Multilocational evaluation of biomass sorghum hybrids under two stand densities and variable water supply in Italy

Industrial Crops and Products 20 (2004) 3–9

Multilocational evaluation of biomass sorghum hybrids under two stand densities and variable water supply in Italy E. Habyarimana a , P. Bonardi a , D. Laureti b , V. Di Bari c , S. Cosentino d , C. Lorenzoni a,∗ a

d

Istituto di Botanica e Genetica Vegetale, Università Cattolica, Via Emilia Parmense, 84-29100 Piacenza, Italy b Istituto Sperimentale Per le Colture Industriali, Sezione Operativa di Osimo, 60027 Osimo (AN), Italy c Istituto Sperimentale Agronomico, Via Celso Ulpiani, 5-70125 Bari, Italy Istituto di Agronomia Generale e Coltivazioni Erbacee, Università di Catania, Via Valdisavoia, 5-95123 Catania, Italy Received 1 April 2002; accepted 22 December 2003

Abstract Sorghum, a C4 plant particularly resistant to drought and high temperatures, is highly competitive amongst biomass crops in dry areas where irrigation water supply is a limiting factor during crop development. This work was undertaken to assess the plant stand density response for the aboveground biomass production in sorghum hybrids under variable regimes of water supply in Italy. The results showed that water stress causes a decrease in dry matter yield to a level yet agronomically interesting. Total dry matter yield versus stand density relationship was dependent on water regime and sorghum genotype. High stand density (20 plants m−2 ) outyielded the low one (10 plants m−2 ) under humid conditions whilst the two population stands had statistically comparable biomass yields under water stressed environments. A dichotomous density response was noticed under humid conditions where one group of hybrids (H128, Abetone, ABF14, ABF20, and ABF306) displayed an increasing biomass production while the second one (H132, ABF18, ABF25, and ABF11) had a steady performance in spite of the increasing plant stand. © 2004 Elsevier B.V. All rights reserved. Keywords: Sorghum hybrid; Plant density; Biomass; Water supply

1. Introduction Sorghum (Sorghum bicolor (L.) Moench) appears extremely interesting among plants for biomass, ∗ Corresponding author. Tel.: +39-0523-599206/599210; fax: +39-0523-599283. E-mail addresses: [email protected] (E. Habyarimana), [email protected] (P. Bonardi), [email protected] (D. Laureti), [email protected] (V. Di Bari), [email protected] (S. Cosentino), [email protected] (C. Lorenzoni).

due to its outstanding daily accumulation of dry matter (Loomis and Williams, 1963). Particular morpho-physiological characteristics confer to this plant a high drought tolerance and a C4 photosynthetic system that allows the most efficient CO2 fixation (Heichel, 1976). In addition, the versatility of use of the product (total mass, soluble sugars, starch, and fiber) has to be underlined (Schaffert and Gourley, 1982). Aerial biomass yields as high as 30 and 53 Mg ha−1 , respectively, under rainfed and 100% ETc restitution regimes were obtained in this

0926-6690/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2003.12.020

4

E. Habyarimana et al. / Industrial Crops and Products 20 (2004) 3–9

crop by Habyarimana et al. (2002) in their works on the evaluation of temperate hybrids and tropical sorghum strains. The authors found that high yielding entries under water deficit conditions maintain their relative productive performance when they are raised under wet environments. Haussmann et al. (1998) and Habyarimana et al. (2002) confirmed the existence of heterosis conferring a productive superiority to sorghum hybrids over the line varieties under water stressed and non soil moisture limiting conditions. However, the results on the density response in sorghum reported in literature can hardly overlap due particularly to discrepancies in categorizing population stands, not to mention the constantly observed genotype × environment interaction (European Energy Crops Internetwork [EECI], 2000). Thus, EECI (2000) reported that high (29 plants m−2 ) and low (7 plants m−2 ) sorghum densities were statistically equivalent as for biomass yields, whilst Berenguer and Faci (2001) found that 30 plants m−2 were more productive than 15 plants m−2 . The observation above calls for further research effort to better understand the population stand response in sorghum crop. The objective of the present work was to evaluate the aerial biomass yields in the recent sorghum hybrid constitutions under two plant densities and variable levels of water supply.

9◦ 41 E, Osimo 43◦ 29 N 13◦ 28 E, Bari 41◦ 07 N 16◦ 51 E, and Catania 37◦ 30 N 15◦ 04 E in Italy in the year 2001. Six of them (hybrids bearing ABF initials) were new constitutions whereas the remnant three, H128, H132, and Abetone, were commercial strains. Two plant densities, that is 10 and 20 plants m−2 (respectively, referred to as low and high density hereafter) were tested at Piacenza, Catania, and Osimo whilst the low population stand with one ratoon crop was assayed at Bari. The experimental design consisted of a split-plot with three replications wherever the two plant stands were a part of the studied factors, and a randomized complete block design otherwise. The main plots were assigned the two population stands while the hybrid materials were allocated in subplots. As for water supply, ETc restitution was 50% at Catania, 100% at Piacenza, and nil at Osimo. At Bari, 50 and 100% ETc restitutions were applied in two trials that were contemporarily conducted side by side. Total aboveground biomass harvest consisted of the entire plants at Piacenza, Bari (principal plus ratoon crops), and Osimo whereas at Catania leaves, stems, and panicles were separately harvested and evaluated. Statistical inferences were based on the factorial analysis of variance, mean separation in case the statistical test applied, and the interaction mean squares partitioned according to Gomez and Gomez (1984).

2. Materials and methods Nine sorghum hybrids (Table 1) were evaluated for biomass yield in four locations viz. Piacenza 45 ◦ 03 N Table 1 Mean values for plant height, dry matter (d.m.) content, and biomass yield of the hybrids in the irrigated trials Hybrids

Plant height (cm)

d.m. content Biomass at harvest (%) yield (d.m.) (Mg ha−1 )

H132 H128 Abetone ABF11 ABF14 ABF18 ABF20 ABF25 ABF306 L.S.D. (P = 0.05)

355 307 333 289 298 294 326 338 294 31.44

30.1 35.6 30.4 35.0 35.7 37.0 33.2 34.6 34.4 3.15

27.7 19.6 23.7 18.6 19.1 20.2 23.4 28.2 21.3 5.19

3. Results and discussion 3.1. Climatic characteristics Monthly rainfall and mean air temperature during the growing season are presented in Fig. 1. The mean temperature peaks were reached in July and August in all sites, and the values varied from 22.6 ◦ C (at Piacenza and Osimo) to 27.4 ◦ C (at Bari). On the whole, rainfall was erratically distributed during the cropping period extending from April through October 2001, and amounted 315, 225, 165, and 30 mm, respectively, at Piacenza, Osimo, Bari, and Catania. 3.2. Aboveground dry matter production Sorghum materials did well (Table 2) under hot (Fig. 1) Mediterranean conditions of Italy. Irrigation was beneficial in general (Fig. 2, Table 1) but in-

E. Habyarimana et al. / Industrial Crops and Products 20 (2004) 3–9

5

Fig. 1. Air temperature (lines) and rainfall (bars) at different locations in 2001.

teresting performance, as translated by an environmental index as high as 15 Mg ha−1 (Table 2) together with total dry matter as high as 20 Mg ha−1 in some hybrids (data not shown), could also be observed at Osimo (Fig. 3) under rainfed conditions. Hybrid variability for biomass performance as statistical main effect was observed throughout the experimental locations. Hybrids ABF25, ABF20, H132, and Abetone took the lead (mean aboveground biomass yield 23–28 Mg ha−1 ) over the genotypes when evaluated under wet trials (Table 1).

The two studied densities did not differ significantly at Osimo (Fig. 3; very high water deficit stress) and Catania (Table 3 and Fig. 4; moderate water deficit stress), while at Piacenza (low water deficit stress) the higher stand proved more productive (23 Mg ha−1 versus 17 Mg ha−1 ) than the low one and the hybrid × density interaction was statistically significant (Table 4). The partitioning of the linear component of this interaction sum of squares allowed the identification of two groups of hybrids contributing to

Table 2 Mean values of the principal parameters observed in different locations Locations

Osimo (AN) Catania Piacenza Bari L.S.D. (P = 0.05) a

Plant height (cm)

176 344 364 235 37.32

Dry mass at harvest

Soil moisture stress

Content (%)

Yield

27.2 37.5 32.1 33.2 4.11

15.60 23.63 20.16 24.58 5.02

Respectively, 100% and 50% ETc restitution, and NA not applicable.

(Mg ha−1 ) Very high Moderate Low None and moderatea NA

6

E. Habyarimana et al. / Industrial Crops and Products 20 (2004) 3–9

Fig. 2. Effects of water regimes on dry matter yield for the low stand density at Bari.

the difference in the pattern the plants responded to the stand density. Biomass yield of individual hybrids in the first group (H128, Abetone, ABF14, ABF20, ABF306) increased significantly with augmentation of plant density whereas a steady

yield was observed in the second group (H132, ABF18, ABF25, ABF11). The mean dry mass weight for the first group increased from 16 to 24 Mg ha−1 , and from 18 to 21 Mg ha−1 for the second group, respectively, under 10 and 20 plants m−2 . The density

Fig. 3. Plant density effects on dry matter yield in different locations.

E. Habyarimana et al. / Industrial Crops and Products 20 (2004) 3–9

7

Table 3 Analysis of variance across 10 and 20 sorghum stand densities for the 10 hybrids tested at Catania Source of variation

Density Error a Hybrid Density × hybrid Error b

Mean squares LW

PW

SW

PH

DMY

0.432ns 0.462 0.843∗∗ 0.579∗ 0.250

0.232ns 2.508 3.783∗∗∗ 1.053ns 0.865

9.267ns 44.727 50.052∗∗∗ 1.645ns 9.246

4734.817ns 3268.217 7537.054∗∗∗ 2495.854∗∗ 718.876

8.273ns 60.829 36.946∗∗ 3.270ns 9.908

LW, PW, SW, PH, DMY, respectively, leaf, panicle, and shoot weight, plant height, and dry mass yield.

linear response within each group was statistically homogeneous (Table 4). The above results suggest that the higher hybrid stand density offers a productive superiority over the low counterpart under non water stressed conditions and that sorghum hybrid density response is genotype-dependent. The statement is in agreement with the findings in the works of Berenguer and Faci (2001) where the authors recommended higher (greater than 20 plants m−2 ) sorghum den-

sities under non soil moisture limiting environments. High and low sorghum densities resulting in comparable dry mass performances under soil water deficit in southern Italy might suggest that high plant density suffered water stress the most (Krieg, 1983) whilst the compensation process (Berenguer and Faci, 2001; Mallikarjun et al., 1997; Ismail and Ali, 1996; Krieg and Lascano, 1990) warranted the low stand density

Fig. 4. Total aerial dry matter partitioning as determined by the weight of leaves (LW), panicles (PW), and shoots (SW) in 10 sorghum hybrids raised in two stand densities at Catania.

8

E. Habyarimana et al. / Industrial Crops and Products 20 (2004) 3–9

Table 4 Analysis of variance for dry mass yield of nine sorghum hybrids evaluated at Piacenza over two plant densities with the partitioning of the interaction sum of squares Source of variationa

Sum of squares

Computed Fb

Density (D) Hybrid (H) D×H DL c × (H1 , H5 , H7 , H8 ) vs. (H2 , H3 , H4 , H6 , H9 ) DL × H1 vs. H5 vs. H7 vs. H8 DL × H2 vs. H3 vs. H4 vs. H6 vs. H9

367.282 657.294 169.805 125.982

396.34∗∗ 10.09∗∗∗ 2.61∗ 17.40∗∗

16.997 26.830

0.59ns 0.93ns

a

H1–9 : H132, H128, Abetone, ABF14, ABF18, ABF20, ABF25, ABF11, ABF306. b ns, *, **, *** not significant, significant at the 0.05, 0.01, and 0.001 probability level, respectively. c D linear component of density. L

produce being less sensitive to drought stress, and therefore, comparing with the higher density one’s. As illustrated by the data from Catania, the two stand densities yielded statistically equally as much leaf, panicle, and shoot weights (Table 3 and Fig. 4), indicating that the compensation in the low density could mainly be associated with higher grain weight per panicle, higher leaf weight per plant, and higher tillering ability (Berenguer and Faci, 2001). The latter may possibly have been the most determinant compensation factor in the biomass materials investigated insofar as shoot weight represented 82–83% of the total aboveground dry matter harvested (Fig. 4), and the two parameters were perfectly associated (r = 0.95, data not shown). Low and high sorghum stand densities being comparable under water stressed conditions was also reported in the latest literature (EECI, 2000; Berenguer and Faci, 2001). As far as water regime response was concerned (Fig. 2), it could be noticed a decrease of 50% in biomass mean yields for the low density under 50% ETc restitution in comparison with the 100% ETc restitution (Fig. 2). Overall, H132 was the most drought stress susceptible hybrid displaying 63% biomass yield reduction whereas ABF25, having the least (40%) water deficit related dry matter yield drop, was accordingly deemed better adapted to soil moisture deficit conditions.

4. Conclusions Biomass yields were higher under irrigation but tempting production levels were achieved in the absence of ETc restitution, which makes sorghum extremely competitive among dryland biomass crops. However, higher performance observed under 100% ETc restitution regime indicates that any effort to maximize sorghum biomass productivity might be subordinated to an adequate water supply. Positive density response was observed under humid conditions where it proved genotype-dependent, whereas under water stressed conditions high plant density could not present any biomass productive advantage in comparison with the low plant stand. Leaf and grain weight along with tillering ability related compensation factors were put forward as the harvest components making the low density less sensitive to drought stress and compare with the high counterpart.

Acknowledgements This work was carried out in the context of TISEN (Tecniche Innovative Sostenibili di Produzione e Trasformazione delle Colture Energetiche e Non Food) project funded by the Italian Ministry of Agriculture.

References Berenguer, M.J., Faci, J.M., 2001. Sorghum (Sorghum bicolor L. Moench) yield compensation processes under different plant densities and variable water supply. Eur. J. Agron. 15, 43–55. European Energy Crops Internetwork, 2000. Description of growing experience on sweet sorghum in Greece. Retrieved August 8, 2003, from http://btgs1.ct.utwent.nl/eeci/archive/ biobase/B10214.html. Gomez, K.A., Gomez, A.A., 1984. Statistical Procedures for Agricultural Research. Wiley, New York. Habyarimana, E., Laureti, D., Di Fonzo, N., Lorenzoni, C., 2002. Biomass production and drought resistance at the seedling stage and in field conditions in sorghum. Maydica 47, 303–309. Haussmann, B.I.G., Obilana, A.B., Blum, A., Ayiecho, P.O., Schiprack, W., Geiger, H.H., 1998. Hybrid performance of sorghum and its relationship to morphological and physiological traits under variable drought stress in Kenya. Plant Breeding 117, 223–229. Heichel, G.H., 1976. Agricultural production and energy resources. Am. Scientist 64, 64–72.

E. Habyarimana et al. / Industrial Crops and Products 20 (2004) 3–9 Ismail, A.M.A., Ali, A.H., 1996. Plant population density effects on yield of sorghum grown in dry-land farming system. Qatar Univ. Sci. J. 16, 83–93. Krieg, D.R., 1983. Sorghum. In: Teare, I.D., Peet, M.M. (Eds.), Crop Water Relations. Wiley, New York, pp. 351–388. Krieg, D.R., Lascano, R.J., 1990. Sorghum. In: Stewart, B.A., Nielsen, D.R. (Eds.), Irrigation of Agricultural Crops. American Society of Agronomy, Madison, WI, pp. 719– 789.

9

Loomis, R.S., Williams, W.A., 1963. Maximum crop productivity: an estimate. Crop Sci. 3, 67–71. Mallikarjun, H., Kachapur, M.D., Gaddanakeri, S.A., Sobarad, P.M., 1997. Performance of sweet sorghum genotypes under different levels of plant population. Cooperative Sugar 28, 834–836. Schaffert, R.E., Gourley, L.M., 1982. Sorghum as an energy source. In: Sorghum in the Eighties, vol. 2. ICRISAT, Patancheru, India, pp. 605–623.