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1.
S. Müller 《Journal of Agronomy and Crop Science》1992,168(4):272-277
N-uptake and N utilization of different fertilizer types by winter wheat – pot experiments with 15 N
The efficiency of top dressing urea, ammonium nitrate and ammonium sulphate fertilizers on winter wheat grown on loamy sand and loessial black soil was studied. At a rate of 0.5 g N per pot on the loamy sand 20 % volatilization losses of NH3 occurred with urea and 10 % on the loessial black soil with urea resp. ammonium sulphate.
The grain yields an N removal correspond to these results. At an amount of 1.6 g N per pot the N-uptake of15 N ranged from 0.589 g (urea) on sandy soils to 1.279 g (ammonium nitrate) which agrees with 76 % an 91 % of the total N uptake. On black soil 0.675 g (urea) and 1.038 g (ammonium nitrate) or 44 % and 51 % of the total uptake are found. 相似文献
The efficiency of top dressing urea, ammonium nitrate and ammonium sulphate fertilizers on winter wheat grown on loamy sand and loessial black soil was studied. At a rate of 0.5 g N per pot on the loamy sand 20 % volatilization losses of NH
The grain yields an N removal correspond to these results. At an amount of 1.6 g N per pot the N-uptake of
2.
The influence of undersown green manure crops for fallows – set-aside land – in view of vegetation-development and the dynamic of nitrate
In view of the establishment of rotational fallows - set-aside land - as well as the bridging of the vegetation-free winter period the suitability of different undersown grasses and legumes m winter cereals was investigated in field trials. Festuca rubra developed well in winter barley and winter wheat. The success of the cultivation of Lolium perenne, Trifolium pratense and Trifolium repens in winter cereals is uncertain because of the risk of light and water deficiences. Dactylis glomerata caused an negative influence on the yield of the cover crop. During the fallow period only low levels of nitrate could be found in the soil. Under fallow tilled repeatedly complete fallow- a nitrate accumulation could be observed during the fallow period. After ploughing up the fallow vegetation, nitrate concentrations - depth 0–150 cm – increased to 60 kg NO3 -N · ha-1 after the natural fallow without seeding, between 60 and 130 kg NO3 -N · ha-1 after Trifolium and between 160 and 210 kg NO3 -N · ha-1 after complete fallow. Lowest nitrate levels were observed from the grass-sites. Undersown Festuca rubra seems to be the best choice in order to compete with weeds, to form a dense sod and to prevent nitrate leaching. In general a seed rate of 8 kg · ha-1 can be recommended. 相似文献
In view of the establishment of rotational fallows - set-aside land - as well as the bridging of the vegetation-free winter period the suitability of different undersown grasses and legumes m winter cereals was investigated in field trials. Festuca rubra developed well in winter barley and winter wheat. The success of the cultivation of Lolium perenne, Trifolium pratense and Trifolium repens in winter cereals is uncertain because of the risk of light and water deficiences. Dactylis glomerata caused an negative influence on the yield of the cover crop. During the fallow period only low levels of nitrate could be found in the soil. Under fallow tilled repeatedly complete fallow- a nitrate accumulation could be observed during the fallow period. After ploughing up the fallow vegetation, nitrate concentrations - depth 0–150 cm – increased to 60 kg NO
3.
Effects of Salinity and Mixed Ammonium and Nitrate Nutrition on the Growth and Nitrogen Utilization of Barley 总被引：7，自引：0，他引：7
A. Ali T. C. Tucker T. L. Thompson & M. Salim 《Journal of Agronomy and Crop Science》2001,186(4):223-228
The absorption and utilization of nitrogen (N) by plants are affected by salinity and the form of N in the root medium. A hydroponic study was conducted under controlled conditions to investigate growth and N uptake by barley ( Hordeum vulgare L.) supplied with five different NH4 + -N/NO3 − -N ratios at electrical conductivity of 0 and 8 dS m−1 . The five NH4 + -N/NO3 -N ratios were 0/100, 25/75, 50/50, 75/25 and 100/0, each giving a total N supply of 100 mg N l−1 in the root medium. A mixed N supply of NH4 + and NO3 − resulted in greater accumulation of N in plants than either NO3 − or NH4 + as the sole N source. Plants produced a significantly higher dry matter yield when grown with mixed N nutrition than with NH4 + or NO3 − alone. Total dry matter production and root and shoot N contents decreased with increasing salinity in the root medium. The interaction between salinity and N nutrition was found to be significant for all the variables. A significant positive correlation (r=0.97) was found between nitrogen level in the plant shoot and its dry matter yield. 相似文献
4.
Root development of sugar beet plants on a sandy loess site with regard to nitrogen nutrition.
Root development of sugar beet plants in a sandy loess soil (Haplic Phaeozem) was observed from the early seedling stage up to harvest by measuring at first the greatest vertical and lateral extension of the root systems of single plants and later the rooting density of the whole plant stands (auger method, profile wall method).
During the seedling stage not only the subsoil, but also large parts of the topsoil between the plants remained unoccupied by the root systems. In this phase the greatest lateral extension of single roots reaches nearly the length of the greatest leaf of the plant. With the closure of the canopy the rooting density in the topsoil accounts to 1–2 cm cm−3 .
In summer roots penetrate to a depth of 100–150 cm with rooting densities of 0.1 to 1 cm - cm−3 . Thus, the plants gain not only access to water reserves, but sometimes meet remarkable amounts of nitrate which under the relatively dry conditions of the region tends to accumulate in 60–120 cm depth and – when taken up by the beet plants in the late stage of growth – affects crop quality negatively. 相似文献
Root development of sugar beet plants in a sandy loess soil (Haplic Phaeozem) was observed from the early seedling stage up to harvest by measuring at first the greatest vertical and lateral extension of the root systems of single plants and later the rooting density of the whole plant stands (auger method, profile wall method).
During the seedling stage not only the subsoil, but also large parts of the topsoil between the plants remained unoccupied by the root systems. In this phase the greatest lateral extension of single roots reaches nearly the length of the greatest leaf of the plant. With the closure of the canopy the rooting density in the topsoil accounts to 1–2 cm cm
In summer roots penetrate to a depth of 100–150 cm with rooting densities of 0.1 to 1 cm - cm
5.
H. Stützel W. Aufhammer A. Rautenkranz B. Wagner J. Falfus E. Nalborczyk 《Journal of Agronomy and Crop Science》1993,170(3):177-186
Yield formation and yield components of a conventional and an epigonal genotype of white lupin ( Lupinus albus )
Differences in yield formation and yield structure of two contrasting Lupinus albus growth types, the conventional, freely branching cultivar Kalina and the epigonal. little branching cultivar Ep I were analyzed. Both cultivars were grown in field experiments at Hohenheim in 1987 and 1988 with a combined variation of population density (30–120 plants/m2 ) and plant distribution. In addition, assimilate distribution within the plant was studied using a 14 C-labelling experiment. – The contributions of branches to light interception of the crops during the generative phase were > 90 % in Kalina as compared to about 30 % in Ep 1 . Relative 14 C uptake of branches was in a similar range, but great proportions of the 14 C taken up by branches was translocated to main stems. No genotype x plant density interactions with respect to grain yield were recorded, indicating that yield formation at main stems and branches was affected by cropping conditions similarly in both genotypes. This applies to the conditions of the experiments, where stress effects were absent. Under these conditions, the conventional genotype showed agronomic, but no physiological disadvantages. 相似文献
Differences in yield formation and yield structure of two contrasting Lupinus albus growth types, the conventional, freely branching cultivar Kalina and the epigonal. little branching cultivar Ep I were analyzed. Both cultivars were grown in field experiments at Hohenheim in 1987 and 1988 with a combined variation of population density (30–120 plants/m
6.
Soybean ( Glycine max L.) nitrogen nutrition is ensured by both symbiotic nitrogen fixation and mineral nitrogen assimilation. The relationship between these two modes of N nutrition was analysed in 3 growth types (determinate, semi-determinate and undeterminate) of soybean. The nitrate reductase activity and nitrogenase activity (acetylene reduction) of plants grown in the field and greenhouse showed that these enzymatic activity acted simultaneously or successively during the growth cycle, depending on the availability of inorganic nitrogen in the growing medium. Undeterminate soybean types had a higher potential nitrate reductase activities than determinate types.
The proportion of N2 fixed as measured by 15 N labelling or stem ureide content indicated that determinate soybeans derived a higher proportion of their N from N2 fixation than the undeterminates. 相似文献
The proportion of N
7.
N2 -Fixation and Yield Structure of White Lupin ( Lupinus albus L.) in Comparison to Vicia faba L. and Glycine max (L.) Merr. on Different Sites
In field studies white lupin ( Lupinus albus L., Eldo ) was compared with faba bean ( Vicia faba L., Herz Freya ) in 1986 and soybean ( Glycine max [L.] Merr., Gambit ) in 1988 on five sites respectively. Total N2 -fixation, which was determined by the extended difference method, and yield components were correlated to weather and soil conditions:
1. While faba bean responded to low pH with delayed nodulation, white lupin showed no decrease in N2 -fixation at pH less than 5.5 as far as soil was not calcareous.
2. The white lupin developed its root system most quickly into further soil depths and produced a root dry weight six times as large as that of faba bean in the soil layer 60-90 cm until the end of July (Bayreuth).
3. Despite on the calcareous sites the white lupin showed the highest total-N2 -fixation (max. 36 g N/m2 ) throughout, the N-gain for the succeeding crop was up to 8 g N/m2 for white lupin and faba bean as well. In contrast the N-balance of soybean was mostly negative.
4. Seed yields of white lupin (48-450 g/m2 ) ranged between those of faba bean (145-549 g/m2 ) and of soybean (89-290 g/m2 ); its raw protein yields were the highest found (max. 158 g/m2 ) though. 相似文献
In field studies white lupin ( Lupinus albus L., Eldo ) was compared with faba bean ( Vicia faba L., Herz Freya ) in 1986 and soybean ( Glycine max [L.] Merr., Gambit ) in 1988 on five sites respectively. Total N
1. While faba bean responded to low pH with delayed nodulation, white lupin showed no decrease in N
2. The white lupin developed its root system most quickly into further soil depths and produced a root dry weight six times as large as that of faba bean in the soil layer 60-90 cm until the end of July (Bayreuth).
3. Despite on the calcareous sites the white lupin showed the highest total-N
4. Seed yields of white lupin (48-450 g/m
8.
Nitrogen Fixation by Hybrids of White Clover (Trifolium repens L.) and Trifolium nigrescens 总被引：1，自引：0，他引：1
M. T. Abberton J. H. MacDuff A. H. Marshall T. P. T. Michaelson-Yeates 《Journal of Agronomy and Crop Science》1999,183(1):27-33
Development of hybrids between white clover ( Trifolium repens L.) and Trifolium nigrescens provides a novel route for genetically improving the reproductive capacity of white clover, provided the hybrids are agronomically viable, particularly with respect to N2 fixation. A comparative study of growth and rates of N2 fixation over 21 days was conducted with the parental species, F 1 hybrids and backcross hybrids, in flowing solution culture, without a supply of mineral N to the plants. T. nigrescens was unable to fix N2 in association with the strains of Rhizobium leguminosarum biovar. trifolii selected for inoculation. Rates of N2 fixation per plant increased in the order T. nigrescens < F 1 hybrid < T. repens < backcross 1. Specific rates of N2 fixation (days 0–21) increased in the order T. nigrescens < F 1 hybrid < backcross 1 < T. repens . Dry matter production and nodule biomass per plant increased at a higher rate in backcross 1 hybrids than in T. repens. The results suggest that the potential for N2 fixation by backcross 1 hybrids is at least as great as that by T. repens . 相似文献
9.
Changes in fertility of ears in monoculm summer barley after application of plant growth regulators
The effect of plant growth regulators (PGR) upon the structure of the ears in the monoculm summer barley Kindred Uniculm was tested during four years in pot experiments.
The influence of CCC + Ancymidol and RSW on yield structure of the whole plant and the ear which was divided in three parts (basal = 1.–5. spike internode, medial = 6.–10. spike internode, apical = off 11. spike internode) was measured. The application of PGR's in EC 32 increased kernel yield every year in a range from 11–21 %. Number of kernels were strongly improved while the thousand kernels weight remained unchanged. The increase in number of kernels in the apical zone was higher (26–64 %) than in the basal zone (0–10 %). Obviously "medial dominance" was reduced as the single kernel weight was the same in untreated plants.
The decrease of GA1 -content was evident after application of PGR's. A correlation between GA1 -content and plant height was found. 相似文献
The effect of plant growth regulators (PGR) upon the structure of the ears in the monoculm summer barley Kindred Uniculm was tested during four years in pot experiments.
The influence of CCC + Ancymidol and RSW on yield structure of the whole plant and the ear which was divided in three parts (basal = 1.–5. spike internode, medial = 6.–10. spike internode, apical = off 11. spike internode) was measured. The application of PGR's in EC 32 increased kernel yield every year in a range from 11–21 %. Number of kernels were strongly improved while the thousand kernels weight remained unchanged. The increase in number of kernels in the apical zone was higher (26–64 %) than in the basal zone (0–10 %). Obviously "medial dominance" was reduced as the single kernel weight was the same in untreated plants.
The decrease of GA
10.
Ammonia Metabolism in the Leaves and Ears of Wheat (Triticum aestivum L.) During Growth and Development 总被引：1，自引：0，他引：1
The pattern of free NH4 + accumulation and its metabolism was studied during the growth and development of field-grown wheat cv. HD 2204 at two applied N levels viz. 30 and 120 kg ha−1 . The study was confined to the 3rd, 5th and flag leaf blades and the developing ears, borne on the main shoot, during their ontogeny. The NH4 + levels were considerably lower in young leaves and increased sharply as the leaves senesced when the activity of glutamine synthetase (GS) declined. In contrast to GS, glutamate dehydrogenase (GDH) remained active even during senescence. Concentrations of protein, free amino acid and total reduced N declined with age in the leaves. An assessment of free NH4 + pool, free amino acid content and the activity of GS and GDH in the floral parts revealed that glumes, awns and grains also were active sites of NH4 + turnover. Higher applied N level not only increased leaf and grain N concentration but also led to higher free NH4 + levels in leaves and in developing ears. Presence of NH4 + in the entrapped transpirate revealed that NH4 + is released from both leaves and ears during senescence. 相似文献
11.
Seasonal Changes in the Photosynthetic Capacity of Winter Rape Plants under Different Nitrogen Regimes Measured in the Field 总被引：1，自引：0，他引：1
Winter rape (cv.'Falcon') grown under different nitrogen regimes (N0 , N120 ; 0 and 120 kg.ha−1 , respectively) in northern Germany was investigated over the 1996 spring–summer season. Using a CO2 , H2 O diffusion porometer, diurnal courses or net photosynthesis and respiration were measured in situ and were related to microclimatic conditions and leaf water relations. Photosynthesis was modelled and daily CO2 gain was calculated. In contrast to the N120 plants, plants of the low nitrogen plot (N0 ) grew less densely and their leaves behaved more like sun leaves. Increased nitrogen supply had little influence on photosynthetic capacity but it increased productivity through higher leaf area index and an extended period of photosynthetic activity. N120 plants also appeared to be better acclimated to hot, summer conditions. Higher nitrogen supply substantially increased seed production with the yield of the N120 plants being 16% of the N0 plants. 相似文献
12.
NO3 dynamics in the soil, yield formation and N uptake of winter wheat as influenced by dosage and distribution effects of N-fertilizer application
In a 4 year series of field trials carried out with 9 regimes of nitrogen fertilizer application at two trial sites with rather shallow top soil layers but large deviations in soil characteristics, grain yield varied between 50 dt/ ha and 120 dt/ha with nitrogen doses from 0–170 kg N/ha. Soil nitrogen supply for wheat grain formation on unfertilized plots reached 80 kg N/ha/year within the narrow range of 75–95 kg N/ha in different years at both sites which amounts to 1.5 % and 0.5 % of the highly different N-content of the trial sites.
The most successful nitrogen application regimes are characterized by modest fertilizer doses in early spring and the delay of supplemental fertilizer doses until growth stage EC 32. They resulted into modest NO) soil content from EC 29 to EC 32 and/or a noticable decrease of soil NO3 content during growth stage EC 30–32, which seems to be responsible for the development of only modest stand densities and reduced straw yield, while the delayed supplementation with nitrogen fertilizer overcompensated these effects mainly by increased grain numbers/ear and a remarkable improvement of harvest index.
The contribution of soil borne nitrogen to kernel yield formation started to decrease with even low dosages of supplemental nitrogen fertilization with the exception of the highest yielding season 1987/88. Top levels of grain yield have been regularly obtained with supplemental nitrogen fertilizer dosages about 40 kg N/ha below grain yield nitrogen extraction if they were added within favorable application regimes. 相似文献
In a 4 year series of field trials carried out with 9 regimes of nitrogen fertilizer application at two trial sites with rather shallow top soil layers but large deviations in soil characteristics, grain yield varied between 50 dt/ ha and 120 dt/ha with nitrogen doses from 0–170 kg N/ha. Soil nitrogen supply for wheat grain formation on unfertilized plots reached 80 kg N/ha/year within the narrow range of 75–95 kg N/ha in different years at both sites which amounts to 1.5 % and 0.5 % of the highly different N-content of the trial sites.
The most successful nitrogen application regimes are characterized by modest fertilizer doses in early spring and the delay of supplemental fertilizer doses until growth stage EC 32. They resulted into modest NO) soil content from EC 29 to EC 32 and/or a noticable decrease of soil NO
The contribution of soil borne nitrogen to kernel yield formation started to decrease with even low dosages of supplemental nitrogen fertilization with the exception of the highest yielding season 1987/88. Top levels of grain yield have been regularly obtained with supplemental nitrogen fertilizer dosages about 40 kg N/ha below grain yield nitrogen extraction if they were added within favorable application regimes. 相似文献
13.
Nitrogen penetration and persistence in soil under uncovered and covered farmyard manure heaps
After deposition of cattle manure for 308 days neither the total nitrogen nor the nitrate but onlv the ammonia content in the soil (0–70 cm) was significantly increased. During a 258 days period from autumn to spring the observed microbial oxidation of penetrated ammonia to nitrate was tardy and by no means quantitative. So leaching of nitrate was hardly to be detected during the whole period. In the soil layer 40–70 cm a maximum of 1.6 g NO3 − -N/m2 was measured, which was in an equivalent range with the amounts detected by large scale investigations in agricultural soils at the same season. Therefore the manure heaps in question did not lead to an uncommon increase of nitrate in soil. The protection of the heaps against precipitation simply brought about small and only a few times significant reductions in soil Nmin content. 相似文献
After deposition of cattle manure for 308 days neither the total nitrogen nor the nitrate but onlv the ammonia content in the soil (0–70 cm) was significantly increased. During a 258 days period from autumn to spring the observed microbial oxidation of penetrated ammonia to nitrate was tardy and by no means quantitative. So leaching of nitrate was hardly to be detected during the whole period. In the soil layer 40–70 cm a maximum of 1.6 g NO
14.
Ten charges of 15 N-labelled straw with different C/N ratios were incubated with lightly loamed sand at 25 °C and 50 % of the maximum water capacity. At the start of the 18-week incubation, mineral nitrogen was added and the 15 Nmin (NH4 and NO3 -N) content was determined six times during the course of the experiment. A slow release of 15 N was observed. After 111 days, between 2.5 and 13.0% of the total applied 15 N was mineralized. The addition of ammonium sulphate caused an increasing degradation of organic N compounds of the straw material even during the first weeks. Finally, between 6.4 and 33.3 %15 N was released. The 15 N release only partially shows the straw degradation. 相似文献
15.
Influence of light quantity on growth and biological nitrogen fixation of white clover ( Trifolium repens L.)
The influence of photon irradiance (Ep ; 100 to 500 μmol m−2 s−1 ) and of the photoperiod (16 or 11 h) on growth and nitrogenase activity of nodulated white clover plants was studied in growth chambers at two nitrate levels (1.0 and 7.5 mM NO3 − ).
Total dry mass production, the root proportion and nitrogenase activity increased with increasing Ep and photoperiod. Nitrogenase activity generally increased proportionally to root mass. Only at low Ep (100 μmol m−2 s−1 ) and under a short photoperiod (11 h) was the specific nitrogenase activity per unit root mass reduced. An abrupt change in Ep led to a rapid and parallel change in nitrogenase activity and relative growth rate.
A higher NO3 − concentration in the nutrient solution (7.5 mM) led to a marked decrease in specific nitrogenase activity, but increased growth between 200 and 500 μmol m−2 s−1 during early development only. At 100 μmol m−2 s−1 , there was no growth response to nitrate, although its effect on nitrogenase activity was more marked than at a higher Ep .
The results show that with changing light quantity, biological nitrogen fixation of white clover adapts to the existing demand for nitrogen and does not limit growth except during early development, even when light supply is low. 相似文献
The influence of photon irradiance (E
Total dry mass production, the root proportion and nitrogenase activity increased with increasing E
A higher NO
The results show that with changing light quantity, biological nitrogen fixation of white clover adapts to the existing demand for nitrogen and does not limit growth except during early development, even when light supply is low. 相似文献
16.
17.
A Field trial was conducted during 1988–89 and 1989–90 at Water Management Research Station, Memari. Bidhan Chandra Krishi Viswavidyalaya, Burdwan, to study the effect of three different irrigation regimes, namely rainfed (I1 ) (No irrigation), one irrigation (I2 ) at flowering and two irrigations (I3 at flowering and at sihqua formation stages) on the grain yield and water expenses on four different rapeseed-mustard cultivars, namely Pusa Bold, Pusa Baroni, Varuna and DIR 247. The variety DIR 247 recorded maximum grain yield (12.1 qha') followed by Pusa Baroni (11.8 q ha−1 ). The variety Varuna showed the lowest water use efficiency (48.1 kg ha−1 cm−1 ) while DIR 247 showed the maximum value of 57.0 kg ha−1 cm−1 . The number of irrigations significantly increased the grain yield. Two irrigations, one at flowering and at siliqua formation stage increased grain yield by 28 % over the rainfed plots. During the crop growth period the actual water expenses among the cultivars in any moisture regime were more or less similar. The interaction between varieties and irrigation levels were, however, not significant. 相似文献
18.
Long days at high latitudes inhibit tillering of cereals and hence seeding rates of 500–700 seeds m−2 are commonly used for spring wheat, barley and oats in Finland. Costs could be reduced by using a lower seeding rate in combination with crop management to produce more head-bearing tillers m−2 . This study was designed to assess possibilities of breaking the uniculm growth habit of spring cereals by (1) lowering the seeding rate from 600 to 300 seeds m−2 and (2) manipulating tiller growth with early mechanical treatments to the crop (rolling, cutting) or chemical applications (foliar urea, CCC and GA). A low seeding rate and early application of foliar CCC at high latitudes, under good moisture conditions prior to heading, promoted 20% more head-bearing tillers and 6% higher grain yield than standard management practices. However, cultivars differed in their response to CCC. The advantageous effects of CCC at a low seeding rate were attributed to increase, over the controls, in contribution of head-bearing tillers to grain yield in wheat (cultivar Heta ), but more grains per head in oats (cultivar Veli ). Varietal recommendations for use of low seeding rate in combination with early CCC spraying should be examined further. 相似文献
19.
H. E. Haeder 《Journal of Agronomy and Crop Science》1989,163(5):289-299
Influence of ascending nitrogen supply on the development of Rhizobium symbiotic bacteria on peas ( Pisum sativum L. ssp. sativum ) in nutritive culture solution
The effect of ascending N-supply with 4 different levels from 0.1 to 1.56 mg atom/L culture solution on juncture, quantity and development of Rhizobium bacteria on peas variety Stehgolt was thoroughly investigated. Contemporaneously, all the inoculated plants set on several noduls. The number of nodules formed per plant was negatively and hasty influenced by the ascending N-supply. Higher N-provision lessen the number of Rhizobium nodules per plant, however, these few achieved their active N2 -Fixation phase (Leghämoglobin formation stage) earlier than those formed under insufficient N-supply. 相似文献
The effect of ascending N-supply with 4 different levels from 0.1 to 1.56 mg atom/L culture solution on juncture, quantity and development of Rhizobium bacteria on peas variety Stehgolt was thoroughly investigated. Contemporaneously, all the inoculated plants set on several noduls. The number of nodules formed per plant was negatively and hasty influenced by the ascending N-supply. Higher N-provision lessen the number of Rhizobium nodules per plant, however, these few achieved their active N
20.
On a brown warp soil (Fluventic Eutrochrept) near Goettingen, Germany, conventional leafed pea ( Pisum sativum L. cvs Messire and Bohatyr) and semileafless types (cvs Profi, Juno and Azur) were grown in mixed stands together with oat ( Avena sativa cvs Alf and Lutz) in substitutively designed experiments from 1995 to 1997. Oat was the dominant component. Crowding coefficients for oat averaged 7.4. No relationship could be detected between the crowding coefficient of oat and any yield advantage from the mixture. Crowding coefficients for pea varied substantially, between 0.1002 (Juno and Alf in 1996) and 0.2979 (Bohatyr and Alf in 1996). Crowding coefficients for semileafless pea cultivars were smaller than for conventional leafed types. The yield advantage of the mixture increased as the crowding coefficient of pea increased. The maximum yield increase for the mixture was achieved when the relative yield total (RYT)=1.17 or + 11 dt grain DM ha–1 for mixtures of the long-strawed conventional leafed cultivars Bohatyr and Alf (in 1996). The crowding coefficients of pea were positively correlated with the level of symbiotically fixed N2 in the mixed stands. When N2 fixation with mixed cropping was about 30 kg N ha–1 , RYT was unity. Increasing symbiotic N2 in the mixtures resulted in increasing yield advantages in the mixture. Short-strawed pea cultivars seem unsuitable for mixing with oat. Plant height of pea appeared to be more important than plant leaf type. Accordingly, mixtures containing the long-strawed semileafless pea cultivars Profi and Alf were more successful. It is concluded that increased competitiveness of the pea component in the mixture with oat entails increasing the level of symbiotic N2 fixation including resource complementarity and thus yield advantage in the mixed stands. 相似文献