Thermal time approach to predicting seedling emergence dates of red clover,white clover and lucerne in farm fields

A practical method for predicting seedling emergence dates of red and white clovers, and lucerne is proposed. The germination response at seven different constant temperatures ranging from 5 to 35°C was examined. Germination rate, which is a reciprocal of the duration for 50% germination of seeds, was linearly regressed against temperature to calculate the base temperature and thermal constant of seed germination. The calculated values were 3·9°C and 15·8 degree days for red clover, 4·2°C and 13·6 degree days for white clover, and 2·9°C and 17·7 degree days for lucerne. Using the base temperatures, thermal constants, and the daily mean air temperatures at the study site, the seedling emergence dates of the three forage legumes were predicted. At the same time, in an outdoor pot experiment, seeds of these legumes were sown approximately every 3 weeks and seedling emergence dates were determined. The predicted dates of seedling emergence generally fitted the observed dates. Another prediction was attempted using the base temperatures, thermal constants, and normal daily mean air temperatures recorded over more than 30 years in the study site. This prediction showed that the seedlings of the three forage legumes began to emerge at the beginning of April and could continue to emerge until the beginning of November when their non‐dormant seeds were present in the site, and that when the seeds were sown from mid‐November of one year to late March of the next year, the emergence of seedlings was delayed until the beginning of April.     

苗带重镇压对土壤环境、玉米生长及产量的影响

采用自主研制的1ZY-6六行可折叠式苗带重镇压器，单体幅宽20cm，滚动压力650g/cm²，对秸秆深翻还田平播和秸秆覆盖还田免耕播种两种耕作方式播后苗带进行重镇压处理，分析玉米播种后苗带重镇压对土壤温湿环境、土壤紧实度、出苗率和产量等影响。结果表明，秸秆深翻还田平播后苗带重镇压与未重镇压作业相比较，土壤含水率、土壤紧实度和玉米产量显著提高(P<0.05)，土壤含水率增加11.42%，土壤紧实度提高127.90%，玉米产量提高4.31%。秸秆覆盖还田免耕播种后苗带重镇压与未重镇压作业相比较，土壤含水率、土壤紧实度和玉米产量显著提高(P<0.05)，土壤含水率增加23.59%，土壤紧实度提高58.88%，玉米产量提高3.39%。苗带重镇压明显提高土壤紧实度、土壤含水率，为玉米生长创造有利的土壤环境，保墒增产作用显著。     

The effects of density, date of inflorescence emergence, date of harvesting and temperature upon seed quality in tetraploid hybrid ryegrasses

Thousand-seed weight, germination and seedling dry weight were measured in some tetraploid hybrid ryegrasses to study variations in seed quality. In cv. Sabrina, seed from spaced plants had a higher 1000-seed weight and seedling dry weight, and a slower germination rate than seed from narrow drills. Seed from later emerging groups of inflorescences had a low 1000-seed weight and seedling dry weight, but a high germination rate. Seeds of cv. Sabrina, Leri and Augusta harvested at between 10 and 25 d after peak anthesis had low 1000-seed weights, low germination rates and low seedling dry weights. Air temperatures between inflorescence emergence and seed maturity also affected seed quality; an increase in temperature from a 15°/10°C regime to a constant 25°C environment reduced 1000-seed weight and seedling dry weight, but increased germination rate. It is concluded that year-to-year variation in seed characters will occur because of temperature and other climatic changes, but seed quality can also be influenced by the time at which the seed is harvested. If combine harvesting is carried out at a moisture concentration of about 400 g kg^-1 (≡40%) then maximum yields of seed of a high quality should be obtained.     

东北黑土不同耕作方式对玉米苗情的影响

吉林中部旱作玉米地区,春旱和冷害是制约苗情的关键气候因素。2004年在吉林东部旱作玉米上,采取不同耕作方式的比较发现,深松的玉米株高和叶面积最大,而翻耕的玉米出苗率较高。地温最高的是翻耕处理,土壤含水量最高的是深松处理,土壤容重最小的是深松处理。与出苗相关性最高的指标是土壤容重,与株高和叶面积相关性最高的指标是土壤含水量,相关系数依次为-0.940,0.878和0.796。深松是有利于玉米出苗的耕作方式。     

Soak conditions and temperature following sowing influence the response of maize (Zea mays L.) seeds to on-farm priming (pre-sowing seed soak)

On-farm seed priming of maize (i.e. soaking seed in water overnight, 17 h) in the semi-arid tropics has been shown to improve crop establishment and yield but the benefits can be variable. In previous work, this variation was thought to result from the interaction between primed seeds and conditions in the seedbed following sowing. To investigate this interaction, experiments were carried out under controlled temperature conditions that represented those of seedbeds in the semi-arid tropics. The conditions during seed priming and during subsequent germination and emergence were investigated as potential causes of variable seedling emergence relative to that of untreated seeds. Priming advanced emergence from moist sand cores at 30 °C/20 °C (day/night), reduced emergence at 35 °C/28 °C and delayed and reduced emergence at 40 °C/28 °C. In drier cores (drained 8 days) at 35 °C/28 °C, priming advanced germination time and did not decrease final percentage emergence. These results confirmed earlier field observations that the effect of priming in maize can vary and lead to positive, neutral or negative effects. Priming decreased the optimum and ceiling temperatures for germination, and unlike untreated seeds, the relationship between germination rate and sub-optimal temperature was not linear in all cases. Pre-humidifying seeds did not enhance the effect of priming, but aerating the soak water did. These results indicate that variable results from priming recorded in the field were not due to imbibitional damage, but may result from the negative effects of hypoxia during soaking exacerbated by moist conditions and high temperatures at sowing. These effects differed between seedlots of different cultivars, indicating the importance of selecting more tolerant maize hybrids to reduce variation in response to priming following sowing in the field. The implications of these findings for the use of primed seeds in the field are discussed.     

A method to assess cultivar differences in rate of physiological ageing of seed tubers

Inter-cultivar differences in rate of physiological ageing of potato tubers were assessed in a laboratory test and field tests. The physiological status of the seed tubers was varied by storing them at 4°C and a range of higher temperatures for 28 weeks (= excluding curing and pre-sprouting periods), after which tubers were desprouted. In a laboratory test, growth vigor was assessed by determining number and weight of sprouts after 28 days of incubation. In a field test, percentage emergence, total plant height, haulm and tuber weights were determined and a stand score was allocated 4 weeks after emergence of the 4°C storage treatment. Ageing indices were calculated by dividing the values for the warm-stored treatments by values for the tubers stored at 4°C. Using the tests the cultivars were scored from 0–10 and ranked accordingly. The indices were more evenly distributed over the range of 0–10 in the field test than in the laboratory test. Fresh haulm yield proved very suitable for calculating ageing indices but it could be replaced by a visual score of the haulm development without a great loss in accuracy     

Accelerated ageing of wheat grains: Part II-influence on thermal characteristics of wheat starch and FTIR spectroscopy of gluten

Wheat quality characteristics are influenced by different factors such as moisture content, storage time and temperature. In this study accelerated ageing of wheat grains was carried out by increasing moisture content (16, 18 and 20%) and keeping the samples in different temperatures (30, 40 and 50 °C) for different periods (2, 5 and 8 days). After milling, the thermal properties of starch and structure of gluten were investigated using Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR); respectively. The experimental set up was designed using response surface methodology and the three distinct factors were combined by central composite design. Results showed that increasing moisture content caused a decrease in onset, peak and end set temperatures of gelatinization while increasing storage time and temperature increased these parameters. By progressing storage time the band intensity of thiol groups decreased while that of disulfide groups of gluten increased indicating an improvement in gluten quality. Increasing moisture content from 16 to 20% and higher storage temperature (50 °C) decreased intensity of disulfide bands.     

Effect of variety and seed dressing on emergence of high-oleic peanut under low temperature and high soil humidity conditions

Low temperature coupled with high soil moisture during sowing to emergence generally results in poor peanut stand, thereby posing a non-negligible threat to peanut production in north and northeast China. Five high-oleic (HO) peanut cultivars and 4 seed dressing treatments capable of controlling several diseases and insect pests along with untreated checks were used to find the best combinations to cope with the dual stresses during sowing to emergence period. High broad-sense hereditability estimates of seedling emergence indicated great potential for genetic improvement of this trait. Analysis of variance in the split-plot experiment showed that the main effects of variety and seed dressing and their interaction on seedling emergence were significant. Seed dressing treatments increased seedling emergence percentage by 2.09–35.00 percent points. Four of the 5 HO peanut cultivars yielded satisfactory results. For Huayu 665, Huayu 668 and Huayu 965, Huweisanbao may be the best option; for Huayu 962, Weilidan was highly acceptable. These combinations will be evaluated further in multiple environments before large-scale extension.     

不同类型玉米杂交种播种深度与出苗相关性的研究

测定4个播种深度处理对玉米4种不同子粒类型的32个品种出苗的影响。结果表明,播种至出苗天数、出苗率、中胚轴长度(干重)、胚芽鞘干重、苗长(干重)与播种深度显著相关。一般玉米种子播种深度应以5.0 cm较好,不同类型玉米种子所适应的播种深度不同,马齿型和半硬粒型品种可适当深播,半马齿型和硬粒型品种应适当浅播,以提高出苗率。     

烯效唑对稻苗的生物学效应

 烯效唑和多效唑浸种对稻苗生长的影响比较研究表明，烯效唑的生物活性约比多效唑高10倍，然而喷苗或土施均降低烯效唑的生物活性。烯效唑浸种对稻苗的影响主要是降低稻苗生长的速率而不是抑制生长，因此，烯效唑是一种植物生长延缓物质．而不是植物生长抑制物质。烯效唑的生物学效应是控制稻苗的高度，促进根系生长、增加干重积累、促进分蘖、提高根冠比。 光、温及土壤水分条件会影响烯效唑的生物效应。     

药剂拌种对花生苗期的影响及田间蛴螬防效评价

为研究花生常用拌种药剂的苗期安全性及田间防效,采用盆栽法测定了3种杀虫剂拌种在不同温度、土壤湿度和播种深度对花生出苗率及生长指标的影响。综合比较得出安全性依次为毒死蜱＞氟虫腈＞吡虫啉;分别加入4种杀菌剂混配拌种后发现,出苗率和其它生长指标均有所提高,其中萎锈•福美双效果最好。田间试验得出：毒死蜱单独拌种具有较高的杀虫增产效果,加入杀菌剂有一定的增效;吡虫啉与萎锈•福美双混配拌种可提高出苗率及防虫效果,增产率为53.59%;氟虫腈拌种后防虫效果较差,与4种杀菌剂混配后增效不显著。     

Factors influencing the effects of fungicide treatment on seedling emergence of perennial ryegrass (Lolium perenne)

Seeds of perennial ryegrass were sown by hand in micro-plots. Six treatment factors were applied, in all combinations, totalling thirty-two treatments. The factors were (a) firm vs light compaction of the seedbed, (b) 1 cm vs 2·5 cm sowing depth, (c) fertilizer applied to seedbed vs no fertilizer, (d) fungicides applied to the seed and seedbed vs no fungicide, (e) pesticide applied to seedbed vs no pesticide, and (f) soil kept moist after sowing vs soil kept dry after sowing. Overall, seedling emergence was increased by moist soil (18%), fungicides (16%) and by sowing at 1 cm depth (8%). In dry soil, fungicides increased emergence by 32% but had no effect in moist soil.
In other experiments, micro-plots were sown at monthly intervals, from April to October. Seeds were either treated with benomyl + captan (3 g + 3 g a.i. (kg seed)⁻¹) or not treated, and the plots were either covered to keep the soil dry, or uncovered. Seedling emergence on uncovered plots was increased significantly, by 16–28%, at the May, June, July and August sowings, when soil temperatures were at their highest and soil moisture contents at their lowest. On covered plots fungicides significantly increased emergence at the June sowing only, by 16%. The reasons for this anomaly are discussed.     

播后镇压覆盖对土壤保水保温和玉米幼苗生长的影响

2011年6～8月进行2期池栽试验,研究土壤水分及农艺措施对夏玉米出苗及幼苗生长效应。结果表明,播种后镇压覆盖能够提高土壤含水量,平衡土壤温度,从而提高夏玉米出苗率,增强幼苗素质,提高苗期田间株高整齐度,有利于培育齐苗壮苗,在土壤水分不太充足时效果更为明显。为保证黄淮海夏玉米区的出苗质量,播种时的土壤最低持水量应保持土壤最大持水量的60%。     

EM包衣对玉米苗期防治丝黑穗病效果研究

采用砂培试验研究了有效微生物菌群(EM)包衣处理对玉米种子萌发、幼苗生长的影响及对不同温湿度处理的EM包衣和未包衣的玉米种子在大田生产环境下的发病率进行比较。结果表明：EM包衣能明显提高玉米种子的发芽势、发芽率、发芽指数及活力指数,减少了玉米种子在土壤中的感病率。在有病菌存在的条件下,包衣处理的玉米幼苗的苗高、根长、叶面积、苗干重均明显高于未包衣的玉米幼苗,促进了幼苗根系生长和地上部分的生长。在病菌环境下,经EM包衣处理的玉米种子,其抗坏血酸含量、可溶性总糖含量及丙二醛含量均低于未包衣的玉米种子;而超氧化物歧化酶活性明显高于未包衣的玉米种子。说明EM包衣处理可增强玉米种子的抗病性,提高对玉米丝黑穗病的防治效果。     

The effect of potato seed tuber age and soil temperature on the phenomenon of non-emergence

Summary In three experiments seed tubers of cvs Jaerla, Bintje and Alpha, stored at 12 °C in the dark, were planted in glasshouses on various dates at soil temperatures varying from 8 °C to 28 °C to study the phenomenon of ‘non-emergence’ with ageing seed tubers. In general the tubers were desprouted before planting. At all plantings cv. Alpha produced normal plants. The cvs Jaerla and Bintje, however, showed high proportions of the ‘little potato’ phenomenon when planted in cold soil, and high proportions of decayed tubers more frequently in warm soil. When using physiologically older seed at later planting dates, both the range of soil temperatures became wider and the proportions of seed tubers experiencing both ‘little potato’ and decay increased.     

中国玉米主产区栽培品种种子质量分析

以黄淮海、华北、西南三区46个玉米栽培品种种子为材料,通过物理化学指标测定、标准发芽及幼苗生长测定、逆境发芽测定、田间出苗率测定、指标间相关性分析、淀粉酶活力测定等对种子质量进行分析评鉴。结果表明,46个品种中马齿型和半马齿型的比例占80.4%。综合各项种子活力指标,排名前4位的高活力品种为先玉047、郑单958、大华玉2号和浚单26。玉米种子容重和总淀粉含量与平均田间出苗率分别呈极显著和显著正相关;发芽势、发芽率及逆境发芽各指标与平均田间出苗率均呈极显著正相关,其中抗冷测定发芽率的相关系数最高(r=0.881)。玉米种子容重和总淀粉含量是高活力玉米种子具备的典型性状,抗冷测定为玉米种子活力检测的最适方法;高活力玉米品种种子萌发中同一时期淀粉酶活力明显高于低活力玉米品种种子。     

吸胀期低温与水分条件对油菜种子萌发的耦合效应

为了探讨晚播油菜适宜播种的田间温度和水分条件,以华杂62和华双5号品种为材料,在土壤和PEG溶液两种介质中研究了吸胀温度与水势对种子萌发的影响。结果表明,吸胀期温度和水分条件对油菜种子的萌发具有显著影响。在5~15℃范围内,种子萌发活力随吸胀期土壤温度的升高而提高。在10℃和15℃下吸胀,土壤相对含水量为58.6%、水势为-0.1MPa时较适宜于种子萌发;在5℃低温下吸胀,适当降低土壤水势有利于种子萌发。华杂62种子具有吸胀冷害现象,在低温和高水势下吸胀,种子萌发活性降低,吸水速度加快,种子浸泡液K+渗漏量升高,而Na+渗漏量和Na+/K+比值降低。华双5号种子则具有较强的抗吸胀冷害能力,表现为在低温下吸胀受水势的影响较小。     

Thermal inactivation of Plasmodiophora brassicae Woron. and its attempted control by solarization in the Salinas Valley of California

Thermal inactivation of resting spores of P. brassicae Woron. in glasshouse soil depended on temperature, duration of treatment, inoculum concentration, and soil moisture. At 42, 44 and 50°C, the relationship between temperature and the time for thermal inactivation plotted on a semi-log scale was linear. Treatment times up to 45 days at 30°C and 37°C did not reduce infectivity. The detection threshold in the system was 10^0·5 spores/g of soil. At all temperatures tested, inactivation was achieved more rapidly in soil infested with 10² spores/g than with 10⁶ spores/g. Heat treatment was more effective in saturated soil than in half-saturated soil. Soil temperatures in the field in the northern Salinas Valley were increased 11–14°C by tarping with clear, polyethylene plastic. The average weekly maximum temperature and minimum temperature at a 10 cm depth under tarps were 38°C and 29°C respectively. Solarization reduced disease development after a 10-week treatment but not after a 5-week treatment.     

河西走廊玉米苗枯病的发生规律及防治方法

经对河西走廊玉米制种产区苗枯病进行田间调查和病原菌形态、培养性状和致病性测定,结果表明:玉米苗枯病是由串珠镰刀菌(Fusarium moniliforme)、禾谷镰刀菌(F.graminearum)、玉米丝核菌(Rhizoctonia)等多种真菌复合侵染引起,其中河西地区主要以串珠镰刀菌(F.moniliforme)为主。带菌的种子和土壤是该病的初侵染来源,品种抗性差,苗期低温高湿及土壤肥力是影响发病的主要因素。选择抗病品种、种子药剂处理、加强肥水管理是防治玉米苗枯病的有效措施。其中以种子量0.15%的多菌灵、福美双等拌种,防治效果分别为94.13%、91.32%。     

Ludwigia hyssopifolia emergence and growth as affected by light, burial depth and water management

Experiments were conducted to evaluate the effects of light, seed burial depth, and flooding on germination, emergence and growth of Ludwigia hyssopifolia. Germination was strongly stimulated by light, suggesting that seeds of this species are positively photoblastic. Seeds sown on the soil surface gave the greatest percentage of seedling emergence in plastic trays, and no seedlings emerged from seeds buried in soil at depths of ≥1 cm. Intermittent or shallow flooding suppressed emergence and growth of L. hyssopifolia. Flooding to a depth of 2 cm for 4 days out of 7 days reduced seedling emergence by more than 71% and seedling dry matter by 97% compared to where the soil had not been flooded. Flooding up to a depth of 10 cm however, when delayed to 21 days after sowing, did not significantly suppress growth of this species. This study illustrates the role of seed burial by tillage and flooding as two important tools for the management of L. hyssopifolia.