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Prospects of whole grain crops of wheat, rye and triticale under different fertilizer regimes for energy production
ARTICLE IN PRESS
Biomass and Bioenergy 31 (2007) 308–317 www.elsevier.com/locate/biombioe
Prospects of whole grain crops of wheat, rye and triticale under different fertilizer regimes for energy production Johannes Ravn Jørgensen, Lise C. Deleuran, Bernd Wollenweber Aarhus Universitet, Faculty of Agricultural Sciences, Department of Genetics and Biotechnology, Research Centre Flakkebjerg, DK-4200 Slagelse, Denmark Received 27 October 2005; accepted 10 January 2007 Available online 23 March 2007
Abstract Cereal grain yield and biomass production are affected by fertilizer application strategies. In order to quantify the performance of wheat, rye and triticale cultivars for use as energy crops, field experiments with either modified phosphorus–potassium or potassium applications were designed at two locations in Denmark over a 3-year period. Five wheat cultivars (‘Astron’, ‘Herzog’, ‘Kosack’, ‘Kraka’ and ‘Ure’), two winter rye cultivars (the population cultivar ‘Motto’ and the hybrid cultivar ‘Marder’) and the triticale cultivar ‘Alamo’ were selected. The grain and straw fractions were analysed for biomass, ash and contents of nitrogen (N), K, Cl, sulphur (S) and Na. Dry matter yields varied between 11.5 and 15.9 t ha1 at the two locations. Triticale and rye had a higher total dry matter yield than wheat, even at lower inputs of N fertilizer. Thus, the constant high yield of rye and triticale is an advantage for biomass for energy purposes. The mineral content of the grain fraction changed only little between years and locations. By contrast, large variations in the analysed ions in the straw fraction between years and locations were observed. The use of K fertilizers resulted in a significantly increased concentration of K in the straw. However, this increased concentration was eliminated in years with high precipitation in the final 3 weeks before harvest, where substantial amounts of K, Cl and S were removed. The results are discussed in relation to the possible use of grain crops for energy production. r 2007 Elsevier Ltd. All rights reserved. Keywords: Bioenergy; Biofuels; Mineral composition; Cereals; Cultivars
1. Introduction Cereals produce biomass in the form of grain and/or straw and are, because of their high dry matter content, easy storable. Moreover, due to the relative short annual rotation, flexible (i.e. depending on demand) biomass production is possible [1]. These features, combined with the fact that cereals have a determinate vegetative growth, mean that cereals can be seen as a promising biomassproducing crop in temperate regions of Europe. In addition, existing agricultural machinery can be used for crop establishment, husbandry and harvest. When cereals are combusted in large-scale power plants, a low content of both sulphur (S) and nitrogen (N) is desirable, due to the possibility of increased emissions of SO 2 and NOx [2,3]. Problems due to corrosion processes, Corresponding author. Tel.: +45 89 99 35 00; fax: +45 89 99 35 01.
E-mail address: [email protected] (J.R. Jørgensen). 0961-9534/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2007.01.001
ash slugging and fouling may arise [4,5]. These problems are partly due to the constraints of the ion-content and -balance within the plant [6]. As both plant biomass and ion content are influenced by mineral nutrition, modification of fertilization strategies may alter these parameters [7]. In cereals (Gramineae), differences in ion content may result from differences in mineral nutrition and ion uptake of the species under investigation [8,9]. For example, nitrate (NO 3 ) nutrition is characterized inter alia by increased cation uptake and leads to the synthesis of carboxylate (anions of organic acids), which contribute significantly to the total anion content [6,8]. By contrast, the use of ammonium (NH+ 4 ) is related to increased anion uptake and can be directly incorporated into carbon skeletons with no additional synthesis of carboxylate [6,8]. An interesting exception are members of the morphologically related Poaceae, Juncaceae and Cyperaceae, who show a highly selective ion uptake (in terms of discrimination against ‘non-target’ ions) and thus are
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thought to be able to maintain a rather constant ion content, which is lower than in other plants [6]. In any case, metabolism of CO2, N2 or NH3 and H2S generates organic compounds containing C, N and S, which, at normal intracellular pH, have a predominance of negative charge (mainly as –COO) over positive charge (predominantly –NH+ 3 ). This difference is measured as the excess of inorganic cations, C+ (K++Na++Ca2++Mg2++ p + NH4 ) over inorganic anions, A p (Cl +NO3 +H2PO4 / 2 2 HPO4 +SO4 ) in the tissue, giving an indirect estimate of the excess of negative charge on organic compounds [8,10]. Ashing of plant samples at temperatures at or above 520 1C volatilizes organic components, leaving K+, Na+, Ca2+, 2 Mg2+, Cl, H2PO and SO2 4 /HPO4 4 , with electroneu 2 trality maintained by OH +HCO 3 +CO3 (replacing the net organic negative charge) [6,10]. The ashing treatment also removes NH+ 4 , NH3 from organic N and NO3 via formation of NOx. Cl will cause HCl emission and deposition resulting in corrosive effects during combustion. SO2 4 will form alkali sulphates and SO2. K+ and Na+, in combination with Cl and SO2 4 , will add to corrosion mechanisms during combustion via wet and/or dry deposition of acid loads. Thus, for the use of combustion material in power plants, relatively small amounts of these ions would be preferred. In addition, dry-ash analysis constitutes a reliable method for the detection of heavy metal content in plant tissues [11], but might also be used as a screening method for the investigation of the constraints of environmental stress [12–14] as indicated by the relationships between ash content and carbon isotope discrimination (D) for example in Triticum durum genotypes, where leaf ash correlated positively with grain D [12]. The aim of the current work was to investigate the effect of fertilization constraints on the performance (plant biomass and ion content) of winter wheat, winter rye and winter triticale for use as energy crops.
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2. Materials and methods 2.1. General experimental design Two field experiments (A and B) were designed as a randomized complete block with a split-plot arrangement of treatments. In both experiments, five wheat cultivars (‘Astron’, ‘Herzog’, ‘Kosack’, ‘Kraka’ and ‘Ure’), two winter rye cultivars (the population cultivar ‘Motto’ and the hybrid cultivar ‘Marder’) and the triticale cultivar ‘Alamo’ were selected. Seeds for experiment A were sown on sandy loam soil in 1993, 1994 and 1995 at Roskilde Research Station (551390 N and 121050 E). Seeds for experiment B were sown on a clay soil in 1994, 1995 and 1996 at Rønhave Research Station (541570 N and 91470 E). Fertilizer was applied as described in Table 1. Herbicide and fungicide treatments were applied according to good experimental practice for control of residual weeds. Plots were harvested with a trials combine harvester according to normal harvest practice and timing. Kernel and straw yield (straw and chaff) were measured for every replicates. Cutting height was adjusted to leave 8–10 cm of stubble. Accumulated precipitation in the final 3 weeks of crop ripening before harvest (Fig. 1) was measured at both locations. 2.2. Experiment A: phosphorus–potassium fertilizer and species/cultivar trials A phosphorus–potassium (PK) fertilizer treatment (PK; +PK) was the main factor in the split-plot arrangement of treatments, with cultivar as the sub-plots. The PK fertilizer (7.2% phosphorus (P) w/w, 18.3% K w/w, 17% Cl w/w and 5.5% S w/w) was applied at 400 kg ha1. Wheat cultivars received 160 kg N ha1 as lime-ammonium nitrate (27% N w/w), rye 120 kg N ha1 and triticale 140 kg N ha1, according to standard recom-
Table 1 Nutrient application (kg ha1) in experiments A (Roskilde Research Station) and B (Rønhave Research Station) Experiment and harvest year
Treatment
Species
N (kg ha1)
P (kg ha1)
K (kg ha1)
Cl (kg ha1)
S (kg ha1)
A: Roskilde 1994, 1995 and 1996
PK
Wheat Rye Triticale Wheat Rye Triticale
160 120 140 160 120 140
— — — 29 29 29
— — — 73 73 73
— — — 68 68 68
— — — 22 22 22
Wheat Rye Triticale Wheat Rye Triticale Wheat Rye Triticale
160 120 120 160 120 120 160 120 120
— — — — — — — — —
— — — 50 50 50 50 50 50
— — — — — — 50 50 50
— — — 22 22 22 — — —
+PK
B: Rønhave 1995, 1996 and 1997
Control
K2SO4
KCl
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a
b 50 1994 1995 1996
40
Precipitation, mm
Precipitation, mm
50
30 20 10 0
1995 1996 1997
40 30 20 10 0
21
18
15 12 9 6 Days before harvest
3
21
18
15 12 9 6 Days before harvest
3
Fig. 1. Accumulated precipitation from 21 days before harvest until harvest at Roskilde (a) and Rønhave (b) Research Stations.
mendations. Individual treatments were replicated four times. All fertilizers were applied in late March or beginning of April (Table 1). Individual plots were 10 rows wide (1.65 m 9.5 m). Dates of sowing were 1 October 1993, 22 September in 1994 and 29 September in 1995. Dates of harvest were 22 and 23 August in both 1994 and 1996 and 10 August in 1995. 2.3. Experiment B: potassium fertilizer and species/cultivar trials As in experiment A, the design was a randomized complete block with a split-plot arrangement of treatments. The potassium fertilizer treatment (control vs. KCl and KCl vs. K2SO4) was the main factor, with cultivar as subplots. Wheat cultivars received 160 kg N ha1 and rye and triticale 120 kg N ha1 each as lime-ammonium nitrate (27% N w/w), according to standard recommendations. Individual treatments were replicated three times. All fertilizers were applied in late March or beginning of April (Table 1). Individual plots were 10 rows wide (1.5 m 8.7 m). Dates of sowing were 23 September 1994 and 19 September in 1995 and 1996. Dates of harvest were 10 August in 1995, 3 September in 1996 and 14 August in 1997.
2.5. Statistical analysis The statistical analysis of the resulting data was performed by F-tests. The denominator in the F-test was the interaction between the studied effects in question and their interactions. Least significant differences (LSD) at the 5% probability level were used to separate means of main effects. The analyses were performed using the Statistical Analysis System (SAS) software package [21]. Comparison of effects (i.e. year, cultivar, N application or interaction between year, cultivar and N application) in a given grain component was made by one-way, two-way or three-way analysis of variance (GLM procedure) followed by Duncan’s means comparison test. 3. Results 3.1. Meteorological data Fig. 1 shows the accumulated precipitation during the last 21 days before harvest at both experimental sites. Highest levels of precipitation were observed in 1994 at Roskilde and in 1997 at Rønhave.
2.4. Chemical analysis
3.2. Experiment A: phosphorus–potassium fertilizer and species/cultivar trial at Roskilde
The harvested biomass samples were dried at 80 1C for at least 24 h and ground. The ash content was calculated from the weight loss of organic material during an ashing process at 525 1C for 6 h [15,16]. The Dumas combustion procedure was used to determine the total N content [17]. Gross heat of combustion was determined by calorimetric methods, according to the American Society for Testing and Materials (ASTM) standard D2382-83. Cl content was determined by potentiometric titration (silver nitrate) of weak (0.1 mol l1) nitric acid extracts [18]. K and Na contents were determined by flame emission photometry on samples ashed at 450 1C for 3 h [19]. Total-S was detected spectroscopically at 560 nm by addition of barium chloride to perchloric acid extracts of plant matter [20]. All results are presented on a dry matter basis.
The results of estimated mean biomass yield, ash content, total-N, analysed ions and gross heating values are presented for the grain fraction in Table 2, for the straw fraction in Table 3 and for the total biomass in Table 4. Overall, grain, straw and total biomass yield, composition and gross heating values were significantly influenced by year and species/cultivar but not by PK fertilizer. However, a significant year fertilizer interaction for both Cl and K was observed. Grain, straw and total biomass yield was significantly lower in 1994 than in 1995 and 1996 (Tables 2–4). Grain yield was highest in Marder and Alamo, while Motto showed the highest straw yield. Total biomass yield was significantly higher for the triticale cultivar Alamo and the rye cultivar Motto than for the wheat cultivars. Of the
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Table 2 The influence of phosphorus–potassium fertilizer and species/cultivar on grain dry matter yield, grain composition and gross heat of combustion in cereals produced at Roskilde Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1994 1995 1996
5.21cy 5.46b 5.92a
15.6a 15.6a 14.0b
18.4c 18.7b 19.3a
4.33b 4.77a 4.23c
0.57c 0.66b 0.75a
1.11b 1.11b 1.44a
0.049a 0.025c 0.039b
18.45a 18.54a 18.41a
Fertilizerz PK +PK
5.49a 5.56a
15.3a 14.8a
19.1a 18.5a
4.49a 4.40a
0.64a 0.68a
1.24a 1.21b
0.039a 0.036a
18.46a 18.47a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
5.33cd 4.94cd 5.09cd 5.29cd 4.72d
14.5bc 14.4c 14.9bc 15.0abc 14.3c
20.4ab 21.5a 19.7b 20.0b 20.6ab
3.88d 4.25c 4.17cd 4.30c 4.19cd
0.70abc 0.72ab 0.62cd 0.73a 0.66abcd
1.28ab 1.27ab 1.31a 1.23b 1.26ab
0.032a 0.038a 0.033a 0.041a 0.033a
18.56a 18.54a 18.59a 18.49ab 18.60a
Rye Marder Motto
6.58a 5.73bc
15.2abc 16.4a
15.0d 14.9d
4.64b 5.07a
0.64bcd 0.65abcd
1.05d 1.14c
0.040a 0.043a
18.21d 18.33cd
Triticale Alamo
6.45ab
15.9ab
18.2c
5.06a
0.57d
1.27ab
0.041a
18.40bc
Means averaged across fertilizer and species/cultivar. y
Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
Table 3 The influence of phosphorus–potassium fertilizer and species/cultivar on straw dry matter yield, straw composition and gross heat of combustion in cereals produced at Roskilde Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1994 1995 1996
6.46cy 8.16a 7.82b
29.34c 46.03b 50.64a
3.98c 5.65b 6.78a
7.29b 14.07a 14.65a
0.61c 2.92b 5.66a
0.31c 0.55b 1.84a
0.079b 0.065b 0.122a
18.84a 18.84a 18.61b
Fertilizerz PK +PK
7.42a 7.51a
41.6a 42.4a
5.4a 5.5a
11.07a 11.28a
2.08a 4.05a
0.83a 0.89a
0.089a 0.089a
18.78a 18.75a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
6.50c 6.84c 7.35bc 7.20bc 6.83c
44.8a 41.6a 43.8a 40.0a 40.3a
6.3a 5.9a 5.5abcd 5.7abc 5.8ab
11.58cde 11.36de 12.65ab 10.91e 11.60bcde
3.17a 2.83a 2.99a 2.79a 3.01a
1.04a 0.91ab 0.97ab 0.95ab 0.91ab
0.079a 0.082a 0.083a 0.095a 0.090a
18.80a 18.85a 18.66a 18.68a 18.58a
Rye Marder Motto
7.53bc 9.07a
42.6a 40.3a
4.8cd 4.7d
12.41abc 12.73a
3.52a 3.13a
0.77b 0.81ab
0.094a 0.096a
18.85a 18.84a
Triticale Alamo
8.31ab
42.6a
5.0bcd
12.25abcd
3.08a
0.33c
0.092a
18.84a
Means averaged across fertilizer and species/cultivar. y
Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
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Table 4 The influence of phosphorus–potassium fertilizer and species/cultivar on dry matter yield, composition and gross heat of combustion on total biomass (grain+straw) in cereals produced at Roskilde Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1994 1995 1996
11.66by 13.64a 13.74a
23.23b 33.80a 34.66a
10.43c 10.87b 12.10a
5.98b 10.35a 10.10a
0.59c 2.01b 3.52a
0.67b 0.76b 1.66a
0.066b 0.049c 0.086a
18.68a 18.70a 18.47b
Fertilizerz PK +PK
12.92a 13.05a
30.4a 30.7a
11.2a 11.1a
8.28a 9.21a
1.47a 2.61a
1.00a 1.03a
0.067a 0.065a
18.61a 18.63a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
11.86c 11.74c 12.41bc 12.49bc 11.55c
31.1ab 30.2b 32.0a 29.6b 29.9b
12.6a 12.4a 11.3c 11.8bc 11.9b
8.11d 8.41d 9.22b 8.17d 8.64cd
2.06a 1.94a 2.03a 1.94a 2.10a
1.26a 1.06bc 1.11ab 1.07bc 1.07bc
0.057ab 0.063ab 0.051b 0.073a 0.067ab
18.62ab 18.72a 18.62ab 18.63ab 18.59ab
Rye Marder Motto
14.08ab 14.77a
29.7b 31.0ab
9.6e 8.7f
8.41d 9.77a
2.14a 2.18a
0.89d 0.94cd
0.068ab 0.075a
18.54b 18.61ab
Triticale Alamo
14.79a
30.9ab
10.7d
9.11bc
1.95a
0.69e
0.069ab
18.62ab
12.98
30.6
11.1
8.74
2.04
1.01
0.066
18.62
Mean
Means averaged across fertilizer and species/cultivar. y Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
estimated total biomass yield, 53% (Marder) to 61% (Motto) originated from the straw (Tables 2–4). The ash content was on average 2.8 times higher in the straw fraction as compared to the grain fraction. Ash content of the straw and the total biomass was significantly lower in 1994. Within the grain fraction, the rye cultivar Motto had a significantly higher ash content than the wheat cultivars (Astron, Herzog, Kosack and Ure) (Table 2). Total-N was, on average, 3.4 times higher in the grain than in the straw fraction. Within years, the greatest variation was found in the straw fraction with the significantly lower N content in 1994 (Tables 2 and 3). Compared to the rye and triticale cultivars, significantly higher N contents were observed in grains of all wheat cultivars while the triticale showed an intermediate value. In the straw fraction of wheat, the Astron and Herzog cultivars had a significantly higher N content than the rye cultivars Marder and Motto and the triticale cultivar Alamo (Table 2). The N content of the total biomass was significantly lower for the rye cultivar Motto followed by Marder and the triticale cultivar Alamo while within the wheat cultivars the significantly higher N content was observed in Astron and Herzog (Table 4). Potassium content was on average 2.7 times higher in the straw fraction as compared to the grain fraction (Tables 2
and 3). The significantly higher K content of the grain fraction was observed in 1995 and the significantly lower for the straw fraction in 1994 (Tables 2 and 3). The significantly higher K content of the grain fraction was observed in Alamo triticale and Motto rye, and the lowest in the wheat cultivars (Table 2). In the straw fraction, highest K contents were observed in Motto rye and the lowest in Kraka wheat (Table 3). In the total biomass, highest values of K were observed in Motto rye (Table 4). Straw content of Cl was on average 4.6 times higher than in grain (Tables 2 and 3). Grain, straw and total biomass content of Cl was significantly lower in 1994 (Tables 2–4). In 1996, the straw content of Cl was 9.3 times higher than in 1994, but only 1.3 times higher in grain (Table 3). No significant differences were found within the species/ cultivars for the Cl content of the total biomass (Table 4). The total-S contents of grain were found to be 42% higher than in straw (Tables 2 and 3). Significantly higher S contents were observed in 1996 for grain, straw and total biomass (Tables 2–4). Marder and Motto rye had the significantly lower S content in grain and Alamo in straw and total biomass (Tables 3 and 4). Straw contents of Na were 2.3 times higher than in grain (Tables 2 and 3). Highest Na contents were observed in 1994 in grain and in 1996 in straw (Tables 2 and 3). No significant differences were observed in straw within
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species/cultivars, and only little differences within grain (Table 2). Minor differences in gross heating values were observed between the straw (18.58–18.85 MJ kg1) and the grain (18.21–18.60 MJ kg1) fraction (Tables 2–4). However, gross heating value in grains of all the wheat cultivars was significantly higher than the two rye cultivars (Table 2). 3.3. Experiment B: potassium fertilizer and species/cultivar trials at Rønhave Results of the estimated mean biomass yield, ash content, total-N and measured ions as well as gross heating values are presented in Table 5 for the grain fraction, in Table 6 for straw fraction and in Table 7 for the total biomass. Overall, grain contents of ash, K, S and Na and gross heating values were influenced by year and species/ cultivar but not by fertilizer treatments (Table 5). Straw yield, composition and gross heating values were significantly influenced by year and species/cultivar but not by fertilizer treatments (Table 6). A non-significant increase in the straw Cl content was observed when the KCl fertilizer was applied, and a non-significant increase in the S content when the K2SO4 fertilizer was applied. Total biomass yield and composition were also significantly influenced by year
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and species/cultivar but not by fertilizer treatments (Table 7). No significant differences between the years of observation for grain yield were observed (Table 5). However straw and total biomass yield was significantly higher in 1995 (Tables 6 and 7). The straw and total biomass yields were significantly higher for the Alamo triticale cultivar than for the wheat cultivars, with intermediate yields for the rye cultivars (Tables 6 and 7). Of the estimated total biomass yield, 53% (Astron) to 57% (Motto) originated from the straw fraction (Table 7). The ash content was on average 3.5 times higher in the straw fraction as compared to the grain fraction (Tables 5 and 6). Grain, straw and total biomass ash content was significantly lower in 1996 (Tables 5–7). Here, the rye cultivar Motto had the highest ash content within the grain. The total-N content in grains was, compared to the straw fraction, on average 3.2 times higher (Tables 5 and 6). The rye cultivars Marder and Motto had significantly lower N contents in grain and total biomass than the wheat and the Alamo triticale cultivars. Within the wheat cultivars, Astron and Hertzog had the highest content. In straw as well as in total biomass, significantly lower N contents were observed in 1995 (Tables 6 and 7).
Table 5 The influence of phosphorus–potassium fertilizer and species/cultivar on grain dry matter yield, grain composition and gross heat of combustion in cereals produced at Rønhave Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1995 1996 1997
6.33ay 6.86a 6.32a
16.5a 12.1b 16.1a
17.5a 17.2a 17.8a
4.55a 4.14b 4.64a
0.69a 0.74a 0.62a
1.20a 1.03c 1.14b
0.026c 0.043b 0.069a
18.24b 18.13c 18.52a
Fertilizerz Control K2SO4 KCl
6.63a 6.44a 6.51a
14.6a 14.8a 15.2a
17.5a 17.3a 17.8a
4.40b 4.49a 4.44ab
0.68a 0.65a 0.71a
1.10a 1.15a 1.11a
0.045a 0.047a 0.045a
18.26a 18.27a 18.38a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
6.56a 6.29a 6.52a 6.19a 6.23a
13.8c 14.3bc 14.3bc 15.0abc 14.3bc
18.7ab 19.8a 17.7bc 18.2bc 18.6abc
3.96d 4.07cd 4.21cd 4.29cd 4.11cd
0.69ab 0.74ab 0.61b 0.87a 0.63b
1.14abc 1.18ab 1.12abc 1.09abc 1.12abc
0.040c 0.038c 0.041c 0.038c 0.045bc
18.33ab 18.38ab 18.32ab 18.32ab 18.43a
Rye Marder Motto
7.08a 6.35a
15.0abc 16.3a
14.5d 14.4d
4.55bc 5.08ab
0.66b 0.64b
1.05c 1.08bc
0.045bc 0.060ab
18.10c 18.27b
Triticale Alamo
7.00a
15.9ab
17.4c
5.30a
0.61b
1.19a
0.055a
18.24bc
6.53
14.9
17.5
4.44
0.68
1.12
0.045
18.30
Mean
Means averaged across fertilizer and species/cultivar. y
Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
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Table 6 The influence of phosphorus–potassium fertilizer and species/cultivar on straw dry matter yield, straw composition and gross heat of combustion in cereals produced at Rønhave Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1995 1996 1997
9.26ay 6.72c 8.28b
59.5a 38.2b 58.3a
4.84b 5.64a 5.69a
14.36a 6.05b 13.74a
4.24a 1.75b 4.17a
0.75b 0.89a 0.67b
0.092b 0.081c 0.128a
18.44b 18.68a 18.51b
Fertilizerz Control K2SO4 KCl
7.99a 8.00a 7.81a
51.2a 50.5a 54.0a
5.4a 5.3a 5.5a
10.88a 11.02a 11.96a
2.59a 2.54a 5.15a
0.65a 1.04a 0.60a
0.109a 0.087a 0.101a
18.56a 18.55ab 18.50b
Species/cultivary Wheat Astron 7.24d Herzog 7.38cd Kosack 7.72cd Kraka 7.93bc Ure 7.93cd
55.4a 54.0ab 54.8ab 46.9b 52.0ab
5.4a 5.7a 5.6a 5.6a 5.6a
9.67c 9.65c 11.49b 9.63c 9.79bc
2.65d 3.38abc 3.24bcd 2.98cd 2.77cd
0.82ab 0.79ab 0.79ab 0.77ab 0.79ab
0.094c 0.079d 0.097bc 0.093c 0.092cd
18.39a 18.52a 18.57a 18.57a 18.50a
Rye Marder Motto
7.99bc 8.50ab
50.8ab 50.2ab
5.1a 5.3a
14.51a 14.08a
3.84ab 4.07a
0.70bc 0.85a
0.119a 0.110ab
18.63a 18.66a
Triticale Alamo
8.88a
51.2ab
4.8a
11.43b
3.72ab
0.60c
0.114a
18.49a
Mean
7.93
51.9
5.4
11.30
3.35
0.77
0.099
18.54
Means averaged across fertilizer and species/cultivar. y Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
In straw, higher K contents were observed than in grain (Tables 6 and 7). Significant lowest K contents in grain, straw and total biomasses were observed in 1996 (Tables 5–7), but the K2SO4 fertilizer increased the grain K content by only 2%. The straw K content was 137% higher in 1995 (and 127% higher in 1997) than in 1996 (Table 6). This variation is reflected also in the K content of the total biomass (Table 7). Alamo and Motto had significantly higher K contents in grain than any of the other wheat cultivars. Straw Cl content was on average 4.9 times higher than in the grain (Tables 5 and 6). In 1995 and 1997, straw content was 2.4 times higher than in 1996. An increase in Cl content of straw from the KCl fertilizer treatment compared with the control was observed (Table 6). Total biomass of all wheat cultivars had a significant lower Cl content than the Alamo triticale and Marder and Motto rye cultivars. Grain content of total-S was 45% higher compared to straw (Tables 5 and 6). The Alamo triticale cultivar had the highest S content in grain and the lowest in straw and total biomass (Tables 5 and 6). Grain content of Na was approximately 50% of the amount in straw (Tables 5 and 6). The significant highest Na content was observed in 1997 (Tables 5–7). The lowest Na content was observed in wheat as compared to triticale and rye
(Tables 5 and 6). Generally, no differences in the gross heating values in all treatments and fractions were observed. 4. Discussion and conclusion During the 3 years of observation with wheat, triticale and rye reported here, mean yield was as high or higher than that reported from other European yield trials [22]. This corresponds well with data from FAO and other reports that wheat yield increases in the northwestern part of Europe are the highest in Europe [23]. Within each of the locations and years of observation, the grain yield was very stable whereas some variation was observed within straw yield. None of the tested wheat cultivars accumulated as much total biomass as the triticale and rye cultivars. This higher yield of the triticale and rye cultivars compared to the wheat cultivars originated primarily from straw. The two tested rye cultivars differed in their relationship between grain and straw (harvest index), where Marder had the highest grain yield and the lowest straw yield. This will influence their overall performance and has to be taken into consideration when applied for biofuel. A major scope in breeding of new wheat cultivars has been an improvement of the harvest index based on an increased grain fraction and decreased
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Table 7 The influence of phosphorus–potassium fertilizer and species/cultivar on dry matter yield, composition and gross heat of combustion of total biomass (grain+straw) in cereals produced at Rønhave Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1995 1996 1997
15.60ay 13.58c 14.58b
42.0a 25.0c 39.9b
10.0c 11.5a 10.9b
10.21a 5.10b 9.76a
2.83a 1.24b 2.62a
0.93a 0.96a 0.87b
0.066b 0.062b 0.101a
18.36a 18.41a 18.49a
Fertilizerz Control K2SO4 KCl
14.64a 14.44a 14.30a
34.9a 34.8a 36.5a
10.8ab 10.7b 11.1a
7.91a 8.27a 8.54a
1.81a 1.75a 3.26a
0.84a 1.09a 0.82a
0.081a 0.069a 0.074a
18.42a 18.42a 18.42a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
13.67b 13.67b 14.24b 14.13b 14.06b
34.0ab 36.0ab 36.6a 33.3ab 35.7ab
11.7ab 12.1a 11.0c 11.2c 11.3bc
7.06e 7.20e 8.31cd 7.44de 7.41de
1.74c 2.20b 2.07bc 2.08bc 1.85bc
0.96a 0.96a 0.95a 0.91ab 0.93a
0.069b 0.059c 0.072b 0.067b 0.071b
18.35a 18.44a 18.45a 18.50a 18.46a
Rye Marder Motto
15.12ab 14.85ab
32.6b 36.0ab
9.4e 9.2e
2.73a 2.66a
0.85bc 0.93a
0.085a 0.087a
18.28a 18.48a
Triticale Alamo
15.88a
36.5a
10.2d
9.02bc
2.66a
0.84c
0.090a
18.37a
14.46
35.4
10.8
8.25
2.24
0.92
0.075
18.42
Mean
9.28b 10.37a
Means averaged across fertilizer and species/cultivar. y Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
straw-fraction [24]. Thus a new breeding goal for wheat cultivars for use as biofuel may be a reduced harvest index. This strategy could also be applied to rye and triticale. After N, P is the second most frequently limiting macronutrient for plant growth. However, in many agricultural systems (i.e. the sandy loams of eastern Denmark), the P-use efficiency by crops is low and even relatively mild deficiencies can significantly reduce plant growth. In response to persistently low levels of available P in the rhizosphere, plants have developed highly specialized mechanisms to acquire and utilize P from the environment. Thus, extrusion of H+ and indeed of phosphatases into the rhizosphere, as well as amino- and organic acid exudation [25] in specific regions of the root (i.e. as spatio-temporal exudative bursts from proteoid roots) are known to increase in P-starved plants [26]. This property is of importance for nutrient acquisition as well as for plant– microbe interactions, both pathogenic and symbiotic, and may be viewed as third adaptation related to how plants themselves are able to increase nutrient acquisition, the others being nodulation and mycorrhiza. These properties could be exploited further by plant breeding. In addition, P deficiency has severe effects on uptake, transport and assimilation of N and C. Experimental evidence has indicated a restriction of NO 3 uptake [27,28].
This has been attributed to possible signal mechanisms i.e. via cycling of amino- (especially asparagine) or organic acids between shoots and roots regulating N uptake [29]. The implications of root-induced acidification with NH+ 4 nutrition for P-use efficiency have been studied less intensively, and did not result in higher P-uptake rates [25]. The partitioning of carbon into organic- and amino acid fractions are likely to be modified by P deficiency, as carboxylate synthesis is predicted to shift from anaplerotic primary metabolism to enhanced organic acid (mainly malate and citrate) and/or H+ excretion [30]. In spite of low input of K and P in some of the treatments, no reductions in yield were observed, which was probably due to the high availability of potassium and phosphorus in the soils of the two experimental sites caused by previous cultivation. Compared with woody solid biofuels, whole crop cereals as well as grain and straw fractions are characterized by higher concentrations of ash, N, K, S and Cl [31]. Straw generally has a higher content of ash, Cl and Na than grains, whereas grains contain more N and S. This information is essential if straw and grain are used separately for combustion. The mineral content of the grain fraction altered only little between years and locations. By contrast, large
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variations in the mineral content of the straw fraction between years and locations were observed. Variation of the K and Cl content in straw and in total biomass was influenced more strongly by precipitation before harvest than by fertilizer (Fig. 1, Tables 4 and 7). The highest content of K and Cl in straw was observed when the precipitation was close to zero 3 weeks before harvest at both locations. In addition, the lowest K and Cl content in the straw fraction and in the total biomass was found to correlate with precipitation levels of about 25 mm within the last 10 days before harvest (Fig. 1, Tables 4 and 7). Our results support the conclusion by Sander [2] and Allica et al. [32] that application of Cl-free fertilizer to the crops by use of K2SO4 instead of KCl improves the fuel quality without negatively influencing yield. In conclusion, this study shows that the dry matter yield of wheat, rye and triticale was high and stable at the two locations over the 3-year period of investigation. Here, triticale (Alamo) and rye (Marder and Motto) showed the highest yield (14.1–15.9 t ha1) compared to wheat (11.6–14.2 t ha1). This occurred in spite of a lower input of N fertilizer. Thus, this constant high yield of rye and triticale would be an advantage for the use of biomass for energy purposes. The concentration of elements relevant for combustion can vary significantly between years. In years where the cereals are ripened and senescence has coursed the straw to dry up, precipitation removed substantial amounts of K, Cl and S. This must be taken into considerations when the harvest of cereals for energy purposes is planned, as the crops are harvested relatively late to increase the chances for precipitation to remove K, Cl and S. The use of K fertilizers containing Cl and S resulted in a significantly increased concentration of these elements in the straw. In our experiments, triticale followed by rye had the best yield and quality demands of cereals grown for energy use. Acknowledgements The study was financed by the Danish Research Secretariat, Ministry of Agriculture and Fisheries. The authors thank the staff at Rønhave and Roskilde Research Stations for their help. References [1] Nonhebel S. Energy yields in intensive and extensive biomass production systems. Biomass and Bioenergy 2002;22:159–67. [2] Sander B. Properties of Danish biofuels and the requirements for power production. Biomass and Bioenergy 1997;12:177–83. [3] Becher S. Biogene Festbrennstoffe als Substitut fu¨r fossile Brennstoffe-Energie- und Emissionsbilanzen. IER Forschungsbericht 50, Stuttgart, 1998. [4] Obernberger I, Bidermann F, Widmann W, Riedl R. Concentrations of inorganic elements in biomass fuels and recovery in the different ash fractions. Biomass and Bioenergy 1997;12:211–24. [5] Jenkins BM, Bakker RR, Wei JB. On the properties of washed straw. Biomass and Bioenergy 1996;10:177–200.
[6] Wollenweber B, Kinzel H. Role of carboxylate in the nitrogen metabolism of plants from different natural habitats. Physiologia Plantarum 1988;72:321–8. [7] Belda RM, Delapuente LS. Mineral-nutrition of wheat. 1. Organ and crop stage relationships. Journal of Plant Nutrition 1992;15:359–69. [8] Raven JA, Wollenweber B. Temporal and spatial aspects of acid–base regulation. In: Randall DD, Sharp RE, Novacky AJ, Blevins DG, editors. Current topics in plant biochemistry and physiology, vol. 11; 1992. p. 270–94. [9] Wollenweber B, Raven JA. Nitrogen acquisition from atmospheric NH3 by Lolium perenne: utilization of NH3 and implications for acid–base balance. Botanica Acta 1993;106:42–51. [10] Van Tuil HDW, Lampe JEM, Dijkshoorn W. The possibility of relating the ash alkalinity to the organic salt content. Jaarbook Instituut voor Biologisch Sheikundig Onderzoek van Landbougewassen, 1964. p. 157–60. [11] Claussen T. Dry ash, a better reference base than dry matter for heavy metals and other persistent pollutants. Plant and Soil 1990;127:91–5. [12] Araus JL, Amaro T, Casadesus J, Asbati A, Nachit MM. Relationships between ash content, carbon isotope discrimination and yield in durum wheat. Australian Journal of Plant Physiology 1998;25: 835–42. [13] Araus JL, Casadesus J, Asbati A, Nachit MM. Basis of the relationship between ash content in the flag leaf and carbon isotope discrimination in kernels of durum wheat. Photosynthetica 2001;39: 591–6. [14] Merah O, Deleens E, Souyris I, Monneveux D. Ash content might predict carbon isotope discrimination and grain yield in durum wheat. New Phytologist 2001;149:275–82. [15] Anonymous. Arbejdsmetoder. I. del Kemiske undersøgelser af mel og mejeriprodukter m.m. samt foderstoffer. J.H. Schultz Bogtrykkeri, 1958. [16] Anonymous. AOAC. 15 ed. Official methods of analysis, 1990. p. 777. [17] Hansen B. Determination of nitrogen as elementary N: an alternative to Kjeldahl. Acta Agriculturae Scandinavica 1989;39:113–8. [18] Lacroix RL, Keeney DR, Walsh LM. Potentiometic titration of chloride in plant tissue extracts using the chloride ion electrode. Communications in Soil Science and Plant analysis 1970;1:1–6. [19] Anonymous. Kommissionens første direktiv af 15. Juli 1971 om fastsættelse af fællesskabsanlysemetoder til den officielle kontrol af foderstoffer. (The first Commission directive of 15 July 1971 on the determination of Community analytical methods for the official control of feeds.) De Europæiske Fællesskabers tidende L155/13, 1971. p. 436–9. [20] Nes P. Routine measurement of total sulphur in biological material. New Zealand Journal of Science 1979;22:269–72. [21] Anonymous. SAS Institute. SAS/STAT software: changes in enhancements through release 6.12. Cary, NC: SAS Institute; 1997. [22] Venendaal R, Jorgensen U, Foster CA. European energy crops: a synthesis. Biomass and Bioenergy 1997;13:147–85. [23] Olesen JE, Bindi M. Consequences of climate change for European agricultural productivity, land use and policy. European Journal of Agronomy 2002;16:239–62. [24] Shearman VJ, Sylvester-Bradley R, Scott RK, Foulkes MJ. Physiological processes associated with wheat yield progress in the UK. Crop Science 2005;45:175–85. [25] Kirk GJD, Santos EE, Santos MB. Phosphate solubisation by organic anion excretion from rice growing in aerobic soil: rates of excretion and decomposition, effects oh rhizosphere pH and effects on phosphate solubility and uptake. New Phytologist 1999;142: 185–200. [26] Dinkelaker B, Hengeler C, Marschner H. Distribution and function of proteoid roots and other root clusters. Botanica Acta 1995;108:183–201. [27] Jeschke WD, Kirkby EA, Peuke AD, Pate JS, Hartung W. Effects of P deficiency on assimilation and transport of nitrate and phosphate in
ARTICLE IN PRESS J.R. Jørgensen et al. / Biomass and Bioenergy 31 (2007) 308–317 intact plants of castor bean (Ricinus communis L.). Journal of Experimental Botany 1997;48:75–91. [28] Cui M, Caldwell M. Nitrate and phosphate uptake by Agropyron desertorum and Artemisia tridenta from soil patches with balanced and unbalanced nitrate and phosphate supply. New Phytologist 1998;139:267–72. [29] Touraine B, Clarkson DT, Muller B. Regulation of nitrate uptake at the whole plant level. In: Roy J, Garnier E, editors. A whole plant perspective on carbon–nitrogen interactions. The Hague: SPB Academic Publishing; 1994. p. 11–30.
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[30] Raven JR, Handely L, Wollenweber B. Plant nutrition and water use efficiency. In: Bacon M, editor. Water use efficiency in plant biology. Oxford: Blackwell Science Publications; 2004. p. 162–88. [31] Obernberger I. Decentralized biomass combustion: state of the art and future development. Biomass and Bioenergy 1998;14: 33–56. [32] Allica JH, Mitre AJ, Bustamante JAG, Itoiz C, Blanco F, Alkorta I, et al. Straw quality for its combustion in a straw-fired power plant. Biomass and Bioenergy 2001;21:249–58.
Biomass and Bioenergy 31 (2007) 308–317 www.elsevier.com/locate/biombioe
Prospects of whole grain crops of wheat, rye and triticale under different fertilizer regimes for energy production Johannes Ravn Jørgensen, Lise C. Deleuran, Bernd Wollenweber Aarhus Universitet, Faculty of Agricultural Sciences, Department of Genetics and Biotechnology, Research Centre Flakkebjerg, DK-4200 Slagelse, Denmark Received 27 October 2005; accepted 10 January 2007 Available online 23 March 2007
Abstract Cereal grain yield and biomass production are affected by fertilizer application strategies. In order to quantify the performance of wheat, rye and triticale cultivars for use as energy crops, field experiments with either modified phosphorus–potassium or potassium applications were designed at two locations in Denmark over a 3-year period. Five wheat cultivars (‘Astron’, ‘Herzog’, ‘Kosack’, ‘Kraka’ and ‘Ure’), two winter rye cultivars (the population cultivar ‘Motto’ and the hybrid cultivar ‘Marder’) and the triticale cultivar ‘Alamo’ were selected. The grain and straw fractions were analysed for biomass, ash and contents of nitrogen (N), K, Cl, sulphur (S) and Na. Dry matter yields varied between 11.5 and 15.9 t ha1 at the two locations. Triticale and rye had a higher total dry matter yield than wheat, even at lower inputs of N fertilizer. Thus, the constant high yield of rye and triticale is an advantage for biomass for energy purposes. The mineral content of the grain fraction changed only little between years and locations. By contrast, large variations in the analysed ions in the straw fraction between years and locations were observed. The use of K fertilizers resulted in a significantly increased concentration of K in the straw. However, this increased concentration was eliminated in years with high precipitation in the final 3 weeks before harvest, where substantial amounts of K, Cl and S were removed. The results are discussed in relation to the possible use of grain crops for energy production. r 2007 Elsevier Ltd. All rights reserved. Keywords: Bioenergy; Biofuels; Mineral composition; Cereals; Cultivars
1. Introduction Cereals produce biomass in the form of grain and/or straw and are, because of their high dry matter content, easy storable. Moreover, due to the relative short annual rotation, flexible (i.e. depending on demand) biomass production is possible [1]. These features, combined with the fact that cereals have a determinate vegetative growth, mean that cereals can be seen as a promising biomassproducing crop in temperate regions of Europe. In addition, existing agricultural machinery can be used for crop establishment, husbandry and harvest. When cereals are combusted in large-scale power plants, a low content of both sulphur (S) and nitrogen (N) is desirable, due to the possibility of increased emissions of SO 2 and NOx [2,3]. Problems due to corrosion processes, Corresponding author. Tel.: +45 89 99 35 00; fax: +45 89 99 35 01.
E-mail address: [email protected] (J.R. Jørgensen). 0961-9534/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2007.01.001
ash slugging and fouling may arise [4,5]. These problems are partly due to the constraints of the ion-content and -balance within the plant [6]. As both plant biomass and ion content are influenced by mineral nutrition, modification of fertilization strategies may alter these parameters [7]. In cereals (Gramineae), differences in ion content may result from differences in mineral nutrition and ion uptake of the species under investigation [8,9]. For example, nitrate (NO 3 ) nutrition is characterized inter alia by increased cation uptake and leads to the synthesis of carboxylate (anions of organic acids), which contribute significantly to the total anion content [6,8]. By contrast, the use of ammonium (NH+ 4 ) is related to increased anion uptake and can be directly incorporated into carbon skeletons with no additional synthesis of carboxylate [6,8]. An interesting exception are members of the morphologically related Poaceae, Juncaceae and Cyperaceae, who show a highly selective ion uptake (in terms of discrimination against ‘non-target’ ions) and thus are
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thought to be able to maintain a rather constant ion content, which is lower than in other plants [6]. In any case, metabolism of CO2, N2 or NH3 and H2S generates organic compounds containing C, N and S, which, at normal intracellular pH, have a predominance of negative charge (mainly as –COO) over positive charge (predominantly –NH+ 3 ). This difference is measured as the excess of inorganic cations, C+ (K++Na++Ca2++Mg2++ p + NH4 ) over inorganic anions, A p (Cl +NO3 +H2PO4 / 2 2 HPO4 +SO4 ) in the tissue, giving an indirect estimate of the excess of negative charge on organic compounds [8,10]. Ashing of plant samples at temperatures at or above 520 1C volatilizes organic components, leaving K+, Na+, Ca2+, 2 Mg2+, Cl, H2PO and SO2 4 /HPO4 4 , with electroneu 2 trality maintained by OH +HCO 3 +CO3 (replacing the net organic negative charge) [6,10]. The ashing treatment also removes NH+ 4 , NH3 from organic N and NO3 via formation of NOx. Cl will cause HCl emission and deposition resulting in corrosive effects during combustion. SO2 4 will form alkali sulphates and SO2. K+ and Na+, in combination with Cl and SO2 4 , will add to corrosion mechanisms during combustion via wet and/or dry deposition of acid loads. Thus, for the use of combustion material in power plants, relatively small amounts of these ions would be preferred. In addition, dry-ash analysis constitutes a reliable method for the detection of heavy metal content in plant tissues [11], but might also be used as a screening method for the investigation of the constraints of environmental stress [12–14] as indicated by the relationships between ash content and carbon isotope discrimination (D) for example in Triticum durum genotypes, where leaf ash correlated positively with grain D [12]. The aim of the current work was to investigate the effect of fertilization constraints on the performance (plant biomass and ion content) of winter wheat, winter rye and winter triticale for use as energy crops.
309
2. Materials and methods 2.1. General experimental design Two field experiments (A and B) were designed as a randomized complete block with a split-plot arrangement of treatments. In both experiments, five wheat cultivars (‘Astron’, ‘Herzog’, ‘Kosack’, ‘Kraka’ and ‘Ure’), two winter rye cultivars (the population cultivar ‘Motto’ and the hybrid cultivar ‘Marder’) and the triticale cultivar ‘Alamo’ were selected. Seeds for experiment A were sown on sandy loam soil in 1993, 1994 and 1995 at Roskilde Research Station (551390 N and 121050 E). Seeds for experiment B were sown on a clay soil in 1994, 1995 and 1996 at Rønhave Research Station (541570 N and 91470 E). Fertilizer was applied as described in Table 1. Herbicide and fungicide treatments were applied according to good experimental practice for control of residual weeds. Plots were harvested with a trials combine harvester according to normal harvest practice and timing. Kernel and straw yield (straw and chaff) were measured for every replicates. Cutting height was adjusted to leave 8–10 cm of stubble. Accumulated precipitation in the final 3 weeks of crop ripening before harvest (Fig. 1) was measured at both locations. 2.2. Experiment A: phosphorus–potassium fertilizer and species/cultivar trials A phosphorus–potassium (PK) fertilizer treatment (PK; +PK) was the main factor in the split-plot arrangement of treatments, with cultivar as the sub-plots. The PK fertilizer (7.2% phosphorus (P) w/w, 18.3% K w/w, 17% Cl w/w and 5.5% S w/w) was applied at 400 kg ha1. Wheat cultivars received 160 kg N ha1 as lime-ammonium nitrate (27% N w/w), rye 120 kg N ha1 and triticale 140 kg N ha1, according to standard recom-
Table 1 Nutrient application (kg ha1) in experiments A (Roskilde Research Station) and B (Rønhave Research Station) Experiment and harvest year
Treatment
Species
N (kg ha1)
P (kg ha1)
K (kg ha1)
Cl (kg ha1)
S (kg ha1)
A: Roskilde 1994, 1995 and 1996
PK
Wheat Rye Triticale Wheat Rye Triticale
160 120 140 160 120 140
— — — 29 29 29
— — — 73 73 73
— — — 68 68 68
— — — 22 22 22
Wheat Rye Triticale Wheat Rye Triticale Wheat Rye Triticale
160 120 120 160 120 120 160 120 120
— — — — — — — — —
— — — 50 50 50 50 50 50
— — — — — — 50 50 50
— — — 22 22 22 — — —
+PK
B: Rønhave 1995, 1996 and 1997
Control
K2SO4
KCl
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310
a
b 50 1994 1995 1996
40
Precipitation, mm
Precipitation, mm
50
30 20 10 0
1995 1996 1997
40 30 20 10 0
21
18
15 12 9 6 Days before harvest
3
21
18
15 12 9 6 Days before harvest
3
Fig. 1. Accumulated precipitation from 21 days before harvest until harvest at Roskilde (a) and Rønhave (b) Research Stations.
mendations. Individual treatments were replicated four times. All fertilizers were applied in late March or beginning of April (Table 1). Individual plots were 10 rows wide (1.65 m 9.5 m). Dates of sowing were 1 October 1993, 22 September in 1994 and 29 September in 1995. Dates of harvest were 22 and 23 August in both 1994 and 1996 and 10 August in 1995. 2.3. Experiment B: potassium fertilizer and species/cultivar trials As in experiment A, the design was a randomized complete block with a split-plot arrangement of treatments. The potassium fertilizer treatment (control vs. KCl and KCl vs. K2SO4) was the main factor, with cultivar as subplots. Wheat cultivars received 160 kg N ha1 and rye and triticale 120 kg N ha1 each as lime-ammonium nitrate (27% N w/w), according to standard recommendations. Individual treatments were replicated three times. All fertilizers were applied in late March or beginning of April (Table 1). Individual plots were 10 rows wide (1.5 m 8.7 m). Dates of sowing were 23 September 1994 and 19 September in 1995 and 1996. Dates of harvest were 10 August in 1995, 3 September in 1996 and 14 August in 1997.
2.5. Statistical analysis The statistical analysis of the resulting data was performed by F-tests. The denominator in the F-test was the interaction between the studied effects in question and their interactions. Least significant differences (LSD) at the 5% probability level were used to separate means of main effects. The analyses were performed using the Statistical Analysis System (SAS) software package [21]. Comparison of effects (i.e. year, cultivar, N application or interaction between year, cultivar and N application) in a given grain component was made by one-way, two-way or three-way analysis of variance (GLM procedure) followed by Duncan’s means comparison test. 3. Results 3.1. Meteorological data Fig. 1 shows the accumulated precipitation during the last 21 days before harvest at both experimental sites. Highest levels of precipitation were observed in 1994 at Roskilde and in 1997 at Rønhave.
2.4. Chemical analysis
3.2. Experiment A: phosphorus–potassium fertilizer and species/cultivar trial at Roskilde
The harvested biomass samples were dried at 80 1C for at least 24 h and ground. The ash content was calculated from the weight loss of organic material during an ashing process at 525 1C for 6 h [15,16]. The Dumas combustion procedure was used to determine the total N content [17]. Gross heat of combustion was determined by calorimetric methods, according to the American Society for Testing and Materials (ASTM) standard D2382-83. Cl content was determined by potentiometric titration (silver nitrate) of weak (0.1 mol l1) nitric acid extracts [18]. K and Na contents were determined by flame emission photometry on samples ashed at 450 1C for 3 h [19]. Total-S was detected spectroscopically at 560 nm by addition of barium chloride to perchloric acid extracts of plant matter [20]. All results are presented on a dry matter basis.
The results of estimated mean biomass yield, ash content, total-N, analysed ions and gross heating values are presented for the grain fraction in Table 2, for the straw fraction in Table 3 and for the total biomass in Table 4. Overall, grain, straw and total biomass yield, composition and gross heating values were significantly influenced by year and species/cultivar but not by PK fertilizer. However, a significant year fertilizer interaction for both Cl and K was observed. Grain, straw and total biomass yield was significantly lower in 1994 than in 1995 and 1996 (Tables 2–4). Grain yield was highest in Marder and Alamo, while Motto showed the highest straw yield. Total biomass yield was significantly higher for the triticale cultivar Alamo and the rye cultivar Motto than for the wheat cultivars. Of the
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Table 2 The influence of phosphorus–potassium fertilizer and species/cultivar on grain dry matter yield, grain composition and gross heat of combustion in cereals produced at Roskilde Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1994 1995 1996
5.21cy 5.46b 5.92a
15.6a 15.6a 14.0b
18.4c 18.7b 19.3a
4.33b 4.77a 4.23c
0.57c 0.66b 0.75a
1.11b 1.11b 1.44a
0.049a 0.025c 0.039b
18.45a 18.54a 18.41a
Fertilizerz PK +PK
5.49a 5.56a
15.3a 14.8a
19.1a 18.5a
4.49a 4.40a
0.64a 0.68a
1.24a 1.21b
0.039a 0.036a
18.46a 18.47a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
5.33cd 4.94cd 5.09cd 5.29cd 4.72d
14.5bc 14.4c 14.9bc 15.0abc 14.3c
20.4ab 21.5a 19.7b 20.0b 20.6ab
3.88d 4.25c 4.17cd 4.30c 4.19cd
0.70abc 0.72ab 0.62cd 0.73a 0.66abcd
1.28ab 1.27ab 1.31a 1.23b 1.26ab
0.032a 0.038a 0.033a 0.041a 0.033a
18.56a 18.54a 18.59a 18.49ab 18.60a
Rye Marder Motto
6.58a 5.73bc
15.2abc 16.4a
15.0d 14.9d
4.64b 5.07a
0.64bcd 0.65abcd
1.05d 1.14c
0.040a 0.043a
18.21d 18.33cd
Triticale Alamo
6.45ab
15.9ab
18.2c
5.06a
0.57d
1.27ab
0.041a
18.40bc
Means averaged across fertilizer and species/cultivar. y
Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
Table 3 The influence of phosphorus–potassium fertilizer and species/cultivar on straw dry matter yield, straw composition and gross heat of combustion in cereals produced at Roskilde Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1994 1995 1996
6.46cy 8.16a 7.82b
29.34c 46.03b 50.64a
3.98c 5.65b 6.78a
7.29b 14.07a 14.65a
0.61c 2.92b 5.66a
0.31c 0.55b 1.84a
0.079b 0.065b 0.122a
18.84a 18.84a 18.61b
Fertilizerz PK +PK
7.42a 7.51a
41.6a 42.4a
5.4a 5.5a
11.07a 11.28a
2.08a 4.05a
0.83a 0.89a
0.089a 0.089a
18.78a 18.75a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
6.50c 6.84c 7.35bc 7.20bc 6.83c
44.8a 41.6a 43.8a 40.0a 40.3a
6.3a 5.9a 5.5abcd 5.7abc 5.8ab
11.58cde 11.36de 12.65ab 10.91e 11.60bcde
3.17a 2.83a 2.99a 2.79a 3.01a
1.04a 0.91ab 0.97ab 0.95ab 0.91ab
0.079a 0.082a 0.083a 0.095a 0.090a
18.80a 18.85a 18.66a 18.68a 18.58a
Rye Marder Motto
7.53bc 9.07a
42.6a 40.3a
4.8cd 4.7d
12.41abc 12.73a
3.52a 3.13a
0.77b 0.81ab
0.094a 0.096a
18.85a 18.84a
Triticale Alamo
8.31ab
42.6a
5.0bcd
12.25abcd
3.08a
0.33c
0.092a
18.84a
Means averaged across fertilizer and species/cultivar. y
Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
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Table 4 The influence of phosphorus–potassium fertilizer and species/cultivar on dry matter yield, composition and gross heat of combustion on total biomass (grain+straw) in cereals produced at Roskilde Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1994 1995 1996
11.66by 13.64a 13.74a
23.23b 33.80a 34.66a
10.43c 10.87b 12.10a
5.98b 10.35a 10.10a
0.59c 2.01b 3.52a
0.67b 0.76b 1.66a
0.066b 0.049c 0.086a
18.68a 18.70a 18.47b
Fertilizerz PK +PK
12.92a 13.05a
30.4a 30.7a
11.2a 11.1a
8.28a 9.21a
1.47a 2.61a
1.00a 1.03a
0.067a 0.065a
18.61a 18.63a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
11.86c 11.74c 12.41bc 12.49bc 11.55c
31.1ab 30.2b 32.0a 29.6b 29.9b
12.6a 12.4a 11.3c 11.8bc 11.9b
8.11d 8.41d 9.22b 8.17d 8.64cd
2.06a 1.94a 2.03a 1.94a 2.10a
1.26a 1.06bc 1.11ab 1.07bc 1.07bc
0.057ab 0.063ab 0.051b 0.073a 0.067ab
18.62ab 18.72a 18.62ab 18.63ab 18.59ab
Rye Marder Motto
14.08ab 14.77a
29.7b 31.0ab
9.6e 8.7f
8.41d 9.77a
2.14a 2.18a
0.89d 0.94cd
0.068ab 0.075a
18.54b 18.61ab
Triticale Alamo
14.79a
30.9ab
10.7d
9.11bc
1.95a
0.69e
0.069ab
18.62ab
12.98
30.6
11.1
8.74
2.04
1.01
0.066
18.62
Mean
Means averaged across fertilizer and species/cultivar. y Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
estimated total biomass yield, 53% (Marder) to 61% (Motto) originated from the straw (Tables 2–4). The ash content was on average 2.8 times higher in the straw fraction as compared to the grain fraction. Ash content of the straw and the total biomass was significantly lower in 1994. Within the grain fraction, the rye cultivar Motto had a significantly higher ash content than the wheat cultivars (Astron, Herzog, Kosack and Ure) (Table 2). Total-N was, on average, 3.4 times higher in the grain than in the straw fraction. Within years, the greatest variation was found in the straw fraction with the significantly lower N content in 1994 (Tables 2 and 3). Compared to the rye and triticale cultivars, significantly higher N contents were observed in grains of all wheat cultivars while the triticale showed an intermediate value. In the straw fraction of wheat, the Astron and Herzog cultivars had a significantly higher N content than the rye cultivars Marder and Motto and the triticale cultivar Alamo (Table 2). The N content of the total biomass was significantly lower for the rye cultivar Motto followed by Marder and the triticale cultivar Alamo while within the wheat cultivars the significantly higher N content was observed in Astron and Herzog (Table 4). Potassium content was on average 2.7 times higher in the straw fraction as compared to the grain fraction (Tables 2
and 3). The significantly higher K content of the grain fraction was observed in 1995 and the significantly lower for the straw fraction in 1994 (Tables 2 and 3). The significantly higher K content of the grain fraction was observed in Alamo triticale and Motto rye, and the lowest in the wheat cultivars (Table 2). In the straw fraction, highest K contents were observed in Motto rye and the lowest in Kraka wheat (Table 3). In the total biomass, highest values of K were observed in Motto rye (Table 4). Straw content of Cl was on average 4.6 times higher than in grain (Tables 2 and 3). Grain, straw and total biomass content of Cl was significantly lower in 1994 (Tables 2–4). In 1996, the straw content of Cl was 9.3 times higher than in 1994, but only 1.3 times higher in grain (Table 3). No significant differences were found within the species/ cultivars for the Cl content of the total biomass (Table 4). The total-S contents of grain were found to be 42% higher than in straw (Tables 2 and 3). Significantly higher S contents were observed in 1996 for grain, straw and total biomass (Tables 2–4). Marder and Motto rye had the significantly lower S content in grain and Alamo in straw and total biomass (Tables 3 and 4). Straw contents of Na were 2.3 times higher than in grain (Tables 2 and 3). Highest Na contents were observed in 1994 in grain and in 1996 in straw (Tables 2 and 3). No significant differences were observed in straw within
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species/cultivars, and only little differences within grain (Table 2). Minor differences in gross heating values were observed between the straw (18.58–18.85 MJ kg1) and the grain (18.21–18.60 MJ kg1) fraction (Tables 2–4). However, gross heating value in grains of all the wheat cultivars was significantly higher than the two rye cultivars (Table 2). 3.3. Experiment B: potassium fertilizer and species/cultivar trials at Rønhave Results of the estimated mean biomass yield, ash content, total-N and measured ions as well as gross heating values are presented in Table 5 for the grain fraction, in Table 6 for straw fraction and in Table 7 for the total biomass. Overall, grain contents of ash, K, S and Na and gross heating values were influenced by year and species/ cultivar but not by fertilizer treatments (Table 5). Straw yield, composition and gross heating values were significantly influenced by year and species/cultivar but not by fertilizer treatments (Table 6). A non-significant increase in the straw Cl content was observed when the KCl fertilizer was applied, and a non-significant increase in the S content when the K2SO4 fertilizer was applied. Total biomass yield and composition were also significantly influenced by year
313
and species/cultivar but not by fertilizer treatments (Table 7). No significant differences between the years of observation for grain yield were observed (Table 5). However straw and total biomass yield was significantly higher in 1995 (Tables 6 and 7). The straw and total biomass yields were significantly higher for the Alamo triticale cultivar than for the wheat cultivars, with intermediate yields for the rye cultivars (Tables 6 and 7). Of the estimated total biomass yield, 53% (Astron) to 57% (Motto) originated from the straw fraction (Table 7). The ash content was on average 3.5 times higher in the straw fraction as compared to the grain fraction (Tables 5 and 6). Grain, straw and total biomass ash content was significantly lower in 1996 (Tables 5–7). Here, the rye cultivar Motto had the highest ash content within the grain. The total-N content in grains was, compared to the straw fraction, on average 3.2 times higher (Tables 5 and 6). The rye cultivars Marder and Motto had significantly lower N contents in grain and total biomass than the wheat and the Alamo triticale cultivars. Within the wheat cultivars, Astron and Hertzog had the highest content. In straw as well as in total biomass, significantly lower N contents were observed in 1995 (Tables 6 and 7).
Table 5 The influence of phosphorus–potassium fertilizer and species/cultivar on grain dry matter yield, grain composition and gross heat of combustion in cereals produced at Rønhave Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1995 1996 1997
6.33ay 6.86a 6.32a
16.5a 12.1b 16.1a
17.5a 17.2a 17.8a
4.55a 4.14b 4.64a
0.69a 0.74a 0.62a
1.20a 1.03c 1.14b
0.026c 0.043b 0.069a
18.24b 18.13c 18.52a
Fertilizerz Control K2SO4 KCl
6.63a 6.44a 6.51a
14.6a 14.8a 15.2a
17.5a 17.3a 17.8a
4.40b 4.49a 4.44ab
0.68a 0.65a 0.71a
1.10a 1.15a 1.11a
0.045a 0.047a 0.045a
18.26a 18.27a 18.38a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
6.56a 6.29a 6.52a 6.19a 6.23a
13.8c 14.3bc 14.3bc 15.0abc 14.3bc
18.7ab 19.8a 17.7bc 18.2bc 18.6abc
3.96d 4.07cd 4.21cd 4.29cd 4.11cd
0.69ab 0.74ab 0.61b 0.87a 0.63b
1.14abc 1.18ab 1.12abc 1.09abc 1.12abc
0.040c 0.038c 0.041c 0.038c 0.045bc
18.33ab 18.38ab 18.32ab 18.32ab 18.43a
Rye Marder Motto
7.08a 6.35a
15.0abc 16.3a
14.5d 14.4d
4.55bc 5.08ab
0.66b 0.64b
1.05c 1.08bc
0.045bc 0.060ab
18.10c 18.27b
Triticale Alamo
7.00a
15.9ab
17.4c
5.30a
0.61b
1.19a
0.055a
18.24bc
6.53
14.9
17.5
4.44
0.68
1.12
0.045
18.30
Mean
Means averaged across fertilizer and species/cultivar. y
Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
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Table 6 The influence of phosphorus–potassium fertilizer and species/cultivar on straw dry matter yield, straw composition and gross heat of combustion in cereals produced at Rønhave Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1995 1996 1997
9.26ay 6.72c 8.28b
59.5a 38.2b 58.3a
4.84b 5.64a 5.69a
14.36a 6.05b 13.74a
4.24a 1.75b 4.17a
0.75b 0.89a 0.67b
0.092b 0.081c 0.128a
18.44b 18.68a 18.51b
Fertilizerz Control K2SO4 KCl
7.99a 8.00a 7.81a
51.2a 50.5a 54.0a
5.4a 5.3a 5.5a
10.88a 11.02a 11.96a
2.59a 2.54a 5.15a
0.65a 1.04a 0.60a
0.109a 0.087a 0.101a
18.56a 18.55ab 18.50b
Species/cultivary Wheat Astron 7.24d Herzog 7.38cd Kosack 7.72cd Kraka 7.93bc Ure 7.93cd
55.4a 54.0ab 54.8ab 46.9b 52.0ab
5.4a 5.7a 5.6a 5.6a 5.6a
9.67c 9.65c 11.49b 9.63c 9.79bc
2.65d 3.38abc 3.24bcd 2.98cd 2.77cd
0.82ab 0.79ab 0.79ab 0.77ab 0.79ab
0.094c 0.079d 0.097bc 0.093c 0.092cd
18.39a 18.52a 18.57a 18.57a 18.50a
Rye Marder Motto
7.99bc 8.50ab
50.8ab 50.2ab
5.1a 5.3a
14.51a 14.08a
3.84ab 4.07a
0.70bc 0.85a
0.119a 0.110ab
18.63a 18.66a
Triticale Alamo
8.88a
51.2ab
4.8a
11.43b
3.72ab
0.60c
0.114a
18.49a
Mean
7.93
51.9
5.4
11.30
3.35
0.77
0.099
18.54
Means averaged across fertilizer and species/cultivar. y Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
In straw, higher K contents were observed than in grain (Tables 6 and 7). Significant lowest K contents in grain, straw and total biomasses were observed in 1996 (Tables 5–7), but the K2SO4 fertilizer increased the grain K content by only 2%. The straw K content was 137% higher in 1995 (and 127% higher in 1997) than in 1996 (Table 6). This variation is reflected also in the K content of the total biomass (Table 7). Alamo and Motto had significantly higher K contents in grain than any of the other wheat cultivars. Straw Cl content was on average 4.9 times higher than in the grain (Tables 5 and 6). In 1995 and 1997, straw content was 2.4 times higher than in 1996. An increase in Cl content of straw from the KCl fertilizer treatment compared with the control was observed (Table 6). Total biomass of all wheat cultivars had a significant lower Cl content than the Alamo triticale and Marder and Motto rye cultivars. Grain content of total-S was 45% higher compared to straw (Tables 5 and 6). The Alamo triticale cultivar had the highest S content in grain and the lowest in straw and total biomass (Tables 5 and 6). Grain content of Na was approximately 50% of the amount in straw (Tables 5 and 6). The significant highest Na content was observed in 1997 (Tables 5–7). The lowest Na content was observed in wheat as compared to triticale and rye
(Tables 5 and 6). Generally, no differences in the gross heating values in all treatments and fractions were observed. 4. Discussion and conclusion During the 3 years of observation with wheat, triticale and rye reported here, mean yield was as high or higher than that reported from other European yield trials [22]. This corresponds well with data from FAO and other reports that wheat yield increases in the northwestern part of Europe are the highest in Europe [23]. Within each of the locations and years of observation, the grain yield was very stable whereas some variation was observed within straw yield. None of the tested wheat cultivars accumulated as much total biomass as the triticale and rye cultivars. This higher yield of the triticale and rye cultivars compared to the wheat cultivars originated primarily from straw. The two tested rye cultivars differed in their relationship between grain and straw (harvest index), where Marder had the highest grain yield and the lowest straw yield. This will influence their overall performance and has to be taken into consideration when applied for biofuel. A major scope in breeding of new wheat cultivars has been an improvement of the harvest index based on an increased grain fraction and decreased
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Table 7 The influence of phosphorus–potassium fertilizer and species/cultivar on dry matter yield, composition and gross heat of combustion of total biomass (grain+straw) in cereals produced at Rønhave Research Station Treatment
Yield (t ha1)
Ash (g kg1)
N (g kg1)
K (g kg1)
Cl (g kg1)
S (g kg1)
Na (g kg1)
Energy (MJ kg1)
Year 1995 1996 1997
15.60ay 13.58c 14.58b
42.0a 25.0c 39.9b
10.0c 11.5a 10.9b
10.21a 5.10b 9.76a
2.83a 1.24b 2.62a
0.93a 0.96a 0.87b
0.066b 0.062b 0.101a
18.36a 18.41a 18.49a
Fertilizerz Control K2SO4 KCl
14.64a 14.44a 14.30a
34.9a 34.8a 36.5a
10.8ab 10.7b 11.1a
7.91a 8.27a 8.54a
1.81a 1.75a 3.26a
0.84a 1.09a 0.82a
0.081a 0.069a 0.074a
18.42a 18.42a 18.42a
Species/cultivary Wheat Astron Herzog Kosack Kraka Ure
13.67b 13.67b 14.24b 14.13b 14.06b
34.0ab 36.0ab 36.6a 33.3ab 35.7ab
11.7ab 12.1a 11.0c 11.2c 11.3bc
7.06e 7.20e 8.31cd 7.44de 7.41de
1.74c 2.20b 2.07bc 2.08bc 1.85bc
0.96a 0.96a 0.95a 0.91ab 0.93a
0.069b 0.059c 0.072b 0.067b 0.071b
18.35a 18.44a 18.45a 18.50a 18.46a
Rye Marder Motto
15.12ab 14.85ab
32.6b 36.0ab
9.4e 9.2e
2.73a 2.66a
0.85bc 0.93a
0.085a 0.087a
18.28a 18.48a
Triticale Alamo
15.88a
36.5a
10.2d
9.02bc
2.66a
0.84c
0.090a
18.37a
14.46
35.4
10.8
8.25
2.24
0.92
0.075
18.42
Mean
9.28b 10.37a
Means averaged across fertilizer and species/cultivar. y Within year, fertilizer or species/cultivar and columns, means followed by the same letter are not significantly different, by LSD at the 0.05 probability level. z Means averaged across year and species/cultivar. y Means averaged across year and fertilizer treatments.
straw-fraction [24]. Thus a new breeding goal for wheat cultivars for use as biofuel may be a reduced harvest index. This strategy could also be applied to rye and triticale. After N, P is the second most frequently limiting macronutrient for plant growth. However, in many agricultural systems (i.e. the sandy loams of eastern Denmark), the P-use efficiency by crops is low and even relatively mild deficiencies can significantly reduce plant growth. In response to persistently low levels of available P in the rhizosphere, plants have developed highly specialized mechanisms to acquire and utilize P from the environment. Thus, extrusion of H+ and indeed of phosphatases into the rhizosphere, as well as amino- and organic acid exudation [25] in specific regions of the root (i.e. as spatio-temporal exudative bursts from proteoid roots) are known to increase in P-starved plants [26]. This property is of importance for nutrient acquisition as well as for plant– microbe interactions, both pathogenic and symbiotic, and may be viewed as third adaptation related to how plants themselves are able to increase nutrient acquisition, the others being nodulation and mycorrhiza. These properties could be exploited further by plant breeding. In addition, P deficiency has severe effects on uptake, transport and assimilation of N and C. Experimental evidence has indicated a restriction of NO 3 uptake [27,28].
This has been attributed to possible signal mechanisms i.e. via cycling of amino- (especially asparagine) or organic acids between shoots and roots regulating N uptake [29]. The implications of root-induced acidification with NH+ 4 nutrition for P-use efficiency have been studied less intensively, and did not result in higher P-uptake rates [25]. The partitioning of carbon into organic- and amino acid fractions are likely to be modified by P deficiency, as carboxylate synthesis is predicted to shift from anaplerotic primary metabolism to enhanced organic acid (mainly malate and citrate) and/or H+ excretion [30]. In spite of low input of K and P in some of the treatments, no reductions in yield were observed, which was probably due to the high availability of potassium and phosphorus in the soils of the two experimental sites caused by previous cultivation. Compared with woody solid biofuels, whole crop cereals as well as grain and straw fractions are characterized by higher concentrations of ash, N, K, S and Cl [31]. Straw generally has a higher content of ash, Cl and Na than grains, whereas grains contain more N and S. This information is essential if straw and grain are used separately for combustion. The mineral content of the grain fraction altered only little between years and locations. By contrast, large
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variations in the mineral content of the straw fraction between years and locations were observed. Variation of the K and Cl content in straw and in total biomass was influenced more strongly by precipitation before harvest than by fertilizer (Fig. 1, Tables 4 and 7). The highest content of K and Cl in straw was observed when the precipitation was close to zero 3 weeks before harvest at both locations. In addition, the lowest K and Cl content in the straw fraction and in the total biomass was found to correlate with precipitation levels of about 25 mm within the last 10 days before harvest (Fig. 1, Tables 4 and 7). Our results support the conclusion by Sander [2] and Allica et al. [32] that application of Cl-free fertilizer to the crops by use of K2SO4 instead of KCl improves the fuel quality without negatively influencing yield. In conclusion, this study shows that the dry matter yield of wheat, rye and triticale was high and stable at the two locations over the 3-year period of investigation. Here, triticale (Alamo) and rye (Marder and Motto) showed the highest yield (14.1–15.9 t ha1) compared to wheat (11.6–14.2 t ha1). This occurred in spite of a lower input of N fertilizer. Thus, this constant high yield of rye and triticale would be an advantage for the use of biomass for energy purposes. The concentration of elements relevant for combustion can vary significantly between years. In years where the cereals are ripened and senescence has coursed the straw to dry up, precipitation removed substantial amounts of K, Cl and S. This must be taken into considerations when the harvest of cereals for energy purposes is planned, as the crops are harvested relatively late to increase the chances for precipitation to remove K, Cl and S. The use of K fertilizers containing Cl and S resulted in a significantly increased concentration of these elements in the straw. In our experiments, triticale followed by rye had the best yield and quality demands of cereals grown for energy use. Acknowledgements The study was financed by the Danish Research Secretariat, Ministry of Agriculture and Fisheries. The authors thank the staff at Rønhave and Roskilde Research Stations for their help. References [1] Nonhebel S. Energy yields in intensive and extensive biomass production systems. Biomass and Bioenergy 2002;22:159–67. [2] Sander B. Properties of Danish biofuels and the requirements for power production. Biomass and Bioenergy 1997;12:177–83. [3] Becher S. Biogene Festbrennstoffe als Substitut fu¨r fossile Brennstoffe-Energie- und Emissionsbilanzen. IER Forschungsbericht 50, Stuttgart, 1998. [4] Obernberger I, Bidermann F, Widmann W, Riedl R. Concentrations of inorganic elements in biomass fuels and recovery in the different ash fractions. Biomass and Bioenergy 1997;12:211–24. [5] Jenkins BM, Bakker RR, Wei JB. On the properties of washed straw. Biomass and Bioenergy 1996;10:177–200.
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