湖北省小麦适宜播期的叶龄积温法确定

为探明气候变暖背景下湖北省各地小麦适宜播期,同时为鄂北地区小麦亩产千斤提供理论支撑,本研究对2008~2012年湖北省郧西等10个地区的气象数据进行了分析,依据在前期研究基础上提出的湖北省小麦主导品种郑麦9023的叶热间距,运用叶龄积温法推算得出郧西等10个地区的小麦适宜播期。生产上各地可根据此次研究结果,结合当地气象预报、土壤墒情以及小麦品种特性等适当调整小麦播期,确保小麦壮苗越冬、高产稳产。     

Duration of vegetative and generative development phases in oat cultivars released since 1921

Genetic yield improvements in oat (Avena sativa L.) cultivars grown at high latitudes have resulted from marked changes in harvest index and yield components. This study was designed to investigate whether such changes have entailed alterations in duration of different developmental phases: vegetative, generative and grain filling phases and pre-anthesis generative sub-phases such as pre-fertile, pre-abortion, fertile pre-abortion, fertile and abortion sub-phases. We tested 14 oat cultivars released between 1921 and 1988 and 6 breeding lines. Ten randomly sampled plants of each oat entry were collected every 3–4 d (18 times) from seedling emergence until pollination, and apical developmental stages were determined on the most advanced spikelet. Cumulated degree-days (Cdd) for each critical developmental stage and component phases were determined (5 °C as a base temperature). At each measurement the number of leaves, green leaves and tillers on main shoot, apex length (mm) and height to the uppermost node, and stipule (cm) were recorded. Phyllochron (°C d leaf⁻¹) and relative elongation rates (RER) for height characterising traits were calculated. Grain filling was the only period altered by breeding, while no consistent effects on duration of vegetative and generative pre-anthesis phases and sub-phases were detected. Different developmental phases were interrelated: in some cases cultivars with similar duration of pre-anthesis phase, however, differed in duration of some pre-anthesis sub-phases. Their duration was not, however, consistently associated with measured growth and yield parameters. Likely long days that make the northern growing conditions exceptional and unique, substantially narrowed the differences among oat entries in duration of different developmental phases, thereby making their role also less critical in yield determination contrary to the situation in the main global temperate cereal production regions.     

Productivity impacts of the system of rice intensification (SRI): A case study in West Bengal,India

The system of rice intensification (SRI) has generated considerable debate globally, particularly with regard to its potential to raise rice yields. Proponents of SRI have reported that the average rice yield with SRI is double the current average yield and can be increased to the level of three to four times. Opponents say the reported high yields are due to measurement error and that usual information expected in support of these fantastic yields is missing. The number of SRI adopters has increased in India in recent years. We evaluate the impact of adoption of SRI practices on rice yields, the economics of paddy cultivation and labour inputs based on field research conducted in Purulia, West Bengal, India. Paddy yields with SRI were higher than those under conventional paddy cultivation by 32% and net returns were higher by 67%. Labour input was reduced by 8%. SRI adoption enabled farmers consistently to enhance paddy yields, increase returns and save labour; and enhance productivity with respect to the key inputs in terms of paddy output per unit of seed, fertilizer and labour-day. SRI promises to be a significant alternative for not only raising paddy yields, but also for managing paddy based farming in resource-starved regions.     

Tillering Responses to High Red/ Far-Red Ratio of Four Japanese Wheat Cultivars

Abstract

The effect of high red/ far-red ratio (R/FR) on tillering in wheat and its cultivar differences were investigated with a pot experiment. Four Japanese wheat cultivars with a different degree of winter habit: Abukumawase, Sanukinoyume 2000, Norin 61 and Iwainodaichi, were grown under the tunnels with different R/FR conditions: one tunnel covered with a light control film which attenuates irradiance in the far red range (high R/FR) and the other with a transparent polyethylene film with a white shading cloth (control). The high R/FR treatment increased R/FR by 25%, and slightly decreased air temperature. The low temperature in high R/FR had some effect on the time of the developmental stage; however, physiological responses to high R/FR and its cultivar differences were observed. Tillering dynamics was quantified and analyzed based on phyllochron, site-filling and the time of cessation of tillering. The high R/FR significantly delayed the time in calendar days of full expansion of flag leaf and anthesis, but the effect of treatment was not significant in growing degree days. The high R/FR had no significant effect on the phyllochron and the maximum number of leaves on the main stem. The maximum number of tillers per plant was significantly increased and the cessation of tillering was significantly delayed by the high R/FR in all cultivars. In conclusion, the increase in the number of tillers in the high R/FR was attributed mainly to the delay of the cessation of tiller emergence, along with the significant increase in rate of tillering in some cultivars.     

The Effect of Day to Night Temperature Variation on Leaf Development in Wheat

Summary

The rate of leaf development in wheat is related to time and temperature in units of degree-days (DD) leaf^?1 (phyllochron). Experiments were conducted in controlled environment chambers to study the effect of day to night variation in temperature on leaf development in two wheat cultivars, Penawawa and Stephens. Plants were grown at constant 20°C, and in eight day/night temperature ranges as wide as 8/32°C to 32/8°C, all with a mean temperature of 20°C. The leaf number on the main stems was counted (in Haun units) every other day, from the emergence of the 2nd leaf until the emergence of the 5th leaf. Leaf phyllochron values were derived from the inverse of the slopes of the linear regression of leaf number on DD. Phyllochron values ranged from 99 to 153 DD leaf^?1. The phyllochron values were greater when higher temperatures were imposed at night under extreme day to night temperature treatment.     

Corn stubble height and residue placement in the northern US Corn Belt II. Spring microclimate and wheat development

Crop residue management systems are yet needed in the northern Corn Belt of the USA that hasten sowing and early establishment of crops in the spring. This study was conducted to investigate the effect of corn stubble height and residue placement on the soil microclimate and associated development of wheat in early spring. Treatments were established after corn harvest in the autumn of 1993–1995 and included 60 cm stubble, 30 cm stubble, 30 cm stubble with adjacent interrows devoid of and covered with prostrate residue (30 cm stubble with banded residue), 0 cm stubble, and 0 cm stubble without prostrate residue. Five rows of wheat were sown by hand into one corn interrow on 12 April 1994, 3 April 1995, and 24 April 1996. Leaf development on the main stem was assessed twice weekly until late May. Net and reflected global radiation, soil temperature, and soil water content were measured in each treatment throughout the spring. Vegetative development of wheat was hastened in soils with little residue cover (0 cm stubble without residue treatment and the bare interrow of the 30 cm with banded residue treatment). Averaged across years, the phyllochron ranged from 75 °C day per leaf for treatments with little residue cover to 92 °C day per leaf for the residue interrow of the 30 cm stubble with banded residue treatment. Vegetative development in treatments with little residue cover was hastened by soil temperatures that were at least 1 °C higher throughout spring than those of the residue interrow of the 30 cm stubble with banded residue treatment. The 0 cm stubble without residue treatment was warmer because of a smaller albedo (at least 0.03) and greater net radiation (at least 0.5 MJ m⁻² per day) compared with all other treatments. Little difference in soil water content was found among treatments, although treatments with little residue cover were wetter in two of the three springs. Based on the results of this study, one can conclude that soils with little residue cover or that have taller stubble on the surface will absorb more radiation and thereby enhance soil warming and early development of plants in the northern Corn Belt of the USA.     

Genetic variability in duration of pre-heading phases and relationships with leaf appearance and tillering dynamics in a barley population

The stem elongation phase seems critical in yield potential determination in barley (Hordeum vulgare L.). Extending its duration, without modifying total time to anthesis, has been proposed as a promising breeding tool. A prerequisite for its use is that the duration of phases before and after jointing (that including leaf and spikelet initiation, LS, and that of stem elongation, SE) should be under different genetic control. In addition, little is known about the implications of changes in the duration of LS and SE upon other developmental traits which could affect other aspects of yield generation, such as phyllochron and tillering. Thus, the objectives of the present work were to study the genetic variability in LS and SE, in traits related to leaf appearance and tillering, as well as their relationships, in a double-haploid (DH) population derived from the cross Henni × Meltan. DH lines and both parents were studied in four field trials. Despite the similarity in development between parents, there was significant genetic variability in duration of both LS and SE (i.e. considerable transgressive segregation was observed), with no major genetic correlations found between them. Although some significant genetic correlations were found between duration of phases and leaf appearance and tillering traits, it has been shown that modifying the duration of LS does not necessarily imply concomitant changes in traits that could be important for an early expansion of the crop canopy (i.e. phyllochron, onset and rate of tillering).     

The components of lucerne (Medicago sativa) leaf area index respond to temperature and photoperiod in a temperate environment

Irrigated crops of ‘Grasslands Kaituna’ lucerne were grown for 5 years in a temperate climate at Lincoln University, Canterbury, New Zealand (43°38′S, 172°28′E). From these the response of the components of leaf area index (LAI) to environmental factors was determined. A broken stick temperature threshold with a base temperature (T_b) of 1 °C at air temperatures (T_a) <15 °C and a T_b = 5 °C for T_a ≥ 15 was required to accumulate thermal time (Tt). Using this, the appearance of nodes on the main-stem (phyllochron) was constant in Tt within a re-growth cycle (30–42 days). The phyllochron was 37 ± 7 °Cd but declined from 60 to 37 °Cd as photoperiod decreased from 15.7 to 11.4 h. Branching began at the appearance of the fifth main-stem node with 2.5 secondary nodes produced per main-stem node in spring re-growth cycles but only 1.7 produced in summer. Leaf senescence increased from 0.3 to 1.08 leaves per main-stem node after the appearance of the ninth node. Spring re-growth cycles had a mean individual leaf area of 170 mm² compared with 400 mm² for summer re-growth cycles. These results demonstrate systematic variation in LAI components and suggest they need to be considered separately in response to environmental factors to provide a quantitative framework for crop simulation analyses of lucerne canopy development.