苜蓿草机械化收获叶草比损失试验研究

叶草比是表征苜蓿草营养的重要参数,为了研究苜蓿草机械化收获中叶草比的损失情况,从而更好的控制苜蓿草中营养物质的损失,通过试验获得割草、搂草、捆草作业前后叶草比、含水率、粗蛋白等主要参数数据,进行了各参数关系研究,验证了国外苜蓿机械化收获损失模型,初步探索和建立了适合中国北方的叶草比损失模型以及粗蛋白损失预测模型。试验结果表明:割―搂―捆过程中,含水率约下降了62.4%,叶草比大约下降了22.5%,粗蛋白含量下降了4.4%,其中损失主要发生在搂草捆草作业中;在建立的叶草比损失模型中,割草损失模型较好,搂草、捆草的叶草比损失模型需要进一步进行参数修正。     

Irrigation effects on the growth, yield, and water use efficiency of alfalfa

A field study was conducted in the semiarid region of northern Sudan to investigate the effects of variable irrigation on the growth, yield, and water use efficiency (WUE) of alfalfa (Medicago sativa L.). Treatments were 65 mm of water applied every 7 days, 80 mm of water applied every 10 days, or 104 mm of water applied every 13 days. The heavy, infrequent irrigation reduced stem height, stem density, leaf area index (LAI), total biomass production, and the WUE of alfalfa plants. Maximum yields for six harvests were 15.3, 12.9, and 11.2 ton ha^–1 and the WUE values were 0.12, 0.10, and 0.08 ton ha^–1 cm^–1 for the frequent, less-frequent, and infrequent irrigation regimes, respectively. In all the treatments, alfalfa dry matter yield was positively correlated with stem height and LAI. The relationship between dry matter yield and total water use was a linear function (R ²=0.99), regardless of the irrigation treatment. Alfalfa growth, yield, and WUE remained high during the relatively cool months and declined during the hot period under the three water regimes. It was concluded that alfalfa grown under semiarid conditions should be watered lightly and frequently to attain high yields and high WUE. Received: 19 February 1996     

Crown moisture and prediction of plant mortality in drought-stressed alfalfa

Withholding alfalfa (Medicago sativa L.) irrigations during the summer, a practice referred to as summer irrigation termination (SIT), can conserve substantial amounts of water in long-season desert environments; however, plant mortality associated with SIT may be substantial. Proper timing of re-irrigation is critical for minimizing mortality and yield reductions following SIT. Procedures that would permit probable mortality prediction during drought stress would improve management efficiency with SIT. This study was conducted to determine (1) whether plant mortality occurs once the moisture content of the plant woody stem portions (crown) falls below some critical threshold and (2) if such a threshold could be used to predict the likelihood of plant mortality during SIT. Crown samples were taken from single, spaced, field-grown plants in Tucson, Arizona, at the end of a 84-day SIT period in 1994. A crown moisture content of about 42% was identified as a likely threshold critical for crown tissue SIT survival. This value was then used to predict whole-plant mortality of alfalfa grown in solid-seeded plots comparable to commercial fields. Crown samples were taken at five locations within the field along a solid gradient that was related to plant mortality. At each sampling location, the proportion of samples with less than 42% crown moisture was used to predict plant mortality. Predicted mortality slightly overestimated actual mortality but differences between predicted and observed mortality were significant for only one of five sampling locations. Alfalfa growers may be able to use this simple method of crown moisture determination to prevent permanent yield reductions by initiating irrigation before substantial portions of crowns fall below the threshold moisture content of 42%. Received: 10 May 1996     

Spatial variability of heavy metals in irrigated alfalfa fields in the upper Rio Grande River basin

Reduced quality of wastewater discharged into the Rio Grande River is reported to be the cause of crop contamination and heavy metal transport onto fertile soils. This study was conducted to characterize Cd, Pb, Ni, Zn, Cr, and Co concentrations in two alfalfa (Medicago saliva L.) fields irrigated with river water (in Texas) or wastewater mixed with river water (in Mexico) and to examine spatial variability of acid-extractable metal deposition in soil and in uptake by alfalfa. Multiple transects were established in both fields for intensive forage collection and soil sampling to depths of 1.2 m, with spacing every 7.6 or 15.2 m. Metal concentrations rarely exceeded 20 mg kg⁻¹ with the exception of Zn. Relative metal concentrations were in the order Zn > Cr > Ni > Pb > Co > Cd in both fields, and were highly correlated with clay content within the plow zone. Linear and spherical variogram models best described surface metal deposition with spatial dependence > 100 m with regard to irrigation delivery. However, increasing metal concentrations below the plow zone at the Texas site, inconsistent geostatistical trends for soil Zn and Ni, and no association of Pb with soil texture suggested that irrigation delivery was not the exclusive transport source. Estimated metal loads from river water over a 50-year period suggested that irrigation may account for up to 31 % of surface metals. It is likely that atmospheric fallout from a local ore smelter and indigenous background levels significantly contributed to observed soil metal levels. Metal concentrations in unwashed alfalfa forage tissue were at least five times less than those in soil and showed no consistent association with soil concentrations. Metal concentrations in alfalfa forage posed no toxicity threat to animals or public health. Blending wastewaters in the Rio Grande River and canal system has diluted heavy metals to low concentrations for irrigation, but not to more stringent levels for fish and wildlife. Degraded waters could be diverted from the river and directly used for irrigation under careful water and soil management.     

Corn and alfalfa production as influenced by limited irrigation

Summary Several corn and alfalfa varieties were subjected to varying levels of water deficits under field conditions over a two-year period at the Utah State University Evans farm at Logan, Utah. Dry matter yields of corn and alfalfa varieties showed a linear relationship to evapotranspiration (E _t . In most cases grain yields also showed a linear response to E _t . When relative yields of dry matter and grain of corn varieties were related to relative E _t it was found that the slopes of the linear regression lines changed more between the two years than between the varieties within a given year. It was found that yields predicted by Hanks' (1974) model were highly correlated with measured yields for both corn and alfalfa.in coperation with Agric. Exp. StnGraduate student and professor, respectively     

Determination of evapotranspiration and basal crop coefficient of alfalfa with a weighing lysimeter

The aim of this study was to determine the evapotranspiration and basal crop coefficient of alfalfa with a weighing lysimeter. Lysimeter experiments were conducted at Ankara Research Institute of Rural Services, Turkey during 1995–1997. Penman–Monteith, Makkink (FAO-radiation (FAO-Rad)) and Penman-FAO methods performed satisfactorily for estimating the reference evapotranspiration of alfalfa in semi-arid climate conditions. Measured evapotranspiration rates were 1470, 1557 and 1161 mm in 1995, 1996 and 1997, respectively. Basal crop coefficients were computed from evapotranspiration measurements and weather data. The estimated values of the basal crop coefficients for alfalfa at the four growth stages of an individual cutting period were 0.71, 1.78 and 1.51 for initial, mid and late season, respectively.     

Drought stress and alfalfa production in a mediterranean environment

Summary Plots with alfalfa (Medicago sativa L.) were exposed to water deficit during two consecutive summers. Drought stress treatments which lasted between 2 and 8 months during the first growing season had no carry-over effect on growth during the following winter and early spring of the subsequent year, compared with that observed in the fully irrigated plots. It was found that the capability of roots to extract water, and the rate of recovery from water stress after rewetting in autumn was independent of the duration of the drought. Water extraction varied curvilinearly with soil depth regardless of soil water content. Good agreement was found between an exponential model which was fitted to water extraction data in our experiment and data of root mass distribution taken from experiments conducted in the United States. This gives reasonable confidence in the prediction of the use of soil water reserves by plants under stress. A balance between saving of irrigation water and the expected loss of yield was determined. It is suggested that when water resources are limited in summer, irrigation of an established stand of alfalfa can be adjusted to water availability, without a decrease in water use efficiency.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1762-E, 1986 series     

Response of alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis> L.) to diurnal and nocturnal saline sprinkler irrigations. I: total dry matter and hay quality

Little information is available on the quantitative effects on crops of saline sprinkler irrigations and the presumable beneficial effects of nocturnal versus diurnal irrigations. We measured crude protein content, carbon isotope discrimination and total dry matter (TDM) of alfalfa (Medicago sativa L.) subject to diurnal and nocturnal saline sprinkler irrigations. The work was carried out in Zaragoza (Spain) during the 2004–2006 growing seasons with a triple line source sprinkler system using synthetic saline waters dominated by NaCl with an irrigation water EC ranging from 0.5 to 5.6 dS m⁻¹. The quality of alfalfa hay assessed through its crude protein concentration was not significantly affected by salinity. Carbon isotope discrimination, an indicator of the effect of osmotic stress on plant water status, tended to decrease with increases in salinity. Based on a piecewise linear response model, alfalfa grown under saline sprinkler irrigation was shown to be more tolerant (threshold soil salinity, EC_e = 3.5 dS m⁻¹) than in previous experiments under surface irrigation (threshold EC_e = 2.0 dS m⁻¹) at relatively low salinity values, but became more sensitive at higher salinity values as shown by the higher absolute slope (13.4%) for sprinkler as compared to surface irrigation (7.3%). No significant differences in TDM were found between diurnal and nocturnal saline sprinkler irrigations. The recommended practice of irrigating at night for sprinkler irrigation using saline water is therefore not supported by our results in alfalfa grown under semiarid conditions.     

喷灌条件下不同茬次紫花苜蓿的耗水规律与灌溉制度

紫花苜蓿每年刈割多次,其不同茬次间的耗水规律与灌溉制度存在较大差异.在鄂尔多斯市鄂托克前旗牧区节水灌溉示范区进行紫花苜蓿中心支轴式喷灌灌溉试验,利用水量平衡原理计算得出喷灌条件下不同茬次紫花苜蓿耗水量,研究分析不同茬次紫花苜蓿耗水规律、产量、水分生产率和灌溉制度.结果表明:研究区第一、二和三茬紫花苜蓿耗水量总体呈现递增趋势,而不同茬次紫花苜蓿耗水强度呈现低-高-低变化规律;不同茬次紫花苜蓿产量差异明显,其中第二茬紫花苜蓿产量最高,第一茬产量次之,第三茬产量最低,对应不同茬次紫花苜蓿水分生产率也呈现相同的变化规律;一般年份紫花苜蓿喷灌条件下推荐灌溉制度为全生育期灌水7次,灌溉定额270~315 mm,其中第一茬灌水3次,灌溉定额120~135 mm,第二茬灌水2次,灌溉定额75~90 mm,第三茬灌水2次,灌溉定额75~90 mm.该研究成果对于多茬牧草灌溉决策和牧区节水灌溉工程设计具有一定意义.     

In situ use of groundwater by alfalfa

Disposal of saline drainage water is a significant problem for irrigated agriculture. One proposal is to recycle drainage water to irrigate salt tolerant crops until the volume has been reduced sufficiently to enable final disposal by evaporation. Part of this concept requires in situ crop water reuse from shallow groundwater; and data is needed to quantify the potential use of groundwater by alternative crops. A column lysimeter study was initiated to determine the potential crop water use from shallow groundwater by alfalfa as a function of groundwater quality and depth to groundwater. The results demonstrated that up to 50% of the crop water use could be met from shallow groundwater (<1.2 m) with an electrical conductivity less than 4 dS/m, and that the potential crop water use from deeper groundwater (2 m) increased over the years. The columns with high salinity (>4 dS/m) in the shallow groundwater experienced increased salinity in the soil profile with time, which resulted in reduced crop water use from shallow groundwater. Yields decreased with time as the groundwater salinity increased and periodic leaching will be required for in situ use to be a sustainable practice. Statistical analysis of crop yield demonstrated that there was significant use of groundwater with an EC of 6 dS/m for a few years.     

朔州市紫花苜蓿生长期气候条件分析

苜蓿是一种使用价值和经济价值均较高的牧草,朔州市广泛推广种植苜蓿对于农民增收、社会经济发展有着重要的意义。本文通过研究苜蓿生长的特征指标,结合中国气象局和山西省气象局信息中心整编的1991～2020年30年平均温度、降水、光照、风速、蒸发量、积温等朔州部分资料,指出朔州市的年积温、年平均气温和日照等气象要素符合紫花苜蓿的生长发育需求,年降水量对紫花苜蓿的正常生长发育有所不足,在灌溉条件能够得到保证的前提下可以进行规模化种植。朔州市平川区和山区种植紫花苜蓿会有一定的差异性,平川区比山区更适宜种植,山区特别是不平整地块种植苜蓿可用于放牧或提升当地生态效益。朔州市在6月中旬至7月中旬为最佳播种紫花苜蓿时期,4～6月如果土壤墒情好,或有灌溉条件的也可以种植苜蓿。平川区的紫花苜蓿一年适宜刈割4次,山区的紫花苜蓿一年适宜刈割3次。朔州市种植紫花苜蓿具有较好经济价值和使用价值,可以进行大面积推广种植,本文的研究结论可为朔州市紫花苜蓿种植提供一定的依据。     

Exploring the scope for improving biocontrol of black vine weevil,Otiorhynchus sulcatus,with Heterorhabditis spp. at low temperatures: A simulation study

Control success with heterorhabditid nematodes varies with nematode species, isolate, production and storage conditions, and environmental conditions after application. These factors affect nematode behaviour. A model was developed that simulates movement of a nematode population in space and time from the moment of application on a sand column until penetration into a host. It was used to identify, (1) which nematode traits can best be used for improvement, and (2) what is the most promising strategy of improvement. The sensitivity of simulated control success of Heterorhabditis spp. against larvae of the black vine weevil, Otiorhynchus sulcatus, at low temperatures, to changes in nematode behavioural parameters was quantified and related to genetic or environmental variation found in the nematodes. Parameters characterizing nematode movement had little influence on simulated control success. Parameters characterizing aggregation and arrestment had a large effect on control, but there is no variation in Heterorhabditis for these traits. Parameters characterizing penetration had a moderate effect on control. The most promising option to enhance control by Heterorhabditis in this system would be to raise the proportion infectious nematodes of an isolate up to its genetic maximum, by improving production and storage conditions. Variation in biocontrol would be reduced, resulting in a more reliable product.     

Effects of water table management on soil salinity and alfalfa yield in a semi-arid climate

A lysimeter experiment was conducted to investigate the effect of water table management (WTM) on distribution of soil salinity and annual alfalfa (Medicago scutellata) yield. Subirrigations with three levels of water table namely, 0.5 (WT0.5), 0.7 (WT0.7), and 1.0 m (WT1.0) and a free drainage (FD) conventional irrigation treatment were selected for this study. All treatments were arranged in a complete randomized block design with three replicates. The results of this study indicated that the average soil electrical conductivity of the saturated extract (ECe) in the root zone gradually increased and exceeded the designated crop threshold value (4 dS/m) after the first forage harvest in subirrigated lysimeters. A higher salt accumulation was observed at the WT0.5 treatment. The average dry matter yield of annual alfalfa in WT0.5 and WT0.7 treatments was found to be 52 and 73% higher compared with the control treatment, respectively.     

苜蓿段长度对干燥速度与悬浮速度影响的试验

在薄层干燥试验台上进行薄层干燥试验,研究不同长度苜蓿段在压扁和未压扁两种情况下含水率及干燥速度随时间的变化规律。并在悬浮试验台上做悬浮试验,研究苜蓿段长度对悬浮速度的影响。     

Minimizing salt in drain water by irrigation management — Leaching studies with alfalfa

An alfalfa experiment was conducted in the Wellton-Mohawk Irrigation and Drainage District of Southwest Arizona to determine the potential for minimizing the salt load in irrigation return flow by decreased leaching. Three leaching treatments of 5, 10, and 20%, replicated five times, were imposed on a 2-ha field. The crop was irrigated with Colorado River water (electrical conductivity of 1.3 dS m^?1) through a lateral-move, spray-type irrigation system. Results were compared with those of an adjacent area irrigated with level basin flooding.The average annual evapotranspiration during the 4-year study was 1930 mm. Several indirect measures of the leaching fractions attained gave average values of 6.4, 9.3, and 13.1% for the three leaching treatments. Mean annual yields were 21.5 and 22.9 Mg ha^?1 for 1977 and 1978 in the experimental plots, with no significant differences among leaching treatments, and 25.7 and 20.8 Mg ha^?1 in the adjacent flooded check. The results suggest that full yields could be attained with as little as 5% leaching.Estimates based on average on-farm irrigation efficiency for alfalfa in the District in 1979, indicate that 5% leaching, if attainable, would reduce the salt load in the irrigation return flow by 39 000 Mg year^?1 on 8 000 ha of alfalfa.     

Economic incentives reduce irrigation deliveries and drain water volume

This paper describes the application of an economic incentive program to achieve water quality objectives by motivating improvements in farm-level water management practices. The program includes farm-specific water allotments, tiered water pricing, and low-interest loans for purchasing irrigation equipment. The implementation of this program in a California water district has resulted in significant reductions in irrigation deliveries and drain water volume. Since the program was implemented, average irrigation depths have declined by 25% on cotton fields, 9% on tomatoes, 10% on cantaloupes, 30% on seed alfalfa, and 29% on grain fields. The average volume of drain water collected each year in subsurface drainage systems has declined from 4.8 million m³ during 1986 through 1989 to 2.6 million m³ during 1990 through 1993. These results confirm that economic incentives can be effective in generating improvements in water quality.     

Conserving water in arid regions: Exploring the economic feasibility of alternative crops

Urban expansion in western arid regions has increased competition for available water supplies, encouraging more efficient agricultural water use. The implementation of alternative low water-use crops is one option for producers, but is it economically feasible? This study uses the EPIC model to model yields to alternative crop production under differing irrigation levels. Risk analysis, or the distribution of returns, to alternative crop production is examined through the use of SIMETAR. Data on current and alternative crops for this study include cost and return studies, producer interviews, and field trials in Northwest Nevada. Study results show that there are alternative crops that could be feasibly substituted for alfalfa or used as a diversification strategy, while reducing water use by at least one-half.     

Crop yield and soil water restoration on 9-year-old alfalfa pasture in the semiarid Loess Plateau of China

The alfalfa pastureland in the semiarid Loess Plateau region of Northwest China usually has dry soil layers. A field experiment was conducted from October 2000 to October 2004 to examine soil water recovery and crop productivity on a 9-year-old alfalfa pasture. This experiment included six treatments: alfalfa pasture for 10-14 years, a conventional farming system without prior alfalfa planting, and four alfalfa-crop rotation treatments. For the rotation treatments, after 9 years of alfalfa selected crops were planted from 2001 to 2004 in the following sequence: (1) millet, spring wheat, potatoes, peas; (2) millet, corn, corn, spring wheat; (3) millet, potatoes, spring wheat, corn; (4) millet, fallow, peas, potatoes. The results showed that dry soil layers occurred in alfalfa pasture. We then plowed the alfalfa pasture and planted different crops. The soil water gradually increased during crop growth in the experimental period. The degree of soil water recovery in the four alfalfa-crop rotation treatments was derived from comparison with the soil water in the conventional system. After 4 years, the soil water recovery from the alfalfa-crop rotation systems at 0-500 cm soil depth was 90.5%, 89.8%, 92.2% and 96.7%, respectively. Soil total N content and soil respiration rate were high in the alfalfa-crop rotation systems. The yields of spring wheat in 2002, peas in 2003 and potatoes in 2004 in the alfalfa-crop rotation systems were not significantly different from yields in the conventional system. In the alfalfa-crop rotation systems, the yields of spring wheat and peas were greatly influenced by rainfall and were lowest in the dry year of 2004; the yields of corn and potatoes had a direct relationship with water use and were lowest in 2003. In summary, soil water in dry soil layers can recover, and crop yields in the alfalfa-crop systems were equal to those of the conventional system.     

Extending results from agricultural fields with intensively monitored data to surrounding areas for water quality management

A 45% reduction in riverine total nitrogen flux from the 1980-1996 time period is needed to meet water quality goals in the Mississippi Basin and Gulf of Mexico. This paper addresses the goal of reducing nitrogen in the Mississippi River through three objectives. First, the paper outlines an approach to the site-specific quantification of management effects on nitrogen loading from tile drained agriculture using a simulation model and expert review. Second, information about the net returns to farmers is integrated with the nitrogen loading information to assess the incentives to adopt alternative management systems. Third, the results are presented in a decision support framework that compares the rankings of management systems based on observed and simulated values for net returns and nitrogen loading. The specific question addressed is how information about the physical and biological processes at Iowa State University’s Northeast Research Farm near Nashua, Iowa, could be applied over a large area to help farmers select management systems to reduce nitrogen loading in tile drained areas. Previous research has documented the parameterization and calibration of the RZWQM model at Nashua to simulate 35 management system effects on corn and soybean yields and N loading in tileflow from 1990 to 2003. As most management systems were studied for a 6 year period and in some cases weather had substantial impacts, a set of 30 alternative management systems were also simulated using a common 1974-2003 input climate dataset. To integrate an understanding of the economics of N management, we calculated net returns for all management systems using the DevTreks social budgeting tool. We ranked the 35 observed systems in the Facilitator decision support tool using N loading and net returns and found that rankings from simulated results were very similar to those from the observed results from both an onsite and offsite perspective. We analyzed the effects of tillage, crop rotation, cover crops, and N application method, timing, and amount for the 30 long term simulations on net returns and N loading. The primary contribution of this paper is an approach to creating a quality assured database of management effects on nitrogen loading and net returns for tile drained agriculture in the Mississippi Basin. Such a database would systematically extend data from intensively monitored agricultural fields to the larger area those fields represent.     

Effects of applied water and sprinkler irrigation uniformity on alfalfa growth and hay yield

This study was conducted to investigate the effects of applied water and sprinkler irrigation uniformity on alfalfa (Medicago sativa L.) growth and hay yield in a semi-arid region. Field experiments were carried out in 2006 in Varamin, Iran, on three plots of 25 m × 30 m. Each plot was subdivided into 25 subplots of 5 m × 6 m. Different irrigation depths and sprinkler water uniformities were obtained by various scenarios of sprinkler nozzle pressure. In each plot, applied water was measured at 250 points (125 points above and 125 points below canopy) and the soil water content of 40 cm deep below soil surface was monitored at 25 points, each in the center of a subplot, throughout the irrigation season. The results showed that sprinkler water and soil water content uniformity varied between 66-78 and 88-91%, respectively. The findings revealed that soil water content uniformity was around 20% higher than sprinkler water uniformity. The irrigation uniformity below the canopy was estimated to be 2.5% greater than above the canopy, and canopy-intercepted water could account for 11-15% of the total seasonal applied water. Evaluation showed that alfalfa leaf area index relies more heavily on farm water application uniformity than hay yield and crop height. The experimental results illustrated that water distribution in sprinkler irrigation systems has a direct effect on alfalfa growth, hay yield and water productivity such that the applied water reduction and the increased sprinkler water uniformity led to an increased alfalfa water productivity of 2.41 kg m⁻³.