants within a row increase or row spacing decreases. The number of plants per unit of area (plant population) influence over the castor plant stem diameter than the plant arrangement (Table 5). Plants with thinner stems are favorable to mechanized harvesting. In all cropping seasons, FCA-PB genotype produced a higher number of racemes per plant than IAC 2028 (Table 5). In spring–summer cropping seasons, where there was more rainfall (Table 1) and plant growth, a higher number of racemes per plant were produced. The plant arrangement with the lowest plant population (0.90 m × 0.44 m) provided a higher number of racemes per plant than treatments with a higher plant population (Table 5). The lowest plant population provided wider spacing between plants within row and row spacing and, consequently, lower competition among plants, resulting in a higher number of reproductive structures as observed also by Kittock and Williams (1970) and Bizinoto et al. (2010). In plants with wider spacing, there is more area for light capitation and no interference or competition as in those with smaller spacing; therefore, there is higher dry matter production and more adequate productive architecture, and its potential is shown during raceme growth (Flénet et al., 1996; Cox and Cherney, 2011). Severino et al. (2010) found that castor plants without defoliation produced a mean of 4.5 racemes per plant, while the plants defoliated at 60% only bore 1.3 racemes per plant. The number of fruits per raceme was affected by the genotype × plant arrangement interaction, in both cropping seasons (Table 7). The FCA-PB genotype produced the same number of fruits per raceme, which was not altered by plant arrangements in spring–summer cropping season, but in fall–winter season, the number of fruits per raceme was higher in the widest plant arrangement (0.90 m × 0.44 m) (Table 8). In spring–summer, IAC 2028

Table 7 Number of fruits per raceme, number of seeds per fruit, 100 seed weight, seed yield and seed oil content of castor as affected by genotypes and plant arrangement in spring–summer and fall–winter cropping seasons across two agricultural years at Botucatu, São Paulo State, Brazil. Variation sources Spring–summer Genotype (G) FCA-PB IAC 2028 Plant arrangement (P) 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m Interaction G × P (Pr > F) Fall–winter Genotype (G) FCA-PB IAC 2028 Plant arrangement (P) 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m Interaction G × P (Pr > F)

Fruit raceme−1

Seed fruit−1

100 seed weight (g)

Seed yield (kg ha−1 )

Seed oil content (%)

22.8 32.4

2.8a 2.8a

37.4b 40.1a

3761a 3667a

50.2a 50.0a

29.9 24.9 26.7 26.9 29.5 0.002

2.8a 2.8a 2.8a 2.8a 2.7a 0.346

39.0a 39.1a 38.7a 37.9a 39.2a 0.271

3069c 3529bc 3718b 3938ab 4315a 0.108

50.3a 49.7a 49.8a 49.9a 51.0a 0.450

17.2 20.1

2.5a 2.6a

42.1b 51.3a

1822a 1817a

45.9b 47.8a

22.2 17.1 17.5 18.0 18.6 <0.001

2.5a 2.6a 2.6a 2.6a 2.5a 0.176

48.1a 46.0ab 45.2b 46.6ab 47.7ab 0.089

1689b 1671b 1850ab 1975a 1917ab 0.056

46.4a 46.1a 45.9a 47.6a 48.1a 0.485

Values in column, within each factor (genotype and plant arrangement) and cropping season, followed by the same letter are not significantly different at p ≤ 0.05 according to Tukey’s test.

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Table 8 Genotype × plant arrangement interaction for fruits per raceme in spring–summer and fall–winter cropping seasons across two agricultural years at Botucatu, São Paulo State, Brazil. Plant arrangement

Genotype FCA-PB

IAC 2028

23.2aB 21.9aB 22.1aB 23.1aB 23.5aB

36.6aA 27.8bA 31.3bA 30.7bA 35.6aA

19.9aB 16.8bA 16.7bB 15.4bB 17.2bB

24.5aA 17.4dA 18.5cdA 20.5bA 20.0bcA

−1

Fruit raceme – Spring–summer 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m Fruit raceme−1 – Fall–winter 0.90 m × 0.44 m 0.90 m × 0.20 m 0.75 m × 0.24 m 0.60 m × 0.30 m 0.45 m × 0.40 m

Values followed by same lower case letter in the columns and upper case letter in the rows, within each year and variable, are not significantly different at p ≤ 0.05 according to Tukey’s test.

produced a higher number of fruits per raceme in plant arrangements with wider distance between plants within row (Table 3), which were 0.90 m × 0.44 m and 0.45 m × 0.40 m. In fall–winter, the highest number of fruits per raceme was observed in the widest plant arrangement. Plant arrangements with a higher plant population (55,000 plants ha−1 ) produced a lower number of fruits per raceme, but in this plant population, narrower row spacing increased the number of fruits per raceme (Table 8). These results suggested that in wider row spacing there was more inter-specific competition compared to narrower row spacings with the same plant population, reducing the size of reproductive structures and, consequently, the number of fruits per raceme. The number of fruits per raceme is related to plant sexual expression, which is controlled by hormones and influenced by several environmental factors (Khryanin, 2002; Severino et al., 2010). Rocha et al. (1964) and Kittock and Williams (1970) verified a lower seed yield per raceme of castor due to higher plant density within a row. The IAC 2028 genotype had a greater number of fruits per raceme than the FCA-PB (Table 8). Plants with a higher raceme insertion produce less reproductive structures, and negative correlations between height of insertion of the first raceme and the number of racemes per plants have already been verified (r = −0.56, p < 0.001 in spring–summer and r = −0.67, p < 0.001 in fall–winter). The number of seeds per fruit was not influenced by the studied factors (Table 7), because this characteristic presents high genetic heritability, which is little influenced by environmental or exogenous factors (Freire et al., 2007). Severino et al. (2010) found no alteration in the number of seeds per fruit of castor plants even under high levels of defoliation. The IAC 2028 genotype presented higher values of 100 seed weight in both cropping seasons (Table 7). In spring–summer, 100 seed weight did not respond to plant arrangement, but was influenced in the fall–winter cropping season. The lowest 100 seed weight was obtained in 0.75 m × 0.24 m plant arrangement and the highest in the widest plant arrangement.Seed yield of castor genotypes did not differ in both cropping seasons (Table 7). The highest number of fruits per raceme and 100 seed weight produced by the IAC 2028 genotype (Tables 7 and 8) balanced its lowest number of racemes per plant. According to Severino et al. (2010), the number of racemes per plant is an important yield component of the castor crop. The plant population increase associated with reduction of row spacing increased seed yield in both cropping seasons (Table 7). In spring–summer, castor yielded 40.6% more in 0.45 m × 0.40 m compared to 0.90 m × 0.44 m and 22.6% more compared to 0.90 m × 0.20 m. Canecchio Filho (1954), Kittock and

Williams (1970) and Carvalho et al. (2010) also obtained a castor seed yield increase with a plant population per area increase. In fall–winter, castor yielded 16.9% more in 0.60 m × 0.30 m compared with 0.90 m × 0.44 m, but seed yield did not differ between 0.90 m × 0.44 m and 0.90 m × 0.44 m, i.e., as plant population increased from 25,000 plants ha−1 to 55,000 plants ha−1 , seed yield was not afected, using the same row spacing (0.90 m). These results show that with row spacing reduction, plant density decreases within a row (Table 3), with a better plant distribution in the area and lower competition among plants, causing increases of seed yield (Rocha et al., 1964; Flénet et al., 1996). In fall–winter cropping season, seed yields and plant arrangement effects on seed yield were lower than in spring–summer due to less rainfall and lower temperatures in this period (Table 1), which caused lower plant growth (Tables 5 and 7). The IAC 2028 genotype presented significantly higher seed oil content than FCA-PB only in the fall–winter cropping season (Table 7), but the difference between seed oil content of the genotypes was only 4.1% in that cropping season. Seed oil content was not affected by plant arrangement (Table 7). According to Moshkin (1986) and Severino et al. (2006b,c), oil content in castor seeds is a characteristic of high hereditability. Kittock and Williams (1970) did not find a change in seed oil content of castor plants submitted to different plant populations. On the other hand, Severino et al. (2006a) verified an increase in seed oil content of castor when of row spacing increased, keeping plant density within a row. According to these authors, the influence of environmental factors and growth traits in castor seed oil content is actually a poorly understood aspect as results diverge from one experiment to another. Koutroubas et al. (1999), studying castor genotypes in two environments for three years in Greece, found that seed oil content was variable between years and locations, and that, when the yield was higher, oil content decreased, showing a negative correlation between the two factors; however, in the present study, this correlation was not found.

4. Conclusion The IAC 2028 genotype presented the greatest plant height, first raceme insertion height, basal stem diameter, number of fruits per raceme and 100 seed weight; however, seed yield and seed oil content were equal between genotypes, regardless of the plant arrangement. Wider stems and higher number of racemes per plant and fruits per raceme were observed with a 0.90 m × 0.44 m plant arrangement, but due to the lowest plant population (25,000 plants ha−1 ) in this plant arrangement, the higher values of the yield components mentioned above did not result in higher yield. In plant arrangements with highest plant population (55,000 plants ha−1 ), castor plants produced lower basal stem diameter, number of racemes per plant and number of fruits per raceme, but higher seed yield, especially when narrower row spacing (0.45 or 0.60 m) was used. The effect of plant population and row spacing combinations, i.e., of plant arrangement, was more intense in the spring–summer cropping season.

Acknowledgements To FAPESP (Fundac¸ão de Amparo à Pesquisa do Estado de São Paulo) for supporting this research and providing scholarships to the second author. To CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for providing scholarships to the first and fifth authors.

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References Araújo, A.E., Suassuna, N.D., Coutinho, W.M., 2007. Doenc¸as e seu manejo. In: Azevedo, D.M.P., Beltrão, N.E.M. (Eds.), O Agronegócio da Mamona no Brasil. , second ed. Embrapa Algodão, Campina Grande, pp. 283–303. Babita, M., Maheswari, M., Rao, L.M., Shanker, A.K., Rao, D.G., 2010. Osmotic adjustment, drought tolerance and yield of castor (Ricinus communis L.) hybrids. Environ. Exp. Bot. 69, 243–249. Baldwin, B.S., Cossar, R.D., 2009. Castor yield in response to planting date at four locations in the south-central United States. Ind. Crops Prod. 29, 316–319. Barnes, D.J., Baldwin, B.S., Braasch, D.A., 2009. Degradation of ricin in castor seed meal by temperature and chemical treatment. Ind. Crops Prod. 29, 509– 515. Bedane, G.M., Gupta, M.L., George, D.L., 2009. Effect of plant population on seed yield, mass and size of guayule. Ind. Crops Prod. 29, 139–144. Bezerra, A.A.C., Tavora, F.J.A.F., Freire Filho, F.R., Ribeiro, V.Q., 2009. Características de dossel e de rendimento em feijão-caupi ereto em diferentes densidades populacionais. Pesqui. Agropecu. Bras. 44, 1239–1245. Bizinoto, T.K.M.C., Oliveira, E.G., Martins, S.B., Souza, S.Â., Gotardo, M., 2010. Cultivo da mamoneira influenciada por diferentes populac¸ões de plantas. Bragantia 69, 367–370. Canecchio Filho, V., 1954. Resultados de experiências com espac¸amento da mamoneira anã, variedade I.A. 38. Bragantia 13, 297–305. Carvalho, E.V., Sá, C.H.A.C., Costa, J.L., Afférri, F.S., Siebeneichler, S.C., 2010. Densidade de plantio em duas cultivares de mamona no sul do Tocantins. Rev. Ciênc. Agron. 41, 387–392. Cox, W.J., Cherney, J.H., 2011. Growth and yield responses of soybean to row spacing and seeding rate. Agron. J. 103, 123–128. Faostat – Food and Agriculture Organization of the United Nations, 2009. Production – castor oil seeds. Disponível em: http://faostat.fao.org/site/567/ DesktopDefault.aspx?PageID=567 (accessed 24.02.11). Ferreira, D.F., 2008. SISVAR: um programa para análises e ensino de estatística. Rev. Symposium 6, 36–41. Flénet, F., Kiniry, J.R., Board, J.E., Westgate, M.E., Reicosky, D.C., 1996. Row spacing effects on light extinction coefficients of corn, sorghum, soybean, and sunflower. Agron. J. 88, 185–190. Freire, E.C., Lima, E.F., Andrade, F.P., Milani, M., Nóbrega, M.B.M., 2007. Melhoramento genético. In: Azevedo, D.M.P., Beltrão, N.E.M. (Eds.), O Agronegócio da Mamona no Brasil. , second ed. Embrapa Algodão, Campina Grande, pp. 169–194. Hall, J., Matos, S., Severino, L.S., Beltrão, N.E.M., 2009. Brazilian biofuels and social exclusion: established and concentrated ethanol versus emerging and dispersed biodiesel. J. Clean. Prod. 17, S77–S85. Henderson, T.L., Johnson, B.L., Schneiter, A.A., 2000. Row spacing, plant population, and cultivar effects on grain amaranth in the northern Great Plains. Agron. J. 92, 329–336.

249

Kasperbauer, M.J., Karlen, D.L., 1994. Plant spacing and reflected far-red light effects on phytochrome-regulated photosynthate allocation in corn seedlings. Crop Sci. 34, 1564–1569. Khryanin, V.N., 2002. Role of phytohormones in sex differentiation in plants. Russ. J. Plant Physiol. 49, 545–551. Kittock, D.L., Williams, J.H., 1970. Effects of plant population on castorbean yield. Agron. J. 62, 527–529. Koutroubas, S.D., Papakosta, D.K., Doitsinis, A., 1999. Adaptation and yielding ability of castor plant (Ricinus communis L.) genotypes in a Mediterranean climate. Eur. J. Agron. 11, 227–237. Lima, R.L.S., Severino, L.S., Sampaio, L.R., Sofiatti, V., Gomes, J.A., Beltrão, N.E.M., 2011. Blends of castor meal and castor husks for optimized use as organic fertilizer. Ind. Crops Prod. 33, 364–368. Loomis, R.S., Amthor, J.S., 1999. Yield potential, plant assimilatory capacity, and metabolic efficiencies. Crop Sci. 39, 1584–1596. Moshkin, V.A., 1986. Growth and development of the plant. In: Moshkin, V.A. (Ed.), Castor. Amerind, New Delhi, pp. 36–42. Nass, L.L., Pereira, P.A.A., Ellis, D., 2007. Biofuels in Brazil: an overview. Crop Sci. 47, 2228–2237. Raij, B.van., Andrade, J.C., Cantarella, H., Quaggio, J.A., 2001. Análise Química Para Avaliac¸ão da Fertilidade de Solos Tropicais. Instituto Agronômico, Campinas, p. 284. Rocha, J.L.V., Conecchio Filho, V., Freire, E.S., Scaranari, H., Pettinelli, A., 1964. Adubac¸ão da mamoneira. IV – experiências de espac¸amento × adubac¸ão (2a série). Bragantia 23, 257–269. Savy Filho, A., 2005. Mamona Tecnologia Agrícola. EMOPI, Campinas, p. 105. Savy Filho, A., Amorim, E.P., Ramos, N.P., Martins, A.L.M., Cavichioli, J.C., 2007. IAC2028: nova cultivar de mamona. Pesqui. Agropecu. Bras. 42, 449–452. Severino, L.S., Coelho, D.K., Moraes, C.R.A., Gondim, T.M.S., VALE, L.S., 2006a. Otimizac¸ão do espac¸amento de plantio para a mamoneira cultivar BRS Nordestina. Rev. Bras. Oleagin. Fibr. 10, 993–999. Severino, L.S., Freire, M.A.O., Lucena, A.M.A., Vale, L.S., 2010. Sequential defoliations influencing the development and yield components of castor plants (Ricinus communis L.). Ind. Crops Prod. 32, 400–404. Severino, L.S., Milani, M., Moraes, C.R.A., Gondim, T.M.S., Cardoso, G.D., 2006b. Avaliac¸ão da produtividade e teor de óleo de dez genótipos de mamoneira cultivados em altitude inferior a 300 metros. Rev. Ciênc. Agron. 37, 188–194. Severino, L.S., Moraes, C.R.A., Gondim, T.M.S., Cardoso, G.D., Beltrão, N.E.M., 2006c. Crescimento e produtividade da mamoneira influenciada por plantio em diferentes espac¸amentos entre linhas. Rev. Ciênc. Agron. 37, 50–54. Silva, A.G., Crusciol, C.A.C., Soratto, R.P., Costa, C.H.M., Ferrari Neto, J., 2010. Produc¸ão de fitomassa e acúmulo de nutrientes por plantas de cobertura e cultivo da mamona em sucessão no sistema plantio direto. Ciênc. Rural 40, 2092– 2098. Statsoft, 1995. STATISTICA Release 5. StatSoft, Tulsa, OK.