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1.
A relay cropping system of cereals, whereby winter wheat (Triticum aestivum L.) was undersown in two‐row spring barley (Hordeum distichum L.), was established in a field trial in central Sweden in 1999 and continued until 2000. The purpose of the study was to examine crop and weed responses to different plant densities of the undersown winter crop. Winter wheat was sown at four seed rates (187, 94, 47 and 0 kg ha?1) immediately after the sowing of barley. Barley was harvested in the first autumn after sowing and winter wheat in the second autumn. The grain yield of barley was not affected by the seed rate of wheat, and averaged 4580 kg ha?1. Winter wheat did not vernalize during the first growing season but remained at the vegetative stage. The grain yield of wheat was 1990 kg ha?1 for the lowest and 5610 kg ha?1 for the highest seed rate of wheat. Whilst the undersowing process itself stimulated weed emergence in this experiment, increasing the undersowing seed rate reduced the population of perennial weeds by 40–70 %. In the second growing season, the total biomass of weeds was 66 % higher at the highest seed rate compared with the lowest seed rate. 相似文献
2.
A 3-year experiment was conducted on an extensively managed hay meadow to assess the effect of management intensity and sward density on growth of meadow fescue. Two management treatments, intensive (6 cuts, 240 kg N ha−1 year−1) and extensive (3 cuts, 75 kg N ha−1 year−1), with and without gaps around the meadow fescue plants, were applied.
The highest yields were obtained under frequent defoliation. The yield of meadow fescue when grown in gaps increased four- to fivefold on an area basis in the first growing season, and reached a factor of 17 the following year. However, the difference between the treatments with and without gaps decreased strongly during the third growing season.
The contribution of meadow fescue to the total yield remained high and constant in swards with gaps combined with extensive management for the 3 years. In contrast, in swards with gaps combined with intensive management, the yield contribution of meadow fescue decreased, and in swards without gaps it remained very low under both management regimes.
The results show that meadow fescue was a weak competitor. Its response to management intensity was strongly affected by light intensity and soil water content. Low light intensity and dry top soils enhanced the suppression of meadow fescue. 相似文献
The highest yields were obtained under frequent defoliation. The yield of meadow fescue when grown in gaps increased four- to fivefold on an area basis in the first growing season, and reached a factor of 17 the following year. However, the difference between the treatments with and without gaps decreased strongly during the third growing season.
The contribution of meadow fescue to the total yield remained high and constant in swards with gaps combined with extensive management for the 3 years. In contrast, in swards with gaps combined with intensive management, the yield contribution of meadow fescue decreased, and in swards without gaps it remained very low under both management regimes.
The results show that meadow fescue was a weak competitor. Its response to management intensity was strongly affected by light intensity and soil water content. Low light intensity and dry top soils enhanced the suppression of meadow fescue. 相似文献
3.
Weed dynamics models are needed to design innovative weed management strategies. Here, we developed a 3D individual-based model called FlorSys predicting growth and development of annual weeds and crops as a function of daily weather and cropping practices: (1) crop emergence is driven by temperature, and emerged plants are placed onto the 3D field map, depending on sowing pattern, density, and emergence rate; plants are described as cylinders with their leaf area distributed according to height; (2) weed emergence is predicted by an existing submodel, emerged weed seedlings are placed randomly; (3) plant phenology depends on temperature; (4) a previously developed submodel predicts available light in each voxel of the canopy; after emergence, plant growth is driven by temperature; when shaded, biomass accumulation results from the difference between photosynthesis and respiration; shading causes etiolation; (5) frost reduces biomass and destroys plants, (6) at plant maturity, the newly produced seeds are added to the soil seed bank. The model was used to test different sowing scenarios in an oilseed rape/winter wheat/winter barley rotation with sixteen weed annuals, showing that (1) crop yield loss was negatively correlated to weed biomass averaged over the cropping season; (2) weed biomass was decreased by scenarios allowing early and homogenous crop canopy closure (e.g. reduced interrows, increased sowing density, associated or undersown crops), increased summer fatal weed seed germination (e.g. delayed sowing) or, to a lesser degree, cleaner fields at cash crop sowing (e.g. sowing a temporary cover crop for “catching” nitrogen); (3) the scenario effect depended on weed species (e.g. climbing species were little affected by increased crop competition), and the result thus varied with the initial weed community (e.g. communities dominated by small weed species were hindered by the faster emergence of broadcast-sown crops whereas taller species profited by the more frequent gap canopies); (4) the effect on weed biomass of sowing scenarios applied to one year was still visible up to ten years later, and the beneficial effect during the test year could be followed by detrimental effects later (e.g. the changed tillage dates accompanying catch crops reduced weed emergence in the immediately following cash crop but increased seed survival and thus infestation of the subsequent crops). This simulation showed FlorSys to predict realistic potential crop yields, and the simulated impact of crop scenarios was consistent with literature reports. 相似文献
4.
Sensitivity of Crops to Increased Ultraviolet Radiation in Northern Growing Conditions 总被引：3，自引：0，他引：3
K. Hakala L. Jauhiainen T. Koskela P. Käyhkö & V. Vorne 《Journal of Agronomy and Crop Science》2002,188(1):8-18
Crops growing at high latitudes are adapted to low intensities of solar ultraviolet B radiation (UV-B). As a result of destruction of stratospheric ozone layer especially at the Polar Regions of the globe, the intensity of UV-B is projected to increase at high latitudes. In order to find out the consequences of increased UV-B on crops, the sensitivity of different varieties of barley, wheat, oats, clover, timothy, meadow fescue, tall fescue and potato was tested in Jokioinen, Finland. The experiment was conducted in the field, under natural light, with a continuous 30 % increase in UV-B. Both increased UV-B and the control with slightly increased UV-A radiation affected the number of lateral shoots in cereals, and the specific leaf area and the content of phenolic substances in grasses. The effects varied according to plant variety and time of growing season. However, no visible damage, nor changes in biomass and yield production were found in any of the crops. Long-term effects on, e.g. genetic stability and germination of crop seed remain to be studied. 相似文献
5.
Field experiments were conducted to determine the direct and residual contributions of legumes to the yield and nitrogen (N) uptake of maize during the wet seasons of 1994 and 1995 at the University Farm, Abubakar Tafawa Balewa University, Bauchi, Nigeria, located in the Northern Guinea savannah of Nigeria. Nodulating soybean, lablab, green gram and black gram contributed to the yield and N uptake of maize either intercropped with the legumes or grown after legumes as a sole crop. Direct transfer of N from the nodulating soybean, lablab, green gram and black gram to the intercropped maize was 24.9–28.1, 23.8–29.2, 19.7–22.1 and 18.4–18.6 kg N ha–1 , respectively. However, the transfer of residual N from these legumes to the succeeding maize crop was 18.4–20.0, 19.5–29.9, 12.0–13.7 and 9.3–10.3 kg N ha–1 , respectively. Four years of continuous lablab cropping resulted in yields and N uptake of the succeeding maize crop grown without fertilizer N that were comparable to the yields and N uptake of the succeeding maize crop supplied with 40–45 kg N ha–1 and grown after 4 years of continuous sorghum cropping. It may therefore be concluded that nodulating soybean, lablab, green gram and black gram may be either intercropped or grown in rotation with cereals in order to economize the use of fertilizer N for maize production in the Nigerian savannah. 相似文献
6.
Soil and climatic conditions in Newfoundland are on the margins of agricultural capability, and almost all feed grain is imported. The overall objective of this work was to develop guidelines for the production of barley in Newfoundland, with the goal of establishing modern cropping recommendations. We conducted a 4-year study near St. John's to examine the effect of seeding rate and topdress ammonium nitrate (N) fertilization rate on Chapais six-row barley ( Hordeum vulgare L.) yield components and grain yield. Increasing seeding rate from 200 to 380 seeds m–2 did not alter grain yield in any year. Increasing topdress fertilization from 0 to 60 kg N ha–1 increased spike density m–2 at harvest, resulting in linear increases in grain yield in all years. Highest N rates had greatest lodging in two years. Based on our results, agronomic recommendations for eastern Newfoundland now include barley seeding rates of 250 ± 50 seeds m–2 , with topdress applications up to at least 30 kg N ha–1 . 相似文献
7.
Growth and yield responses to plant density (6.75 × 104 , 9.75 × 104 and 12.75 × 104 plants ha–1 ) and stage of transplanting (30, 35 and 40 days after sowing) of winter oilseed rape cultivar HO 605 were investigated in two field trials in the 1996/97 and 1997/98 growing seasons at Zhejiang University Farm, Huajiachi Campus, China. Results revealed a progressive decrease in leaf area per plant in response to increasing plant density and delayed transplanting, though leaf area m–2 and leaf area index were higher in high-density plants. Number of effective branches and pod per branch decreased with increasing plant density and delayed transplanting. There were no significant differences in the mean seed weight among treatments. Although the average number of seeds per pod was significantly lower for high-density plants and delayed transplanting, the economically highest seed yields were realized in relatively high-density plants. Seed oil content was negatively affected by increasing plant density, but no significant differences were observed with delayed transplanting. The highest seed yields of 1730.7 and 1748.1 kg ha–1 with no significant differences were observed for plant densities of 9.75 × 104 and 12.75 × 104 plants ha–1 , respectively, transplanted at 35 and 30 days after sowing. 相似文献
8.
H. T. Kunelius K. B. McRae G. H. Dürr S. A. E. Fillmore 《Journal of Agronomy and Crop Science》2004,190(2):130-137
Italian ryegrass (Lolium multiflorum Lam.) and perennial ryegrass (L. perenne L.) can be grown for seed and forage in cold winter regions provided the stand persists well over winter. Seed yield and plant characteristics during primary growth, and forage yield during regrowth, were determined for two Italian and one perennial ryegrass cultivars in Atlantic Canada. Establishment methods and dates included sowing ryegrass in cultivated soil alone or with barley in mid‐May and, after harvesting the barley crop, by sowing ryegrass following conventional or reduced cultivation and by no‐till drilling into barley stubble in mid‐August and early September. Despite some winterkill, particularly in Italian ryegrass, seed and forage yields were adequate in post‐establishment growing seasons. Seed yield for Italian ryegrass was greatest (1270 kg ha?1) when it was sown into cultivated soil in mid‐August and least (890 kg ha?1) when sown alone in May. Italian ryegrass yielded 15–17 % more seed when plots were established in mid‐August rather than in mid‐May or early September. Italian ryegrass cv. Lemtal had a greater density of fertile tillers (1030 m?2) in the sward than cv. Ajax (860 m?2) and its tiller density was greater when seeded into cultivated soil in September than in mid‐August. There were fewer spikelets per seed head for sowing Italian ryegrass with barley in May than for the other methods of establishment. Forage yield in regrowth was greater for Italian ryegrass cv. Ajax (2770 kg ha?1) than for cv. Lemtal (2480 kg ha?1). Seed yield of perennial ryegrass was greater when seeded in mid‐May than in mid‐August or early September. The seed yield of perennial ryegrass was greater when it was sown with barley in May and harvested for grain, than when it was sown alone or with barley harvested at late milk stage. The establishment methods for mid‐August and early September sowing had little effect on seed yield. However, the no‐till and reduced tillage methods resulted in a greater tiller density than sowing into the cultivated seedbed. Fertile tillers tended to be denser under reduced cultivation for sowing in August. Forage yield of perennial ryegrass regrowth was not influenced by the sowing method and timing. In conclusion, Italian and perennial ryegrasses produce adequate seed and forage regrowth under different establishment methods and timing. However, the poor persistence of Italian ryegrass may limit commercial production after the establishment year in Atlantic Canada. 相似文献
9.
组合播种方式对小麦群体及产量形成的影响 总被引：4，自引：1，他引：3
为了提高玉米秸秆还田后小麦播种质量,为广大麦玉轮作区小麦生产提供技术支撑,通过采用将不同小麦播种方式进行组合的研究方法,对小麦群体发育及产量结构进行分析。结果表明：在播量相同情况下,“撒播+宽幅播”的组合播种方式可以显著降低田间缺苗断垄单元的分布,提高田间群体生物量积累。通过试验研究得出：在适宜播量条件下,“撒播+宽幅播”的组合播种播量比例以1:2为宜。‘舜麦1718’在播量为135.0 kg/hm2时,播量比例为1:2的“撒播+宽幅播”的组合播种方式,产量显著高于传统条播、宽幅播及撒播等单一播种方式。 相似文献
10.
Jrgen Berntsen Jrgen E. Olesen Bjrn M. Petersen Elly M. Hansen 《European Journal of Agronomy》2006,25(4):383-390
The long-term effects of undersowing a ryegrass catch crop in cereals was analysed with the FASSET simulation model. The model was tested on a 28-year field experiment with ryegrass catch crops in spring barley. The experiment included treatments with nitrogen (N) fertiliser rates, catch crop use and timing of tillage. The modelled effects of these treatments generally agreed with observations on crop production, soil carbon, soil nitrogen and nitrate leaching. Both the observations and the simulations predicted a yield increase of 7 kg N ha−1 and an increase in nitrate leaching of 13 kg N ha−1 due to a prehistory of 24 years with continuous use of catch crops compared to a prehistory without catch crops.
A range of scenarios was constructed to evaluate the fate of the reduced nitrate leaching on crop N uptake, N leaching, gaseous emissions and change in soil organic N, and how this fate interacts with soils and climate and management. These scenarios showed that 22–30% of the reduced nitrate leaching was subsequently leached during the following decades after termination of catch crop use. Between 35 and 40% of the reduced nitrate leaching was harvested in cereals. The exact distribution depended primarily on the soil texture. The scenarios showed that effects of catch crops should be evaluated on the long-term rather than consider short-term effects only. 相似文献
11.
Quinoa is a potential new seed crop for protein feed and human consumption in Europe, with tolerance to a range of abiotic stresses. For this purpose the study was planned to analyse the effect of important agronomic strategies like nitrogen level, N application strategy, row spacing and harvest time on yield and quality of quinoa. The experiments took place in the field of the experimental station of the Faculty of Science, University of Copenhagen. Three levels of organic nitrogen from slurry was used (60, 120 and 180 kg N ha?1), supplied either all at once at sowing, or split between sowing and beginning of the reproductive phase. The effect of row spacing and harvest time was studied by harvesting seeds at seed maturity, which occurred 2–3 weeks prior to the mechanical harvest by threshing, and a couple of months after. Yield increased significantly (P ≤ 0.05) with an application up to 180 kg N ha?1, reaching 2200 kg ha?1. Increasing N also caused a significantly increased seed weight (up to 3.3 mg) and protein content (up to 17 %). N level did not affect number and amount of weeds. Split application with part of the N applied at bud formation did not have a significant effect on yield. Delayed harvest had a negative influence on seed weight, whereas protein content was stable after harvesting even a month after seed maturity. A late harvest significantly reduced seed germination, being reduced by 50 % after a 2‐month delay. A conclusion from this study is that both yield and protein content of seed can be manipulated by N level and application strategy. Harvest time is important for securing a high seed quality measured as seed germination, seed weight and protein content. A fast germination of quinoa is an important characteristic demonstrating that the crop has good possibilities for being well‐established in the field when free from weeds at the time of sowing. The choice of row spacing is important and depends on weed control method. Weed control strategy should be developed based on modern precision tools. 相似文献
12.
Field experiments were conducted in two successive seasons at the Agricultural Research Centre, Giza, Egypt (on a clay loam soil), to determine the effects of N fertilization (added at rates of 107 and 161 kg N ha–1 ) and foliar application of plant growth retardants (Pix, Cycocel and Alar; each applied once at 300 p.p.m., 75 days after planting) and zinc (applied at 0.0 and 50 p.p.m., two times, 80 and 95 days after planting) on cottonseed, protein and oil yields and oil properties of the Egyptian cotton cultivar Giza 75. The higher N rate, as well as the application of all growth retardants and zinc, resulted in an increase in cottonseed yield ha–1 , seed index, seed protein content, oil and protein yields ha–1 , seed oil refractive index, unsaponifiable matter and total unsaturated fatty acid content (oleic and linoleic). However, those treatments decreased the oil acid value, saponification value, and total saturated fatty acid content. The seed oil content tended to decrease when the high N rate was applied, but tended to increase with the application of all growth retardants and zinc. There were some differences between Pix, Cycocel and Alar regarding their effects on the studied characters. The highest increase in seed yield ha–1 , seed index, and oil and protein yields ha–1 was found with Pix, followed by Cycocel. The Cycocel treatment gave the lowest total saturated fatty acid oil content, followed by Alar. 相似文献
13.
稻秸还田与播种方式影响小麦出苗及产量的大田试验研究 总被引：2，自引：0，他引：2
为了研究水稻秸秆还田与播种方式对小麦出苗及籽粒产量的影响,通过田间大区试验,分析了稻秸机械全量还田与不同播种方式对小麦出苗率、出苗均匀性及产量性状的影响。结果显示,稻秸不还田条件下,机械条播的出苗率显著低于机械匀播和人工撒播,机械条播、机械匀播和人工撒播的出苗率分别为51.84%、90.89%和88.87%;人工撒播的出苗均匀性差于机械条播和机械匀播,3 种播种方式的出苗变异系数分别为0.49、0.26 和0.23。稻秸机械全量还田条件下,不同播种方式处理的出苗率和出苗均匀性都有所降低,其中机械条播的下降幅度较大,出苗率降低了36.54%。小麦出苗率和出苗均匀性通过影响穗数、穗粒数、千粒重而影响籽粒产量,无论稻秸是否还田,机械匀播的产量均高于其余两种播种方式,稻秸不还田和全量还田条件下的产量分别为6091.34 kg/hm2和6476.20 kg/hm2。因此,在稻秸还田小麦生产中,推荐采用机械匀播的播种方式,不仅能提高小麦的田间出苗率,而且能保持较好的出苗均匀性,有利于获得较高的籽粒产量。 相似文献
14.
为了筛选适宜的播期、播量,使良种良法配套,充分发挥该品种的丰产性,通过大田试验,研究了不同播期播量对‘洛麦22’主要性状及产量形成的影响。结果表明：穗数、穗粒数呈现出减少的趋势,随着播量增加,成穗数呈略增加的趋势,对穗粒数和千粒重的影响则较小,籽粒产量最高出现在10月5日这一播期,其产量为8919.0 kg/hm2,播期延迟产量逐渐降低,播量的影响则较小。有效茎蘖数、有效茎蘖率随播期推迟有降低的趋势,说明适期播种有利于提高有效茎蘖数;结实率随播期推迟呈减少趋势,以10月5日播期,播量37.5 kg/hm2和187.5 kg/hm2播期结实性最好,结实率达83.9%和78.2%,可见播量的影响则较小,10月25日播期结实性较10月5日降低17.5%,说明播期越晚结实性越差,故适期播种要比晚播有利于提高结实率。‘洛麦22’适宜播期为10月5日,适宜播量为90~120 kg/hm2。 相似文献
15.
Nitrogen (N) deficiency and weed infestation are main factors limiting yield and yield stability in organic wheat. Organic fertilizers may be used to improve crop performance but off-farm input costs tend to limit profitability. Instead, forage legumes may be inserted into the crop rotation to improve the N balance and to control weed infestation. In opposition to simultaneous cropping, relay intercropping of legumes in organic winter wheat limits resource competition for the legume cover crop, without decreasing the performance of the associated wheat.The aim of this study is to evaluate the effect of spring organic fertilization on the performance of intercropped legumes and wheat, and on services provided by the legume cover.Two species of forage legumes (Trifolium pratense L. and Trifolium repens L.) were undersown in winter wheat (Triticum aestivum L. cv Lona) in five organic fields during two consecutive crop seasons. Organic fertilizer was composed of feather meal and applied on wheat at legume sowing. The cover crop was maintained after the wheat harvest and destroyed just before sowing maize.Spring organic nitrogen fertilization increased wheat biomass (+35%), nitrogen (+49%), grain yield (+40%) and protein content (+7%) whatever the intercropping treatment. At wheat harvest, red clover biomass was significantly higher than white clover one (1.4 vs. 0.7 t ha−1). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5 t ha−1 whatever the specie. No significant difference in forage legume biomass production was observed at cover killing. Nitrogen accumulation in legume above-ground tissues was significantly higher for white clover than for red clover. Both red and white clover species significantly decreased weed infestation at this date. Nitrogen fertilization significantly increased weed biomass whatever the intercropping treatment and decreased nitrogen accumulation in both clover species (−12%).We demonstrated that nitrogen fertilization increased yield of wheat intercropped with forage legume while the performance of legumes was decreased. Legume growth was modified by spring fertilization whatever the species. 相似文献
16.
The presented work was conducted on calli of spring barley and meadow fescue that differed in degree of sensitivity to leaf spot pathogen Bipolaris sorokiniana . Callus reaction to fungus phytotoxins was examined on the basis of the amount of total phenolics and heat emission. The study was conducted dynamically – the measurements were performed after 1, 3, 6, 10, 24, 48, 72, 168 and 240 h after the moment when the calli were elicited with fungus metabolites. The greatest metabolic activity of fescue calli was observed between the 6th and the 24th h after treatment with phytotoxins and amounted to 170 % of control values. On the 10th day of culture this activity dramatically decreased in comparison with control (17 %). In the case of barley calli, increased heat emission was registered during the first 10 h of pathogenesis (130–150 % of control values). Calli of both studied plant species also differed in the dynamics of phenolic content changes. In meadow fescue tissue a significant decrease in phenolic level in comparison with control (40 %) was observed after the 7th day of experiment. In barley calli the amount of total phenolics decreased within the first 3 h (60–70% of control). The results obtained show that spring barley and meadow fescue differ in the rate of reaction to B. sorokiniana phytotoxins with regard to changes in metabolic activity and phenolic content. It also suggests a different degree of the plants sensitivity to the studied pathogen on tissue level. 相似文献
17.
R. Akanvou L. Bastiaans M. J. Kropff J. Goudriaan & M. Becker 《Journal of Agronomy and Crop Science》2001,187(2):111-120
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. 相似文献
18.
19.
Concern about the effects of pesticides on the environment and the desire to reduce purchased inputs are stimuli to reduce herbicide use. Field research was conducted for three growing seasons to compare the chemical contamination and effectiveness of three weed management practices. Weed control treatments included application of a herbicide mixture of 1.5 kg ai ha−1 of atrazine plus 0.9 kg ai ha−1 of pyridate, this mixture being broadcast alone or band-applied in combination with mechanical weeding, and mechanical weeding alone. The results show that it is possible to decrease the amount of atrazine residue in soil with the band-applied treatment. Such a method is very attractive because crop yields were not decreased, at least in the short run. However, we do not yet know the long-term efficiency of this method regarding groundwater quality, weed population dynamic and crop yield. Further work is therefore needed to assess the long-term impact of this weeding method. 相似文献
20.
Upendra M. Sainju Wayne F. Whitehead Bharat P. Singh Shirley Wang 《European Journal of Agronomy》2006,25(4):372-382
Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha−1) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha−1 than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha−1. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha−1. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha−1 than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha−1 than in rye and weeds with 0 or 60 kg N ha−1. Increased N supplied by hairy vetch or 120–130 kg N ha−1 increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha−1. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha−1. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production. 相似文献