Cereal Grain Yield Research Articles

Impact of weather on yield components of spring cereals over 30 years

This investigation examines the relationships between atmospheric influences and the grain yield of spring cereals (spring barley, oats). Also, three yield components — crop density (ears/panicles m −2), number of kernels per ear/panicle and kernel weight — are considered. The study uses data of a long-term field experiment at Berlin–Dahlem for the period between 1962 and 1996. The results show that grain yields as well as the formation and differentiation of yield parameters are clearly influenced by weather fluctuations. Altogether it is possible to explain nearly 60% of the grain yield variability by meteorological variables for both species. The yield components are strongly influenced by weather in different months: the number of kernels per ear/panicle in May during spikelet formation and development, the crop density in June during tiller reduction (declining number of tillers due to intraspecific competition effects), and, finally, the kernel weight in June and July during grain filling. Grain yields of spring barley are mainly influenced by crop density and number of kernels per ear; for the grain yield of oats, the most important component is the number of kernels per panicle, which depends highly on the weather conditions in May.

The effect of incorporation time of different crops on the residual effect on spring cereals

The effect of the time of incorporation of different green manures and barley residues on the grain yield of spring cereals in two successive seasons was studied in seven field trials. Annual hairy vetch (Vicia villosa Roth), red clover (Trifolium pratense L.), westerwold ryegrass (Lolium multiflorum Lam. var. westerwoldicum) and straw of spring barley (Hordeum vulgare L.) were incorporated into the soil by ploughing in early September, late October and the following May, and by reduced tillage in May. Spring barley was established in the following spring, and spring oats (Avena sativa L.) one year later. In general the grain yield of spring barley after legumes was similar to that after barley, in spite of the fact that N fertilization was reduced by 40 kg ha-1. The two autumn ploughing treatments resulted in a good yield of spring barley more reliably than did the spring incorporations. Because delayed autumn ploughing did not decrease the grain yield, a delaying procedure can be recommended for its potential of decreasing nitrogen leaching. Spring ploughing could be used on all but clay soils. Incorporating ryegrass or red clover in spring by using reduced tillage often decreased the grain yield of barley. Timing of incorporation did not have a consistent effect on the grain yield of oats in the third experimental year.;

Genotype by environment interaction for grain yield and carbon isotope discrimination of barley in Mediterranean Spain

Carbon isotope discrimination (Δ) has been found to be either positively or negatively related to grain yield of small grain cereals when grown in contrasting environments. In order to clarify a possible association between grain yield of barley (Hordeum vulgare L.) and Δ of mature kernels, five 6-rowed and five 2-rowed barley cultivars were evaluated in 22 rainfed environments of northern Mediterranean Spain. Analyses of variance suggested that the genotypic Δ values were more consistent across environments than the genotypic yields. Genotype×environment (G×E) interaction for grain yield was further explored by fitting an AMMI (additive main effects and multiplicative interaction) model. The first 2 multiplicative axes were found significant. The AMMI2 model provided more accurate estimates of genotypic yields within environments than the conventional unadjusted means across replicates. AMMI2 estimates were used for input into cluster analysis, grouping environments that ranked genotypic yields similarly. Three major groups were obtained, with average yields of 2.42 t/ha (cluster I), 3.06 t/ha (cluster II), and 5.16 t/ha (cluster III). The genotypic ranking for Δ did not vary substantially across clusters, but it changed for grain yield. The average genotypic yields in the low-yielding cluster I ranked opposite to those in the high-yielding cluster III, suggesting the existence of a crossover point at an intermediate yield level. The association between grain yield and Δ for genotypic means within clusters was variable. In cluster I, yield and Δ tended to be negatively related, whereas they were positively related in clusters II and III. Genotypes with lower Δ, i.e. with higher transpiration efficiency, performed better in low-yielding environments (mostly those grouped in cluster I). On the contrary, a high genotypic Δ was of advantage in medium (cluster II) and high-yielding environments (cluster III). This observation supports the assumption that drought tolerance and high yield potential under non-limiting growing conditions may be antagonistic concepts in barley. Genotypic means for kernel number per m 2 and Δ were consistently and positively related within clusters, suggesting that a constitutively high Δ may have been driven by a large genotypic reproductive sink. The convenience of using Δ as a selection criterion in areas exhibiting a considerable G×E interaction for grain yield is discussed.

Mineral accumulation, carbon isotope discrimination and indirect selection for grain yield in two-rowed barley grown under semiarid conditions

Mineral accumulation in vegetative plant parts and in mature kernels has been proposed as an indirect selection criterion, either in addition to, or in substitution of, carbon isotope discrimination ( Δ), to assess grain yield of temperate cereals in Mediterranean areas. However, the association between mineral concentration, in different plant parts, and grain yield is not yet fully understood. In order to study these relationships, four rain-fed trials were established in northeastern Spain involving 10 two-rowed barley ( Hordeum vulgare L.) cultivars. Carbon isotope discrimination and total ash concentration were measured at maturity in kernels and straw. As expected, the Δ values of kernels ( Δ-K) and straw ( Δ-S) were positively correlated within environments. By contrast, Δ-K and ash concentration in kernels were often negatively related within environments, which suggests that mineral accumulation in kernels is not associated with the transpiration efficiency of the plants during grain filling. The lack of a positive relationship between ash concentration in the straw and either Δ-K or Δ-S indicates that ash concentration in vegetative tissues sampled at maturity may be of limited value as a surrogate of Δ. Grain yield correlated positively with either Δ-K or Δ-S, and negatively with ash concentration in kernels, especially in the poorest rain-fed environments. However, the ash concentration in the straw was not consistently associated with grain yield. While our results confirm that Δ traits are valid indicators of grain yield under Mediterranean conditions, the use of ash concentration in kernels for screening purposes is not warranted at this time due to the lack of a more accurate understanding of the physiological mechanisms underlying mineral accumulation in kernels. Prediction of grain yield through multiple linear regression has shown, however, that ash concentration in kernels could be used as a complementary criterion to Δ in poor rain-fed environments.

Effects of zinc fertilization and irrigation on grain yield and zinc concentration of various cereals grown in zinc‐deficient calcareous soils

Effects of varied irrigation and zinc (Zn) fertilization (0, 7, 14, 21 kg Zn ha‐1 as ZnSO47.H2O) on grain yield and concentration and content of Zn were studied in two bread wheat (Triticum aestivum), two durum wheat (Triticum durum), two barley (Hordeum vulgare), two triticale (xTriticosecale Wittmark), one rye (Secale cereale), and one oat (Avena sativa) cultivars grown in a Zn‐deficient soil (DTPA‐extractable Zn: 0.09 mg kg‐1) under rainfed and irrigated field conditions. Only minor or no yield reduction occurred in rye as a result of Zn deficiency. The highest reduction in plant growth and grain yield due to Zn deficiency was observed in durum wheats, followed by oat, barley, bread wheat and triticale. These decreases in yield due to Zn deficiency became more pronounced under rainfed conditions. Although highly significant differences in grain yield were found between treatments with and without Zn, no significant difference was obtained between the Zn doses applied (7–21 kg ha‐1), indicating that 7 kg Zn ha‐1 would be sufficient to overcome Zn deficiency. Increasing doses of Zn application resulted in significant increases in concentration and content of Zn in shoot and grain. The sensitivity of various cereals to Zn deficiency was different and closely related to Zn content in the shoot but not to Zn amount per unit dry weight. Irrigation was effective in increasing both shoot Zn content and Zn efficiency of cultivars. The results demonstrate the existence of a large genotypic variation in Zn efficiency among and within cereals and suggest that plants become more sensitive to Zn deficiency under rainfed than irrigated conditions.

Comparison of two spring seeding methods to establish forage cover crops in relay with winter cereals

The establishment of cover crops, in relay, to minimise soil erosion, improve soil physical condition and provide a main-season crop in rotation with potatoes ( Solanum tuberosum L.) is a recommended agronomic practice in Atlantic Canada. This is usually achieved by seeding winter rye ( Secale cereale L.) or winter wheat ( Triticum aestivum L.) immediately after potato harvest for ground cover followed, the next spring, by inter-seeding an annual or biennial forage crop by drilling. Spring drill seeding can, however, be delayed or prevented by wet ground conditions, thus, making broadcast seeding a considered alternative. This study examined, therefore, the comparative merits of spring broadcast seeding and drill seeding of two adapted forages, Italian ryegrass ( Lolium multiflorum Lam.) and red clover ( Trifolium pratense L.), into a standing crop of fall-seeded winter rye or winter wheat. Crop performance was evaluated, using meter-square quadrats, as ground coverage and grain yield (of cereals). Soil compaction, evaluated as shear strength in the 0–15 cm layer (avoiding wheel tracks) of a fine sandy loam (Orthic Podzol), was greater after drill seeding than after broadcast seeding by a factor of 7.2% and was attributed to the greater ground-contact mass of the drill seeder. The forage crops provided 5.5% more ground coverage with drill seeding than with broadcast seeding. However, seeding method had no effect on the cereal host crops' ground coverage or grain yield. Ryegrass coverage was 123% of red clover coverage and winter rye coverage was 176% of winter wheat coverage. Forage coverage, in this study, suffered no setback because of the greater soil compaction associated with drill seeding. However, soils are subject to greater compaction under wetter conditions, thus, broadcast seeding is expected to be a better option, the wetter the spring.

Differential response of rye, triticale, bread and durum wheats to zinc deficiency in calcareous soils

Field and greenhouse experiments were carried out to study the response of rye (Secale cereale L. cv. Aslim), triticale ( Triticosecale Wittmark. cv. Presto), two bread wheats (Triticum aestivum L, cvs. Bezostaja-1 and Atay-85) and two durum wheats (Triticum durumL. cvs. Kunduru-1149 and C-1252) to zinc (Zn) deficiency and Zn fertilization in severely Zn-deficient calcareus soils (DTPA-Zn=0.09 mg kg 1 soil). The first visible symptom of Zn deficiency was a reduction in shoot elongation followed by the appearance of whitish-brown necrotic patches on the leaf blades. These symptoms were either absent or only slight in rye and triticale, but occurred more rapidly and severely in wheats, particularly in durum wheats. The same was true for the decrease in shoot dry matter production and grain yield. For example, in field experiments at the milk stage, decreases in shoot dry matter production due to Zn deficiency were absent in rye, and were on average 5% in triticale, 34% in bread wheats and 70%, in durum wheats. Zinc fertilization had no effect on grain yield in rye but enhanced grain yield of the other cereals. Zinc efficiency of cereals, expressed as the ratio of yield (shoot dry matter or grain) produced under Zn deficiency compared to Zn fertilization were, on average, 99% for rye, 74% for triticale, 59% for bread wheats and 25% for durum wheats. These distinct differences among and within the cereal species in susceptibility to Zn deficiency were closely related to the total amount (content) of Zn per shoot, but not with the Zn concentrations in shoot dry matter. For example, the most Zn-efficient rye and the Zn-inefficient durum wheat cultivar C-1252 did not differ in shoot Zn concentration under Zn deficiency, but the total amount of Zn per whole shoot was approximately 6-fold higher in rye than the durum wheat. When Zn was applied, rye and triticale accumulated markedly more Zn both per whole shoot and per unit shoot dry matter in comparison to wheats. The results demonstrate an exceptionally high Zn efficiency of rye and show that among the cereals studied Zn efficiency declines in the order rye>triticale>bread wheat>durum wheat. The differences in expression of Zn efficiency are possibly related to a greater capacity of efficient genotypes to acquire Zn from the soil compared to inefficient genotypes.

Effect of sowing point design and tillage practice on the incidence of Rhizoctonia root rot, take-all and cereal cyst nematode in wheat and barley

Effect of tillage treatments on the cereal root diseases, rhizoctonia root rot, take-all and cereal cyst nematode, and on grain yield of cereals were tested in 4 field experiments over 3 years. Conventionally cultivated treatments were compared with a range of direct-drill treatments using either a standard tined seed drill equipped with 10 cm sowing points, a specialised drill designed to give minimal soil disturbance or a standard tined seed drill equipped with a range of commercial or modified narrow points designed to provide soil disturbance from 0 to 5.0 cm below seed depth. Direct-drilled treatments that disturbed the soil below seed depth (DDD) and treatments that included 1 cultivation prior to sowing (CPS) resulted in a reduction of rhizoctonia root rot when compared with direct-drilled treatments that did not disturb the soil below seed depth (DDN). When seasonal conditions encouraged volunteer plant growth before sowing, a chemical fallow treatment applied 3 weeks before sowing significantly reduced rhizoctonia root rot in all direct-drilled plots. This was a significant factor in DDD treatments providing effective control of rhizoctonia root rot. Take-all was present in 3 of the 4 experiments. In 2 experiments, take-all was significantly higher in plots following DDN treatments than DDD or CPS treatments and in 1 experiment there was no effect of tillage. Cereal cyst nematode was present in 1 of the 4 experiments. The level of root damage from cereal cyst nematode was least in plots following DDN treatments, higher following DDD treatments and highest following CPS treatments. The influence of tillage practice on grain yield was closely related to the effect of tillage on cereal root disease when levels of disease were moderate to high. Where the incidence of root disease was low, grain yield differences due to tillage treatments were generally related to agronomic factors such as seed depth and seedbed condition.

Effect of sulphur fertilizers on the grain yield and sulphur content of cereals

SUMMARYIn order to determine whether cereal crops require fertilizer sulphur (S) in areas estimated as receiving < 20 kg S/ha per year from the atmosphere, the effects of applying agricultural gypsum (10, 20, 30, 40, 60 and 80 kg S/ha), ammonium sulphate (24 and 48 kg S/ha) and foliar-applied elemental S (10 kg S/ha) fertilizers were compared with a nil-S control in replicated field experiments at 12 sites in England and Wales during 1987–90. Averaged across all S treatments, significant (P ≤ 0·01) positive yield responses of 0·4 t/ha were obtained in winter barley at three sites in 1990 on sandy soils in Wales (two sites) and in south-west England (one site). There was no yield advantage in applying > 10 kg/ha of S as gypsum at these sites. Yield responses were best predicted by a nitrogen: S concentration ratio ≥ 17:1 in leaf tissue at anthesis and a S concentration of ≤ 0·1% in the grain dry matter at harvest.Significant increases in total S and sulphate-S concentrations in leaf tissue at anthesis were obtained from increasing the rates of gypsum applied at ten of the sites, but a significant increase in the concentration of S in the grain at harvest was obtained at only one site. There was no difference in effectiveness between gypsum and foliar-applied elemental sulphur when compared at a single rate of 10 kg S/ha. Comparison of the increases in leaf-S status from maximum application rates of ammonium sulphate and gypsum suggested that ammonium sulphate was the more effective Sfertilizer source. The results confirm that S deficiency is starting to appear in cereal crops in England and Wales.

Yield components in relation to grain yield losses of barley fertilized with nitrogen

Application of nitrogen (N) fertilizer above the optimum rate suppresses grain yield of cereals in environments in which water supply is limited towards the end of the growing season. The aim of this study was to examine the effect of N fertilizer application on yield components of barley. The two-rowed barley locally named Kantara was grown for eight growing seasons in different long-term rotational experiments at two locations under rainfed conditions (200 to 450 mm) in Cyprus. Four rates of ammonium sulphate (0, 30, 60 and 90 kg N ha−l) were applied at sowing.Nitrogen application linearly increased the number of spikes per unit area and linearly decreased the weight per grain. The number of grains per spike and grain yield per unit area showed a quadratic response to nitrogen application, in which an initial increase was followed by a reduction at higher rates of N application. Stepwise regression analysis showed that the importance of variation in each yield component for explaining variation in grain yield varied with season, with the weight per grain being usually the least important, though always being statistically significant. Most of the variation in grain yield was explained by the number of grains per spike and by the number of tillers M−2. Strategies for managing N fertilizer application for specific environment and rotation systems for avoiding yield loss are suggested.

Effects of Temporary Water Stress After Anthesis on Grain Yield and Yield Components in Different Tiller Categories of Two Spring Wheat Varieties

AbstractWater stress might limit grain yields of cereals under humid conditions. The objective of this study was to investigate the effect of a temporary water shortage at three different stages after anthesis on the grain yield and yield components of different tiller categories in two spring wheat varieties. A pot experiment with controlled water supply and rain shelters was conducted in 1984 and 1985 in Kiel, N. W. Germany. The water stress (pF 2.9 to 3.4) was imposed either between anthesis to early milk development of the caryopsis (WS1) (EC 65 to EC 72 according to Zadoks scale), early milk development to late milk development of the caryopsis (WS2) (EC 72 to EC 77) and late milk development to maturity (WS3) (EC 77 to EC 92). The control had a constant water supply throughout the growing season of between pF 2.2 to 2.5.The water stress treatment WS1 significantly reduced the single plant yield by 10 % (1984) and 15 % (1985) in one variety (Selpek), whereas the other variety was unaffected. The response of both varieties to the two later treatments was smaller and insignificant.In the first year the yield decrease in the variety Selpek after the WS1 treatment was mainly caused by a lower number of ears per plant compared with the untreated control (WS0). In the second year (1985) additionally a lower grain weight of the second category shoots caused by a reduction of the number of kernels per ear contributed to the decrease of the single plant yield. The yield component thousand grain weight could not compensate for the reduction in the number of kernels per ear.

Early Generation Selection for Grain‐Filling Period in Wheat

Grain‐filling period (GFP) may be a useful physiological selection trait that could influence grain yield of cereals. This study was conducted to estimate heritability of GFP and to determine the response to selection for long and short GFP in six genetically diverse populations of spring wheat (Triticum aestivum L. emend. Thell.). Selections were made in the F2 generation and selected progenies were evaluated in replicated field tests in the F3 generation. The tests were seeded under normal and late conditions at Rampur, Nepal, in 1990. Date of seeding had a significant effect on GFP, grain and biomass yield, harvest index, and hundred kernel weight. Selection in the F2 for long and short GFP was effective in identifying F3 lines with long and short GFP, respectively. Also, selection for long GFP usually resulted in higher grain and biomass yield. Average harvest index and hundred kernel weight of the long GFP lines were higher than those of the short GFP fines. Realized heritability estimates for GFP were intermediate to high in magnitude (0.52–0.86). Duration of GFP had a high positive genotypic correlation with grain yield (0.52–0.79), harvest index (0.50–0.80), and hundred kernel weight (0.53–0.72). Results indicated that selection for long GFP in early segregating generations should bring about positive improvements in these yield components.

Effects of withholding phosphate and potash fertilizer on grain yield of cereals and on plant-available phosphorus and potassium in calcareous soils

To determine to what extent extractable phosphorus (P) and potassium (K) in calcareous soils can be depleted without yield loss in cereal crops, all combinations of 0 and 22 kg ha−1 of fertilizer P and 0 and 42 kg ha−1 of fertilizer K were applied each year at two sites in south-west England. At a site with a shallow chalk soil in a grass-arable rotation and at a site with a shallow limestone soil in continuous cereals, withholding P fertilizer for more than 3 years was judged to be detrimental to grain yield. A yield benefit to applied K was obtained in the ninth and subsequent years at the chalk site but withholding K fertilizer did not reduce yield at the limestone site over an 8-year period.On non-fertilized plots, extractable P and K concentrations in the soil declined by approximately 50 per cent at both sites but the rate of decline was faster at the limestone site, where the amounts of P and K in the soil were initially greater. Extractable P and K in the soil were also not maintained on fertilized plots even though the amount of fertilizer P (both sites) and fertilizer K (limestone site) applied was equal to or greater than the calculated offtake of P and K in the crop. Extractable K in the soil stabilized towards the end of the run-down period, indicating a release of non-exchangeable K. The results highlight the shortcomings of P and K fertilizer policies which rely solely on soil analysis or which simply match crop offtake.

Partitioning of injuries caused by winter, fungal diseases and viral infections in cereals

The objective of this study was to clarify whether the critical levels of winter damage, viral infections and foliar diseases of cereals could be established by the Cate-Nelson procedure. This information would help the State Granary representatives and computer modelists, as well as farmers and consultants to understand the yearly variations in grain yields of cereals. Three winter rye, spring wheat and oat cultivars were used. The severity of leaf diseases and percentages of winter damage were observed visually. When winter damage exceeds 19%, a yield reduction of 44% (1804 kg ha-1) in winter rye may be expected. The critical level of Septoria nodorum infection in spring wheat was 37%. Above this critical level a yield reduction of 33% (1393 kg ha-1) was estimated. In oat canopy an area of > 38% infected by barley yellow dwarf virus (BYDV) decreased the grain yield significantly by 30% (1718 kg ha-1).

Agronomic response of six-row barley cultivars to supplemental fertilization and late-season fungicide treatments

Management practices such as the use of fertilizers and fungicides can have positive effects on grain yield and quality of cereals, especially where diseases are a concern. Six cultivars of six-row barley (Hordeum vulgare L.) were tested at two fertility levels (standard and high) with a late-season application of the foliar fungicide Tilt (propiconazole) to determine their agronomic responses to these management practices. In 1988, when yields were limited because of early season drought, only Leduc showed a positive yield response to the Tilt, even though it has the highest level of genetic resistance to scald and net blotch of the cultivars tested. In 1989, when yields were again limited by adverse environmental conditions, no response to Tilt was found. In 1990, when growing conditions during the season were excellent, Empress, Noble and Samson had positive responses to Tilt application. Tilt had no effect on grain protein, maturity, or harvest index; it slightly improved test weights and kernel weights and decreased percent thins; and it had variable effects on height, number of viable tillers m−2, and kernel number spike−1. Yield response to Tilt was not affected by fertility regime. High fertility (112 kg ha−1 N 37 kg ha−1 P) resulted in an overall increase in yield of 0.62 t ha−1 from the standard fertility treatment (84 kg ha−1 N 27 kg ha−1 P); decreased harvest index; delayed maturity in 1989 only; increased height, number of viable tillers m−2, and kernel number spike−1; increased protein content of the grain in 1988 only; and had no effect on test weight, kernel weight and percent thins. Because of the variability of response from year to year and cultivar to cultivar, the economic feasibility of Tilt application may be limited.Key words: Hordeum vulgare L., propiconazole, soil fertility, management

Performance of S2 Winter Barley Progenies from Original and Improved Populations Developed via Recurrent Selection

AbstractThe effect of recurrent selection procedure for improving grain yield in autogamous cereals was evaluated in a six‐rowed winter barley population. Gain from selection was estimated by field testing 90 random S2 lines from each of the C0, C1 and C2 populations. Response to selection for grain yield was 0.78 t/ha from C0 to C1 and 1.09 t/ha from C1 to C2. Broad‐sense heritability and genotypic variance for grain yield remained high in all cycles which suggests further gain from additional selection cycles. Yield increase was due to a higher number of seeds/m2. Significant differences among mean values were observed for heading date (189 days in C0 and 182 days in C2), whereas no variation was seen for plant height and 1000‐kernel weight. The proposed recurrent selection procedure appears effective to improve the population and to extract superior genotypes for varietal development.

Effects of perennial forage-legume living mulches on no-till winter wheat and rye

No-till winter cereals sown in narrow rows may compete successfully with perennial forage-legume living mulches that can fix nitrogen (N), conserve soil, increase dry-matter production, and suppress weeds. The effects of small-grain species, mulch species, and top-dress N on grain and mulch yield and the grain N concentration of winter cereals direct-drilled into legume living mulches were examined in a two-year field study in New York, U.S.A., on soils of the Lima and Kendaia series: fine-loamy, mixed, mesic Glossoboric and Aeric Hapludalfs. Wheat ( Triticum aestivum L.) or rye ( Secale cereale L.) were grown in monoculture or drilled into summer-established plots of alfalfa ( Medicago sativa L.), birdsfoot trefoil ( Lotus corniculatus L.), crownvetch ( Coronilla varia L.), ladino clover ( Trifolium repens L. forma lodigense Hort ex. Gams), red clover ( T. pratense L.), or white clover ( T. repens L.). Spring top-dress N was applied at 0 or 56 kg N ha −1. Cereals were reseeded for a second season. Mulches generally interfered more and yielded more with wheat than with rye. Birdsfoot trefoil, crownvetch, and white clover had little effect on grain-yield the first year; birdsfoot trefoil and crownvetch interfered strongly with cereals the second year. Red clover did not affect rye grain-yield in the absence of top-dress N, but did tend to reduce wheat yield. Top-dress N increased cereal grain-yield and decreased mulch yield. In general, legume mulches did not appear to enhance cereal N nutrition the first year; red and white clovers appeared to contribute N to rye the second year. Second-year grain-yields were generally lower than first-year yields, due to increased interference from living mulches and broadleaf weeds. All living mulches except crownvetch suppressed weeds the second year. The results indicate that some species of perennial forage legumes may be suitable for use as living mulches for direct-drilled small grains, especially tall early winter cereals.

Evaluation of two rock phosphates and a calcined rock phosphate as maintenance fertilizers for crop ? pasture rotations in Western Australia

Two long-term (11 and 12 y) field experiments in south-western Australia are described that measured the relative effectiveness of three rock phosphate fertilizers (C-grade ore, Calciphos and Queensland (Duchess) rock phosphate), single, double and triple superphosphate. The experiments were on established subterranean clover (Trifolium subterraneum) — based pasture that had received large, yearly, applications of single superphosphate for many years before the experiments began so that in the first year the nil phosphorus (P) treatment produced 80 to 90% of the maximum yield. The experiments were conducted using a rotation of one year cereal crop (oats,Avena sativa at one site, and barley,Hordeum vulgare, at the other): 2 y pasture, a typical rotation on farms in the region. Five levels of each P fertilizer were applied every third year with the crop. Grain yield of cereals, P content of grain, pasture yield, and bicarbonate-soluble P extracted from the soil (available P) were used to estimate fertilizer effectiveness values.

High Phytomass Producing Oats for Cultivation in Northern Growing Conditions

AbstractIt has been argued that the breeding of cultivars with higher weight per panicle but constant phytomass (i.e., improved harvest index) is unlikely to improve grain yield of cereals in the future. To examine this question in oats, this study observed relationships between above‐ground phytomass production and grain yield as well as 18 morphological and physiological traits representing maturity class and architecture of oat stand. The study was conducted in two dissimilar growing seasons. Material consisted of 29 Finnish and Scandinavian oat cultivars and breeding lines. Correlations between phytomass and other traits were evaluated by linear regression analysis. The study revealed that there has already been a trend toward improving the above‐ground phytomass production in cereal breeding in Finland. The phytomass elevation can be attributed to both higher panicle weight as well as increased above‐ground vegetative phytomass. Thus, improved grain yield of oats is not merely a consequence of increased harvest index, as is often mentioned, but is also a result of higher phytomass as such. The weight of the above‐ground phytomass did not correlate with undesirable traits such as plant height or susceptibility to lodging, but it did have a positive relationship with days to yellow ripening. The applicability of phytomass weight in indirect yield breeding of oats in the northern growing conditions is discussed.

RELATIVE MEASURES OF SOIL BULK DENSITY TO CHARACTERIZE COMPACTION IN TILLAGE STUDIES ON FINE SANDY LOAMS

Field studies concerned with soil physical properties require methods to quantify and characterize soil compaction, especially for tillage experiments. The bulk densities of a Charlottetown and Gowanbrae fine sandy loam were related to a maximum or standard compaction state for each soil to obtain a measure of relative compaction. The two soils were both classified as Orthic Humo-Ferric Podzols. Relative compaction was closely related to the volume of macropores (r2 = 0.85). Over a 3-yr period, mouldboard ploughing loosened the soil to give an average relative compaction of 77%. Subsequent soil consolidation and settling increased relative compaction to 84% over the growing season. Direct-drilling maintained relative compaction at a limited range of 88–91%. Relative grain yield of cereals was related (r2 = 0.69) using a polynomial curve to relative compaction. A range of 77–84% relative compaction was associated with a relative grain yield ≥ 95%. A relative compaction of 84–89% was considered the equilibrium soil density level for the two soils under study. This range was related to a macropore volume of 13.5–10% which is adequate for permeability but possibly inadequate for optimum soil aeration under a humid soil moisture regime. Overall, relative compaction provided a useful index or standard to assess changes in soil bulk density and proved to be a biologically meaningful soil physical parameter. Key words: Soil compaction indices, relative compaction, Podzolic soil, fine sandy loam, cereal yield