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1、Research on Sweet sorghum Biomass and partitioningBIN ZHANG1, 2, J. SPIR2, 3, LI PU HAN2,4, ZU XIN LIU1, 2 AND GANG HUI XIE1, 2*College of Agronomy and BiotechnologyChina Agricultural University, Beijing-100 193 P. R. China*(e-mail : hlk12)(Received : October 2012)ABSTRACTSweet sorghum turned out to
2、 be a crop that is well-adapted to the prevailing conditions in north -west China if water availability is secured. Hybrid cultivars ZS 1 and CT 2 were the most promising sweet sorghum cultivars for multi-purpose biomass production, because of the high AGDB varying between 25.1 and 29.0 t/ha and a g
3、rain yield centering around 11.2 t/ha. Inbred cultivar Rio was the best performer in stem dry biomass, a potential feedstock for biofuel. In conclusion, biomass and grain yields of hybrid cultivars of sweet sorghum turned out to be higher than those of inbred cultivars.Nitrogen supply affected plant
4、 height, stem dry biomass, leaf dry biomass and AGDB significantly, but not grain yield. In addition, regardless of cultivars, nitrogen fertilizers improved the stem proportion, but decreased the grain proportion thus lowering the harvest index. Further in-depth studies on nitrogen responses at vari
5、ous levels of water supply are needed.Key words : Crop growth rate, energy crop, genotypes, grain yield, nitrogen fertilizer, Sorghum bicolor (L.) MoenchINTRODUCTION1College of Agronomy and Biotechnology, China Agricultural University, Beijing-100 193, P. R. China. 2National Energy R & D Center for
6、Biomass, China Agricultural University, Beijing -100 193, P. R. China. 3Center for Crop System Analysis, Plant Sciences Group, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.4Center for Agricultural Research, Institute of Genetics and Developmental Biology,Chinese A
7、cademy of Science, Shijiazhuang-, China.Sweet sorghum is considered as one of the potential energy crops throughout the world, for its wide range of adaptability (Gnansounou et al., 2005; Kangama and Rumei, 2005; Calvino and Messing, 2012), including its tolerance to drought and salinity (Tsuchihash
8、i and Goto, 2004; Rajagopal, 2008; Wortmann et al., 2010), and a remarkable yield potential even in marginal environments (Cosentino, 1996; Foti et al., 1996; Steduto et al., 1997; Amaducci et al., 2004). In China, the current agricultural policy encourages to develop sweet sorghum production on mar
9、ginal agricultural land in order to grow energy crops without competition in land use for food crops. Sweet sorghum not only produces grain which may be used for food or feed, but also abundant sugars present in its stalks have potential for a wide range of applications (Gao et al., 2010). The devel
10、opment of sweet sorghum production in arid regions and on other marginal land based on technological, economic and ecological advanced knowledge may improve sustainable agricultural land use. Furthermore, a bio-based economy may enhance socio-economic development, because it may maintain farmers inc
11、omes and social sustainability (Parikka, 2004; Xiong et al., 2008). In the north-western region of China with a special topography and large areas of arid land, low fertility sandy land and low-lying saline-alkaline land, growing sweet sorghum is considered as an option for sustainable agricultural
12、development. However, little is known about the performance of hybrid and inbred cultivars of sweet sorghum in terms of biomass, grain yield and dry matter partitioning under the climatic conditions of north-west China.Water availability and productivity will be most decisive for the long-term produ
13、ction potential of crops (Wang et al., 2009). Vadez et al. (2011) studied a wide collection of sorghum genotypes. They found that yield was closely related to harvest index (HI) and transpiration efficiency (TE). Yield differences under terminal drought were also affected by water extraction during
14、grain filling. Nitrogen fertilization is another important agronomic practice for achieving optimal crop production. However, there is little information demonstrating the effects of nitrogen fertilization on the aboveground dry biomass (AGDB) production of sweet sorghum under marginal conditions. I
15、t has been reported that sweet sorghum biomass yield increased with an application of fertilizer (N/ha) in India (Miri and Rana, 2012) and Turkey (Turgut et al., 2005) and tended to increase in the south-eastern of the USA (Erickson et al., 2011). However, Wortmann et al. (2010) found no effect of n
16、itrogen at rates varying from 0 to 80 kg N/ ha on sweet sorghum biomass in six out of seven sites and years under the dryland conditions of Nebraska. Cosentino et al. (2012) reported that nitrogen supply did not affect total dry matter yield in Italy. However, not much information is available regar
17、ding nitrogen response of sweet sorghum under the growing conditions of north-west China.In this study, we focused on the performance of hybrid and inbred cultivars under irrigated conditions at two nitrogen levels in the arid environment of Urumchi in north-west China. We conducted a field experime
18、nt with four cultivars of sweet sorghum at two nitrogen levels (control and 150 kg N/ha). The objectives of this study were : (1) to assess attainable biomass, grain yield and dry matter partitioning of hybrids and inbreds when water is not a limiting factor; (2) to analyze differences between culti
19、vars in crop growth rates during successive growth stages; and (3) to evaluate the response of hybrid and inbred cultivars of sweet sorghum to nitrogen.MATERIALS AND METHODSStudy SiteThe field study was conducted in 2009 at the Sanping Experimental Station (4301N, 8837E) of Xinjiang Agricultural Uni
20、versity in Urumchi, north-west of China. The region belongs to a temperate continental arid type climate with a short spring and autumn, long winter and summer. The effective growth period for sorghum crops is from May to September, when minimum temperatures are not limiting crop growth. The multi-a
21、nnual daylight duration is 2835 h and the mean air temperature is 8.0C. Annual precipitation was 300 mm in 2009 with about 70 mm monthly rainfall in April and May (Fig. 1). The data on sunshine hours and temperatures were collected from a weather station adjacent to the experimental field and are pr
22、esented in Table 1. No data were available for solar radiation. The soil was sampled at a profile depth of 20 cm before planting. The soil type was loam (sand, silt and clay accounted for 27.7, 47.4 and 24.9%, respectively) with a pH 7.56, organic matter 15.3 g/kg, total nitrogen 0.84 g/kg, availabl
23、e P 10.9 mg/kg and available K 249 mg/kg.Precipitation (mm)Fig. 1. Monthly precipitation in 2009 at Urumchi, north-west China.Experimental Design and Crop CultivationSweet sorghum hybrid cultivars were : Zaoshu-1 (ZS 1) and Chuntian-2 (CT 2), and the inbred cultivars : Rio and Lvneng-3 (LN 3). The p
24、erformance of the cultivars was tested at two fertilizer nitrogen levels : control (N0) and 150 kg N/ha (N150) in a completely randomized block design with four replications. The field was ploughed before winter and harrowed immediately after the first irrigation. Plastic film cover was used before
25、sowing to increase soil temperature, to reduce evaporation and to restrain weeds.Table 1. Monthly maximum, minimum and mean air temperature (C), and sunshine hours (h) at Urumchi, north-west ChinaMonthMaximum airMinimum airMean airSunshinetemperaturetemperaturetemperaturehours(C)(C)(C)(h)Jan.-5.3-13
26、.1-9.9129Feb.-4.5-11.7-8.896Mar.7.4-1.22.5264Apr.18.98.613.0288May22.311.116.1307Jun.26.915.820.8336Jul.29.818.723.7329Aug.29.318.022.9333Sep.22.812.116.8291Oct.16.36.810.9255Nov.1.4-4.9-2.3115Dec.-5.0-14.1-10.0101The plot size was 8 3.5 m2. Sweet sorghum was sown at a grid of 0.70 0.25 m2 oriented
27、in a north-south direction on May 4 in 2009. Nitrogen was applied as urea in a split-dressing with 60% (90 kg/ha) before sowing, and the remaining 40% (60 kg/ha) at the elongation stage. The application of P and K was 60 kg P2O5/ha as calcium superphosphate and 30 kg K2O/ha as potassium sulfate; tho
28、se were applied before sowing and an additional 30 kg K2O/ha at the elongation stage. Standard culture practices were the same in all plots. Sweet sorghum was over planted and thinned to one plant in each hole. Irrigation was applied to each plot until saturated soil water content was reached. The t
29、otal amount of irrigation was 505 mm. Total water input (rainfall and irrigation) during the growing season amounted to about 750 mm.Sampling and MeasurementsThe dates of some sweet sorghum phenological characteristics (Vanderlip and Reeves, 1972) such as emergence, heading and grain physiological m
30、aturity, were recorded at 50% values. Ten consecutive aboveground sweet sorghum plants in the central row were tagged and cut from each plot at different stages for each cultivar. At heading and maturity, each plant was separated into leaves and stems, and at grain maturity, each plant was separated
31、 into leaves, stems, panicle and roots for assessing dry matter partitioning. Sub-samples were oven-dried in an electric oven at 75C for 72 h. The grains were threshed and the panicle axis and rachis branches were cut and mixed with stem pieces proportionately based on dry weights. At physiological
32、maturity, plant height, stem diameter and lodging rates were recorded.Calculation and Statistical AnalysisHarvest indices of each tissue for four sweet sorghum cultivars were calculated as the ratio of each organ dry biomass to above ground dry biomass. Crop growth rate (CGR) was calculated as per s
33、tandard procedure (Watson, 1967) and expressed as g/m2/day.Means and standard deviations were calculated for the four replicates from each treatment. Analysis of variance (ANOVA) was conducted using the general linear model (GLM) to identify differences in the main factors (cultivar choice and nitro
34、gen level) and their interaction by applying SAS 9.2. Least significant difference multiple range test at P0.05 level and T-test were used to identify statistical significances among the parameters.RESULTS AND DISCUSSIONPhenology and Growth DurationTable 2. Effects of cultivar and N treatments on pl
35、ant height, stem diameter and lodging rate (meanstandard deviation) at maturity of sweet sorghum grown in 2009 at Urumchi, north-west ChinaCultivar andPlant heightStem diameterLodging ratenitrogen(cm)(cm)(%)N0N150MeanN0N150MeanN0N150MeanZS 1 (hybrid)2526.22608.32567.9c2.30.22.30.12.30.2a0.30.30.3bCT
36、 2 (hybrid)22812.823713.323212.9d2.40.12.40.12.40.1a2.22.72.4bRio (inbred)31921.233621.132821.5a1.90.12.00.12.00.1b8.67.88.2aLN 3 (inbred)27716.631517.429625.8b2.00.12.20.12.10.1b1.70.91.3bMeans27038.528944.727942.12.20.22.20.22.20.23.22.93.1ANOVAPPPCultivars0.00010.00010.0001Nitrogen0.00520.21760.4
37、031Interaction0.15340.79640.4453Different letters within each treatment factor (cultivar or nitrogen) indicate least significant differences at P0.05 after subjecting data to analysis of variance (ANOVA).Growth cycle duration from sowing to physiological maturity was significantly longer for inbred
38、cultivar Rio (138 days) than for LN 3 (125 days), while the hybrid cultivars showed an intermediate duration of about 130 days (Fig. 2). The longer duration of the growth cycle of Rio was brought about by a longer period from elongation to heading. Differences in growth duration between cultivars we
39、re closely associated with differences in heading dates. It was also visually observed that the inbred cultivars showed earlier leaf senescence than the hybrids.Fig 2. Main duration of successive phenological phases (d) for cultivars Zaoshu-1 (ZS1), Chuntian-2 (CT2), Rio, and Lvneng-3 (LN3) of sweet
40、 sorghum grown in 2009 at Urumchi, Northwest China.Morphological and Physiological CharacteristicsThere was no significant interaction between cultivar and nitrogen treatments for any of the morphological parameters reported in Table 2; therefore, the main effects are discussed separately.Plant heig
41、ht, stem diameter and lodging rate of four sweet sorghum cultivars at physiological maturity are presented in Table Plant heights of inbred cultivars were higher than those of hybrid cultivars (P0.05), but reversely stem diameters of hybrids were thicker. No statistical significant difference in ste
42、m diameter was found between the two hybrids.Plant height of the inbred cultivar Rio (328 cm) was the tallest, followed by inbred cultivar LN 3 (297 cm), hybrid cultivars ZS 1 (257 cm) and CT 2 (233 cm). Cultivar Rio had significantly (P0.05) the highest lodging rate (8.2%), but no significant diffe
43、rences in lodging rate were observed among the other cultivars. At physiological maturity, plant height was significantly (P0.001) higher with a fertilizer N rate of 150 kg/ha for all cultivars, especially for the inbred cultivars Rio and LN 3. The plant height increased from 319 and 277 to 336 and
44、315 cm for Rio and LN 3, respectively. However, no significant effects of nitrogen on stem diameter and lodging rate were observed (Table 2). Biomass AccumulationCultivar choice and nitrogen fertilizer significantly (P0.001) affected aboveground biomass (AGDB) at the intermediate sampling stages and
45、 at maturity. No significant interactions between cultivar and nitrogen were observed. Mean aboveground dry biomass showed a progressive increase from 1.4 t/ha at elongation to 13.0 t/ha at heading, and reached a maximum of 25.8 t/ha at physiological maturity (Table 3). At the elongation stage, the
46、highest AGDB was shown by hybrid ZS 1 (1.6 t/ha) and the lowest was obtained by inbred Rio (1.2 t/ha). At heading stage, Rio showed statistically a higher AGDB (15.7 t/ha) than the other three cultivars, with no significant differences among the other three cultivars. Hybrid cultivars showed a signi
47、ficantly (P0.05) higher AGDB than inbred cultivars at physiological maturity. The highest AGDB was observed with the hybrid ZS 1 (27.7 t/ha), followed by hybrid CT 2 (26.7 t/ha); lower values of AGDB were observed in the inbred cultivars Rio (25.4 t/ha) and LN 3 (23.2 t/ha). Differences in AGDB were significant between the inbred cultivars, but not in hybrids.Table 3. The effect of cultivar and N treatments on aboveground dry biomass (t/ha) (meanstandard deviation) at three growth stageselongation, headin