Durum Wheat Grain Yield Research Articles

Sowing date affect spikelet number and grain yield of durum wheat

Shifts in sowing date change the combination of temperature and photoperiod to which durum wheat is exposed, affecting crop phenology and grain yield. Three durum wheat ( Triticum turgidum L. var. durum ) varieties were field sown at month intervals over a whole year. The number of spikelets on the main culm and the duration of the period of spikelet initiation were recorded. Grain yield, spike number, and mean kernel weight were determined, too. With all sowing dates, plants formed a spike within the main culm and reached the stage of first node detectable. Physiological maturity was achieved only for sowings performed between October and May. Grain yield was highest in November and both yield and yield components were strongly affected by sowing date. The number of spikelets ranged from 11 to 24, according to sowing date and variety. It decreased from November to May in consequence of the shorter initiation period, and we hypothesize that a 12-h-daylength or longer interrupts spikelet initiation. The de...

Analysis of Genotype × Environment Interactions for Grain Yield in Durum Wheat

Genotype × environment (GE) interactions are important sources of variation in crop breeding programs. The objectives of this study were (i) to analyze GE interactions on grain yield of one bread wheat (Triticum aestivum L.) and 19 durum wheat [T. turgidum L. subsp. durum (Desf.) Husn.] genotypes by the additive main effects and multiplicative interaction (AMMI) model, and (ii) to evaluate genotype (G), environment (E), and GE interactions with the statistical parameters of AMMI statistic coefficient (D), AMMI stability value (ASV), regression coefficient (b) and ecovalence (W2). Main effects due to E, G, and GE interaction as well as first three interaction principal component axes (IPCA 1 to 3) were found to be significant (P < 0.01). The AMMI biplots distinguished genotypes with wide and specific adaptation and environments with high and low genotype discrimination ability. Ranking the statistical parameters indicated that they are similar in general, especially for the genotypes with similar responses and also for the environments with similar discrimination ability. The results show that the statistical parameters as well as the AMMI model are useful for analyzing GE interaction. Based on the AMMI model, the recommended genotypes had more grain yield improvement in favorable than unfavorable environments. The genotypes selected based on stability of grain yield combined high stability and high‐yielding performance.

Pattern analysis of genotype-by-environment interaction for grain yield in durum wheat

SUMMARYPattern analysis, cluster and ordination techniques, was applied to grain yield data of 20 durum wheat genotypes grown in 19 diversified environments during 2005–07 to identify patterns of genotype (G), environment (E) and genotype-by-environment (G×E) interaction in durum multi-environment trials (METs). Main effects due to E, G and G×E interaction were highly significant, and 0·85 of the total sum of squares (SS) was accounted for by E. Of the remaining SS, the G×E interaction was almost 12 times the contribution of G alone. The knowledge of environmental and genotype classification helped to reveal several patterns of G×E interaction. This was verified by ordination analysis of the G×E interaction matrix. Grouping of environments, based on genotype performance, resulted in the separation of different types of environments. Pattern analysis confirmed the cold and warm mega-environments, and allowed the discrimination and characterization of adaptation of genotypes. However, several patterns of G×E interaction in Iran's regional durum yield trials were further discerned within these mega-environments. The warm environments tended to be closer to one another, suggesting that they discriminate among durum genotypes similarly, whereas cold environments tended to diverge more. The dwarf and early maturing breeding lines from ICARDA with low to medium yields and high contribution to G×E interaction were highly adapted to warm environments, whereas the tall and later maturing genotypes with low to high yields were highly adapted to the cold environments of Iran.

Influence of Phosphorus, Nitrogen, and Potassium Chloride Placement and Rate on Durum Wheat Yield and Quality

Information regarding the impact of P and KCl rate and placement in conjunction with N rate on durum wheat (Triticum turgidum L. var. durum) is limited in the Great Plains. Our objectives were to determine the effects of N, P, and KCl fertilizer rate and P and KCl placement on grain yield and quality of durum wheat grown on low P soils. Nine combinations of N and P fertilizer and five combinations of N, P, and KCl applied with the seed and in a side band, were compared over 3 yr at Indian Head, SK, in fields with soil P levels <9 kg ha−1. Grain yield increased 15% as N application increased from 45 to 140 kg ha−1. Grain yield increased by 10% as the P rate increased from 0 to 17 kg ha−1 under dry conditions in 2003, but not in 2002 and 2004. No interaction was detected between N and P for grain yield. Grain yield was unaffected by KCl application and P or KCl placement, in the high K soils included in the study. Grain protein increased from 123 to 150 g kg−1 as N fertilizer rate increased, but decreased from 140 to 136 g kg−1 as more P was applied. However, Red smudge decreased as P increased. Results from this study indicate that N application does not affect the amount of P required by durum wheat and that yield responses to P can occur in soils low in P under dry conditions.

Post-emergence application of N fertilizer to improve grain yield and quality of irrigated durum and bread wheat

Field studies were conducted for 3 yr (2001 to 2003) at two irrigated sites in southern Alberta to determine if post-emergence N application (38 kg N ha-1) was warranted for durum (Triticum turgidum L.) and bread wheat (T. aestivum) in soils with relatively high N. Greater efficacy occurred with in-crop surface-applied granular ammonium nitrate (AN) compared with foliar-applied urea-ammonium-nitrate (UAN) solution. Early AN application usually improved grain yield compared with the fertilized control (38 k g N ha-1 applied at seeding), while late application reduced grain yield, but increased grain protein concentration and end-use quality. Key words: Triticum turgidum, Triticum aestivum, nitrogen fertilizer, foliar, timing, split N, grain protein concentration

Fertilisation and weed control effects on yield and weeds in durum wheat grown under rain‐fed conditions in a Mediterranean climate

Summary A field study was undertaken to examine the effect of fertiliser type and weed control system on grain yield, yield components and weed population in durum wheat (Triticum turgidum. var. durum) grown in a 4‐year rotation [bare fallow–barley (Hordeum vulgare)–vetch (Vicia sativa)–wheat]. Fertilisation treatments were: no fertilisation, organic fertilisation with 2500 kg ha−1 of compost (sheep manure and cereal straw) and chemical fertilisation with 100–60–60 kg ha−1 of NPK. Weed‐control treatments were: no control, herbicide, harrowing with long‐flex spring tines and strip sowing with inter‐row hoeing. Chemical fertilisation increased grain yield with respect to the other treatments, amongst which no significant differences were noted. Weed‐control systems afforded no improvement in yield compared with controls; indeed, yields obtained using inter‐row hoeing were lower. The weed population consisted of a large variety of species, of which the most important were Convolvulus arvensis and Polygonum aviculare. Application of weed‐control systems reduced weed density. Herbicide was the most effective, reducing weed biomass by 80%, whilst harrowing and hoeing reduced weed biomass by 40% and 52% respectively. Inter‐row hoeing does not appear to be a viable alternative to herbicides, when used as the sole weed control method in a non‐diverse cropping system in Mediterranean climates. The lack of response to compost suggests a need for further long‐term research.

Estimates of heterosis and association of genetic distance with heterosis in durum wheat under different moisture regimes

The objectives of the present study were to evaluate heterosis for grain yield and yield components in durum wheat, and to assess the prediction potential of amplified fragment length polymorphism (AFLP) based and agronomic trait based genetic distances (GD and MD, respectively) to F1 performance, mid parent heterosis (MPH), and specific combining ability effects (SCA) under well-watered and moisture stress conditions. Six parental genotypes with different responses to moisture stress and their 15 F1 crosses were evaluated for their responses to moisture stress conditions in a glasshouse. Some cross combinations showed significant MPH for grain yield and yield components. The expression of heterosis for grain yield was greater under moisture stress conditions than under well-watered conditions. Cluster analysis of the parental lines based on agronomic performance under stress conditions was similar to cluster analysis result based on AFLP marker profiles. F1 performance was strongly correlated to both SCA effects and MPH under both stress and well water conditions. The correlation between SCA and MPH was very high under both treatment conditions for all traits. Correlation between GD and MD was significant only under stress conditions. Positive correlation was found only for the association between GD v. F1 performance and GD v. SCA effects for harvest index (HI) under well-watered conditions. None of the correlations between MD and SCA effects were significant. The absence of association between GD and heterosis for yield and most agronomic traits implied that heterozygosity per se diversity is not a good predictor of heterosis or F1 performance under both well-watered and stressed conditions.

Dry matter accumulation and remobilization of durum wheat as affected by soil gravel content

Soil gravel content affects many soil physical properties, i.e. bulk density, porosity, water infiltration and storage, as well as crop yield. Little is known regarding the influence of soil gravel content on grain yield of durum wheat ( Triticum durum Desf.). In this paper the accumulation of dry matter during the vegetative and reproductive periods and the contribution of pre-anthesis assimilates to grain yield have been evaluated in two durum wheat varieties grown on soils with 0, 10, 20, and 30% gravel content. The two varieties showed similar behaviour and more soil gravel decreased plant biomass both at anthesis and at maturity. Soil gravel content greatly reduced grain yield and dry weight of all plant parts both at anthesis and maturity. Post-anthesis dry matter accumulation was 16% lower in plants grown on 30% gravel soil and dry matter remobilization was 53% lower, compared to plants grown in gravel-free soil. The differences in growth rate were attributed to the restriction of the volume of soil available for root growth.

Parametric stability analyses for grain yield of durum wheat

Grain yield of 15 durum wheat (Triticum durum Desf.) genotypes consisting of 13 cultivars and 2 advanced lines, tested in a randomized complete block design with four replications across 8 environments of Central Anatolian Region of Turkey was analyzed using nine parametric stability measures. The objectives were to assess genotype-environment interactions (GEI), determine stable genotypes, and compare mean grain yield with the parametric stability parameters. To quantify yield stability, nine stability statistics were calculated (b<sub>i</sub>, S<sup>2</sup><sub>di</sub>, R<sub>i</sub><sup>2</sup>, W <sub>i</sub><sup>2</sup>, σ<sub>i</sub><sup>2</sup>, S<sup>2</sup><sub>i</sub>, α<sub>i</sub> and λ<sub>i</sub>). Yilmaz-98, Cakmak-79, Kiziltan-91, Selcuklu-97 and C-1252 were more stable cultivars, which had 9, 8, 6, 6, 6 out of all 9 stability statistics used, respectively. Especially, among these cultivars, Yilmaz-98 and Cakmak-79 were the most stable cultivars. Furthermore, three-dimensional plots of mean response versus each stability statistic were shown to visually evaluate the yield potential and stability estimates of the genotypes. Genotype mean yield (–x) was significantly positively correlated to the regression coefficient (b<sub>i</sub>), environmental variance and genotype to the environmental effects (α<sub>i</sub>), indicating that high grain yielding genotypes had larger values b<sub>i</sub>, S<sup>2</sup><sub>i</sub>, and α<sub>i</sub>, S<sup>2</sup><sub>i</sub>, W <sub>i</sub><sup>2</sup>, CV<sub>i</sub>, α<sub>i</sub> and b<sub>i</sub>, were significantly correlated, indicating that they measured similar aspects of stability

Yield and Yield Attributes of Durum Wheat Genotypes as Affected by Boron Application in Boron-Deficient Calcareous Soils: An Evaluation of Major Turkish Genotypes for Boron Efficiency

Field studies were conducted to determine yield and yield attributes of six durum wheat (Triticum durum Desf.) genotypes namely; Kızıltan-91, Ç-1252, Selçuklu-97, Kunduru-1149, Yılmaz-98, and Çakmak-79, as affected by applications of different levels of boron (B) (0, 1, 3, and 9 kg B ha−1 delivered as boric acid, H3BO3) in soils deficient in available B (0.19 mg B kg−1) and high in lime (CaCO3) content (20.7%) during two consecutive growing seasons; 2000–2001 and 2001–2002. Agronomic characteristics such as grain yields, spike sterility rates, number of grains per spike, number of spikelets per spike, number of spikes per m2, grain weight per spike, thousand grain weights, test weights, and flag leaf B concentration were investigated. Grain yields in all genotypes were significantly increased by B applications compared to the control. Applications of 1 and 3 kg B ha−1 increased yield an average of 11 and 9% respectively, while 9 kg B ha−1 resulted in lower overall yield increase (7%). Genotypes studied have shown significant variations with respect to their responses to additional B. Kunduru-1149 and Çakmak-79 gave the highest grain yield (4080 and 4315 kg ha−1 respectively) at 1 kg B ha−1, whereas Kızıltan-91 and Yılmaz-98 yielded best (4475 and 5010 kg ha−1 respectively) at 3 kg B ha−1. Interestingly, other two genotypes, Ç-1252 and Selçuklu-97, reached to the highest level of grain yield (4320 and 4360 kg ha−1 respectively) at the highest B level (9 kg ha−1). Yield attributes also showed significant variations with respect to their responses to B application. Kızıltan-91 and Kunduru-1149 appeared to have high sensitivity to B deficiency. On the other hand, Çakmak-79 and Selçuklu-97 were B deficiency tolerant genotypes. The study clearly showed that B deficiency could result in significant yield losses in durum wheat under experimental conditions tested. Hence, B contents of soils for the cultivation of durum wheat should be analyzed in advance to devoid of yield losses. Plant tissue analyses can also result in grain yield predictions. Genotypes proven as tolerant/sensitive to high/low B levels may offer valuable genetic materials for use in B-related breeding programs. Considering relationships between flag leaf B concentrations and grain yield, it was clear that when climatic conditions (second year) suit wheat cultivation, B application in B-deficient soils can make profound contributions to grain yield in wheat compared to adverse climatic conditions (first year). Clear positive contribution of B application to grain yield in durum wheat can be more evident under better climatic conditions.

Estimation of grain yield by near-infrared reflectance spectroscopy in durum wheat

Near-infrared Reflectance Spectroscopy (NIRS) is widely used for routine, non-destructive assessment of grain quality in cereals. In this work, we assess the use of NIRS as an indirect indicator of grain yield (GY) in durum wheat grown in Mediterranean conditions. Plants were grown under rain-fed conditions in two sites in NW Syria, Breda and Tel Hadya, and a third trial was planted at Tel Hadya under support irrigation. We measured the spectral reflectance signature between 1100 and 2500 nm in flour from the same grains harvested for yield determination. By Partial Least Squares (PLSR), we obtained a model of the association between agronomic determinations of GY and these spectra. We found significant (p < 0.001) relationships between GY and NIRS-predicted values, with r 2= 0.36 (N= 96), r 2= 0.72 (N= 72) and r 2= 0.52 (N= 138) in Breda, and Tel Hadya rainfed and irrigated, respectively. Full cross validation of these models gave r 2 between 0.31 and 0.33 (p < 0.001). When we applied the models to the samples from the other two trials, we found a general decrease in their predictive ability. Compared with other grain traits (carbon isotope discrimination, grain weight, ash and nitrogen content), NIRS showed a similar or even stronger relationship with GY, at least when validated in the same trial. We concluded that NIRS could be used to rank GY during the early generations of a breeding program, when performing yield trials is less feasible. However, further research is required to identify the environments in which this technique is more reliable, as well as to evaluate the heritability of NIRS-predicted GY.

Comparison of flag leaf and ear photosynthesis with biomass and grain yield of durum wheat under various water conditions and genotypes

Comparaison des relations entre photosynthese de la feuille etendard et de l'epi avec la biomasse et le rendement en grain chez le ble dur sous differents regimes hydriques. Traditionnellement, lorsque l'activite de la photosynthese de cereales est etudiee, l'importance est attribuee aux feuilles, negligeant ainsi le role d'autres organes comme l'epi. Ici, une etude comparative de l'effet du statut hydrique sur l'activite photosynthetique au niveau de la feuille etendard et de l'epi ainsi que leurs relations avec la biomasse totale aerienne et le rendement en grain a maturite a ete menee chez le ble dur. Quatre varietes locales et 2 cultivars adaptes aux zones semi-arides du sud du Maroc ont ete mis en croissance dans des pots en conditions de serre. Cinq differents regimes hydriques ont ete instaures du debut de l'elongation des tiges jusqu'a maturite. La biomasse et le rendement en grain sont alors enregistres. Des mesures de la photosynthese nette (A), de la conductance stomatique (g s ) et de la transpiration (T) ont ete effectuees au niveau de l'epi et de la feuille a l'anthese. Pour les deux organes, on note une diminution de tous ces parametres en condition de stress hydrique, alors que les rapports A/T et A/g s augmentent. L'effet du genotype a ete significatif pour tous les caracteres etudies. En conditions irriguees, la photosynthese de l'epi est beaucoup plus elevee que celle de la feuille. Au fur et a mesure que le stress hydrique se developpe, la photosynthese de l'epi diminue moins que celle de la feuille etendard. Independamment du niveau du stress applique, on note une meilleure correlation de la photosynthese de l'epi avec la biomasse et le rendement par rapport a celle notee avec la feuille etendard. Neanmoins, a mesure que le stress hydrique s'accentue, cette correlation avec la feuille etendard s'ameliore, suggerant un changement progressif de la limitation du rendement des organes « puit » aux organes « source ». Au niveau de l'epi, les rapports A/T et A/g s montrent aussi une meilleure correlation que celles de la feuille etendard a la fois avec la biomasse et le rendement; pour la plupart des regimes hydriques, la correlation est negative. Ces resultats suggerent l'importance du role photosynthetique de l'epi dans l'elaboration du rendement par rapport a celui de la feuille etendard, non seulement en conditions de secheresse mais aussi son absence de stress.

Evaluation of Grain Yield and Its Components in Durum Wheat under Mediterranean Conditions

Grain yield of durum wheat (Triticum turgidum L. var. durum) under Mediterranean conditions is frequently limited by both high temperature and drought during grain growth. Path coefficient analyses, based on an ontogenetic diagram, were conducted to study grain yield formation under different temperature and moisture regimes across Spain. Six ICARDA–CIMMYT inbred lines and four Spanish commercial cultivars were grown during 1998 and 1999 at two temperature regimes (cool and warm) and under both rainfed and irrigated conditions. Path coefficient analysis revealed that grain yield under cooler conditions was mostly determined by kernel weight, whereas the number of spikes per square meter predominantly influenced grain production in the warmer environments. The number of kernels per spike had a significant contribution to grain yield, especially under drought stress conditions. These associations do not clearly appear in the simple correlation analysis. Compensatory effects among yield components were almost absent in the cooler environments, probably due to the relative availability of water and N during the critical phases of plant development. Contrarily, under warmer conditions, negative effects of the number of spikes per square meter were registered on both the number of kernels per spike and kernel weight. Path analysis appears to be a useful tool for understanding grain yield formation and provides valuable additional information for improving grain yield via selection for its yield components.

Influence of Diverse Cropping Sequences on Durum Wheat Yield and Protein in the Semiarid Northern Great Plains

Crops grown in previous years impact the amounts of residual soil water and nutrients available for subsequent plant growth. Appropriate sequences allow efficient use of the available soil resources by the crop to increase yields at a system's level. This study was conducted to determine whether the grain yield and grain crude protein concentration (GCPC) of durum wheat (Triticum turgidum L.) were related to crops grown in the previous 2 yr. Durum was grown following pulses [chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.), and dry pea (Pisum sativum L.)], oilseed [mustard (Brassica juncea L.) or canola (B. napus L.)], and spring wheat (Triticum aestivum L.) in southwest Saskatchewan from 1996 to 2000. Durum increased grain yields by 7% and GCPC by 11% when grown after pulse crops rather than after spring wheat. Durum after oilseeds increased grain yield by 5% and GCPC by 6%. Pulse and oilseed crops grown for the previous 2 yr increased durum grain yield 15% and GCPC 18% compared with continuous wheat systems. Fall residual soil NO3–N and available soil water accounted for 3 to 28% of the increased durum yield in two of five site‐years, whereas those two factors accounted for 12 to 24% of the increased GCPC in three of five site‐years. Durum grain yield was negatively related to GCPC. The relationship was stronger when durum was preceded by oilseeds compared with pulses. Broadleaf crops in no‐till cropping systems provide significant rotational benefits to durum wheat in the semiarid northern Great Plains.

Environmental and genetic determination of protein content and grain yield in durum wheat under Mediterranean conditions

AbstractThe unpredictability of the Mediterranean climate causes fluctuations in wheat yield and quality, but offers the opportunity for obtaining high‐quality durum wheat in terms of grain protein content. Twenty‐five durum wheat genotypes were grown under irrigated and rainfed conditions at each of two latitudes in Spain during 1998 and 1999. Differences between latitudes in grain protein content and chlorophyll content in the flag leaf were attributable to nitrogen fertilization management. Cycle length until anthesis was less affected by the environment than grain‐filling duration, and was longer under irrigated conditions than in the rainfed sites. A negative asymptotic curve was the best equation to fit the relationship between yield and protein content, suggesting that yield improvements in fertile environments may be attained with negligible reductions in protein content. ‘Jabato’, ‘Waha’, ‘Lagost‐3’, ‘Massara‐1’ and ‘Vitŕon’ showed medium to high yield, yield stability and high protein content. Chlorophyll content in the flag leaf, measured at anthesis with the soil‐plant analysis development (SPAD) portable field unit, may be useful for the fast and cheap detection of durum wheat genotypes with high grain protein content in drought‐stressed Mediterranean environments.

Sowing date and nitrogen rate effects on dry matter and nitrogen partitioning in bread and durum wheat

Grain yield and protein in bread and durum wheat are determined by the plant efficiencies in partitioning dry matter (harvest index, HI) and nitrogen harvest index (NHI) to the grain. Responses of HI and NHI to two rates of preplant N supply (105 and 170 kg N ha −1) were characterized for nine bread and five durum wheat genotypes along with a triticale genotype in three sowing dates. Genotype×N input interaction was significant for several characters in early sowing (26 October 1993), for shoot biomass at anthesis, grain yield, and straw yield in optimum sowing (6 December 1993), and for grain yield in late sowing (5 February 1993). Although plants removed more N from the soil in early than in optimum sowing, mean HI and NHI in the former, 38.5 and 66.3%, were lower than those in the latter, 45.5 and 71.2, respectively. On average, plants lost more N from anthesis to maturity at early (16 kg ha −1) than at optimum sowing date (6 kg ha −1). Mean HI and NHI in optimum and late sowing dates were similar, but mean grain yield in the former (4.9 t ha −1) was greater than that in the latter (4.0 t ha −1). The high rate of N supply reduced mean HI and NHI at all sowing dates. Mean HI and NHI were highly positively correlated ( r=0.89). Depending upon sowing date and N input, negative significant correlation was found between grain yield and N concentration ranging from −0.59 to −0.66. Grain yield and shoot biomass at anthesis were highly correlated ( r=0.74), indicating the importance of preanthesis assimilated carbohydrates in grain filling in most genotypes. Mean postanthesis N accumulation by plants was relatively small, indicating that most of grain N was translocated from preanthesis assimilated N. A substantial amount of N remained in the straw. Despite substantial genotypic variation, only a few genotypes had mean grain yield, grain N concentration, HI, and NHI greater than the overall mean. Wheat germplasm is needed that can easily accumulate N before and after anthesis and efficiently translocate it to the grain with a minimum of N loss from plants after anthesis. Further improvement in N uptake and partitioning should be undertaken in wheat under low N input.

Stability of Carbon Isotope Discrimination and Grain Yield in Durum Wheat

Carbon isotope discrimination (Δ) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in bread wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), with potential value for durum wheat (Triticum turgidum convar. durum Desf. MacKey). We evaluated the genetic variation for Δ, the relationship between Δ and grain yield, and the magnitude of genotype × year (G × Y) interactions in durum wheat. Field experiments were conducted under Mediterranean conditions on 144 durum wheat accessions during three successive years. Grain yield and carbon isotope discrimination of flag leaves (ΔF) and kernels (ΔK) were measured. Large genotypic and year variation was observed for ΔF and ΔK. Flag leaf Δ was correlated with grain yield in 2 yr characterized as having greater water limitation (r = 0.29 − 0.38, P &lt; 0.001). Conversely, ΔK and grain yield were significantly correlated in all 3 yr (r = 0.49 − 0.52, P &lt; 0.001). In addition, G × Y interactions were significant for ΔF, ΔK and grain yield. However, significant correlations (P &lt; 0.001) were noted for ΔK across years. As a result, ΔK may serve as a better predictive criterion for higher grain yield under Mediterranean conditions.

Ash content might predict carbon isotope discrimination and grain yield in durum wheat.

• Dry mass per unit of leaf area (LDM) and ash content were evaluated as alternative criteria for carbon isotope discrimination (Δ) in durum wheat (Triticum durum) flag leaves and grains. • Using correlation analysis the relationships between the three parameters (LDM, Δ, ash content) and productivity were determined over three consecutive years in 37 field-grown durum wheat genotypes under contrasting drought conditions. • Highly significant differences were found between years and among genotypes for all measured traits. Grain Δ and ash content, and LDM and flag leaf Δ were negatively correlated under nondroughted conditions. Positive correlations were found between grain yield, harvest index and both Δ and ash content of the flag leaf under drought. No significant correlations were found between LDM and both Δ and grain yield. • Differences in LDM do not predict variations in Δ, whereas ash content of grain and flag leaf (under droughted conditions) might be useful in predicting Δ and grain yield. Ash content might provide an alternative screening method in the improvement of drought tolerance and yield stability in durum wheat.

Ash content might predict carbon isotope discrimination and grain yield in durum wheat

Ash content might predict carbon isotope discrimination and grain yield in durum wheat

Influence of source, timing and placement of nitrogen on grain yield and nitrogen removal of durum wheat under reduced- and conventional-tillage management

Effective fertilizer management is critical to maintain economic production and protect long-term environmental quality. Field studies were conducted over 4 yr at two locations in southwestern Manitoba to determine the effect of source, timing and placement of N on grain yield and N recovery of durum wheat (Triticum durum L. ‘Sceptre’) under reduced-tillage (RT) and conventional-tillage (CT) management. The effect of N management on durum grain yield and N recovery differed with soil type and tillage system. On the clay loam (CL) soil, lower yields with fall- as compared with spring-banded N were more frequent under RT than CT. Lower yields occurred more frequently with fall-applied as compared with spring-applied urea ammonium nitrate (UAN) than when urea or NH3 was the N source. On the drier fine sandy loam (FSL) soil, fall applications of N generally produced similar to higher grain yield than did spring applications. Differences among fertilizer sources and tillage systems were much less frequent with spring than fall applications of N. Where differences occurred, durum grain yields were higher with in-soil than surface applications of urea or UAN. In-soil applications of urea and UAN increased durum grain yield as compared with surface applications more frequently under RT than CT on the CL soil where yield potential was high, whereas increases on the FSL were as common under CT as under RT. On soils with a high yield potential, enhanced immobilisation and/or volatilisation of surface-applied N may reduce grain yield by reducing available N, particularly under RT. Selection of a suitable source-timing and placement combination to optimise crop yield may be more important under RT than CT. Key words: Conservation tillage, direct seeding, placement