Establishment, Development and Yield of Forage Legumes and Grasses as Cover Crops in Grain Corn in Eastern Canada

Interseeded cover crops can minimize soil erosion, increase organic matter and nutrient levels and the yield of subsequent crops. However, their performance is very sensitive to local conditions. Field experiments were conducted at two Quebec locations in 1993 and 1994 in order to evaluate the potential use of forage legumes and grasses as interseeds in corn in eastern Canada. Twelve forage species were evaluated. Fall rye ( Secale cereal L.), hairy vetch ( Vicia villosa Roth), a mixture of red clover ( Trifolium pratense L.) and ryegrass ( Lolium multiflorum Lam), a mixture of white clover ( Trifolium repens L.) and ryegrass, subterranean clover ( Trifolium subterraneum L.), yellow sweet clover ( Melilotus officinalis Lam.), black medic ( Medicago lupulina L.), Persian clover ( Trifolium resupinatum L.), strawberry clover ( Trifolium fragiferum L.), crimson clover ( Trifolium incarnatum L.), annual alfalfa ( Medicago saliva L.) and berseem clover ( Trifolium alexandrinum L.) were seeded at two planting dates (10 and 20 days after corn emergence). The control treatments were: hand weeding, chemical weeding and non-weeded. Early seeded forages established better and had higher biomass accumulation than the late seeded ones. In the presence of larger weed populations, the interseeded forages did not develop well due to competition with the weeds. At Macdonald crimson clover provided good soil cover while Persian clover, fall rye and alfalfa provided relatively little cover. Strawberry clover and hairy vetch did not provide early ground cover due to their late development. Forage mixtures of red or white clover and rye grass established well and achieved high populations at the end of the growing season. Fall rye provided good early ground cover but senesced by the middle of the season. The better establishment and early germination of crimson clover caused a 19% reduction in corn grain yield in 1993. In 1994 none of the cover crops caused a reduction in corn yield.     

Performance of Legume Mixtures under Small-plot Periodic Grazing

The potential of pastures sown with species mixtures of tropical legume species compared with single species was investigated in subhumid west Africa, over a period of three grazing seasons. Through compensation and complementation of the individual legume species, the mixtures were seasonally and temporally (seasonal refers to different seasons in a year, temporal to different years) more stable than the single species stands. Crude protein contents of individual legumes in the mixtures were higher than of the same species grown in single stands, indicating possible synergistic effects in the mixtures. The ability of legume mixtures to withstand environmental and management variations and, thus, their subsequent potential for on-farm utilization under farmers' conditions are discussed.     

Interactive Effect of Sulphur and Nitrogen on the Oil and Protein Contents and on the Fatty Acid Profiles of Oil in the Seeds of Rapeseed (Brassica campestris L.) and Mustard (Brassica juncea L. Czern. and Coss.)

In long-term field experiments on loamy sand and sandy loam, legumes (pea and lupine) stimulated microbial activity in the rhizosphere more than cereals (winter rye, winter wheat and spring barley), maize and oil flax. In the rhizosphere of winter wheat and maize, microbial activity and the bacteria species Pseudomonas , Agrobacterium and Xanthomonas were more stimulated by organic manuring than by mineral fertilization. A positive correlation between the stimulated bacteria species and the growth of young plants was found. Various mineral nitrogen applications had no influence on the rhizosphere microflora. The leghemoglobin content of pea nodules – an indicator of nitrogen fixation activity – was reduced by high nitrogen application in crop rotation.     

滨海盐碱地棉花熟相调控技术及其机理

熟相是指棉株吐絮成熟期的衰老表现,有正常成熟、早衰和贪青晚熟等熟相之分,实现正常熟相需要协调的库源关系和根冠关系.整枝、嫁接和环割等措施通过改变棉花库源关系和根冠关系,导致细胞分裂素和脱落酸含量发生变化,引起早衰或贪青晚熟等异常熟相.品种自身的遗传背景、栽培措施和外界环境等都可以改变库源关系、根冠关系及相关的植物激素平...     

Organic Recycling for Soil Quality Conservation in a Sub-tropical Plateau Region

The long-term effect of organic recycling on some aspects of quality in a lowland rice soil of an Indian plateau region was studied. The experiment was set up at the agricultural experimental farm of the Indian Statistical Institute, Giridih, Bihar, India. Two rice cultivars, and treatments with four organic supplements (cowdung manure, Leuceana leaves, decomposed farm residue and Sesbania ), chemical fertilizers (urea, superphosphate and muriate of potash) and no input were arranged in a factorial randomized block design. Organic supplements improved soil quality parameters such as water holding capacity, total organic C, microbial biomass C, urease and acid phosphatase activities of soils in comparison to chemical fertilizers and no input. Among the organic supplements, cowdung manure gave significantly higher organic C (1.39%), microbial biomass C (276.46 μg g⁻¹ dry soil), urease activity (32.79 and 21.22 μg urea hydrolized g⁻¹ dry soil h⁻¹ at 37 °C by the buffer and non-buffer method, respectively) and acid phosphatase activity (1.99 μmol p-nitrophenol released g⁻¹ dry soil h⁻¹ at 37 °C) than the others. The conversion of organic C into biomass C (2.46%) was highest in Leuceana -treated soil.     

Effects of Cropping System, Seed Bed Management and Fertility Interactions on Biomass of Crops Grown on a Vertisol in the Central Highlands of Ethiopia

In the Ethiopian highlands, where integrated crop and livestock production takes place, the inadequate supply, in both quantity and quality, of feeds during the year is a major constraint. Native pastures and crop residues are the major feed sources, but their quality is often poor. Integration of forage legumes in the cropping system is one alternative to improve the fodder quality. Results of field work conducted over two seasons in order to assess and evaluate the potential yields of crops, crop/forage combinations and rotation systems on a Vertisol under two seed bed preparation systems showed that intercropping wheat with clover or sequential cropping of an oat/vetch mixture followed by chickpea provided high-quality fodder; the effect was greater under fertilized conditions. In addition, where monocropping treatment was tested, legume–cereal rotation resulted in higher grain and fodder yield when compared to cereal–cereal rotation. The study also showed that two short-duration crops could be produced in sequence per year. It is therefore suggested that the Vertisols in the Ethiopian highlands could provide a good opportunity for longer period cropping using improved food and forage crops, thereby improving the availability and quality of animal feed and protecting the land against erosion.     

中国北方主要作物根系生长的研究

本文对中国北方１８种没类型的作物及２种农田杂草的根系生长深度、生物量与地上部的关系进行了两年观察,所有１８种作物及２种杂草根深分布在４０－３００ｃｍ之奶系最浅的为芝麻,最深的为大麻。一般高秆作物根系相对较深,但矮秆作物也有根深者,如甜菜、花生、小麦等;一般生育期短、耐瘠抗旱喜欢冷的作物根系分布较浅,根系深浅与作物类型无关,不论谷类、纤维类、豆类、甚至块根块茎类都有深浅之差。所有１８种作物株高根深的     

Uniformity, Performance and Seed Quality of Soybean (Glycine max (L.) Merrill) Seed Crops Grown from Sub-samples of One Seed Lot Obtained after Selection for Physical Seed Attributes

In a glasshouse experiment it was examined whether narrow grading and selection from a commercial soybean seed lot cultivar 'IAS-5', could improve the uniformity of the seed crop grown from it and thereby enhance yield, quality and uniformity of seeds produced. The classes created were: Control (original seed lot); Size-graded seeds (projected area measured by image analysis 37–46 mm²); Non-cracked seeds; Yellow seeds; Size-graded sound seeds (size-graded, non-cracked, yellow, non-wrinkled, non-etched). Compared to the control, percentage of emergence, survival and number of yielding plants were enhanced in crops from non-cracked, yellow or size-graded sound seeds. Differences in plant numbers did not result in differences in crop yield. The different seed lots also did not differ in crop uniformity: time interval between stages of plant development, plant height 20 days after sowing, yield components, physical or physiological quality attributes of seeds produced, and respective coefficients of variation were similar. Fewer plants survived in crops showing a larger variation in plant height 20 days after sowing, thus reducing differences in initial plant-to-plant variation. Creating more uniform crops by additional grading or selection of commercial seed lots may therefore not be promising.     

Effect of Secondary Salinization on Photosynthesis in Fodder Oat (Avena sativa L.) Genotypes

The effect of secondary salinization on photosynthesis was studied in fodder oat genotypes Kent, JHO-829, JHO-881, UPO-94 and OS-6 at the flower initiation stage. With an increase in the electrical conductivity (EC) of irrigation water, the net photosynthesis rate (P_N) and the transpiration rate (E) of all the genotypes decreased. The intercellular CO₂ concentration (Ci) increased in all genotypes at 10 dS m^−1. Stomatal resistance (R_s) had a strong negative correlation with PN and E. The increase in Ci together with the increase in the R_s shows that at higher EC non-stomatal factors also start contributing to the limitation of photosynthesis. This study suggests that secondary salinization effects are strongly under stomatal control at lower saline water irrigation levels, but at higher levels non-stomatal factors may come into play.     

非生物胁迫对能源作物糖分产量影响的研究进展

利用受环境因子胁迫不利于生产粮食的农田种植能源作物,不仅能保证农业的可持续发展,还可为生产生物质能源提供原料,缓解能源危机.由于能源作物中的糖分是生产生物质燃料乙醇的基础,所以本文综述了水分、盐碱、温度、NPK(氮、磷、钾)养分、种植密度、植物激素和重金属等因子对能源作物糖分积累的影响,发现干旱、盐碱、适宜低温等非生物...     

Physiological Genetics of Salt Tolerance in Wheat (Triticum aestivum L.): Performance of Wheat Varieties, Inbred Lines and Reciprocal F1 Hybrids under Saline Conditions

Four bread wheat cultivars were studied at two salinity levels. Tobari 66 had the lowest uptake of Na⁺ and Cl⁻, and the highest K⁺/Na⁺ ratio; Pato had the highest uptake of these ions and Lyallpur 73 was intermediate. Intervarietal differences were greater at higher salinity, suggesting that they were not caused by variation at the Kna1 locus. There were significant differences between inbred lines for Na⁺, particularly in Blue Silver, suggesting the possibility of selecting genotypes with enhanced tolerance from within existing cultivars. Pato, Tobari 66 and their reciprocal F₁ hybrids were further evaluated at four salinity levels. The hybrids exhibited similar relative grain yield to Tobari, with better Na⁺ and Cl⁻ exclusion and higher K⁺/Na⁺ ratios than Pato. Overall, Tobari had the highest absolute yield under salinity, and the hybrids were closer to Tobari than to Pato. Tiller and grain numbers, 100-grain weight and yield were more affected by salinity than were height, spike length and spikelet number. We conclude that intervarietal variation for salt tolerance in wheat is controlled by genes which could be transferred to sensitive genotypes to improve their tolerance, and that the K⁺/Na⁺ ratio of the youngest leaf could be used to screen for salt tolerance.     

Effects of Irrigation at Different Growth Stages on Vegetative Growth of Mung Bean, Vigna Radiata (L.) Wilczek, in Dry and Intermediate Zones of Sri Lanka

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.     

Effect of the Organic Residues of Miscanthus × giganteus on the Soil Organic Matter Level of Arable Soils

During a complex investigation programme on the evaluation of the long-term ecological impact of cropping Miscanthus , the substrate composition of residues in 4–8-year-old stands of Miscanthus × giganteus and the contribution of Miscanthus residues to soil organic matter (SOM) were investigated. Only about 50 % of the above-ground biomass produced yearly was suitable for harvest because of pre-harvest losses and harvesting residues. The potential supply to SOM was therefore 3.1 t ha⁻¹ carbon annually accumulated by the litter, and 9.1 t ha⁻¹ carbon accumulated by rhizomes and roots in the long term. These organic residues mineralized differently in laboratory experiments at generally high rates of decomposition. Analysis of soluble portions of the organic substance of these biomass components by hydrolysis with hot water, 2 % HCl and 80 % H₂SO₄ confirmed the results. Setting the SOM effect of an equivalent farmyard-manure (FYM) supply to 100 %, Miscanthus residues reached 60 % (stubble, rhizomes), 80–90 % (pre-harvest losses) and 100 % (roots). Established Miscanthus stands are able to produce about 8.2 t ha⁻¹ organic substance, which is comparable with FYM in terms of SOM impact. This kind of calculation showed higher values for Miscanthus than for the agricultural crops investigated to date. An SOM increase of about 0.5 % on sandy soils and 0.2 % on silt soil was determined after 6–8 years of cropping Miscanthus × giganteus .     

多年生作物的研究进展

多年生作物是指生活周期年复一年,能多年生长,或地上部分在冬季枯萎,来年继续生长和开花结实的作物。多年生作物对于保持和改善农业生态系统,提高粮食产量有着重要作用。本文阐述了多年生作物在农业生产中的优势,探讨了多年生作物在农业生态环境中的利用价值,综述了多年生作物的创造途径,并对多年生作物的未来进行了展望。     

Characterization of Growth, Nitrogen Accumulation and Competitive Ability of Six Tropical Legumes for Potential Use in Intercropping Systems

Legume cover crops can be successfully used as intercrop or relay crops in low-input farming systems. To select appropriate species for intercropping, experiments were conducted in the savannah zone of Côte d'Ivoire during the wet seasons of 1997 and 1998 to determine the growth and nitrogen (N) accumulation of six cover legumes as well as the characteristics indicative of competitive ability. The species included the erect growing Crotalaria juncea and Cajanus cajan , the creeping species Mucuna pruriens var. cochinchinensis and Calopogonium mucunoides and the bushy herbaceous species Aeschynomene histrix and Stylosanthes hamata . Marked differences in phenology were observed as S. hamata and C. juncea flowered around 45–55 days after sowing (DAS) and the other species around 80–95 DAS. C. juncea and C. cajan produced close to 9 ton dry matter ha^–1, whereas the other species produced less than half this amount. The average estimated amount of accumulated N, based on leaf material, was around 70 kg ha^–1 for all species except S. hamata and A. histrix , which only produced around 25 kg ha^–1. Based on morphological characteristics, C. juncea , C. cajan and the short-lived M. pruriens were identified as potentially most competitive, indicating that productivity and competitive ability are strongly linked. The implications of these findings for intercropping systems in upland rice production are discussed.     

Leguminous Cover Crop Effects on Nitrogen Mineralization Rates and Kinetics in Soils

Soils were collected from an experimental site (initiated in 1991) at which leguminous crops were grown as natural soil cover in the interspaces of a 19‐year‐old coconut plantation. Atylosia scarabaeoides, Centrosema pubescens, Calopogonium mucunoides and Pueraria phaseoloides were grown in separate plots during the rainy season and ploughed into the soil towards the end of the monsoon (in December every year). Soil samples were collected from this site at the end of the 7th year and incubated in PVC columns at 35 ± 1°C and 0.01 MPa moisture content for 36 weeks. The soils were then leached at periodic intervals for up to 36 weeks and nitrogen (N) mineralization rates and kinetics were determined by the double exponential model. The N mineralization rates were highest during the first week and decreased with time in all soils. Soils amended (in situ ploughing) with cover crops leached 191 mg kg^–1 more NO₃^– + NO₂^–‐N than the unamended control. The per cent organic N mineralized (total and net) and the cumulative inorganic N mineralized (NO₃^– + NO₂^–‐N) varied with the amount (biomass) and type of cover crop incorporated into the soil. In general, soils amended with cover crops had greater N mineralization potentials and rate constants than the unamended control. The kinetic parameters N_oS and N_o(1 – S) and their respective rate constants h and k also varied with the amount and type of cover crops incorporated into the soil. The results further indicated that the lignin + polyphenol : N ratio of the cover crops is extremely important in predicting the rate of decomposition and N mineralization in soils.     

Standorterhebungen zur Stickstoffdynamik nach Anbau von Körnerleguminosen

Field studies on nitrogen dynamics after cultivation of grain legumes Field trials were conducted in order to study the nitrogen dynamics in soil after cultivation of grain legumes and to investigate the possibility of reduction of nitrate leaching due to catch crops or suitable following crops. Accordingly, in 1989/90 soil samples were taken on 12 farms at depths of 0–80 cm in 4 week intervals and analysed for NO₃-N. Furthermore, Brassica napus and Sinapis alba were sown after grain legumes on two farms, and at the experimental station Roggenstein field trials were carried out with different catch crops (Sinapis alba, Raphanus sativus, Lolium multiflorum and Pisum sativum) after grain peas. Considerable amounts of nitrogen (100–150 kg N/ha) in the form of crop residues (straw and grains) were left on the fields cultivated with grain legumes. After harvesting, nitrate content in the soil layer 0–80 cm was on grain legume fields almost twice as high as on fields cultivated with winter wheat. During autumn, the soil nitrate contents increased remarkably. In the soil layer 0–80 cm the maximum values rose to 140 kg N/ha after peas, to 120 kg N/ha after faba beans and only to 65 kg N/ha after winter wheat. The more intensive N-mineralization after peas compared to faba beans is due to a lower C/N-ratio of crop residues and an earlier harvest time of 2-3 weeks of peas. In winter extremely high N-leaching was measured on fallow land after cultivation of grain legumes. Cultivation of catch crops makes it possible to retain up to 110 kg N/ha in plant material. Raphanus sativus and Sinapis alba are most suitable for this purpose due to their high N-uptake even when they are sown late. Ploughing up catch crops in autumn results in a fast mineralization of their immobilized nitrogen. This implies the risk of N-leaching into deeper soil layers during winter, depending on the amount of rainfall and water capacity of the soil. Particularly on soils with low water capacity, early N-mineralization needs to be prevented by cultivating catch crops which freeze off or survive in winter. Cultivation of Brassica napus (winter form) after grain legumes leads to an extensive uptake of soil nitrate before the beginning of the seepage period, and therefore almost excludes enhanced N-leaching.     

Application of Fertilizers for Increased Saffron Yield

Research was undertaken to determine the response of newly planted saffron to the application of different levels of nitrogen (0, 50 and 100 kg N · ha^?1 · year^?1), phosphorus (0, 25, and 50 kg P₂O₅ · ha^?1 · year^?1), and composted cow manure (0, 20, and 40 tons · ha^?1 · year^?1) in terms of fresh flower weight (FFW), saffron yield (SY) and leaf biomass. The experiments were conducted in Birjand, and Ghaen, Khorasan province, Iran, from 1991 to 1993. Significant differences were found between the two locations and among the years within each location for FFW and SY. Averaged over all treatments and years, mean values for FFW and SY were 644.3 and 9.1 kg · ha^?1, respectively, at Birjand, and 296.0 and 3.7 kg · ha^?1, respectively, at Ghaen. At Birjand, mean FFW in the three consecutive years was 229.0, 796.2, and 907.8 kg · ha^?1 and mean SY was 3.4, 10.6, and 13.4 kg · ha^?1. The corresponding means at Ghaen were 87.5, 225.9, and 574.7 kg · ha^?1 for FFW and 1.3, 3.2, and 6.7 kg · ha^?1 for SY. Simple correlation coefficients between FFW and SY were positive and highly significant. At both locations, FFW and SY increased significantly from year to year. The rate of increase, however, decreased with the age of the saffron field because of overcrowding of new corms. Different combinations of fertilizers had either a negative or nonsignificant effect on FFW and SY. The application of phosphorus fertilizer did not result in increased FFW and SY. The application of 40 tons · ha^?1 of cow manure in the first year followed by no fertilizer in the second year and by 20 tons · ha^?1 in the third year increased FFW and SY at Birjand. The use of 100 kg · ha^?1 nitrogen only in the third year also increased FFW and SY at Birjand. At Ghaen, only the application of 50 kg · ha^?1 nitrogen in the third year resulted in increased FFW and SY.     

Variation in Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan): A potential perennial grain legume

Illinois bundleflower, Desmanthus illinoensis (Michaux) MacMillan, is an herbaceous perennial legume native to the central and southeastern USA. It has been identified as a potential perennial grain legume. To describe variation among natural populations for agriculturally desirable characteristics, 141 accessions of D. illinoensis and one of D. leptolobus were evaluated in common garden plantings established in 1988 and 1990. Characteristics showing diversity among populations included seed yield, plant height, growth habit, days to maturity, 100 seed weight, and shatter resistance. Eight characteristics were analyzed by principal components and cluster analysis. The resulting four clusters accounted for 56% of the variation among accessions. One cluster was distinctive in having plants with vigorous, prostrate first year growth, poor winter hardiness, and large seed. Three accessions also had indehiscent legumes useful for breeding shatter resistance. There appears to be sufficient variation to support genetic improvement of agricultural characteristics of Illinois bundleflower. This revised version was published online in August 2006 with corrections to the Cover Date.     

作物打顶栽培研究进展

打顶是作物栽培过程中一项重要而又特殊的技术措施。近年来,打顶栽培技术广泛应用于棉花、烟草、芝麻、中药材、花卉等作物栽培当中,已成为提高作物产量和品质的重要手段。本文从打顶对作物生长发育及产质量的影响和增产增质的内在机理等方面进行了阐述,并分析了作物打顶栽培中存在的问题及发展趋势。