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1.
海河低平原区杨农复合模式内作物生产力与生态因子的关系 总被引：1，自引：0，他引：1
定位监测河北省衡水地区不同种植格局的杨农复合模式(杨树林龄为6～7年)内土壤含水量、PAR(光合有效辐射)和温度的变化,分析该地区杨农复合模式内作物生产力与生态因子的关系。研究表明,杨农复合模式的PAR较粮单作模式降低了32.43%～76.71%,土壤含水量降低了18.67%～42.75%,不同杨农复合模式的PAR和土壤水分间也存在显著差异(P0.05);复合系统的黑麦草生物量与PAR的相关性最大,饲用大豆生物量与PAR和0～40cm土壤体积含水量间的相关性都较大,相关系数均超过0.7500(P0.05)。提高杨农复合模式的PAR和土壤含水量均可有效提高作物生物量,鉴于该地区水资源缺乏,通过间伐或修枝等措施提高复合模式内的PAR是提高作物生物量的可行措施。 相似文献
2.
In the year 1979, 1981 and 1982 two-factorial experiments with the factors genotypes and crop densities were conducted, connected with the following agrometeorological analyses:
a) outside the canopies: determination of air temperature, air humidity, wind velocity, precipitation, global radiation and photosynthetically active radiation (PAR)
b) in the interior of the canopies: measurements of air temperature at cobheight, of precipitation components, of the penetration of PAR and of the leaf area index.
The following results were obtained:
a) Influence of high crop densities
1. In high crop densities the greatest part of radiation was absorbed, so that at 30 plants/m2 57% and at 70 plants/m2 only 28% of the PAR reached cob height.
2. As a consequence of temperature and decrease of radiation the contents in the leaves of biological energy, of water soluble K.H. and rough protein were reduced.
b) Influence of the leaf posture
3. For genotypes with erected leaf posture the leaf temperatures increased by 0.3°C, on the ground even by 1.2°C above the values of the stand with horizontal leaf posture.
4. Higher air temperatures were measured in the stands with erected leaf posture than in those with a horizontal one.
5. In the cool year 1981 on days with temperatures above 27°C outside the stands, those temperatures were exceeded during 7 hours in canopies with erected leaf posture at a higher plant density (30 plants/m2 ) and only during 2 hours in canopies with a horizontal leaf posture. 相似文献
a) outside the canopies: determination of air temperature, air humidity, wind velocity, precipitation, global radiation and photosynthetically active radiation (PAR)
b) in the interior of the canopies: measurements of air temperature at cobheight, of precipitation components, of the penetration of PAR and of the leaf area index.
The following results were obtained:
a) Influence of high crop densities
1. In high crop densities the greatest part of radiation was absorbed, so that at 30 plants/m
2. As a consequence of temperature and decrease of radiation the contents in the leaves of biological energy, of water soluble K.H. and rough protein were reduced.
b) Influence of the leaf posture
3. For genotypes with erected leaf posture the leaf temperatures increased by 0.3°C, on the ground even by 1.2°C above the values of the stand with horizontal leaf posture.
4. Higher air temperatures were measured in the stands with erected leaf posture than in those with a horizontal one.
5. In the cool year 1981 on days with temperatures above 27°C outside the stands, those temperatures were exceeded during 7 hours in canopies with erected leaf posture at a higher plant density (30 plants/m
3.
The response of crop growth and yield to CO2 and ozone is known to depend on climatic conditions and is difficult to quantify due to the complexity of the processes involved. Two modified mechanistic crop simulation models (AFRCWHEAT2-O3 and LINTULCC), which differ in the levels of mechanistic detail, were used to simulate the effects of CO2 (ambient, ambient ×2) and ozone (ambient, ambient ×1.5) on growth and developmental processes of spring wheat in response to climatic conditions. Simulations were analysed using data from the ESPACE-wheat project in which spring wheat cv. Minaret was grown in open-top chambers at nine sites throughout Europe and for up to 3 years at each site.
Both models closely predicted phenological development and the average measured biomass at maturity. However, intermediate growth variables such as biomass and leaf area index (LAI) at anthesis, seasonal accumulated photosynthetically active radiation intercepted by the crop (ΣIPAR), the average seasonal light use efficiency (LUE) and the light saturated rate of flag leaf photosynthesis (Asat) were predicted differently and less accurately by the two models. The effect of CO2 on the final biomass was underestimated by AFRCWHEAT2-O3 due to its poor simulation of the effect of CO2 on tillering, and LAI.LINTULCC overestimated the response of biomass production to changes in CO2 level due to an overprediction of the effect of CO2 on LUE. The measured effect of ozone exposure on final biomass was predicted closely by the two models. The models also simulated the observed interactive effect of CO2 and ozone on biomass production. However, the effects of ozone on LAI, ΣIPAR and Asat were simulated differently by the models and less accurately with LINTULCC for the ozone effects on LAI and ΣIPAR. Predictions of the variation between sites and years of growth and development parameters and of their responses to CO2 and ozone were poor for both AFRCWHEAT2-O3 and LINTULCC. It was concluded that other factors than those considered in the models such as chamber design and soil properties may have affected the growth and development of cv. Minaret. An analysis of the relationships between growth parameters calculated from the simulations supported this conclusion. In order to apply models for global change impact assessment studies, the difficulties in simulating biomass production in response to CO2 need to be considered. We suggest that the simulation of leaf area dynamics deserves particular attention in this regard. 相似文献
4.
5.
Light interception and radiation use efficiency in temperate quinoa (Chenopodium quinoa Willd.) cultivars 总被引：1，自引：0，他引：1
Sea level quinoas are grown at low altitudes in Central and Southern Chile. Both sensitivity to photoperiod and response to temperature largely determine quinoa adaptation, but crop biomass production must be quantified to evaluate agronomic performance. The objectives of this work are: (i) to characterize development effects on leaf area evolution for genotypes of sea level quinoa differing in cycle length, (ii) to quantify the extinction coefficient (k) for photosynthetically active radiation (PAR) and radiation use efficiency (RUE) from emergence up to the beginning of grain filling and (iii) to identify which crop attributes related to canopy architecture should be considered to improve biomass production. Four cultivars (NL-6, RU-5, CO-407 and Faro) were cropped in Pergamino (33°56′S, 60°35′W, 65 m a.s.l.), Argentina, at three densities (from 22 to 66 plants m−2) in two consecutive years under field conditions with adequate water and nutrient supply. Thermal time to first anthesis and maximum leaf number on the main stem were linearly correlated (r2 = 0.87; p < 0.0001). Leaf area continued to increase during the flowering phase, notably in NL-6, the earliest genotype. There were significant differences in maximum plant leaf area between cultivars. Increasing density reduced plant leaf area but effects were comparatively small. Estimated k was 0.59 ± 0.02 across genotypes and was higher (p < 0.05) for 66 plants m−2. Values for RUE changed as cumulative intercepted PAR (IPAR) increased; at initial stages of development RUE was 1.25 ± 0.09 g MJ IPAR−1, but if cumulative IPAR was higher than 107.5 ± 10.4 MJ IPAR m−2, RUE was 2.68 ± 0.15 g MJ IPAR−1. That change occurred when leaf area index (LAI) and fraction of PAR intercepted were still low and ranged from 0.61 to 1.38 and from 0.33 to 0.51, respectively. No significant association was found with any developmental stage. Our results agreed to the notion that RUE variation during pre-anthesis phases is largely determined by LAI through its effect on radiation distribution within the canopy. Biomass production could be improved if periods of interception below 50% of incoming PAR were reduced to ensure high RUE. This seems to be possible in temperate areas both by the use of late genotypes with a higher number of leaves on the main stem and by early genotypes provided adequate plant density is chosen. Early increment in LAI and overlapping of the leaf area increase period with the flowering phase are desirable strategies for earliest genotypes to maximize yield. 相似文献
6.
M.E. Shibu P.A. Leffelaar H. van Keulen P.K. Aggarwal 《European Journal of Agronomy》2010,32(4):255-271
LINTUL3 is a crop model that calculates biomass production based on intercepted photosynthetically active radiation (PAR) and light use efficiency (LUE). It is an adapted version of LINTUL2 (that simulates potential and water-limited crop growth), including nitrogen limitation. Nitrogen stress in the model is defined through the nitrogen nutrition index (NNI): the ratio of actual nitrogen concentration and critical nitrogen concentration in the plant. The effect of nitrogen stress on crop growth is tested in the model either through a reduction in LUE or leaf area (LA) or a combination of these two and further evaluated with independent datasets. However, water limitation is not considered in the present study as the crop is paddy rice. This paper describes the model for the case of rice, test the hypotheses of N stress on crop growth and details of model calibration and testing using independent data sets of nitrogen treatments (with fertilizer rates of 0–400 kg N ha?1) under varying environmental conditions in Asia. Results of calibration and testing are compared graphically, through Root Mean Square Deviation (RMSD), and by Average Absolute Deviation (AAD). Overall average absolute deviation values for calibration and testing of total aboveground biomass show less than 26% mean deviation from the observations though the values for individual experiments show a higher deviation up to 41%. In general, the model responded well to nitrogen stress in all the treatments without fertilizer application as observed, but between fertilized treatments the response was varying. 相似文献
7.
J. N. Gupta 《Journal of Agronomy and Crop Science》1987,159(5):293-298
Ecophysiological balance among four available prominent grassland communities (dominated with 1. Heteropogon contortus, 2. Eremopogon foveolatus , 3. Sporobolus diander , 4. Themeda quadrivalvis besides the prominency of Desmostachya bipinnata in all the communities) were studied by analysing their biomass structure, production and rate of litter decomposition of component taxa. These communities have different pattern of management and utilization aspect. Jhansi is geographically situated at 78°35' E long, and 25°27' N lat. about 275 MSL; and its climate is of tropical monsoonic. The soil at all the sites were sandy and sand percentage ranges between 59–80%. The thorough analysis reveal that in tropical monsoonic climatic situation the biomass production reached at potential level in wet situation (July-September with moderate temperature 32°C) which gradually drops and thus reached poor biomass production under cold dry situation during February. The rhythmic situation for the presence of potential aboveground production m−2 was recorded in the month of April in site IV and May in site I. Apparently poor aboveground production in the month of January in site II and December in site III was due to dormant situation of the species during this period. Similar observations recorded with litter availability. It is significant to narrate that litter decomposition rate reached from 82–99% indicating its pattern of utilization as an automatic system of green manuring. 相似文献
8.
不同密度下棉花群体光辐射空间分布及生物量和纤维品质的变化 总被引：8，自引：1，他引：7
【目的】研究不同密度群体棉花生育期、光合有效辐射(PAR)分布、叶面积指数(LAI)和干物质累积特征值的差异。【方法】供试品种为转Bt(Bacillus thuringiensis)基因杂交种中棉所75(CCRI 75)和常规品种鲁棉研28(SCRC 28),2012和2013年密度处理为1.5万、5.1万和8.7万株·hm~(-2)。【结果】不同密度群体在棉花不同生育期PAR存在显著差异,且冠层光透射率随密度增加而减少,不同种植密度的棉花群体冠层株型结构各不相同,不同群体棉花茎叶的空间分布决定PAR的分布;LAI随生育进程呈现出开口向下的抛物线,不同的密度群体LAI均在播种后60 d左右开始快速增加,100 d或110 d后LAI开始急速下降;随密度增加最大生物量累计值减少,且营养器官占单株总干物质的比例增加,而生殖器官所占比例下降;密度显著影响马克隆值大小,高密度下马克隆值最大。【结论】本研究为棉花田间管理、合理密植提供理论依据。 相似文献
9.
棉花冠层光合有效辐射空间分布插值方法 总被引：3，自引：2，他引：1
获取冠层光合有效辐射PAR(Photosynthetically active radiation)信息对于作物估产、长势监测以及优化种植有重要意义。运用地统计学空间网格法原理测定了鲁棉研28号的棉花冠层PAR值,综合应用等值线图、残差和交叉验证比较分析了12种插值方法,发现克里金插值法最优;进一步利用克里金插值法分析了冀958、中棉所60、零式果枝品系L0三个品种PAR透射光的空间分布特征,等值线图显示PAR透射光空间分布与株型对光的影响一致,即验证了克里金插值法为模拟研究棉花冠层PAR值的最佳方法。 相似文献
10.
兴安落叶松人工林生物量和生产力的探讨 总被引：1，自引：0，他引：1
本文对内蒙呼盟地区海拔88—1200m的兴安落叶松(Larix gmelini [Rupr.]Rupr.)27年生人工人林分生物量和生产力进行测定的研究.由于人工林的林分单一,下木和草木植物相对数量低于1%,所以根据调查资料,只建立了估测兴安落叶松各器官生物量的回归方程,方程的相关系数和估测的精度均较高,具有理论和实践方面的价值.结果表明:兴安落叶松林总生物量约在121.36吨/公顷,净生产力为4.495吨/公顷.年左右. 相似文献
11.
基于吸收光合有效辐射和光合有效辐射截获量监测棉花生长状况 总被引：2，自引：0，他引：2
通过光量子传感器,获取了2个棉花品种不同种植密度冠层6个关键生育时期的光合有效辐射（PAR）,分析了吸收光合有效辐射（APAR）和光合有效辐射截获量（FAPAR）与棉花冠层生长特征的关系。结果表明;棉花开花期和花铃期,为APAR与FAPAR高值期,盛铃期和盛铃末期下降,吐絮期为低值期;利用多元统计分析技术,分别建立了棉花APAR、FAPAR与棉花冠层叶面积指数、覆盖度、地上鲜生物量和地上净初级生产力的相关关系模型。采用APAR与覆盖度,FAPAR与叶面积指数相关性最高的模型方程,分别估算棉花覆盖度和叶面积指数,实测值与估测值之间呈极显著的线性相关关系,估算精度分别为99.1%和99.5%。 相似文献
12.
本研究旨在探讨冬小麦–夏玉米周年生产条件下黄淮海区夏玉米的适宜熟期与积温需求特性。选用郑单958(ZD958)、先玉335(XY335)、登海605(DH605)、登海618(DH618)和登海661(DH661),设置5月21日、5月31日、6月10日和6月20日4个播期,研究表明,播期对夏玉米生理成熟所需积温无显著影响,各品种生理成熟所需要的积温主要取决于品种自身的特性,DH618、XY335、ZD958、DH605、DH661的生育期和生理成熟所需要积温分别为110、112、116、116、121 d和2800、2880、2945、2950、3025°C d。冬小麦-夏玉米周年生产条件下,夏玉米最大可能的生长期约107~112 d(自6月15日至10月1~5日),积温约2800°C d,难以满足现有品种的生产需要。夏玉米直播晚收、冬小麦适期晚播有利于周年产量提高,但目前广泛推广的夏玉米品种生育期过长(约120 d),适时晚收仍难以完全生理成熟,机收籽粒损伤严重。可见,冬小麦–夏玉米周年生产条件下夏玉米最大可能的生长期和有效积温不能满足目前广泛推广的夏玉米品种所需生育持续期和积温,且适时晚收仍难以完全生理成熟,黄淮海区亟需生育期适宜(生育期≤107 d)的高产夏玉米新品种。 相似文献
13.
随着农业的发展,越南秸秆资源总量不断增加。但秸秆资源综合利用程度较低,产业化发展滞后,秸秆焚烧而引发的环境问题日益突出。近年来,高温热裂解生物质炭化与生物质农业应用成为秸秆资源化的新方向。笔者以越南广宁省为研究对象,通过随机走访农村并发放调查问卷,采集农业废弃物利用信息,特别是资源化利用中存在的实际问题,进而采用成本效益分析方法估算农户规模水稻秸秆生产生物质炭的经济效益。结果表明:农户秸秆炭化收益最高可达1275元/(hm2·a),生物质炭的碳交易收益可达117元/(hm2·a)。笔者还分析了农业废弃物制成生物质炭对环境和社会的效益,以期为越南乃至东盟国家秸秆炭化的资源化利用提供科学依据与生物质炭产业发展的参考。 相似文献
14.
W. Aufhammer W. Wägner H.-P. Kaul E. Kübler 《Journal of Agronomy and Crop Science》2000,184(4):277-286
Radiation use by oil seed crops — a comparison of winter rape, linseed and sunflower For the production of grain crops rich in oil, winter rape, linseed and sunflower are similarly suitable at many arable locations. We wanted to compare the extent to which radiation (PAR) is intercepted and utilized by the individual species for dry matter and yield production. For this purpose, a 2‐year field experiment comprising the factors genotype, N fertilization and soil tillage was conducted. For five phases of crop development, growth rates (CGR, RGR and NAR) and PAR utilization were calculated. At full ripeness, total dry matter, grain, oil and energy yields, the crop‐ and year‐specific PAR supply, its interception and utilization for dry matter production and the resulting energy binding were determined. Due to the different individual vegetation periods, the PAR supply of the crops differed. The crop assimilation areas also differed, with values for winter rape and sunflower higher than those for linseed. The yield productivity of winter rape and sunflower was also higher than that of linseed. N fertilization increased yield to different extents for the different crops. On average, winter rape and sunflower produced the same amounts of dry matter and energy yield. Due to a higher harvest index, sunflower had the highest grain yield, and because the oil concentration in grain was comparatively high sunflower produced the highest oil yield, too. Under cool and wet climate conditions, however, the productivity of sunflower is offset by a relatively high yield risk because of uncertain ripening. The highest PAR utilization by linseed did not compensate for its very short vegetation period in combination with the lowest PAR interception. 相似文献
15.
Although experiments have previously been carried out to determine the optimum sowing time of sesame, very few attempts have been made to determine the effects of macro and micro climatic variation on yield. Thus a field experiment was conducted at the University Research Farm, Bidhan Chandra Krishi Viswavidyalaya, Kalyani, India on an Entisol (alluvial, sandy loam) in the summer seasons of 1996 and 1997 to assess the effects of macro and micro climatic variations on yield of sesame for various dates of sowing. The number of seeds per capsule of sesame was highest in the crop sown on 19 February, although up to the 18 April sowing there was no significant variation. There was no appreciable variation in thousand-seed weight with date of sowing. Crops sown on 19 February and 1 March produced statistically similar yields. The average reduction in yield of sesame was 78.5 and 213 %, respectively, for crops sown on 10 February and 28 April, compared with the crop sown on 19 February. The cultivar Rama produced higher yields than B-67 and Kanke-1. Ambient temperature above 30 °C up to 100 % flowering had a direct positive effect on sesame yield. Crop exposure to 60–70, 70–80 and 80 % relative humidity up to 100 % flowering had a direct negative effect. Temperature profile at 50 days after emergence (DAE), relative humidity at 60 DAE, and photosynthetically active radiation (PAR) at 30 and 40 DAE within the crop canopy had direct positive effects on yield. Regression models suggested that temperature profile and PAR within the crop canopy produced 72 and 35 % variation in yield, respectively. 相似文献
16.
紫花苜蓿光合生产与干物质积累模拟模型研究 总被引：8，自引：0，他引：8
依据紫花苜蓿生物学特性，通过田间试验和广泛收集资料，构建了紫花苜蓿光合生产与干物质积累模拟模型。该模型包括光合作用、呼吸作用、叶面积消长、干物质积累、同化物分配和产量形成等过程，考虑了温度对光合作用的影响。计算得到紫花苜蓿不同生育时期的干物质转换系数( β )和同化物分配分配系数[C(d)I]，确定了主要紫花苜蓿品种的光合参数(a 和Pmax)。分别利用北京和太原不同年份和不同品种的试验资料对地上部生物量、产量和叶面积指数模型进行了检验。结果表明，模型对叶面积动态、地上部生物量和产量模拟效果较好，叶面积指数、地上部生物量、茎和叶生物量的决定系数分别为0.98、0.95、0.96和0.88（n=20），产量均方差(RMSE)为103 kg hm-2，相对均方差(NRMSE)为2.1% (n=102)。模型不仅具有较强的机理性，而且有较好的拟合性。 相似文献
17.
F.J. Villalobos L. Testi J. Hidalgo M. Pastor F. Orgaz 《European Journal of Agronomy》2006,24(4):296-303
The wide variability and complexity of olive orchards makes it difficult to provide solutions to the numerous management questions using a pure experimental approach. In this paper we calibrate and validate a simple model of olive orchard productivity based on the Radiation-Use Efficiency (RUE) concept of Monteith. A calibration experiment was performed in Cordoba from 1998 to 2001 with drip-irrigated olive trees cv. ‘Arbequina’. Destructive samples of 18 trees and non-destructive measurements on 80 trees were used to determine RUE and dry matter partitioning coefficients. Validation experiments were performed in 18 drip-irrigated orchards of seven locations in Southern Spain, including two cultivars (‘Arbequina’ and ‘Picual’). Average RUE was 0.86 g dry matter (MJ PAR)−1 which is equivalent to 1.56 g glucose (MJ PAR)−1. Aboveground accumulated biomass was allocated equally to fruits and vegetative growth, which in turn was partitioned into 30% for leaves and 70% for stems, branches and trunk. The fraction of oil in fruits was 0.38 which implies that the average ratio oil yield/intercepted PAR, which is an equivalent RUE for oil production (o), is 0.17 g oil (MJ PAR)−1. The prediction of oil yield as the product of 0.17 and total intercepted PAR was tested successfully in the validation experiments (relative RMSE = 0.26). Errors of this simple model were partly due to alternate bearing and partly to a decrease in o as canopy size increases, which deserves further research. The concept of o may be also useful for the evaluation of alternate bearing in olive trees.
Estimated potential carbon sequestration by intensive irrigated olive orchards in Southern Spain was 7 t CO2 ha−1 year−1 which is much higher than that of other agricultural systems in Europe.
The simple model of growth and yield presented herein is the core of a complete model of olive growth and yield and may be useful not only for evaluating productivity at different scales but also for solving different management problems (nutrient requirements, plant protection, etc.) 相似文献
18.
Mung bean crops in the subhumid zones of Sri Lanka experience significant drought periods. The objective of this study was to quantify the growth response of mung bean to irrigation at different phenological stages and thereby determine the optimum irrigation regime to maximize growth. Four field experiments were conducted at two sites in 1995 and 1996. The crop duration of mung bean was divided into three stages: vegetative (from germination to appearance of first flower), flowering (from appearance of first flower to 75 % pod initiation) and pod-filling (from 75 % pod initiation to maturity). Eight treatments were devised to represent all possible combinations of irrigation at the three stages. Maximum leaf area index (ranging from 0.6 to 2.6 across treatments) and total leaf area duration were increased significantly by irrigation during the vegetative stage. Specific leaf weight decreased and maximum total crop biomass (150–400 g m−2 ) increased with the number of stages irrigated. Irrigation decreased the absolute root biomass and increased the shoot:root ratio. It is concluded that, in this agroclimatic zone of Sri Lanka, irrigation of mung bean during the vegetative stage is critical for maximizing leaf area. However, biomass production can be maximized by increasing the number of stages irrigated irrespective of irrigation at any specific stage. 相似文献
19.
Pearl millet ( Pennisetum glaucum L.R.Br.) hybrid MH 179 was grown under two moisture regimes viz., optimal moisture and rainfed conditions. The field experiment was continued for three consecutive rainy seasons to quantify the pearl millet development with thermal time. The possible influence of variation in natural sowing date on the relationships between crop development and thermal time have been described. At cardinal temperatures of 10°C (base temperature below which pearl millet development ceases), 33°C (optimal temperature for development) and 45°C (maximum temperature at and above which no development takes place), the crop required 1490–1794°Cd thermal time to reach physiological maturity. The thermal time requirement for different developmental stages was influenced by the sowing time and moisture availability during the growing season of the crop.
The leaf tip appearance on the main shoot of pearl millet in relation to thermal time was almost linear under both moisture conditions requiring about 44–50°Cd ± 2.6 °Cd leaf−1 , till the appearance of the flag (last) leaf. However, leaf tip appearance on primary tillers was slightly slower and required 53-58°Cd ± 4.7°Cd for each new leaf. Appearance of first primary tiller was later (at 320°Cd after emergence) under the rainfed condition as compared to the crop under the optimal moisture (at 250°Cd).Thereafter, the tiller appearance in relation to thermal time under both moisture conditions was at a linear rate of about 53-56°Cd ± 9.5°Cd tiller−1 .
Effect of microclimatic variations, canopy temperature, radiation and photoperiod on the phenology-thermal time relationships have been discussed under both the moisture conditions. 相似文献
The leaf tip appearance on the main shoot of pearl millet in relation to thermal time was almost linear under both moisture conditions requiring about 44–50°Cd ± 2.6 °Cd leaf
Effect of microclimatic variations, canopy temperature, radiation and photoperiod on the phenology-thermal time relationships have been discussed under both the moisture conditions. 相似文献
20.
In order to evaluate the possibility of reducing energy input in giant reed (Arundo donax L.) as a perennial biomass crop, a field experiment was carried out from 1996 to 2001 in central Italy. Crop yield response to fertilisation (200–80–200 kg ha−1 N–P–K), harvest time (autumn and winter) and plant density (20,000 and 40,000 plants per ha) was evaluated. The energy balance was assessed considering the energy costs of production inputs and the energy output obtained by the transformation of the final product. The crop yield increased by +50% from the establishment period to the 2nd year of growth when it achieved the highest dry matter yield. The mature crop displayed on average annual production rates of 3 kg dry matter m−2, with maximum values obtained in fertilised plot and during winter harvest time.
Fertilisation mainly enhanced dry matter yield in the initial period (+0.7 kg dry matter m−2 as years 1–6 mean value). The biomass water content was affected by harvest time, decreasing by about 10% from autumn to winter. With regard to plant density, higher dry matter yields were achieved with 20,000 plants per ha (+0.3 kg dry matter m−2 as years 1–6 mean value).
The total energy input decreased from fertilised (18 GJ ha−1) to not fertilised crops (4 GJ ha−1). The higher energetic input was represented by fertilisation which involved 14 GJ ha−1 (fertilisers plus their distribution) of total energy costs. This value represents 78% of total energy inputs for fertilised crops.
Giant reed biomass calorific mean value (i.e., the calorific value obtained from combustion of biomass sample in an adiabatic system) was about 17 MJ kg−1 dry matter and it was not affected by fertilisation, or by plant density or harvest time. Fertilisation enhanced crop biomass yield from 23 to 27 dry tonnes per ha (years 1–6 mean value). This 15% increase was possible with an energy consumption of 70% of the overall energy cost. Maximum energy yield output was 496 GJ ha−1, obtained with 20,000 plants per ha and fertilisation. From the establishment period to 2nd–6th year of growth the energy production efficiency (as ratio between energy output and energy input per ha) and the net energy yield (as difference between energy output and energy input per ha) increased due to the low crop dry biomass yield and the high energy costs for crop planting. The energy production efficiency and net energy yield were also affected by fertilisation and plant density. In the mature crop the energy efficiency was highest without fertilisation both with 20,000 (131 GJ ha−1) and 40,000 plants per ha (119 GJ ha−1). 相似文献