Determination of agronomic practices for the management of blight of chickpea caused by <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> in Turkey: 1. Appropriate sowing date

In order to determine the most appropriate dates for planting chickpea in central Anatolia, Turkey, six cultivars were planted at three sites that differed in disease pressure. In two of the sites, disease pressure from Ascochyta rabiei was promoted by spreading infected chickpea debris on the soil surface at the time of planting and, at one of these, sprinkle irrigation was applied. In the third site, where conditions were dryer, no artificial inoculum was provided. Plants from seeds sown in early March had the most disease and in the sprinkle irrigated plots the disease severity ranged from 7.8 on the most susceptible cv. Canitez to 3.3 on the least susceptible Gokce as scored on the 1–9 scale where 1 = no disease and 9 represents a plant killed by the fungus. There was an inverse relationship between disease severity and yield, production from blight resistant cultivars of around 2,000 kg ha⁻¹ being more than twice that of susceptible ones. Delaying planting for 3–5 weeks reduced the severity of ascochyta blight but also reduced the yields in four of the six cultivars. In contrast, reduction in disease severity by delayed sowing resulted in yield increases for the susceptible cvs Canitez and Local, although yield level was not as much as those of the less susceptible cvs sown early. Delay of 6–9 weeks almost eliminated ascochyta blight but yields of all cultivars were seriously compromised by drought stress. In consequence, chickpea farmers are recommended to use resistant or tolerant cultivars and sow early in March. For less resistant cultivars, sowing in early April is recommended. Further delay is not recommended unless irrigation is provided and fungicide spraying is recommended where signs of infection are present under conditions conducive to the disease.     

Disease-yield relationship in barley.

The effect of disease on growth and yield of two barley cultivars sown at different times and in different years was investigated in New Zealand. The data were used to develop yield-loss models based on both disease severity (measured as green leaf area) and yield target (estimated by duration of crop growth). Disease influenced yield differently in Triumph and Sonya barley (spring and winter types, respectively), and yield components were affected to different degrees. Empirical yield-loss models for individual cultivars, sowing dates and seasons had different slope values, and the best models were based on measurements of disease at different growth stages. Combined models were less significant and explained less variation in yield than the individual models. Models which included the duration of crop growth as an estimate of yield target improved the fit to the data. Empirical models were specific to cultivar, sowing date and season, suggesting that they were not applicable in the varying conditions tested. The inclusion of estimated yield target improved the general applicability of models, and provided a method of using models in crops sown at different times and in different seasons, without measuring yield target directly.     

Effect of sowing date and host resistance on the establishment and development of Orobanche crenata in faba bean and common vetch

The effect of early and late sowing dates on the establishment of Orobanche crenata Forsk. (crenate broomrape) in resistant and susceptible cultivars of faba bean (Vicia faba L.) and vetch (Vicia sativa L.) were studied over four seasons in southern Spain. Differences in establishment, development and shoot emergence of the parasite were compared. With resistant faba bean and vetch cultivars, there was reduced attachment and shoot emergence of O. crenata with all sowing dates. Susceptible cultivars were more severely affected by the parasite with early sowing. Orobanche crenata development was also delayed in resistant cultivars. Crop yield, estimated by the number of pods per plant, decreased with late sowings. The combined use of resistant cultivars and early sowing is a useful tool as part of an integrated control strategy. Resistant cultivars allow early sowing (with low O. crenata attack), thus avoiding yield losses due to the short crop cycle with late sowing.     

播期和晚播秸秆覆盖对加工番茄干物质积累和产量的影响

为了探讨播期及晚播期条件下秸秆覆盖保护对加工番茄干物质积累和产量形成的影响。在2009年和2010年以里格尔87-5为材料进行了播期(4月10日、4月25日、5月10日和5月20日)和晚播秸秆覆盖(5月10日F+J和5月20日F+J)的试验。结果表明:在北疆气候条件下播期和秸秆覆盖对移栽和直播加工番茄的物质积累和产量形成都有显著的影响。随着播期的推迟,移栽和直播植株总干物质积累量和产量呈显著下降趋势。移栽和直播单株产量均以4月25日最高,分别为4 498.2 g/株和3 955.9 g/株,显著高于其他播期。在产量构成因子中,播期对移栽和直播植株单株有效结果数影响显著,对平均单果重影响不显著。晚播条件下秸秆覆盖后植株生长较同播期不覆盖处理得到明显改善,移栽植株总干重增加15.5%和9.6%,产量增加36%和39.8%;直播植株总干重增加27.8%和15.7%,产量增加12.2%和9%。秸秆覆盖后移栽植株平均单果重显著增加,而直播植株保持不变或略有降低。     

Effect of sowing dates and fertilizer on the severity of stem borer (Busseola fusca Fuller,Lepidoptera: Noctuidae) on sorghum in Eritrea

The influence of sowing date and fertilizer application on the incidence anddamage ofthe maize stemborer (Busseolafusca Fuller) in sorghum(Sorghumbicolor L.) was investigated at the Halhale Research Centre in Eritrea during 1997 - 99. The trials were conducted in a splitplot design with sowing date as the main plot and fertilizer as subplots. There were six sowing dates at an interval of 15 days starting fromearly April tomid-June. There were fertilized and unfertilized subplots. Data on larval count, per cent infestation, per cent deadheart, heading and maturity dates, plant height and yield were recorded for each plot. Fertilizer had no effect on the incidence and damage of the stem borer (B. fusca). There was no interaction between fertilizer and sowing dates on the larval population and damage by stem borers. Sowing date had a significant effect on stem borer incidence and damage levels. Early sowing dates (April 1 and 15) had a significantly lower number of larvae, infestation, deadheart and gave higher yields compared with the other sowing dates while late sowing dates (mid-May- mid-June) resulted in significantly higher infestation and damage. The highest infestation and damage were recorded from mid-May sowings. High stem borer infestations in delayed sowing was due to the coincidence of the susceptible stage of the crop (3 - 6 weeks after germination) with high populations ofstemborer larvae fromthe first generationin late June and July. Mid- and late sown crops were also later attacked by the second generation at the grain-filling stage in September- October. These results indicate that early planting (April) is effective in reducing stem borer damage on sorghum in the highlands of Eritrea.     

Quantification of within‐season focal spread of wheat take‐all in relation to pathogen genotype and host spatial distribution

Within season gradient of wheat take‐all was measured in field experiments according to line or random sowing host spatial distribution, and two Gaeumannomyces graminis var. tritici (Ggt) isolates (G1i and G2i), representative of the G1 and G2 genotype groups in terms of aggressiveness. Root disease incidence and severity were assessed at six dates from early March to late June on plants located at regular distances from the inoculum sources. Simple models relating disease intensity at different levels of hierarchy fitted observed data well, and indicated a strong disease aggregation both within and among plants. Disease severity on source plants placed nearby the inoculum source increased over time, ranging from 5 to 46% at the first assessment, and from 55 to 98% at the last assessment, being in general larger for G2i than G1i. In line‐sown plots, disease progressed steadily along the line but did not extend beyond 20 cm, seldom reaching the neighbour line. Disease rarely reached 25 cm in the direct‐seeded crop stands. These results indicate that Ggt intensifies but does not spread to a large extent during a cropping season. Distance from the source, pathogen genotype and assessment date had a significant effect on disease severity according to mixed model analyses, disease spread being larger for G2i than G1i. However, no significant effect of host spatial distribution could be detected. Yield loss within 20 cm of the source plant ranged between 20 and 40%, and was not significantly affected by pathogen genotype or host spatial distribution.     

Evaluation of oilseed rape seed yield losses caused by <Emphasis Type="Italic">Leptosphaeria biglobosa</Emphasis> in central China

Phoma stem canker of oilseed rape (Brassica napus), caused by Leptosphaeria maculans/L. biglobosa is a globally important disease. Severe phoma stem canker symptoms have been observed on winter oilseed rape in China but the seed yield loss caused by this disease remains unknown. In May 2012 and May 2013, 17 and 13 crops were surveyed, respectively, in seven counties of Hubei Province, central China. Stems with phoma stem canker disease symptoms were sampled for pathogen isolation and identification. Only L. biglobosa was identified by culture morphology and species-specific PCR; no L. maculans was found. To evaluate the yield losses, yield components (number of branches per plant, number of pods per plant, 1000-seed weight, number of seeds per pod) were assessed on healthy and diseased plants sampled from crops in four counties and on plants from inoculated pot experiments (plants of three cultivars were inoculated at the green bud stage by injecting L. biglobosa conidia into the stem between the first and second leaf scars). Results of the field surveys showed that diseased plants had 14–61% less branches and 32–83% less pods than healthy plants, respectively. The estimated seed yield loss varied from 10% to 21% and from 13% to 37% in 2012 and 2013, respectively. In the pot experiments, there were no differences in numbers of branches or pods but there were differences in number of seeds per pod between inoculated and control plants. For the three cultivars tested, the inoculated plants had yield losses of 29–56% compared with the control. This study indicates that L. biglobosa could cause substantial seed yield loss in China.     

Effect of rust (Uromyces viciae-fabae) on yield components of faba bean

Epidemics of faba bean rust (Uromyces viciae-fabae) differing in duration and final severity were induced by a point inoculation. Relationships between disease severity observed on three canopy layers (top, middle and bottom) at different assessment dates and yield components (grain weight per stem, average grain weight, number of grains per pod and number of pods per stem) were established. Epidemics occurring after the initiation of pod setting had no effect on yield components. Earlier epidemics significantly decreased the grain weight per stem, the average grain weight, and the number of pods per stem, but only marginally affected the number of grains per pod. The yield components generally decreased with increasing severity level, but a few parabolic relationships were observed at a late stage in crop development. The effect of rust on yield components could be predicted by a critical point model using disease severity assessed on the middle or bottom canopy layer in the mid-flowering stage. Rust severity greater than 5% during that critical stage would substantially decrease final yield, and fungicide spraying against rust would be advised.     

Effect of Winter Planting Date on Oil Yield and Fatty Acids of New Spring Canola (Brassica napus L.) Cultivars Under Foliar Zinc Spray

Canola (Brassica napus L.) oil yield and fatty acid composition are the function of genotype, climate conditions, morphology, and physiology as well as crop management. In this study, the reaction of different canola cultivars—in terms of seed oil content and fatty acids—to different planting dates and foliar zinc application during two experimental years (2016–2017) was investigated in the field in arid and semi-arid regions of Karaj, Iran. The experiment was performed as a factorial split plot in a randomized complete-block design with three replications. Three sowing dates (February 9, 19, 29) and two foliar zinc applications (non-application as control and zinc application; spraying in the stem elongation stage) were factorially randomized to main plots, and canola cultivars (Sarigol, Dalgan, Salsa, and Solar) were allocated to sub-plots. The results indicated that the effect of year, planting date, zinc application, cultivar, and the interaction effect of planting date and cultivar on quality traits (glucosinolate and fatty acids) and seed yield were significant (p?<?0.01). The delay in winter planting of spring canola cultivars caused a significant reduction in seed yield, oil yield, and the content of oleic, linoleic, and palmitic fatty acids and increased the content of linolenic, erucic, stearic, arachidic, and behenic fatty acids and glucosinolate. The highest seed yield (4732.2?kg/ha), oil yield (2066?kg/ha), and oleic acid content (66.52%) were observed in the Dalgan cultivar in the zinc application treatment with normal planting date (February 9). The Salsa cultivar had the highest content of erucic acid (0.46%) and glucosinolate (17.3?μmol/g meal) in the control treatment with the last planting date. Because the quality of edible canola oil depends on the increase in unsaturated fatty acids, particularly oleic and linoleic acids, and the reduction of erucic acid and glucosinolate, planting Dalgan cultivar with zinc application at the normal planting date is recommended for the study area and similar areas.

     

Yield Components and Fatty Acids Variation of Canola Cultivars Under Different Irrigation Regimes and Planting Dates

To investigate the effect of different planting dates and irrigation regimes on six canola cultivars, a 2-year (2014–2016) experiment was conducted at the Seed and Plant Improvement Institute of Karaj. The experiments were conducted as the factorial split-plot in a randomized complete block design including six canola cultivars (Gabriella, Brutus, Triangle, Marathon, Danube, and Natali), two irrigation regimes (fully irrigated and irrigation termination at the flowering stage) and two planting dates (October 1 and November 1). The results showed that irrigation termination from the flowering stage prevented the supply of required material for filling the seeds and the metabolism of the seed compounds and reduced the growth period of the seed. Therefore, a reduction was observed in the content of oleic and linoleic acids and proline. Also, water deficit stress caused an increase in the glucosinolate content of the seed. The response of canola cultivars was different in terms of fatty acids, so that the Natali cultivar had higher palmitic, oleic acids, and proline content compared to the other cultivars at both planting dates. Fully irrigated treatment and planting date of October 1 produced the highest amount of seed and oil yield (4659 and 2073?kg ha^?1), palmitic acid (5.5%), and proline (22.7?μmol/g) content, and the lowest glucosinolate content (13.2?mg/g). Generally, the Natali cultivar and planting date of October 1 and the fully irrigated regime are highly recommended in the studied area regarding qualitative traits and yield of canola.

     

Quantitative aspects of Orobanche crenata infestation in faba beans as affected by abiotic factors and parasite soil seedbank

The interactions between the root parasitic weed Orobanche crenata Forsk. and its host plant faba bean ( Vicia faba L.) were quantified under controlled and field conditions at ICARDA's Tel Hadya research station. In the field experiments conducted in 1993–94 and 1994–95 faba beans were sown on two dates, in plots with 0, 50, 200 and 600 O. crenata seeds kg^–1 soil, under both limited and sufficient moisture supply. The effects of temperature on the duration of the early developmental stages of O. crenata were investigated in a growth chamber. The extent of O. crenata infestation was closely related to the number of parasite seeds in the soil. The seed-density treatment with 600 seeds kg^–1 soil resulted in complete crop failure. Furthermore, O. crenata infestation was higher under sufficient than under limiting water supply conditions, irrespective of sowing date. Only in the moderately infested plots, did shifting of the planting time of faba bean result in a significant decrease in parasite dry weight and an increase in crop seed yield. The timing of germination, attachment and further developmental stages of O. crenata was not related to faba bean growth stage and was affected primarily by soil temperature. The duration of O. crenata developmental stages was estimated using the thermal time concept. The relationship between total number of parasite attachments at the harvest of the faba bean crop and O. crenata seed density was dependent on maximum faba bean root-length density measured by the start of pod-filling in each treatment combination of sowing date and moisture supply. The results are discussed with reference to implications for the development of a dynamic simulation model for the prediction of faba bean yield losses caused by O. crenata .     

Red leaf blotch (Dactuliochaeta glycines) of soybeans (Glycine max) and its relationship to yield

Red leaf blotch of soybeans, caused by Dactuliochaeta glycines, was evaluated on soybean plants in field plots located in Zambia. Two experiments were conducted in each of two seasons. Experiment 1 had four cultivars that were either fungicide-sprayed or not sprayed. Disease severity was greatest on leaves at the lowest nodes from early vegetative through the reproductive growth stages. Area under the disease progress curve (AUDPC) values and percentage of nodes defoliated at growth stage R5 were significantly ( P  = 0.05) greater in unsprayed plots for all cultivars in both seasons. Yield losses ranged from 8 to 37% while reduced seed size ranged from 21 to 29% for the four cultivars. Number of pods per plant in fungicide-sprayed plots did not differ from those in unsprayed plots. However, the number of seeds per plant and seeds per pod were significantly ( P  = 0.05) greater in sprayed than unsprayed plots for some cultivars. In experiment 2, cultivar Tunia was either fungicide-sprayed at different times or not sprayed. The lowest attached leaf had the most variation in the amount of disease while ratings of the most median leaf in the canopy were generally less variable. The AUDPC values calculated from the lowest attached leaf, the mean of all attached leaves, and the median attached leaf differed significantly ( P  = 0.05) the number of times plants were sprayed with fungicide. Defoliation and vertical incidence of red leaf blotch from lower to higher nodes were significantly ( P  = 0.05) reduced in fungicide-sprayed plots in one season, but not the other. One thousand-seed weight and yield differed significantly ( P  = 0.05) with treatment as one application of triphenyltin acetate increased yields by 18% over unsprayed plots in season 1. One thousand-seed weight and yield, regressed on the AUDPC for the median leaf in the canopy, explained 92 and 72% of the variation, respectively.     

Effect of defoliation by livestock on stem canker caused by Leptosphaeria maculans in Brassica napus

Brassica napus (canola, oilseed rape), an important break crop for cereals across the Australian wheat belt, is being rapidly adopted as a dual‐purpose (forage and grain) crop in mixed farming systems. Stem canker caused by the fungus Leptosphaeria maculans is the most important disease of B. napus in Australia. The primary source of inoculum is airborne ascospores released during autumn/winter which coincides with the grazing of dual‐purpose crops. Field experiments were defoliated by sheep to determine the effect of grazing on blackleg stem canker severity at plant maturity in B. napus cultivars differing in their resistance level and grazed at different times. One cultivar was sown on different dates to investigate the impact of grazing at the same time, but at different growth stages. Defoliation by mowing was compared to defoliation by livestock. Similar amounts of dry matter remained after defoliation by machinery (0·66 t ha^?1) or livestock (0·52 t ha^?1). However, stem canker severity was higher in the grazed (40% of crown cross‐section diseased) compared with the mown (25%) treatment, which was higher than the ungrazed control (9%). Stem canker severity generally increased with grazing, but the increase was eliminated or reduced in cultivars with good resistance. Grazing during vegetative plant growth minimized the increase in stem canker severity compared with grazing during reproductive growth. Currently, cultivars with good L. maculans resistance are recommended in high disease situations. To avoid excessive yield loss in dual‐purpose B. napus crops due to L. maculans it is recommended that such cultivars are grown even in low‐moderate disease situations.     

Cultivar mixture effects on disease and yield remain despite diversity in wheat height and earliness

Cultivar mixtures can stabilize yield and reduce pathogen spread in plant populations. A field experiment was performed to determine (a) whether a large difference between the cultivars in the mixture (e.g., plant height or earliness) would have an impact on mixture performance, and (b) whether such differences would modify the classical rules for mixture design. Mixtures were constituted from wheat cultivars with diversity for many traits, including plant height, flowering date, disease resistance, and yield potential. The field experiment was conducted over 3 years, testing each year 72–90 mixtures of two, four, or eight cultivars, and their corresponding pure stands. Disease severity and yield of cultivar mixtures were strongly related to the mean values of the component cultivars in pure stands. Despite the considerable diversity of the mixtures tested, the classic rules (e.g., proportion of susceptible cultivars) already tested in mixtures with similar height and earliness were effective for decreasing disease severity. Agronomic heterogeneity for traits such as plant height, yield potential, or earliness of the cultivars in mixtures did not have a negative impact on disease severity and yield relative to pure stands. Increasing the number of cultivars in the mixture from two to eight had no impact on the mean disease severity and yield of the mixtures, but reduced the variability of disease severity and yield in the mixture relative to pure stands. These results suggest that it may be possible to increase within-field wheat diversity by combining more contrasting cultivars in mixtures than was previously thought.     

Sunflower Response to Application of L-Ascorbate Under Thermal Stress Associated with Different Sowing Dates

Unlike edaphic factors, it is difficult to control climatic conditions and their changes that affect plant growth and development. To deal with such posture, farmers have to cultivate their crops at the right time. From this point, over two–year of 2014 and 2015, a field experiment was performed at El-Nubaria region, El-Behaira Governorate, Egypt, to assess the response of sunflower to different combinations between sowing dates (early, mid and delayed) and ascorbic acid treatments (with ascorbic acid and without ascorbic acid). Ascorbic acid was sprayed at 30, 40 and 50 days after sowing. The results showed that sowing sunflower in mid sowing (May 21) achieved the highest values of cumulative heat units utilization efficiency as well as all growth and yield traits, while the lowest values were recorded under the delayed sowing date (June 21). Application of ascorbic acid was effective for promoting growth and yield traits under all studied sowing dates. Ascorbic acid achieved 11.6, 10.1, 10.7 and 12.9% increases under early sowing, and 9.5, 6.6, 8.6 and 10.3% increases under delayed sowing in head diameter, seed weight plant^?1, seed yield and oil yield, respectively. Comparing to mid sowing?×?without ascorbic acid, application of ascorbic acid alleviated seed yield losses associated early sowing from 15.7–6.6% and from 23.0–16.4% with delayed one. In conclusion, for remediating the thermal stressful impacts of early or late sowing of sunflower, farmers are advised to treat crop plants with ascorbic acid to avoid yield losses.

     

Quantitative studies on downy mildew (<Emphasis Type="Italic">Peronospora destructor</Emphasis> Berk. Casp.) affecting onion seed production in southern Uruguay

Onion downy mildew (Dm) symptoms and damage on seed production fields in southern Uruguay were quantified during two seasons as the progress of incidence, severity, and as the effect of the level of seed-stalks infections on seed yield and quality. In addition, the effects of two plantation dates and two plant densities on Dm were studied in a factorial experiment. Maximum incidence along the season ranged from 15 to 65% in four commercial fields in 2005 and two fields in 2006. Maximum severity ranged from 4.5 to 9.3% of leaf area affected in 2005, and 0.35 to 1.17% in 2006. Whereas Dm incidence varied among studied fields, disease progress as Dm severity varied mainly between studied years. Crop rotation, crop vigour and plant density were identified as major factors affecting Dm variation in the field. Intensive fungicide schedules did not control Dm when other conditions favoured the disease. A high level of Dm severity defined as large necklace spots on seed-stalks significantly reduced seed yield in comparison with healthy seed-stalks in 2005, as well as seed yield and germination in 2006. Weight of 1,000 seeds was not significantly reduced by Dm infections on seed-stalks. Six genera of fungi were recovered from seeds harvested on highly infected seed-stalks (Stemphylium, Fusarium, Alternaria, Penicillium, Aspergillus and Botrytis), but not Peronospora. Late planting date and low plant density had significantly lower Dm incidence and severity. This finding questioned the early planting dates and high densities previously recommended in order to achieve high yielding crops. The combination of several practices to reduce initial inoculum, susceptibility status of the host, and environmental conditions promoting the disease is discussed as forming a basis for effective disease control.     

Effect of host and inoculum patterns on take-all disease of wheat incidence,severity and disease gradient

The importance of the spatial aspect of epidemics has been recognized from the outset of plant disease epidemiology. The objective of this study was to determine if the host spatial structure influenced the spatio-temporal development of take-all disease of wheat, depending on the inoculum spatial structure. Three sowing patterns of wheat (broadcast sowing, line sowing and sowing in hills) and three patterns of inoculum (uniform, aggregated and natural infestation) were tested in a field experiment, repeated over 2 years. Disease (severity, root disease incidence, plant disease incidence and, when applicable, line and hill incidences) was assessed seven times during the course of each season and the spatial pattern was characterized with incidence-incidence relationships. In the naturally infested plots, disease levels at all measurement scales were significantly higher in plots sown in hills, compared to plots sown in line, which were in turn significantly more diseased than plots with broadcast sowing. Disease aggregation within roots and plants was stronger in line and hill sowing than in broadcast sowing. Analysis of the disease gradient in the artificially infested plots showed that the disease intensified (local increase of disease level) more than it extensified (spatial spread of the disease), the effect of the introduced inoculum was reduced by 95% at a distance of 15 cm away from the point of infestation. Yield was not significantly affected by sowing pattern or artificial infestation.     

Factors associated with mortality of the overwintering generation of<Emphasis Type="Italic">Sesamia nonagrioides</Emphasis> under field conditions

Factors affecting overwintering mortality in the Mediterranean corn stalk borer,Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae), were investigated under field conditions in the southeast Mediterranean region of Turkey. During two consecutive years larvae and pupae were sampled from December to April in maize plots sown on three different dates. Field-collected larvae and pupae were reared and the emerged parasitoids were recorded. An effect of sowing date on total numbers ofS. nonagrioides was found with reduced populations in the early sown plots. Larval parasitism did not significantly affect overwintering mortality.Habrobracon hebetor (Say) (Hymenoptera: Braconidae) caused 11% parasitism and was found only in the first year of the study. Pupal parasitoids were predominantlyIchneumon sarcitorius caucasicus Meyer,Barichneumon sp. andPimpla spuria Gravenhorst (Hymenoptera: Ichneumonidae) and the parasitism level was 11% in both years of the study.     

Effects of Sowing Dates and Seeding Rates on Nitrogen and Water Use Efficiency of Facultative Wheat

In this study, effects of different sowing dates and seeding rates on N uptake efficiency (NUE), N translocation efficiency (NTE), agronomic efficiency (AE), physiological efficiency (PE), water use efficiency for grain yield (WUE_g) and water use efficiency for biomass (WUE_b) of facultative wheat were investigated. As the average of cropping year, sowing dates and seeding rates, N uptake efficiency (NUE), N translocation efficiency (NTE), agronomic efficiency (AE), physiological efficiency (PE), water use efficiency for grain yield (WUE_g) and water use efficiency for biomass (WUE_b) values were respectively obtained as 1.17?kg N_uptake/kg N_applied, 68.5%, 36.9?kg grain/kg N_applied, 31.2?kg grain/kg N_uptake, 5.19?kg ha^?1 mm^?1 and 18.04?kg ha^?1 mm^?1.

Nitrogen and water use efficiencies decreased with delayed sowing dates and increased with increasing seeding rates. It is possible to maintain a high wheat yield, nitrogen and water use efficiency by increasing plant density through winter sowing. It was concluded based on present findings that sowing date and seeding rates had significant effects on nitrogen and water use efficiencies and winter sowing should be practiced as not to cause yield losses and high seeding rates (575 seeds m^?2) yielded greater nitrogen-water use efficiencies.

     

水稻品种生育期、田块和播种期对稻曲病发生严重度的影响

利用早熟组和晚熟组各8个水稻品种采用随机区组设计连续进行两年田间试验,分析生育期与稻曲病严重度的关系,同时采用晚熟组5个品种分析田间厚垣孢子数量、播期与稻曲病发生严重度的关系。结果表明,水稻生育期、田间菌量与稻曲病田间发生的严重度呈显著正相关。早熟组各水稻品种的发病率均显著低于晚熟组各水稻品种,2005年晚熟组和早熟组品种的病穴率、病穗率和病粒率分别为76.3%、26.6%、4.6%和5.4%、0.8%、0.02%,2006年分别为75.7%、29.8%、4.7%和16.8%、3.3%、0.08%。此外,在上一年田间遗落菌量多的田块中各水稻品种稻曲病的发生程度显著高于菌量小的田块。晚熟组水稻品种的发病严重度与播种期无明显的相关性。据此认为,以种植晚熟水稻品种为主的北方稻区,种植早熟品种或进行轮作是防治该病的有效方法。