Chemical Composition and Energy Value of Maize Silage Made on Farms in England and Wales 1984-92

The chemical composition of 960 samples of maize silage, made on commercial farms in England and Wales between 1984-1992, is described. The average composition was 302 g/kg dry matter (d.m.), pH 3·78, ammonia-N 60 g/kg N, 87 g/kg d.m. crude protein (CP), 292 g/kg d.m. modified acid detergent fibre (MADF), 678 g/kg d.m. neutral-detergent cellulase digestible organic matter (NCDG) and 301 g/kg d.m. starch. The predicted mean metabolizable energy content was 10·5 MJ/kg d.m. There was significant year-to-year variation for each variable. Ammonia-N and ash contents were negatively correlated and starch and metabolizable energy content were positively correlated with silage d.m. content.The results indicated that in recent years maize silage has consistently been made with d.m. contents above 300 g/kg, which should produce little or no effluent, and will lead to high silage intakes by animals.     

不同水肥作用下西藏青稞生长动力学机制与模拟研究

【目的】构建西藏高原地区多因子作用下的青稞动态生长模型。【方法】于2016─2017年在西藏农牧学院农田水利试验场,监测了不同水分和氮素状态下的青稞动态生长过程,基于方差分析法研究了水分和氮素对青稞动态过程的交互作用,在此基础上构建了包括4个自由度、描述土壤水分和氮素对春青稞干物质形成以及累积过程函数关系,构建了多因子作用条件下的青稞动态关系模型,分别采用2016年和2017年的试验资料对模型进行了参数率定和验证。【结果】西藏高原地区青稞动态生长过程受到了多种因素的影响,青稞的干物质增量和累积量与土壤水分和氮素投入量表现出非线性响应关系;采用偏相关系数能够有效地反映青稞的产量与干物质指标关系。模拟不同水分和氮素条件下的青稞生长过程与实测结果相比,全生育内Nash-Sutcliffe系数平均值为0.873;5%的显著水平下,不存在系统性偏差。【结论】构建的青稞动态生长关系模型能够描述西藏地区气候和土壤条件对青稞生长动态过程影响机理,具有较高的模拟精度。     

Simulation of the effects of rumen function on the flow of nutrients from the stomach of sheep: Part 1—Description of a computer program

A computer program to simulate rumen function in sheep is described. It predicts the degradation of dietary components within the rumen, products of fermentation, microbial growth yields and the flow of protein and other materials from the rumen.Input information includes: feed intake; modulus of fineness of the diet, chemical composition of the diet in terms of β-hexose, α-hexose, soluble carbohydrates, true protein, non-protein nitrogen, total fatty acids, inorganic sulphur and ash; potential degradability of β-hexose and protein; factors indicating the fractional reduction in maximum rate of degradation of β-hexose, α-hexose and protein due to chemical and physical properties of the diet; and time spent feeding and ruminating. Inflow to the rumen of protein, non-protein nitrogen and inorganic sulphur in saliva is predicted, and the amount of each salivary and dietary substrate degraded in the rumen, flowing intact from the rumen or accumulating within the rumen is assessed. Adenosine triphosphate (ATP) released during fermentation is used for maintenance of the existing microbial mass. If ATP release is insufficient a portion of the microbial mass is catabolised, otherwise microbial growth can occur and some degraded substrates are incorporated directly into microbial protoplasm. Possible limits to microbial growth from an insufficiency of amino acids, ammonia, total nitrogen or inorganic sulphur are assessed, and the change in rumen microbial population is determined from the difference between growth and outflow of micro-organisms.Predictions from the program are shown to be stable and to respond appropriately to changes in intake and composition of the diet.     

不同水肥耦合条件下水稻干物质积累与分配特征

2009年5—9月在湖北省灌溉试验中心站以优质水稻新两优香4为材料,采用长期淹灌和间歇灌溉2种灌溉模式,结合3种施肥(氮及磷肥)水平F1、F2、F3,研究了不同水肥耦合条件下水稻产量形成过程和干物质积累与分配特征。结果表明,不同水肥处理下水稻各生育期干物质积累的动态变化相似,分蘖前期水稻干物质的积累量随施肥的增加而上升,到一定程度则会下降,不同灌溉模式间的差别不明显。从分蘖后期到抽穗开花期,不同水肥处理水稻干物质的积累总量均明显增大,且不同处理间差异显著,F1、F2、F3处理抽穗开花期间歇灌溉模式干物质积累量比淹灌模式分别大12.1%、22.1%、61.9%。间歇灌溉模式水稻干物质净积累量(NDMA)和群体生长速率(CGR)峰值随施肥量的增加发生改变,由出现在低肥水平(F1)的抽穗开花期至乳熟期转变为高肥水平(F2,F3)的分蘖后期至拔节孕穗期,且NDMA和CGR显著增大。不同水肥处理水稻黄熟期干物质在各器官间的分配不同,但均表现出相同趋势,即由高到低依次为籽粒、茎、叶、根。不同灌溉模式水稻的收获指数随施肥量的增加而下降,淹灌模式下收获指数下降明显,相对F1处理,F2、F3处理下分别下降12.4%、17.9%。干物质积累过程的拟合结果表明,三次曲线模型比Logistic模型的拟合精度高。     

Dynamics of plant and animal production of a subterranean clover pasture grazed by sheep: Part 1—Field measurements for model calibration

A grazing system with Merino sheep and subterranean clover pasture was studied in a 550 mm rainfall, mediterranean climate in Western Australia.Changes over twelve months in seed, the quantities of green and dry herbage, soil moisture, animal intake and liveweight, wool growth and body composition were measured. Six paddocks, representing two soil types, were grazed continuously at 8·75 sheep per hectare. The system was also simulated and the actual results were compared with those from the simulation model.From a seed pool in March of 300 kg ha^?1, 80% of which was soft and non-dormant, 4000 clover seedlings per square metre became established; subsequent drought reduced this to 1450 plants per square metre. From measurements of soil moisture it was shown that this population survived at available moisture levels as low as 0·5 mm in the main root zone in gravelly sandy loam. Pasture growth rate reached a spring peak of 102 kg ha^?1 day^?1 and total growth (estimated from pasture grazed for 26 weeks) was 6700 kg ha^?1 for 500 mm of rainfall between germination and maximum biomass. At maturity, burr and seed made up 57% of the plant residues on offer, with a seed pool of 1160 kg ha^?1. During the summer this biomass decreased at 5 kg ha^?1 day^?1 without grazing and 19 kg ha^?1 day^?1 under grazing.The liveweight losses and gains of the sheep were atypical, no liveweight gain until 1200 kg ha^?1 of gree herbage was available—about treble the expected amount. Measurements of food intake indicate a gross inefficiency in energy utilisation during the winter and a low intake of energy in the spring.Total green and dry plant residues showed general agreement between actual and simulated results for most of the growing season. However, the field data highlighted error in the pasture sub-model which were corrected and are reported elsewhere.     

Effect of small irrigation amounts on the yield of wheat

Yields of dryland crops are governed by the moisture in the soil profile at seeding and by rainfall during the growing season. Occasionally limited amounts of water may also be available for irrigation. Field experiments were conducted over a period of 4 years on loamy sand and 3 years on sandy loam to study the effects of pre-seeding, post-seeding and split application of limited amounts of water on root growth, water use, dry matter accumulation and grain yield of wheat. This article reports the treatment effects on dry matter accumulation and grain yield.Early season water stress decreased the rate of dry matter accumulation. Grain yield responded significantly to irrigation 30 days after seeding irrespective of the amount of water, year and soil type. Yield with post-seeding irrigation averaged 3518 kg ha^?1 against 2317 kg ha^?1 for unirrigated control in loamy sand and 4440 kg ha^?1 against 3391 kg ha^?1 in sandy loam. The increase in yield was manifested by a significant increase in the number of effective tillers per m row length, number of grains per ear and thousand grain weight.     

Development and evaluation of integrated water and nitrogen model for maize

Maize (Zea mays L.) is an important food crop for irrigated regions in the world. Its growth and production may be estimated by different crop models in which various relationships between growth and environmental parameters are used. For simulation of maize growth and grain yield, a simulation model was developed (Maize Simulation Model, MSM). Dynamic flow of water, nitrogen (N) movement, and heat flow through the soil were simulated in unsteady state conditions by numerical analysis in soil depth of 0–1.8 m. Hourly potential evapotranspiration [ET_p(t)] for maize field was estimated directly by Penman–Monteith method. Hourly potential evaporation [E_p(t)] was estimated based on ET_p(t) and canopy shadow projection. Actual evaporation of soil surface was estimated based on its potential value, relative humidity of air, water pressure head and temperature at soil surface layer. Actual transpiration (T_a(t)) was estimated based on soil water content and root distribution at each soil layer. Hourly N uptake by plant was simulated by N mass flow and diffusion processes. Hourly top dry matter production (HDMA^j + 1, where j is number of hours after planting) was estimated by hourly corrected intercepted radiation (RSLT^j + 1) by plant leaves [determined from leaf area index (LAI^j + 1)] with air temperature, the maximum and minimum plant top N concentration and the amounts of nitrogen uptake. The value of LAI^j + 1 at each hour was estimated by the accumulated top dry matter production at previous hour using an empirical equation. Maize grain yield was estimated by a relationship between harvest index and seasonal plant top dry matter production. The model was calibrated using data obtained under field conditions by a line source sprinkler irrigation. When the values of water and nitrogen application were optimum, grain yield (moisture content of 15.5%) was 16.2 Mg ha⁻¹. Model was validated using two independent experimental data obtained from other experiments in the Badjgah (Fars province). The experimental results validated the proposed simulation model fairly well.     

Water use — Yield relations for cowpea and maize

Three cowpea varieties and one maize variety were subjected to varying irrigation treatments, ranging from water deficits to over-irrigation, on a silty loam soil classified as an Alfisol at Ile-Ife, Nigeria. There was a strong curvilinear relation between cowpea yield and evapotranspiration (R² = 0.86 for dry matter yield and R² = 0.87 for dry seed yield). The values of the correlation coefficient dropped to 0.62 and 0.66 for dry matter and seed yields, respectively, when a linear relation was used. When data for over-irrigated fields were omitted from the calculation, a linear relationship yielded R² values close to unity (R² = 0.99). Similar results were obtained on maize dry matter and grain yields in relation to evaporation.     

杂交子代与亲本群体沙棘叶有机酸、脂肪及其它常规成分含量及变化研究

本文对水利部沙棘开发管理中心内蒙古2个育种基地共8个沙棘群体的沙棘叶在不同时期叶中有机酸、脂肪、灰分、粗蛋白、全氮以及粗纤维常规成分进行了含量及时间上的变化规律的分析。结果表明,一次杂交对子代叶中常规生化成分的改良效果不显著,子代群体叶中的常规生化成分与双亲相近,更好的改良途径需进一步研究。     

生物质原料持续供应条件下理化特性研究

以北京市大兴某生物质固体成型燃料厂为例,研究了不同季节供应的玉米秸秆、花生壳、木屑3种生物质原料物理和热化学特性的变化规律.结果表明,木屑的全水分质量分数较高,超过40％,花生壳和玉米秸秆为10％左右,不同种类原料的堆积密度、流动特性、发热量、灰分、挥发分等特性有一定差异.木屑的堆积密度较大,挥发分含量较高,灰分含量较低.木屑和花生壳的干燥基发热量较玉米秸秆高,但由于木屑的水分过高导致其收到基发热量较低.不同季节的同类原料理化特性也有差异,特别是水分、发热量、灰分差异显著.全水分含量随当地气候条件而变化,6月份之后,玉米秸秆、花生壳和木屑的干燥基发热量分别降低约7％、3.5％和5％.因此,在生物质原料储藏、运输、压缩成型等设备的设计过程中,应充分考虑不同种类原料堆积密度、流动特性等物理特性的差异,而生物质原料的燃烧过程,不仅涉及不同种类原料的差异,还应考虑不同季节造成的影响.     

Chemical Composition and Energy Value of Big Bale Silages made in England, 1984-1991

Averaged over 8 years, big bale silages made on farms in England had the following composition: dry matter (d.m.) 351 g/kg, pH 5·02, ammonia N 98 g/kg total N, crude protein 112 g/kg d.m., ash 91 g/kg d.m. and calculated metabolisable energy 10·1 MJ/kg toluene d.m.There was significant (p<0·001) year-to-year variation for each component measured. Silage ammonia N content decreased with d.m. content. The results indicated that a d.m. content of 300 g/kg was needed to produce reliably well preserved silage with less than 100 g ammonia N/kg total N. In addition, favourable weather conditions with little rain and high levels of sunshine were required to achieve this.     

酒糟主要成分含量的近红外反射光谱快速分析

从全国21个省份收集78个代表性酒糟样品,采用国标方法测定了其成分含量并进行了统计分析,结果显示粗纤维、粗灰分和粗蛋白3种成分质量分数分布范围分别为1.60%～37.54%、0.74%～26.85%和12.01%～38.69%,标准偏差分别为8.33%、5.21%和7.11%,样品成分含量差异较大。利用NIRS建立了其粗纤维、粗灰分和粗蛋白质量分数的定量分析模型,定标决定系数分别为0.98、0.91和0.96,定标标准误差分别为1.19%、1.58%和1.61%,验证决定系数分别为0.98、0.92和0.96,预测标准误差分别为1.20%、1.57%和1.60%,相对分析误差分别为7.38、3.75和4.98,模型预测精度较高,可以用于实际检测分析。     

大掺量粉煤灰混凝土导温系数试验研究

为研究大掺量粉煤灰混凝土的导温系数,本文利用正交试验测定在粉煤灰掺量、水胶比、砂率、减水剂掺量以及骨料干湿状态五个因素影响下混凝土导温系数的变化规律。结果表明：各因素均为混凝土导温系数的显著性影响因素,其中砂率、粉煤灰和减水剂掺量为极显著影响因素,各因素的影响顺序为：砂率>粉煤灰掺量>减水剂掺量>>骨料干湿状态>水胶比,并得到导温系数取得最大和最小时的最优配合比,最后应用回归分析得到回归方程,为大掺量粉煤灰混凝土导温系数的预估提供参考。     

A model of the life cycle of sheep nematodes and the epidemiology of nematodiasis in sheep

A computer model (NEMAT) of the life cycle of sheep nematodes and of the epidemiology of nematodiasis in sheep was constructed. Its purpose is to predict the development of nematodiasis in weaner sheep and to determine optimum nematode control programmes. It has been developed for use in western Victoria, Australia, but it should also be of use in other localities.NEMAT simulates the growth of perennial ryegrass (Lolium perenne) and subterranean clover (Trifolium subterraneum) pasture and weaner sheep and the development of populations of the sheep nematodes Ostertagia spp. and Trichostrongylus spp. The development and death rate parameters of the free-living stages of these nematodes were estimated by a direct search optimisation procedure specifically developed for this study. The death rates of the parasitic stages of Ostertagia spp. were determined in a field experiment and expressed as a function of the rate of infection and the time of exposure to infection. Other probability density functions and deterministic functions needed to complete the quantification of the sheep-nematode system were derived from published reports or personal communications.NEMAT was validated against data from two independent field experiments carried out in western Victoria. Predicted serial measurements of pasture availability, liveweights, total nematode counts, nematode eggs per gram of faeces and numbers of infective nematode larvae per hectare were compared with those actually observed. The predicted and observed measurements were subjectively similar and could not be differentiated statistically by spectral analysis.NEMAT was then used to evaluate some nematode control programmes in western Victoria. Using observed weather data, it simulated the continuous development of nematode populations during 1957–1976 on pastures set stocked on the 1st of January each year with recently drenched weaner sheep.If sheep were drenched in only one month of the year, the effect of this drench on liveweights and woolweights at the end of the year was greatest if it was given in February. There was a progressive decline in final liveweights and woolweights if it was given in subsequent months to December. If sheep were drenched in February and given a second drench in any one of the remaining months of the year, the effects of this second drench on final liveweights and woolweights was greatest if it was given at the autumn break. A drench in February and a drench and shift to ‘clean’ pasture (<10⁴ nematode larvae per hectare) in July were always sufficient to limit the mean yearly effects of nematodiasis to 1 kg in liveweight and 0·1 kg in woolweight. When such a shift was not possible, a drench in February, another at the autumn break and 0–5 drenches in winter and spring were required to attain similar productivity. The number and timing of these drenches after the autumn break depended on the daily effects of weather on the nematode population and could be determined only by a model of the sheep-nematode system such as NEMAT.     

基于分期播种的气候变化背景下水热因子对春玉米干物质积累及产量的影响

为明确气候变化背景下水热因子对春玉米干物质积累及产量的影响,基于分期播种试验引用关键发育期内积温与土壤贮水量作为水热因子的均一化指标,分析春玉米干物质积累及产量形成对水热变化的响应机制。研究表明,积温的增加对生殖生长的干物质积累优势更为明显,灌浆期温度升高更有利于玉米生物量的积累;积温和土壤水分的匹配通过调整干物质积累速率来影响干物质积累,最终影响产量,抽雄—乳熟期的水热均一指数X对产量的影响最大,玉米各发育阶段X对产量影响的程度由重至轻依次为抽雄—乳熟＞拔节—抽雄＞出苗—拔节＞乳熟—成熟。最大干物质积累速率Vm是限制玉米产量的关键,抽雄—乳熟及拔节—抽雄期的干物质积累速率主要通过最大干物质积累速率对产量起作用。      

苜蓿草干燥试验与收获工艺优化

通过田间试验对苜蓿草干法收获工艺和湿法收获工艺进行了分析,研究了苜蓿草自然晾晒干燥速度特性;研究了苜蓿草在收获过程中营养成分变化和干物质损失规律;解决茎、叶干燥不同步问题和提高苜蓿草营养成分保有率的方法,可实现苜蓿草收获营养成分保有率在90％以上,干物质损失小于2％.     

The effect of irrigation and nitrogen fertilizer on rapeseed (Brassica napes) production in South-Eastern Australia

Summary A field trial was conducted to determine the response of rapeseed (Brassica napus cv. Marnoo) to two irrigation treatments and six nitrogen fertilizer treatments. Dry matter accumulation, leaf area development and seed yield were measured. The dry matter and seed yield response to applied nitrogen was greater under irrigated compared to rainfed conditions. Maximum seed yield (approx. 3.8 t ha^–1) was obtained from the irrigated treatment receiving 100 kg N ha^–1 applied at sowing. This high rate of N application at sowing led to more rapid leaf area development and higher maximum LAI compared to treatments supplied with split application of the same amount of N at sowing and rosette stages. Greater partitioning of dry matter into the leaf component and higher specific leaf areas under the higher N regime were largely responsible for this increase. Higher maximum LAI's were associated with greater numbers of pods per plant, which combined with longer leaf area duration led to higher final seed yields.     

养护制度和大掺量掺和料对混凝土干缩性能的影响研究

养护是获得高性能混凝土的重要环节,针对混凝土所处的环境特点,研究了大掺量矿渣和粉煤灰混凝土的干缩性能以及养护制度对混凝土干缩性能的影响规律。结果表明,在相同养护制度下,掺矿渣和粉煤灰的混凝土各测试龄期干缩率相对基准混凝土试件减小约5%～20%,有利于改善混凝土的干缩性能;延长养护时间有利于改善混凝土的干缩性能,养护时间宜根据需要适当延长,一般情况下不宜低于3d,且养护时间和养护方法对大掺量掺和料混凝土显得尤为重要。     

Modeling the effect of abrupt changes in nitrogen availability on lettuce growth,root–shoot partitioning and nitrate concentration

A four-compartment lettuce model designed to predict the effects of abrupt changes in nitrogen availability is described. Sensitivity analysis is used to determine the parameters to which the predictions are most sensitive. These parameters are estimated using data from experiments in which nitrogen availability was changed abruptly.The model predicts quite well the main observations associated with interruption of nitrogen supply: reduced shoot growth, increased root-to-shoot ratio (RSR), fast depletion of nitrate, and increased dry matter content. The shoot of plants deprived of nitrogen for 25 days is seven to ten times smaller than the shoot of unstressed plants, while their root-to-shoot ratio is about 12 times larger. Restoring nitrogen supply to previously N-starved plants has opposite effects.A simplified model, obtained by imposing a fixed RSR, gives predictions of shoot fresh mass, dry matter content, nitrate concentration and reduced-N content similar to the predictions of the model with variable RSR, except for extreme cases in which the plants are N-deprived throughout the whole growing period. This indicates that proper modeling of root–shoot partitioning is not essential for predicting the effect of abrupt changes of nitrogen availability on shoot growth and internal plant composition.