Konkurrenz und Ertragsvorteile in Gemengen aus Erbsen (Pisum sativum L.) und Hafer (Avena sativa L.)

In field trials on a fertile fluvisol in 1995 and 1996 near Göttingen, Germany, pea (Pisum sativum; cv. Messire/conventional leafed, cv. Profi/semileafless) and oats (Avena sativa; cv. Alf) were grown as sole crops and in substitutive mixtures. The sole crops were established at 80 pea seeds m^?2 and 300 oat seeds m^?2. The mixtures consisted of 67 % (pea) and 33 % (oats) of the monoculture densities, respectively. Interactions of cv. Messire or cv. Profi and oats were similar in 1995 and 1996. The mixtures outyielded the monocultures with respect to total above ground dry matter (RYT = 1.15) and grain yield (RYT = 1.09). Grain yield of pea and oats averaged 4.9 t ha^?1 in monocultures and 5.5 t ha^?1 in mixtures. Oats was relatively the stronger of the two competitors. Decreasing number of pods per plant could be highlighted as the factor for a lower pea seed frequency in the yield of the mixtures. For oats the number of panicles per plant and kernels per panicle were higher in the mixtures compared with the oat monocultures. The average amount of the harvest index (HI) was 0.52 for pea and 0.46 for oats. Favourable growth conditions increased HI values however, prolific vegetative growth in the mixtures resulted in lower HI values. The predicted RYT‐values estimate the maximum combined grain yield of 6.3 t ha^?1 in the mixture of 87 % pea (70 seeds m^?2) and 13 % oats (39 kernels m^?2).     

Spring Cereals for Forage and Grain Production in a Cool Maritime Climate

Newfoundland's climate is marginal for agricultural production. The availability of locally grown cereal grain and high‐quality forage are major limitations to successful animal agriculture in this region. Here, our overall objective was to compare several spring cereal species for both annual forage and grain production in Newfoundland's cool Maritime climate. Several varieties of barley (Hordeum vulgare L.), wheat (Triticum aesitivum L.), oats (Avena sativa L.) and pea (Pisum sativum L.)–cereal mixtures for forage yield and quality, as well as grain yield and maturity, were compared in field trials on the east and west coasts in both 1999 and 2000. Barley headed earliest, yielded greatest forage dry matter, had lowest forage protein and acid detergent fibre (ADF) percentages, and had neutral detergent fibre (NDF) mean values greater than those of pea–cereal mixtures, but less than those of oats and wheat. Forage harvested from pea–cereal mixtures was similar to that of barley for yield, ADF and NDF, while P and protein percentage were much greater. Barley matured 10–15 days earlier than both wheat and oats. In general terms, all three spring cereals exhibited similar grain yield potential. Oats tillered less, but compensated by producing more kernels spike^?1. Days to maturity for cereal grains in western Newfoundland were roughly similar to those reported for the Maritime provinces of Canada. Yield and maturity results for both forage and grain production suggest that eastern Newfoundland is a unique agro‐ecoregion in North America, and agronomic recommendations specific to other regions may not be applicable in this region.     

Breaking Uniculm Growth Habit of Spring Cereals at High Latitudes by Crop Management. II. Tillering, Grain yield and Yield Components

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.     

Intercropping fenugreek (Trigonella foenum‐graecum L.) and barley (Hordeum vulgare L.) with and without biochar: Tests along a competition gradient

Integrating soil amendment biochar to legume‐based intercropping systems may amplify the intercropping benefits and lead to more sustainable production due to its positive effects on the soil physicochemical and biological environment. Fenugreek (Trigonella foenum‐graecum) is a legume used in an intercropping system in several countries in Southern Europe, the Middle East, and Asia. A barley cultivar and an Iranian fenugreek ecotype were studied in two replacement series experiments to find the best combination of the two species as well as the effect of adding biochar to the soil. Fenugreek and barley were grown in 4‐L pots in five density combinations (20:0, 15:5, 10:10, 5:15, 0:20) with and without application of biochar in sandy loam soil. The biomass, nitrogen (N) and carbon (C) amount of the two crops were measured fifty days after sowing, and the Relative Yield Total (RYT) was estimated. Our results showed that biochar application resulted in a higher total biomass, N and C amount in all combinations of fenugreek and barley. Total biomass was increased by biochar 19.2% when fenugreek was grown alone and 8.1 and 12.9% in series with 25 and 50% barley when biochar was added, respectively. Biochar increased dry matter, N and C accumulation in both crop species in the mixtures. An exception was the C amount of barley which was not influenced by biochar in intercropping. RYT values were largest for biomass, C and N amount in mixtures with 15 fenugreek plants per pot and 5 barley plants per pot corresponding to approximately 400 fenugreek plants per m mixed with 130 barley plants per m². Biochar application increased RYT of the total dry weight by 2.7 and 5.5% in mixtures of 25 and 50% barley plants, RYT of the total nitrogen by 0.8% in mixtures with 25% barley plants, and RYT of the total carbon by 2.7 and 6.6% in mixtures with 25 and 50% barley plants. The RYT values declined with increasing number of barley plants as a result of a less competitive ability of fenugreek when growing in high barley densities. The yield was highest with intercropping but monoculture of barley also resulted in high yields. The total highest yield was found when approximately 130 fenugreek plants per m² were mixed with 400 barley plants per m². Mixtures with 75% fenugreek and 25% barley obtained RYT values larger than 1 for biomass, carbon and nitrogen percentages.     

Growth and Yield Response of Facultative Wheat to Winter Sowing, Freezing Sowing and Spring Sowing at Different Seeding Rates

Growth and yield of wheat are affected by environmental conditions and can be regulated by sowing time and seeding rate. In this study, three sowing times [winter sowing (first week of September), freezing sowing (last week of October) and spring sowing (last week of April)] at seven seeding rates (325, 375, 425, 475, 525, 575 and 625 seeds m^?2) were investigated during the 2002–03 and 2003–04 seasons, in Erzurum (Turkey) dryland conditions, using Kirik facultative wheat. A split‐plot design was used, with sowing times as main plots and seeding rates randomized as subplots. There was a significant year × sowing time interaction for grain yield and kernels per spike. Winter‐sown wheat produced a significantly higher leaf area index, leaf area duration, spikes per square metre, kernel weight and grain yield than freezing‐ and spring‐sown wheat. The optimum time of sowing was winter for the facultative cv. Kirik. Grain yields at freezing and spring sowing were low, which was largely the result of hastened crop development and high temperatures during and after anthesis. Increasing seeding rate up to 525 seeds m^?2 increased the spikes per square metre at harvest, resulting in increased grain yield. Seeding rate, however, was not as important as sowing time in maximizing grain yield. Changes in spikes per square metre were the major contributors to the grain‐yield differences observed among sowing times and seeding rates. Yield increases from higher seeding rates were greater at freezing and spring sowing. We recommended that a seeding rate of 525 seeds m^?2 be chosen for winter sowing, and 575 seeds m^?2 for freezing and spring sowing.     

Durum Wheat under Mediterranean Conditions as Affected by Seed Size

This study was carried out in order to determine the effect of seed size on the growth and yield of durum wheat. Four field experiments, composed of six durum wheat (Triticum turgidum L. var. durum) varieties and three seeding sizes were conducted in north‐east Spain in 2000 and 2001 in randomized complete block designs. The growth of seedlings was dramatically affected by seed size. Large seeds produced greater plot stands, but the plants had fewer tillers, leaves and spikes and less green area and dry weight than plots from small seeds. Grain yield was 16 % greater in plots from large seeds, which resulted in greater biomass, green area index, spikes per m² and heavier kernels than in plots from small seeds. Kernel weight was the yield component most related to grain yield in the three seed sizes. The percentage of yield variation explained by kernel weight increased as the weight of kernels increased. This was a consequence of the use of larger seeds, the same effect being observed when the comparison was made between varieties with different kernel weights. Selection for heavy kernel varieties may help to improve the yield of durum wheat in Mediterranean environments similar to that prevailing in north‐east Spain.     

Effects of Seeding Rate on Growth Duration and Accumulation and Partitioning of Dry matter in Oats

Crop management influences considerably the three components of grain yield, growth duration, growth rate, and harvest index (HI). Effects of seeding rate on these yield components in oats ( Avena sativa L.) was assessed in field experiments at the Viikki Experimental Farm, University of Helsinki, Finland (60°13'N) in 1991 and 1992. Three Finnish oat genotypes were evaluated; a long-strawed landrace cultivar, a moderately long-strawed modern cultivar, and a semi-dwarf breeding line. The following traits were measured: grain yield, days from sowing to yellow ripeness, number of tillers on main shoot, phytomass, vegetative phytomass, and their growth rates (PGR and VGR, respectively), panicle weight and its filling rate (PFR), HI, leaf area index (LAI), and at intervals, dry-matter accumulation in leaves and straw.
Increases in seeding rate significantly decreased growth duration and PGR of individual plants but increased PGR on a ground area basis. Seeding rate did not, however, affect HI. When seeding rate was increased from 200 seeds m⁻² to 500 seeds m⁻², reductions in vegetative phytomass, panicle weight, VGR, and PFR for individual plants ranged between 20 and 40 %, depending on genotype. At ≥600 seeds m⁻² differences in these components between seeding rates were modest. However, PGR, VGR, and PFR per unit ground area increased with increasing seeding rates up to 600–700 seeds m⁻². Moreover, the higher the seeding rate, the higher the peak LAI (2.7 maximum) and the earlier the canopy closure. Hence, our results showed that a seeding rate of 600–700 seeds m⁻², which resulted in uniculm growth habit, is advantageous in terms of grain yield at high latitudes due to higher biomass accumulation and subsequently greater interception of PAR.     

Genotypic variation for competitive ability in spring wheat

Herbicides are the primary method of weed control for crop production in developed countries. For economic and environmental reasons alternative control strategies are being devised. One of these strategies is the development of competitive crop cultivars. The objectives of this research were to establish whether spring wheat (Triticum aestivum L.) genotypes differed in competitive ability and if those differences were related to specific growth characteristics. Sixteen genotypes of spring wheat were grown under simulated weed competition conditions at Saskatoon, Canada over a 3–year period. Four high and four low tillering genotypes from each of two crosses (Neepawa/M1417 and Ingal/M1417) were studied. Weeds consisted of cultivated oat (Avena saliva cv. ‘Waldern’) and oriental mustard (Brassicajuncea cv. ‘Cutlass’) sown at two densities (48 and 96 seeds/m² per weed species). Seedling establishment, ground cover, and seed yield for the three species were determined, as was wheat tiller number, spike number, maximum height, leaf area index, leaf orientation, and flag leaf length and size. Significant (P = 0.001) weed rate by genotype interactions involving changes in genotype rank were detected for wheat grain yield, indicating that the 16 wheat genotypes differed in competitive ability. Wheat grain yield reductions averaged over the two weed densities ranged from 45% to 59%. The highest-yielding genotypes under weed-free conditions were not necessarily the highest yielding under weedy conditions. Genotypes which suffered smaller yield reductions were more effective in suppressing weed growth. Although competitive genotypes were generally taller than non-competitive genotypes, other traits such as large seedling ground cover and flag leaf length were associated with wheat yield under competitive conditions.     

The Influence of Different Nitrogen Levels and Seeding Rates on the Dry Matter Production and Nitrogen Uptake of Spelt (Triticum spelta L.) and Wheat (Triticum aestivum L.) under Field Conditions

Dry matter production of two different spelt (Oberkulmer, Hercule) and wheat varieties (Arina, Iena) were investigated at two different seeding rates (S1 = 200 grains/m²; S2 = 400 grains/m²) and two nitrogen levels (N1 = 80 kg N/ha; N2 = 110 kg N/ha). The plot experiments were carried out at two contrasting locations (Muri: altitude 459 m asl); Oberwallestalden: altitude 1011 m asl) over three years (1988–1990). In addition nitrogen uptake and the photosynthetic rate of flag leaves was measured. Neither growth regulators nor fungicides were applied. The average grain yield of spelt was 25 % lower than that of wheat (32 % at Muri, 18 % at Oberwallestalden). At the reduced seeding rate (S1) grain weight and grain number per ear was increased by 33 % and 31 %, respectively as compared to the normal seeding rate (S2). The increase of the grain weight and the grain number per ear was larger for the two varieties of spelt (47 % and 42 %, respectively) than for the wheat varieties (23 % and 22 %, respectively). The photosynthetic rate of the flag leaf of spelt and wheat was not significantly different, at the two growth stages measured (anthesis, anthesis + 23 days). Nitrogen yield in the above ground biomass (g N/m²) was not significantly different between spelt and wheat, neither at the beginning of stem elongation, nor at anthesis. At anthesis the nitrogen yield at the reduced nitrogen level (N1) was 16 % and 13 % lower than at the higher level (N2) for spelt and wheat respectively. A higher nitrogen efficiency of spelt under low input conditions was not apparent. Therefore it was concluded that under low input conditions, spelt is not more efficient in dry matter production than wheat. By comparing the “husked” yield of spelt (grains + glumes; representing the trade form) with the grain yield of wheat, spelt is higher yielding than wheat but only at marginal areas of cereal production.     

Appropriate seeding rate for einkorn,emmer, and spelt grown under rainfed condition in southern Italy

Einkorn (Triticum monococcum L.), emmer (Triticum dicoccum Schübler) and spelt (T. spelta L.) are still cultivated in Italy. These three hulled wheat species are more commonly known as “Farro”. Little is known about agronomic practices that optimise the grain yield of these species.This study has been carried out to establish the appropriate seeding rate for einkorn, emmer and spelt which is grown in southern Italy (Apulia region), a typical Mediterranean environment, where durum wheat is principally cultivated. Two years of experimental field trials were conducted with three seeding rates (100, 150 and 200 viable seeds per square meter).Emmer had the highest hulled grain yield (3.54 t ha⁻¹) followed by spelt (2.80 t ha⁻¹) and einkorn (1.42 t ha⁻¹). Emmer also had a higher kernel weight and was heading earlier than the other species. The bad performance of einkorn can be accountable to the excessive time to reach heading and the natural inclination of plants to lodge, factors that reduce the ability of plant to complete grain ripening, resulting in light and shrivelled kernels. The lower grain yield of spelt in comparison to emmer may be due to later heading.Emmer and spelt performed the best when they were sown at 200 seeds m⁻² (3.85 and 3.09 t ha⁻¹, respectively). In contrast, einkorn showed the highest grain yield (1.69 t ha⁻¹) at the lowest seeding rate (100 seeds m⁻²). Further, additional experimentation is required to confirm this.These results indicate that emmer is the most appropriate hulled wheat species for cropping under southern Italy’s growing conditions, and provide further information about the use of these species in the marginal area preservation or when the cultivation of economically profitable crops is precludes by water deficiency and soil poorness.     

The Impact of Underseeding Barley (Hordeum vulgare L.) on Timothy (Phleum pratense L.)-Clover (Trifolium pratense L.; Trifolium hybridum L.) Forage Production in a Cool Maritime Climate

Growing barley (Hordeum vulgare L.) in the year of forage establishment is a common agronomic practice in marginal growing regions, but is often not recommended to growers. We examined the effect of silage barley production over an establishing timothy (Phleum pratense L.)‐clover (Trifolium pratense L.; Trifolium hybridum L.) forage sward in a 4‐year study near St. John's, Newfoundland, Canada. The experiment compared two barley varieties differing in plant height (semidwarf Chapais and Leger), three barley seeding rates and the effect of a forage understorey on forage (barley) production in the establishment year and forage (timothy‐clover) production in the subsequent year. The taller Leger yielded similar forage biomass to Chapais in the year of forage establishment, which (when planted at 375 plants m^?2) was roughly twice that of a pure‐stand timothy‐clover mix. Increasing the barley seeding rate from 125 to 375 plants m^?2 resulted in a linear increase in forage yield in the year of planting. The production of barley forage in the establishment year resulted in reduced timothy‐clover forage yield in the year following barley planted at 125 and 375 seeds m^?2, but not for barley planted at 250 seeds m^?2. Companion planting also altered forage species composition in that higher barley seeding rates resulted in 12–18 % less timothy and 2–4 % lower fibre levels in the year following planting. Barley seeded at rates of 250–375 seeds m^?2 and undersown with a timothy‐clover mixture (harvested at mid‐milk) resulted in greater forage yield of poorer quality than pure‐stand timothy‐clover in the planting year, and a barley seeding rate of 250 seeds m^?2 did not impede forage production in the subsequent year.     

Annual Medicago as a Smother Crop in Soybean

Use of conservation tillage and narrow row spacing in soybean [Glycine max (L.) Merr.] production has led to increased use of herbicides for weed control. Some producers are seeking alternative weed control methods, such as smother crops, that would reduce dependence on chemical weed control. A successful smother crop must compete strongly with weeds but minimally with the crop. In four environments, we intercropped three annual Medicago spp. (medics) with soybean to test their utility as a smother crop for weed control. Annual medics were intercropped with soybean at rates of 0, 85, 258, or 775 seeds m^?2, and the intercrops were grown with and without weed control. Increasing medic seeding rate decreased weed yields but also reduced soybean herbage and grain yields. For the weed‐controlled treatment, average soybean grain yields declined 7 kg ha^?1 for every 10 seeds m^?2 increase in medic seeding rate. Soybean grain yield was lower when grown with Medicago scutellata L. cv. Sava than when grown with Medicago polymorpha L. cv. Santiago or Medicago lupilina L. cv. George. Soybean grain yield was negatively related (r=?81) to medic herbage production. In the autumn following soybean harvest, medic residue ranged from 200 to 3700 kg ha^?1 depending on the location and seeding rate. Medics provided residue for soil protection, suppressed weeds, but also reduced soybean yields.     

Dry matter yield,nitrogen content,and competition in pea–cereal intercropping systems

Intercrops of pea (Pisum arvense L.), a popular legume used in intercropping systems with winter cereals for forage and silage production, with wheat (Triticum aestivum L.), rye (Secale cereale L.), and triticale (× Triticosecale Wittmack) in two seeding ratios (60:40 and 80:20) were compared with monocrops of pea and cereals for two growing seasons. Growth rate, dry matter yield, and N uptake were determined in each intercropping system. Furthermore, several indices were used to evaluate the intercropping systems and analyze the competition and the interrelationships between mixture components. Growth rate of cereals was lower in the mixtures than in the monocrops. Dry matter yield was higher in triticale monocrop, followed by its two intercrops, and the pea–wheat 80:20 intercrop. Moreover, triticale monocrop, pea–triticale intercrops, and pea–wheat 80:20 intercrop showed the highest crude protein yield and N uptake. The land equivalent ratio (LER), relative crowding coefficient (K), actual yield loss (AYL), and system productivity index (SPI) values were greater for the pea–triticale mixtures and the pea–wheat and pea–rye mixtures (80:20), indicating an advantage of intercropping. In most intercrops, the values of partial K, AYL, aggressivity, and competitive ratio (CR) indicated that the cereal was more competitive than pea. The highest values of monetary advantage index (MAI) and intercropping advantage (IA) were recorded for the pea–triticale and the pea–wheat mixtures (80:20). Overall, pea–triticale and pea–wheat mixtures (80:20) were more productive and produced better forage quality than the other mixtures and thus could be adopted by the farmers as alternative options for forage production.     

The Performance of Pea (Pisum sativum L.) and its Role in Determining Yield Advantages in Mixed Stands of Pea and Oat (Avena sativa L.)

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.     

Leaf Area Duration of Oat at High Latitudes

Contribution of leaf area duration (LAD) to grain yield during the short growing season characteristic of northern latitudes may differ from the marked impact it has at lower latitudes. Three experiments (exps) were carried out at Viikki Experimental Farm, University of Helsinki, Finland (60° 13′N) to compare associations between main shoot and tiller LAD with grain yield, yield components and morpho-physiological traits characterizing plant stand structure. This was done using correlation analysis and principal component analysis (PCA) for data from trials conducted during 1993–1995. Exp I included three N fertilizer rates (80, 120, 160 kg N ha^?1), three seeding rates (250, 500, and 750 seeds m^?2), and tall, moderate, semi-dwarf, and dwarf oat lines. Exp II incorporated two N fertilizer rates (80 and 120 kg ha^?1), three seeding rates (400, 600, and 800 seeds m^?2), and naked and hulled oat lines, and exp III, foliar applications of plant growth regulators [control, chlormequat chloride (CCC), and ethephon], and dwarf, naked, and conventional oat lines. LAD for main shoots and tillers [calculated as ∫ LAI d T, where T is cumulated degree days from seedling emergence to yellow ripening (dd °C)] and 12 morpho-physiological traits were measured. Oat was not able to benefit from high main shoot LAD if drought occurred at grain-fill, but in the absence of severe drought or if it occurred at pre-anthesis, high LAD favoured yield formation. Tiller LAD had a negative impact, if any, on grain yield in cases of an inverse relationship between tiller LAD and yield components on main shoots was recorded. Use of low seeding rates resulted in improved ability of total LAD to contribute to dry-matter production, but was not associated with grain yield. Low seeding rates enhanced formation of high tiller LAD, which was not able to compensate for grain yield reduction caused by fewer main shoots. Foliar application of CCC and ethephon tended to increase the proportion of LAD production by tillers at the expense of grain yield, which can be attributed to lower post-anthesis precipitation. Oat types differed in main shoot and tiller LAD. Disadvantageous characteristics of naked oat, such as low single groat weight, were not associated with insufficient main shoot LAD. High tiller LAD in naked lines and the Minnesota-adapted dwarf line that was not associated with high tiller grain yield in naked lines, in particular, indicates that tiller growth was enhanced at the expense of grain yield production. Application of N fertilizer at various rates did not have any effect on LAD.     

Transfer of Grain Legume Nitrogen within a Crop Rotation Containing Winter Wheat and Winter Barley

In a crop rotation trial, conducted from 1985 to 1988 at TU-Munich's research station in Roggenstein, the transfer of grain legume nitrogen was evaluated in crop rotations containing fababeans and dry peas as well as oats (reference crop) and winter wheat and winter barley as following crops. The results obtained can be summarized as follows: Dinitrogen fixation by fababeans ranged from 165 to 240 kg N ha¹, whereas N₂-fixation by peas amounted from 215 to 246 kg N ha^?1. In all seasons the calculated N-balance where only grain was removed was positive, with a net gain being on average 106 (peas) and 84 (fababeans) kg N ha^?1. After the harvest of peas 202 kg N ha^?1 remained on the field on average over seasons (158 kg N ha^?1 in the above ground biomass and 44 kg N ha^?1 as NO₃-N in 0–90 cm depth). As compared to peas, fababeans left 41 kg N ha^?1 less due to smaller amounts of nitrogen in the straw. After oats very small amounts of residual nitrogen (33 kg N ha^?1) were detected. After the harvest of grain legumes always a very high nitrogen mineralization was observed during autumn especially after peas due to a close C/N-relationship and higher amounts of nitrogen in the straw as compared to fababeans. In comparison with fababeans, N-mineralization after the cultivation of oats remained lower by more than 50%. During winter, seepage water regularly led to a considerable decrease of soil NO₃-N content. The N-leaching losses were especially high after cultivation of peas (80 kg N ha ^?1) and considerably lower after fababeans (50 kg N ha^?1) and oats (20 kg N ha^?1). As compared to oats, a higher NO₃-N content in soil was determined at the beginning of the growing period after preceding grain legumes. Therefore, winter wheat yielded highest after preceding peas (68 dt ha^?1) and fababeans (60 dt ha^?1) and lowest after preceding oats (42 dt ha^?1). The cultivation of grain legumes had no measurable effect on yield formation of the third crop winter barley in either of the growing seasons.     

Can Leaf Chlorophyll Measures at Differing Growth Stages be used as an Indicator of Winter Wheat and Spring Barley Nitrogen Requirements in Eastern Canada?

Plant need-based N management approaches may increase the efficiency of N fertilizer application in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). The leaf chlorophyll concentration estimated through the SPAD-502 meter gives a relative assessment of N status in crop. Field trials were conducted near St John's, Newfoundland, between 1997 and 2000 to describe the relationship between winter wheat and spring barley grain yield, protein content, protein yield and SPAD measurements, as affected by differential stage of crop growth, seeding rate and topdress N fertilizer. Grain yield, protein content, and protein yield of winter wheat and spring barley exhibited linear responses to increasing N topdress application rate. SPAD-502 values were moderately to highly positively correlated with grain yield, protein content, and protein yield as a result of increasing topdress N fertilization, and moderately negatively correlated as a result of increasing seeding rate. It may be difficult to make an N-application rate recommendation based on SPAD measurements, as a critical SPAD value may vary among years, locations, cultivars and soil characters.     

Growth and yield of spring cereals during transition to zero tillage on clay soils

Due to the high cost of fuel and labour associated with conventional tillage, and because of their advantageous environmental consequences, interest in reduced and zero tillage systems has increased. Direct drilling into zero tilled (ZT) soil of two spring barley (Hordeum vulgare L.) cultivars (six-rowed Rolfi and two-rowed Saana), spring oats (Avena sativa L., cultivar Roope), and spring wheat (Triticum aestivum L., cultivar Kruunu) was compared with conventional tillage (CT) and drilling into ploughed soil. Two field experiments were conducted on clay soils (clay content > 50%) between latitudes 60° and 61° N. Seed and fertilizer were placed in the same row in ZT and in separate rows in CT. Oats was the most productive spring cereal species in ZT. Establishment of spring wheat was often poor. Barley was most vulnerable to water surplus during early growth and drought during late growth. High levels of crop residues caused problems in soil drying in spring and growth of monocultures of oats and wheat. A higher seeding rate was advantageous in zero tilled clay soil. The substantial grain yield decrease suggests need for improving ZT.Long-term trials are required to determine whether ZT suits clay soils as soil structure can change over time and weather conditions play a major role in the productivity of differently tilled soils.     

Seed priming improves stand establishment and productivity of no till wheat grown after direct seeded aerobic and transplanted flooded rice

No tillage (NT) in wheat (Triticum aestivum L.) offers a pragmatic option for resolving the time and edaphic conflicts in rice (Oryza sativa L.)–wheat cropping system (RWS). However, poor stand establishment is an issue in NT wheat, which adversely affects crop growth, grain yield, and profitability. Therefore, a 2-year field study was conducted to assess the potential role of seed priming in improving the stand establishment, grain yield, water productivity and profitability of NT and plough till (PT) wheat grown after direct seeded aerobic (conservation) and puddled transplanted flooded (conventional) rice-based systems. For seed priming, wheat seeds were soaked in aerated water (hydropriming) or solution of CaCl₂ (ψs −1.25 MPa; osmopriming) for 12 h, and non-primed seeds were used as control. After harvest of rice, grown as direct seeded aerobic and puddled transplanted flooded crop, primed and non-primed wheat seeds were sown following NT and PT. In both years, stand establishment of NT wheat after direct seeded aerobic and puddled transplanted flooded rice was impeded. Nonetheless, seed priming improved the stand establishment which was visible through earliness and better uniformity of seedling emergence. Overall, primed seeds completed 50% emergence in 6.4 days, against 7.8 days taken by non-primed seeds in NT wheat. The highest emergence index (41.7) was recorded in primed seeds versus 32.0 for non-primed seeds. Improved stand establishment enhanced growth, grain yield, water productivity and profitability in NT wheat. In this regard, osmopriming was the most effective, and produced grain yield of 4.5 Mg ha⁻¹ against 3.8 Mg ha⁻¹ for non-primed seeds in NT wheat. Water productivity of the NT wheat grown from osmoprimed seeds was 8.72 kg ha⁻¹ mm⁻¹ while that from non-primed seeds was 7.21 kg ha⁻¹ mm⁻¹. Among the RWSs, the maximum wheat biomass was produced with PT after direct seeded aerobic rice. However, grain yield, water productivity, and profitability were the highest in NT wheat following direct seeded aerobic rice. Wheat yields grown after direct seeded aerobic rice and transplanted flooded rice were 4.4 and 4.2 Mg ha⁻¹ respectively. Planting NT wheat after direct seeded aerobic rice provided the highest system productivity (1.80) than other RWSs. Thus, seed priming is a viable option to improve the stand establishment, grain yield, water productivity and profitability of NT wheat in the RWS. Nonetheless, osmopriming was a better option than hydropriming in this regard.     

种植密度和播期对冬小麦品种兰考矮早八干物质和氮素积累与运转的影响

以重穗型冬小麦品种兰考矮早八为材料,研究了正常播期(10月10至12日)和适度晚播(10月24至26日)条件下,高(300万株 hm^-2)、中(225万株 hm^-2)、低(150万株 hm^-2)密度对其干物质和氮素积累转运及籽粒产量和品质的影响。结果表明,不同播期条件下,各密度处理开花期和成熟期单茎干物质和氮素积累量均随播种密度降低而增加,适当晚播和中、低密度有利于单茎干物质和氮素积累,尤其是穗部积累量的提高。正常播期和低密度以及晚播和中等密度处理开花前营养器官贮藏干物质向籽粒的转运量和花前贮藏物质对籽粒重的贡献率显著高于其他处理。正常播期和中、低密度处理以及晚播和中、高密度处理显著提高籽粒淀粉和蛋白质的含量与产量以及籽粒产量,使小麦籽粒产量和品质同步提高。在本试验条件下,兰考矮早八兼顾高产和优质的正常播期和晚播的适宜播种密度分别为150~225万株 hm^-2和225~300万株 hm^-2。