Spring Cereals Research Articles

Effects of alternative tillage systems on soil quality and yield of spring cereals on silty clay loam and sandy loam soils in the cool, wet climate of central Norway

Tillage trials were established on a poorly drained silty loam overlying silty clay loam and on a freely drained sandy loam overlying medium sand, in 1988 and 1989, respectively. Autumn and spring ploughing and two ploughless systems were compared for 12–13 years, with three replications at each site. The ploughless treatments comprised deep versus shallow spring harrowing until 1999, and thereafter autumn plus spring harrowing versus spring harrowing only. In 6 years, treatments with and without fungal spraying of the cereal crops were included. In other years, fungicides were not used. Perennial weeds were controlled by herbicides as necessary, on nine occasions up until 2001. Average spring barley ( Hordeum vulgare L.) and spring oat ( Avena sativa L.) yields were similar with spring ploughing as with autumn ploughing at both sites. In treatments without ploughing, average yields on the silty loam over clay were 93% of those obtained with ploughing, and on the sandy loam over sand they were 81%. Smaller and non-significant yield differences were found between spring harrowing versus deep spring harrowing, and between autumn plus spring harrowing versus spring harrowing only. Fungal spraying increased yields markedly at both sites (25%), but there was no significant interaction between this treatment and tillage system. Oat was compared with barley in 2 years, with oat performing better under ploughless tillage. At both sites increases in penetrometer resistance occurred in the topsoil of unploughed treatments. These were considered particularly limiting on the sandy loam. On the silty loam there was an increase in surface horizon porosity in the absence of ploughing, which was associated with an increase in topsoil organic matter content. On this soil there was also a tendency toward lower penetrometer resistance at >30 cm depth on autumn plus spring harrowed soil than on ploughed soil, indicating that the plough pan may have diminished. This was supported by observations of greater earthworm activity on unploughed soil. Soil chemical analyses revealed that mineral N and plant-available P and K accumulated in the upper horizon under ploughless tillage. The percentage yields obtained in individual years with autumn as opposed to spring ploughing, were positively correlated with air temperature during 0–4 weeks after planting on the silty loam, and with precipitation during 0–12 weeks after planting on the sandy loam. In the case of yields obtained with spring harrowing only, relative to spring ploughing, positive correlations were found with 0–4 week temperature on both soil types, suggesting that low early season temperatures may limit yields under ploughless tillage.

Root growth dynamics of spring cereals with discontinuation of mouldboard ploughing

A vigorous root system is essential for efficient use of plant nutrients. This paper focuses on root growth and its response to tillage changes in the most fertile soil horizon, 0–40 cm depth. The field experiment was established in 1995 on clay soil, with 45–50% clay and 5.5% organic matter in the topsoil. Three tillage treatments were mouldboard plough to a depth of 20 cm (conventional), field cultivator to a depth of 8 cm, and no primary tillage (conservation). The field had an oat ( Avena sativa L.)–barley ( Hordeum vulgare L.) crop rotation. In 1997–1998 and 2000, root distribution during the growing season was evaluated by a non-destructive minirhizotron (MR) and video recording method. Root length density and root diameter were also measured once a season (1997 and 1998) by destructive root sampling and image analysis of washed roots. At shoot elongation, root numbers increased more under conventional than conservation tillage, at soil depth of 10–25 cm. The effect was clear for both barley (1997) and oat (2000) with maximum root numbers of 175 and 210 per 100 cm 2 by mouldboard ploughing, but 120 and 170 per 100 cm 2 under unploughed conditions (in the whole 0–0.4 m region). The suboptimal condition of unploughed soil was also indicated by lower shoot nutrient contents at tillering (studied in 1997) and by higher penetrometer resistance (studied in 1998, 2000) and lower macroporosity (studied in 2000) at 10–25 cm soil depth. Root growth dynamics were similar for both plant species. Root diameter was not significantly affected by the tillage treatments. Discontinuation of mouldboard ploughing reduced root growth ( P<0.05) within this clay soil 5 years after the tillage change, although conservation tillage preserved more water for plant use. The data show that a clay soil can be too dense for optimal rooting during the 3rd–6th-years after discontinuation of ploughing.

Climate Change Impacts and Adaptation Strategies in Spring Barley Production in the Czech Republic

The crop model CERES-Barley was used to assess the impacts of increased concentration of atmospheric CO2 on growth and development of the most important spring cereal in Central and Western Europe, i.e., spring barley, and to examine possible adaptation strategies. Three experimental regions were selected to compare the climate change impacts in various climatic and pedological conditions. The analysis was based on multi-year crop model simulations run with daily weather series obtained by stochastic weather generator and included two yield levels: stressed yields and potential yields. Four climate change scenarios based on global climate models and representing 2 × CO2 climate were applied. Results: (i) The crop model is suitable for use in the given environment, e.g., the coefficient of determination between the simulated and experimental yields equals 0.88. (ii) The indirect effect related to changed weather conditions is mostly negative. Its magnitude ranges from −19% to +5% for the four scenarios applied at the three regions. (iii) The magnitude of the direct effect of doubled CO2 on the stressed yields for the three test sites is 35–55% in the present climate and 25–65% in the 2 × CO2 climates. (iv) The stressed yields would increase in 2 × CO2 conditions by 13–52% when both direct and indirect effects were considered. (v) The impacts of doubled CO2 on potential yields are more uniform throughout the localities in comparison with the stressed yields. The magnitude of the indirect and direct effects ranges from −1 to −9% and from +31 to +33%, respectively. Superposition of both effects results in 19–30% increase of the potential yields. (vi) Application of the earlier planting date (up to 60 days) would result in 15–22% increase of the yields in 2 × CO2 conditions. (vii) Use of a cultivar with longer vegetation duration would bring 1.5% yield increase per one extra day of the vegetation season. (viii) The initial water content in the soil water profile proved to be one of the key elements determining the spring barley yield. It causes the yields to increase by 54–101 kg.ha−1 per 1% increase of the available soil water content on the sowing day.

Cropping systems for annual forage production in northeast Saskatchewan

Herbage production for silage and pasture production of annual species was investigated near Melfort in northeastern Saskatchewan. Barley (Hordeum vulgare L.) and oats (Avena sativa L.) were seeded as spring monocrops (SMC) and in binary intercrop (IC) mixtures with fall species including winter wheat (Triticum aestivum L.), fall rye (Secale cereale L.), winter triticale (X Triticosecale Wittmack L.), biennial Italian ryegrass (Lolium multiflorum Lam.) and annual Westerwolds ryegrass (Lolium multiflorum Lam.). Fall species were also seeded as monocrops (FMC). Silage Spring harvest occurred when barley (early-silage cut) and oats (late-silage cut) reached soft dough stage and again late in the autumn. An additional deferred grazing (DG) treatment containing each one fall species was harvested once in the autumn. Mean ranking of spring herbage silage yield was Oat-SMC (100%) &gt; Oat-IC (91%) &gt; Barley-SMC (83%) = Barley-IC (78%) &gt; late-cut FMC (53%) &gt; early-cut FMC (42%) (P ≤ 0.001). SilageSpring herbage yield of IC combinations was similar, but FMCs containing annual ryegrass were 26% to 34% (P ≤ .01) greater than other treatments. Crude protein content (g kg-1) was 14 to 35% higher (P ≤ 0.001) in IC systems than the corresponding SMC. Neutraleutral detergent fibre (NDF) and acid detergent fibre (ADF) content (g kg-1) of barley based systems was 15 and 22% lower (P ≤ 0.001) than those with oats. Ranking and relative productivity for fall pasture was DG (100%) &gt; early-cut FMC (67%) &gt; late-cut FMC (49%) &gt; Barley-IC (30%) &gt; Oat-IC (24%) = Barley-SMC (14%) (P ≤ 0.001). Cropping systems that contained no spring cereal produced 2.37-fold higher (P ≤ 0.001) fall pasture yield than those with spring cereals. Among FMCs, ICs and DG systems, mean yield of ryegrass treatments were generally higher (P ≤ 0.05) than that of fall cereals. Key words: Annual forage, deferred grazing, intercrop, monocrop

Computer aids for plant protection in Latvia*

The main agricultural crops where decision support systems (DSS) can be used via the Internet in Latvia are winter and spring cereals and potato. Two PC‐based models, forming part of a Danish DSS, were tested under the agroecological conditions of Latvia in 1999/2002: PC‐Plant Protection to control diseases in cereals and several modifications of the NegFry model for prediction of potato late blight. The results of 4 years of trials suggest that models that satisfy the needs of one pest may not fit another. The main reasons for failure to adapt PC models are differences in cultivar susceptibility, differences in pathogenicity, simultaneous action of other organisms and spatial placement of crops (forests, rivers and fallow land). For example, it is well known that, with the recent global migration of more aggressive strains and populations of Phytophthora infestans, late blight epidemics have become less predictable and, at the same time, less controllable in potato‐growing areas. For cereals, there is a different spectrum of prevailing pathogens, causing different levels of damage, requiring incorporation into models of thresholds corresponding to local conditions. Data from weekly monitoring of local fields, warnings about the local situation and meteorological information via the Internet are the most important computer‐aided elements for experts in plant protection.

Use of nutrient balances for environmental impact calculations on experimental field scale

Nitrogen (N) leaching was analyzed in relation to nutrient use efficiency, N balance, and mineral N content in the soil in different crop rotations. In spring in the field occupied by sugar beet mineral nitrogen content was 87.8±10.9 kg N ha −1 per year, and after harvest there was a decrease to 46.0±15.7 kg N ha −1 per year. In the fields under winter and spring grain crops, these values were 102.6±54 and 80.5±32.8 kg ha −1 per year, respectively in spring, and 76.0±46.1 and 79.6±34.9 kg N ha −1, respectively, after harvest. The highest leaching from the fields where sugar beet and grain crops were grown was from 7.3 to 39 kg N ha −1 per year, compared to 2–17.1 kg N ha −1 per year from fields with perennial grasses in the rotation. The leaching from sugar beet fields was attributed to mineralization of large amounts of organic residues (tops and small roots) left in the field after harvesting. The quantity of organic matter left after harvesting sugar beet was 2480–7270 kg dry matter (DM) ha −1, compared to barley harvest (490–1150 kg DM ha −1) or winter wheat harvest (1890–2270 kg DM ha −1). The most negative N balance during the 5-year period was in the field with perennial grasses with a total of −426 kg N ha −1. The highest positive balance was for the field with sugar beet in the rotation (+174 kg N ha −1). In the field where cereals dominated the surplus of N was +74 kg N ha −1. Agronomic efficiency (AE) calculated as the ratio between DM yield and amount of fertilizer applied was calculated for main crop groups as well as for the investigated crop rotations with different crop structure. For whole rotations the highest AE was for sugar beet (23.4 kg DM (kg N) −1) followed by winter cereals (8 kg DM (kg N) −1), while the spring cereal yield response to N fertilization was equal to zero. The highest yield response (151 kg DM (kg N) −1) was observed in the rotation where sugar beet comprised 40%, grain crops 40%, and grasses 20% of the rotation period. AE was 42.5 kg DM (kg N) −1 in the rotation with 60% sugar beet and cereal plus leguminous grain crops 40% of the rotation and negative in the 100% grain crop rotation. In summary, the lowest environmental impact in terms of N leaching was in the rotation with grasses. AE was highest in the rotations where sugar beet was included and the area of spring cereals was reduced.

Effects of tillage and reduced herbicide doses on weed biomass production in winter and spring cereals

The effects of different tillage systems and dose reduction on the efficacy of triasulfuron &amp;amp; chlortoluron mixture in the post-emergence control of annual broad-leaved weeds in winter wheat and spring barley were studied on lessive pseudogley soil in north-eastern Croatiaduring 1997&amp;ndash;2000. Total dry biomass production in untreated plots was significantly influenced by tillage and it was lowest in continuous mouldboard ploughing (99 kg/ha), medium and similar in mouldboard ploughing/disk harrowing alternating every second year and in chisel ploughing (218 kg/ha) whereas the biomass was highest in continuous disk harrowing (422 kg/ha). Thereby the proportion of annual broad-leaved weed biomass was 70, 63, and 28%, respectively. Chenopodium album L., Ambrosia artemisiifolia L., Ch. polyspermum L. and Polygonum aviculare L. are the most abundant annual weed species in all tillage treatments. One half and one quarter of the recommended rate decreased the control efficacy of total weed biomass by 12 and 19%, respectively in wheat and by 6 and 15%, respectively in barley compared to the highest dose but they still provided a&amp;nbsp;very good biomass control of main annual weeds (94&amp;ndash;96 percentage units). The efficacy of reduced herbicide doses in the control of annual broad-leaved weeds did not vary significantly between tillage treatments and growing seasons. Significant interaction with continuous disk harrowing tillage and one-quarter herbicide dose was detected in the last year of wheat trial when perennial weeds increased their biomass proportion 8 times compared to four years before.

Changes in the abundance of weeds in spring cereal fields in Finland

SummaryThe data of two weed surveys of spring cereals (conducted in 1982–84 and 1997–99) in Finland were applied to study changes in the total abundance (the number of individuals and dry weight) of the weed community as well as in the abundance and frequency of occurrence of single species. The estimated overall mean for the differences in total dry weight was 31.1 kg ha−1 and the differences in the total number of individuals was 46.6 individuals m−2 with higher numbers in the 1990s. Most of the overall variability in dry weight (63%) and in number of individuals (57%) was attributable to variability between fields within the same farm. None of the environmental variables could explain the variability in the difference in dry weight, or in the number of individuals between decades. Descriptive analysis of the single species data revealed a higher abundance and frequency of occurrence of most species in the 1990s than in the 1980s. No statistically significant differences were detected in the number of individuals of species tolerant of sulfonylureas (pooled data on Galium spurium and Viola arvensis) between decades. The results are discussed in relation to changes in the use of herbicides.

Yield loss in spring-sown cereals related to the weed flora in the spring

Yield loss was related to weed species composition and density in permanent plots, recorded several weeks after sowing of spring cereals in southern Sweden. A range of agronomic situations was included by experimentally varying fertilizer application and sowing density in 33 field trials in different locations during 3 yr. Direct gradient analysis, using yield loss as the sole predictor, arranged weed community composition in the spring along a gradient of small to large yield losses. Yield loss could be explained, to some extent, by the species composition in the spring. Species associated with situations with large losses were hempnettle and wild radish, whereas several benign species were identified based on their association with lack of yield loss. The results suggest that possible predictive tools using spring species composition would be improved if they also considered soil type and seed rate. Some agronomically important weed species were not identified as associated with yield loss when assessed in terms of their abundance in the spring, which may limit the possibilities of basing management decisions on weed plant density in the spring.

Weed species diversity and community composition in organic and conventional cropping of spring cereals

Interest in organic farming is growing rapidly in Europe. The resulting expansion of the organic farming area has been expected to enhance the biodiversity of agricultural habitats. Organic cropping practices can be hypothesized to support a higher number of weed species than conventional cropping and also to favor herbicide-susceptible and less-nitrophilous species. The diversity and species composition of weed communities were compared in spring cereal fields cultivated by organic, conventional cereal and conventional dairy cropping methods in southern Finland between 1997 and 1999. Samples were taken before (May–June) and after (July–August) the treatment of conventional fields with herbicides. The number of species was used as a measure of species diversity. The total and mean numbers of species between cropping practices were compared by applying rarefaction and ANCOVA, respectively. In organically cultivated, fields the adjusted mean number of species per field exceeded that in conventionally cultivated fields by about two species in both May–June and July–August. The total number of species was higher in organically cultivated fields only in July–August. The species composition of organically cultivated fields was closer to that of conventional dairy than to that of conventional cereal fields. Species susceptible to herbicides (e.g. Chenopodium album) were abundant in organically cultivated fields in both sampling periods whereas the relative abundance of some of them declined in conventional fields from May–June to July–August. In conventional fields, the relative abundances of Viola arvensis, Stellaria media and Elymus repens increased from May–June to July–August. Only weak support was found for the hypothesis that organic cropping favors less-nitrophilous weed species. It is concluded that organic cropping promotes weed species diversity at an early phase of cropping history but that a change in species composition would require a longer period of organic cropping.

Long continued applications of N fertilizer to cereals on sandy loam: grain and straw response to residual N

Abstract. The residual value of mineral N fertilizer applied in the spring was investigated in a field experiment where four cereals (winter wheat, winter barley, spring barley and spring oats) had been grown at reduced (0.7N), normal (1N) or high (1.3N) N fertilizer rates for 20 to 28 years. The effect of previous N fertilizer dressing was tested in two succeeding years by replacing the original N rate with five test N rates ranging from 0 to 240 kg N ha−1 for winter cereals and 0 to 200 kg N ha−1 for spring cereals. In the first test year, winter wheat grown on plots previously supplied with the high rate of mineral fertilizer (202 kg N ha−1 yr−1) yielded more grain and straw and had a higher total N uptake than wheat on plots previously supplied with the normal (174 kg N ha−1 yr−1) or reduced (124 kg N ha−1 yr−1) rate. The grain yield response and N uptake was not significantly affected by the N supply in the test year. The winter wheat grown in the second test year was unaffected by the previous N supply. Grain and straw yield response and total N uptake for spring barley, winter barley and oats, were almost identical irrespective of the previous N rate.After 20 to 28 years there were no significant differences in soil C and N (0 to 20 cm) between soil receiving three rates of N fertilizer. Soil from differently fertilized oat plots showed no significant differences in N mineralizing capacity. Nitrate leaching losses from the soils at the three N rates were estimated and the N balances for the 20 to 28 years experimental period calculated. The data indicated a reduction in overall loss of 189 to 466 kg N ha−1 at the normal and high N rates compared with the reduced N rate. We conclude that the N supplying capacity and soil organic matter content of this fertile sandy loam soil under continuous cereal cropping with straw removal was not significantly affected by differences in N fertilizer residues.

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

AbstractNewfoundland'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.

Occurrence and productivity of songbirds in prairie farmland under conventional versus minimum tillage regimes

Abundance and productivity of common bird species in prairie cropland under either conventional or minimum tillage were examined in southern Alberta, Canada. Cover types included spring cereals, winter wheat and summerfallow. Productivity was assessed using observations of nesting and brood-rearing behavior. Five species were sufficiently abundant to allow for some statistical analyses: horned lark ( Eremophila alpestris), savannah sparrow ( Passerculus sandwichensis), Baird’s sparrows ( Ammodramus bairdii), chestnut-collared longspur ( Calcarius ornatus) and McCown’s longspur ( Calcarius mccownii). Abundance varied between conventional and minimum tillage regimes for most species in at least one cover type. Savannah sparrows in spring cereal and winter wheat and chestnut-collared longspurs in summerfallow tended to prefer minimum tillage. McCown’s longspurs and horned larks occurred more frequently on conventional than minimum till spring cereal plots in at least 1 of the 2 years. For savannah sparrows, minimum till spring cereal and winter wheat were more productive than conventional till habitat. Summerfallow of either tillage regime did not appear to be as productive as minimum till cereal fields for this species. Chestnut-collared longspurs occurred predominantly in minimum till summerfallow and spring cereal habitat and showed almost no productivity in conventionally managed plots. McCown’s longspurs tended to have higher productivity in minimum till plots. Horned larks had high productivity in minimum till winter wheat in 1996. Male Baird’s sparrows occupied territories in minimum till winter and spring cereal fields in 1995, but did not attract mates; they were not detected in 1996. Minimum tillage appeared to confer benefits in productivity to species that nested in farmland.

Yield Responses and Nutrient Utilization with the Use of Chopped Grass and Clover Material as Surface Mulches in an Organic Vegetable Growing System

ABSTRACT Trials were performed with red beet and white cabbage in 1998–2001 to assess the effects on yields and nutrient utilization of surface mulch (chopped grass and/or red clover). No other nutrients were applied. Nitrogen (N), phosphorus (P) and potassium (K) contents were measured in mulch, saleable products and above-ground plant residues. A single mulch application of about 12 Mg DM ha−1 increased the yields of both crops significantly. Mean yields of saleable products were increased from 27 to 33, and from 44 to 56 Mg FW ha−1 of red beet and white cabbage, respectively. However, the average apparent recoveries of mulch derived nutrients in above-ground plant parts, calculated by subtraction of uptakes in the control treatment, were only 13, 14 and 18% of N, P and K, respectively. Some 3–10% of the N supplied in mulch was found as mineral N at 0–60 cm soil depth after harvest, and in late autumn approximately half of the P and all the K supplied was found as P-AL or K-AL (ammonium lactate and acetic acid) plus acid-soluble K in the topsoil. Mulch application also increased the yield level of spring cereals grown in the following year by on average 0.6 Mg ha−1, or 20%.

Density and productivity of breeding Skylarks Alauda arvensis in relation to crop type on agricultural lands in western France

Capsule Small field size and the maintenance of set-aside and lucerne are important to ensure high breeding pair densities and productivity. Aims To investigate the effects of crop types and their attributes on density and productivity of breeding Skylark. Methods At each of four selected study sites in western France, territory density, vegetation height, vegetation cover and field size was estimated by field and attempts were made to find nests. Crop types included winter and spring cereals, oilseed rape, sunflower, maize, grass, lucerne, set-aside, and bare ground. Results About 80% of Skylark territories included more than one crop type. Birds preferred small fields and territory density decreased with increasing field size. Density was highest in crops with low vegetation height and cover. Set-aside, lucerne and grass supported highest territory density. Fledging productivity was highest in set-aside and lucerne, and was zero on bare ground. Skylark density decreased throughout the breeding season (-26% in 1999 and -29% in 2000), suggesting an instability in territory distribution or activity in intensive farmland. Conclusions Farming systems that decrease field size and increase set-aside and lucerne instead of oilseed rape, maize and sunflower will benefit Skylark and other declining farmland species.

Simulating field-scale nitrogen management scenarios involving fertiliser and slurry applications

The long-term effects of nitrogen (N) fertiliser and slurry management practices in agricultural systems has been simulated using event driven physically based models. The Swedish soil water model SOIL and its associated nitrogen cycle model SOILN has been used to simulate the long-term impacts (over 12 years) of 360 management scenarios; three slurry applications with 10 spreading dates (involving single and split applications) for surface spreading and injection of slurry, and three fertiliser applications with two spreading dates. The effects of the N management scenarios on NO 3–N drainage flows, total gaseous N losses and crop yields for grass, winter and spring cereals is investigated. Furthermore, seven soils with varying degrees of drainage efficiency and three climatic conditions (East and West coast Scotland and Southern Ireland) are studied. The aim of this work is to produce N-budget tables for an expert agricultural decision system (ADS) which deals specifically with N best management practises for fertiliser and slurry applications. Simulations conducted in this study were based on input parameters calibrated for specific sites in previous studies on hydrology and NO 3–N transport to subsurface drains with associated crop growth. The results of this study show that increasing rates of N applications (in the form of slurry and fertiliser) resulted in a non-linear increase in both the N leached through subsurface drains and the N harvest yield. Surface spreading and injection of slurry gave similar trends. The most important decision about slurry spreading concerns the selection of spreading date and the selection of fields which are likely to produce only moderate leaching effects. Application of slurry in autumn (as a single or split loading), invariably leads to large losses through N leaching, with a single application always resulting in the highest loss. Significant differences are evident for N leaching from the seven soil types. Climatic variation as exemplified in the three meteorological data sets, produces noticeable and significant differences in both N leached and harvest crop totals. This study also aims to identify that a field environmental risk assessment (ERA) using a physically based model such as SOILN can be determined such that strategic agronomic decisions involving N management can be made. In practice this is so provided that a farm manager can recognise and match the actual soil type and drainage condition of the fields on which spreading is to occur with the simulated field types within a similar climate region.

Effects of white clover cultivars on biomass and yield in oat/clover intercrops

Intercropping of spring cereals in a permanent stand of white clover (Trifolium repens L.) is a novel, low input cropping system, and little is known about the agronomic management of this system. An experiment was conducted over two growing seasons in 1998 and 1999 to determine the impact of a white clover intercrop on spring oat (Avena sativa L.) growth and grain yield at three different seeding rates of oat, and also to determine the effect of the three different white clover cultivars (cv. Aran, cv. S184 and cv. Milo), on weed pressure and growth of the oat crop. The clover cultivars differed in stolon morphology and leaf size. Oat in monoculture was included for comparison. The white clover intercrops did not reduce the weed pressure compared with oat in monoculture. Oat grain nitrogen concentration and content was raised in the intercropped oats. Grain yields in an intercrop were similar to those in a monoculture. Oat seeding densities did not affect grain yields. The oat grain yields in 1998 were significantly higher with S184 as intercrop. In 1999 it was directly opposite, grain yields were significantly lower with S184 as intercrop.

Plant Growth Regulator Effects on Spring Cereal Root and Shoot Growth

Plant growth regulators (PGR) shorten the straw of cereals, but their effects on other traits of plant stand structure have been inconsistent. To arrive at an assessment of whole‐plant response, experiments were conducted in the greenhouse to study the effect of PGR applications on root and shoot growth of spring cereals. Ethephon, chlormequat chloride (CCC), and trinexapac–ethyl were applied during early growth stages to barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.) cultivars grown either in sand mixture or in clay illitic topsoil. The effects on root and shoot growth (mg plant−1), root/shoot ratio, tiller number, and weight per main shoot were studied in all cereal species. The response of CO2 exchange rate (CER) (μmol CO2 m−2 s−1) and formation of yield potential to PGR treatment were studied more closely in “Mahti” wheat. The effect of CCC application on root area (cm2), length (cm), specific root length (SRL cm/mg), and width (μm) at soil depths of 0 to 20, 20 to 40, and 40 to 60 cm was studied in Mahti wheat. Plant growth regulator applications reduced main shoot growth in barley and wheat up to 20%. Tiller production was enhanced by ethephon and TE treatment in all species, but not adequately to compensate for PGR‐induced reduction in main shoot growth. Carbon dioxide exchange rate was reduced temporarily by ethephon and TE treatments in Mahti wheat. Plant growth regulator applications have modest potential for modifying traits of spring cereal plant stand structure other than straw length.

Farmland carabid beetle communities at multiple levels of spatial scale

Carabid beetle communities were studied at three levels of spatial scale, i.e. within fields (three sets of traps, mean distance 15 m), between fields (five fields within 1 km from each other) and between patches of farmland (four study areas 4–8 km from each other). We compared carabid assemblages sampled on five crop types in each study area, i.e. ley, set‐aside, spring cereal, potato, and sugar beet. Because of small sample sizes, only the community composition was studied within fields with a DCA ordination, but the differences were small. Analyses of species richness, activity density, community composition as revealed by DCA ordinations, dominance structure, diversity, and evenness showed that carabid communities varied significantly among patches of farmland but not between fields with different crops within the patches. Only the communities of potato fields were found to resemble each other. Only five carabid beetle species showed a preference for crops, and twelve species favoured some study areas. We conclude that the effect of spatial scale should be emphasised in further studies as it seems that carabid beetles may be very localised even in agricultural habitats.

Underseeded clover as a nitrogen source for spring wheat on a Gleysol

Although there is a potential to substantially reduce N fertiliser inputs by cropping spring cereals with an interseeded legume, the agronomic value and the nitrate catch-crop effect associated with this practice are not documented under the conditions of eastern Canada. This 3-yr study estimated N credits and non-N nutritional effects for interseeded clover (Trifolium pratense L. 'Arlington') in spring wheat production (Triticum aestivum L. 'Algot') and assessed fall and spring nitrate (NO3−) in soil. The soil is a St. Urbain clay (Orthic Gleysol) located in the St. Lawrence lowlands. Ammonium nitrate (NH4NO3) was applied at 0, 40, 80, 120 and 160 kg N ha-1 with or without red clover as a companion crop. Clover was incorporated as a green manure crop in mid-November. Clover significantly (P = 0.05) influenced wheat yield response to N fertilisation for 2 of the 3 yr. Clover did not reduce wheat grain yield through competition between the two plant species. Higher wheat yields with clover were attributed to N supplied by clover through mineralisation of residues incorporated in the soil the previous fall. Nitrogen fertiliser replacement value of clover was approximately 80 kg N ha-1 for 1994 and 1995. Clover occasionally increased NO3−-N measured in the soil profile in late fall and in spring. Interseeded red clover may provide most of the N needs of a companion spring wheat crop in fine-textured gleysolic soils, but is an inefficient N catch-crop. Key words: N credits, non-N nutritional effect, N catch-crop