Study on Sowing Date for Mechanicaltransplanting Rice under Wheat-Rice Cropping System in Chengdu Basin

Nurturing sturdy mechanical-transplanting seedlings is the key to achieve high yield using mechanical-transplanting technology under wheat-rice cropping conditions in Chengdu Basin. In this study, super hybrid rice II You 602 was adopted as experimental material, to investigate the effects of sowing date on seedling growth,transplanting quality, growth process and yield of mechanical-transplanting seedlings in wheat-rice cropping region of Chengdu Basin, thus exploring supporting high-yield cultivation techniques for mechanical-transplanting technology in Chengdu Basin, Results showed that the appropriate sowing date for mechanical transplanting in wheatrice cropping region of Chengdu Basin was April 10-15, and the appropriate seedling age was 45-50 d, which led to the highest yield of mechanical-transplanting seedlings. Although postponing sowing was conducive to improving transplanting quality and increasing the percentage of earbearing tillers, it would result in lagged group growth, poor spike quality and reduced effective number of panicles, grain number, seed-setting rate, 1 000-seed weight and other yield components, thus declining the yield. Yield reduction rate would be above 10% with sowing date postponed by 15 d.

Effect of Nitrogen and Density Interaction on Yield Formation of Late Japonica Rice Under Different Transplanting Dates

[Objectives]This study was conducted to clarify the appropriate nitrogen fertilizer amount and transplanting density that should be selected for different transplanting dates.[Methods]The effects of nitrogen fertilizer rate and transplanting density on the traits and yield of late japonica rice in the Jianghuai rice-wheat cropping area under different transplanting dates(transplanting at an appropriate time and delayed transplanting)were studied.[Results]The transplanting date significantly affected the heading,maturity and whole growth period of rice,and when the transplanting date of early-maturing late japonica rice was delayed by 15 d,the growth period was shortened by about 10 d.Nitrogen and density interaction obviously affected the dry matter accumulation and effective tillers of rice,and the dry matter production and effective tiller number of rice treated with B_(1)N_(2) were greater than other treatments.Under the timely transplanting date,the best nitrogen and density combination was 225-300 kg/hm^(2) and 250500 holes/hm^(2),and the nitrogen use efficiency was ideal.It suggests that under the condition of transplanting rice in a timely manner,applying nitrogen fertilizer at an appropriate rate while ensuring a reasonable population density is conducive to the coordination of the number of stems and tillers,the number of grains per panicle,etc.,thereby ensuring the best formation of yield factors in the middle and late stages of rice growth.[Conclusions]This study provides technical support and theoretical reference for reasonable nitrogen and density interaction of rice.

Analysis on Absorption,Utilization and Transfer Efficiency of Nitrogen in High-yield Wheat Cultivars at Different Sowing Dates

This study aimed to analyze the absorption, utilization and transfer char- acteristics of nitrogen in high-yield winter wheat （Triticum aestivum） cultivars at dif- ferent sowing dates, so as to determine the optimum sowing dates for different high-yield wheat cultivars. A field experiment was conducted in the Shajiang black soil of Anhui Province with Jimai 22, Wanrnai 52 and Zhoumai 22, and the effects of early sowing （October 3）, optimum sowing （October 12） and late sowing （October 30） on wheat plant N content and accumulation, pre-and post-anthesis N accumula- tion （NA） of total plant, nitrogen remobUization to grain （NR）, N remobilization effi- ciency （NRE）, contribution of N remobilized to grain （NRC）, grain yield, N use effi- ciency （NUE） and N harvest index （NHI） of different wheat cultivar were investigat- ed. The results showed that sowing date had an impact on N content, absorption and utilization in wheat plants at various growth stages. The NA, NR and NRC of aboveground vegetative organs of wheat before anthesis were higher than those af- ter anthesis. Under the condition of late sowing, the grain N accumulation mainly depended on the N absorption by vegetative organs before anthesis. Under the conditions of optimum and early sowing, the absorbed N after anthesis accounted for a large proportion in grain N accumulation. The N uptake intensity and relative cumulative rate differed greatly among different growth stages and different-genotype wheat cultivars, and the pre-anthesis NA, pre-anthesis NR, pre-anthesis NRE, post- anthesis N assimilation amount and post-anthesis NRC showed significant differ- ences among different wheat cultivars. The grain yields of different wheat cultivars under the early and optimum sowing were all higher than those under the late sowing. The NHI and grain N accumulation were highest under the optimum sow- ing, and the latter significantly decreased with the delay of sowing dates. In con- trast, the NUE was highest under the late sowing, reaching 35.95%-41.32%. It indi- cated that under the condition of late sowing, most of the nitrogen was not ab- sorbed by wheat, but the use efficiency of the absorbed nitrogen significantly in- creased. In overall, the three high-yield wheat cultivars were all suitable for early and optimum sowing. Under the condition of late sowing, the yield of Zhoumai 22 showed the smallest differences with those under early and optimum sowing, and its NUE was significantly improved. Therefore, among the three high-yield wheat culti- vars, Zhoumai 22 was most suitable for late sowing.

Effects of Different Sowing Dates and Sites on Starch RVA Profile Characteristics of Different Ecotypes of Rice (Oryza sativa, L. japonica)

[Objective] This study aimed to investigate the effects of different sowing dates and sites on starch RVA profile characteristics of different ecotypes of japonica rice. [Method] Five different ecotypes of japonica rice were sown at seven different dates in four rice planting regions in Jiangsu Province to analyze the differences in starch RVA profile parameters among different rice varieties. [Result] Among eight parameters of rice starch RVA profile, peak time exhibited no significant differences among different sites, while other seven parameters varied significantly or extremely significantly among different sites, sowing dates and varieties. Specifically, rice variety exerted the most significant effects on rice starch RVA profile parameters. Starch RVA profile characteristics varied significantly among different ecological conditions but exhibited no significant differences among different latitudes. To be specific, in different sites, peak viscosity （PKV）, hot paste viscosity （HPV） and breakdown viscosity （BDV） demonstrated a descending order of Huai＇an 〉 Suzhou 〉 Lianyungang 〉 Yangzhou. Cool paste viscosity （CPV） and consistence viscosity （CSV） were higher in the north than in the south; specifically, CPV and CSV were significantly higher in Lianyungang and Huai＇an than in Yangzhou and Suzhou. Setback viscosity （SBV） showed an increasing trend with increasing latitude; specifically, SBV was significantly lower in Suzhou than in other three sites. Pasting temperature （PAT） and peak time （PET） changed slightly among different latitudes. With the postponing of sowing date, peak viscosity （PKV）, hot paste viscosity （HPV）, cool paste viscosity （CPV） and peak time （PET） showed a decreasing trend, setback viscosity （SBV） and consistence viscosity （CSV） increased, breakdown viscosity （BDV） increased first and then decreased, whereas pasting temperature （PAT） decreased first and then increased. Furthermore, rice starch RVA profile parameters showed the same variation trend with sowing date in different sites; early sowing within suitable sowing dates could effectively improve the parameters of rice starch RVA profile. However, different parameters exerted different variations among different sites and most parameters were higher in the north than in the south, which indicated that starch RVA profile parameters were significantly affected by sowing date in the north of Jiangsu Province. Among eight starch RVA profile parameters, setback viscosity exhibited the maximum variation coefficient, while peak time exhibited the minimum variation coefficient. Among five rice varieties, Nanjing 46 exhibited the highest peak viscosity and breakdown viscosity and the lowest setback viscosity and consistence viscosity, suggesting that Nanjing 46 had the most appropriate starch RVA profile characteristics and the best cooking and eating quality. Lianjing 4 exhibited relatively high peak viscosity and breakdown viscosity, and relatively low setback viscosity and consistence viscosity, suggesting that Lianjing 4 had good starch RVA profile characteristics. Different sowing dates and sites exerted significant effects on starch RVA profiles of different eco- types of japonica rice. Rice starch RVA profile characteristics varied significantly among different sites but exhibited no significant variations among different latitudes. In addition, starch RVA profile characteristics varied significantly among different sowing dates. Therefore, early sowing of the same variety was conducive to improving starch RVA profile characteristics in appropriate planting regions. [Conclusion] This study provided a theoretical basis for producing high-quality rice and improving the eating quality of rice in Jiangsu Province.

Effect of Different Sowing Dates and Densities on Individual Morphological Development of Super Short-season Insect-resistant Cotton

[Objective] The paper was to explore the effect of different sowing dates and densities on individual morphological development of super short-season insect-resistant cotton,confirm their effects on vegetative and reproductive growth of cotton,so as to provide theoretical and practical guidance for sowing date and density management of cotton planting in Jidong cotton growing region in Yellow River Basin.[Method] With super short-season insect-resistant cotton＂546＂as materials,the effects of different sowing dates（sowing dateⅠ：May 20;sowing dateⅡ：June 2;sowing date Ⅲ：June 14）and densities（low density：120 000 plants/hm2;middle density：150 000 plants/hm2;high density：180 000 plants/hm2）on individual morphological development of super short-season insect-resistant cotton were explored.[Result] Different sowing dates and density treatments significantly affected the individual morphological development of super short-season insect-resistant cotton＂546＂.The effectiveness of sowing date was higher than the effectiveness of density,and the effectiveness of sowing date on development of number of individual fruit branches was higher than that on plant height and stem diameter.[Conclusion] The regulation of sowing date and density during the cultivation process of super short-season insect-resistant cotton ＂546＂ in Jidong cotton growing region in Yellow River Basin could effectively promote vegetative and reproductive growth of cotton,strengthening its production base.

Effects of Different Transplanting and Harvest Dates on Yield and Quality of Flue-cured Tobacco Leaves

In this study,the effects of nine different combinations of transplanting and harvest dates on yield and quality of flue-cured tobacco leaves were investigated.The results showed that different combinations of transplanting and harvest dates had few effects on growth period and agronomic characters of tobacco plants but exerted remarkable effects on economic characters and chemical composition of flue-cured tobacco leaves.With the postponing of transplanting stage,output value of flue-cured tobacco leaves increased.Output value of flue-cured tobacco leaves in C1treatment（normal harvest） was higher than that in C2（harvest 7 d later） and C3（harvest 14 d later） treatments.Different combinations of transplanting and harvest dates had significant effects on chemical composition of flue-cured tobacco leaves,which exhibited no obvious law.Overall,flue-cured tobacco leaves in T3C1treatment（transplanting 14 d earlier,normal harvest） displayed excellent performance compared with other treatments.

Effects of Different Sowing Dates and Sites on Grain Quality and RVA Profile of Nanjing 46,a Popular Cultivar of Japonica Rice(Oryza sativa L.)

[Objective] This study was performed to determine the effects of sowing dates and sites on grain quality and Rapid Viscosity Analyzer （RVA） profile of Nan-jing 46. [Method] The field experiments were carried out at five sites in Jiangsu Province, and in every site, the seeds were sowing on seven different dates. RVA related indices were measured after harvest. [Result] Along with the delay of sowing date, the mil ing quality of Nanjing 46 increased at first and then reduced, while its appearance quality went up and the cooling and edible quality decreased. With the sowing sites moving southward, the rice mil ing quality, appearance quality, and cooling and edible quality of Nanjing 46 decreased at first and then increased. Grain traits responded variably to the sowing dates and sites. The brown rice rate, grain width, grain length, length/width, mil ed rice rate and head mil ed rice rate were less affected, while the chalky rice rate and chalkiness degree were more af-fected. The gelatinization temperature, protein content, amylose content, gel consis-tency and eating value were in-between. The RVA profile analysis revealed that the breakdown value, setback value and pasting temperature were affected by the sow-ing date and geographical environment. The peak viscosity, hot viscosity, cool vis-cosity and peak time were influenced more by geographical environment. With the delay of the sowing date, peak viscosity, hot viscosity, cool viscosity, setback value and pasting temperature decreased at first and then increased, while the breakdown value changed inversely, and the peak time did not exhibit a regular trend. With the decrease of latitude, the peak viscosity, hot viscosity, breakdown and cool viscosity declined at first and then increased, the setback value and peak time decreased, while the pasting temperature increased. [Conclusion] This study wil provide refer-ences for the effective production of Nanjing 46.

Optimization of sowing date and seeding rate for high winter wheat yield based on pre-winter plant development and soil water usage in the Loess Plateau,China

Sowing date and seeding rate are critical for productivity of winter wheat(Triticum aestivum L.).A three-year field experiment was conducted with three sowing dates(20 September(SD1),1 October(SD2),and 10 October(SD3)) and three seeding rates(SR67.5,SR90,and SR112.5) to determine suitable sowing date and seeding rate for high wheat yield.A large seasonal variation in accumulated temperature from sowing to winter dormancy was observed among three growing seasons.Suitable sowing dates for strong seedlings before winter varied with the seasons,that was SD2 in 2012–2013,SD3 in 2013–2014,and SD2 as well as SD1 in 2014–2015.Seasonal variation in precipitation during summer fallow also had substantial effects on soil water storage,and consequently influenced grain yield through soil water consumption from winter dormancy to maturity stages.Lower consumption of soil water from winter dormancy to booting stages could make more water available for productive growth from anthesis to maturity stages,leading to higher grain yield.SD2 combined with SR90 had the lowest soil water consumption from winter dormancy to booting stages in 2012–2013 and 2014–2015; while in 2013–2014,it was close to that with SR67.5 or SR112.5.For productive growth from anthesis to maturity stages,SD2 with SR90 had the highest soil water consumption in all three seasons.The highest water consumption in the productive growth period resulted in the best grain yield in both low and high rainfall years.Ear number largely contributed to the seasonal variation in grain yield,while grain number per ear and 1 000-grain weight also contributed to grain yield,especially when soil water storage was high.Our results indicate that sowing date and seeding rate affect grain yield through seedling development before winter and also affect soil water consumption in different growth periods.By selecting the suitable sowing date(1 October) in combination with the proper seeding rate of 90 kg ha–1,the best yield was achieved.Based on these results,we recommend that the current sowing date be delayed from 22 or 23 September to 1 October.

A Dynamic Knowledge Model for Design of Suitable Sowing Date and Sowing Rate in Winter Wheat

Based on research concerning dynamic relationships of winter wheat growth to environments and production conditions, a winter wheat model for selecting suitable sowing date, population density and sowing rate under different varieties, spatial and temporal environments was developed. Case studies on sowing date with the data sets of five different eco-sites, three climatic years and soil fertility levels, and on population density and sowing rate with the data sets of two different variety types, three different soil types, soil fertility levels, sowing dates and grain yield levels indicate a good model performance for decision-making.

Protein and hordein fraction content in barley seeds as affected by sowing date and their relations to malting quality

The effect of sowing date on grain protein, hordein fraction content and malting quality of two-rowed spring barley was investigated by using ten commercial cultivars with different grain protein content and the relationships among these traits were examined. The results showed that grain protein content and B hordein content increased as the sowing date postponed and were significantly affected by sowing date, while C and D hordein contents were less influenced by sowing date. There were significant differences in grain protein and hordein fraction content among the ten cultivars. The coefficient of variation of D hordein content was much larger than that of B and C hordein contents, suggesting its greater variation caused by different sowing dates. Beta-amylase activity and diastatic power were also significantly affected by sowing date, with malt extract being less affected. Significant differences in measured malt quality were found among the ten cultivars. Grain protein was significantly correlated with B hordein and malt extract positively and negatively, respectively. There was no significant correlation between beta-amylase activity or diastatic power and grain protein content. B hordein was negatively and significantly correlated with malt extract, but no significant correlations between C hordein, D hordein and malting quality traits.

Evaluation of the CROPGRO-Peanut model in simulating appropriate sowing date and phosphorus fertilizer application rate for peanut in a subtropical region of eastern India

Projected changes in weather parameters, mainly temperature and rainfall, have already started to show their effect on agricultural production. To cope with the changing scenarios, adoption of appropriate management strategies is of paramount importance. A study was undertaken to evaluate the most appropriate combination of sowing date and phosphorus fertilization level for peanut crops grown in sandy loam soil in a subhumid region of eastern India. Field experiments were conducted during the summer seasons of 2012 and 2013 on peanut crops at the farm of the Indian Institute of Technology, Kharagpur. The DSSAT v4.5 CROPGRO-Peanut model was used to predict the phenology, growth, and yield of peanut crop under combinations of four sowing dates and four phosphorus fertilization levels. The model was calibrated with a 2012 dataset of growth, phenology, and yield parameters for estimating the genetic coefficients of cultivar TMV-2 and was validated with a 2013 dataset of the same parameters. Simulations of pod yield and other yield parameters using the calibrated model were found to be quite accurate. The model was able to reasonably simulate pod yield and final biomass with low normalized root mean square error (RMSE_n), low absolute root mean square error (RMSE_a) and high coefficient of determination (R^2> 0.7) over a wide range of sowing dates and different phosphorus fertilization levels sensitivity analysis indicated that sowing from the second week of January to the end of February with 30–50 kg P_2O_5 ha^(-1)would give the highest pod yield.

Effects of sowing date and ecological points on yield and the temperature and radiation resources of semi-winter wheat

Exploring the effects of sowing date and ecological points on the yield of semi-winter wheat is of great significance.This study aims to reveal the effects of sowing date and ecological points on the climate resources associated with wheat yield in the Rice–Wheat Rotation System.With six sowing dates,the experiments were carried out in Donghai and Jianhu counties,Jiangsu Province,China using two semi-winter wheat varieties as the objects of this study.The basic seedlings of the first sowing date (S1) were planted at 300×10^(4)plants ha^(-1),which was increased by 10%for each of the delayed sowing dates (S2–S6).The results showed that the delay of sowing date decreased the number of days,the effective accumulated temperature and the cumulative solar radiation in the whole growth period.The yields of S1 were higher than those of S2 to S6 by 0.22–0.31,0.5–0.78,0.86–0.98,1.14–1.38,and 1.36–1.59 t ha^(–1),respectively.For a given sowing date,the growth days increased as the ecological point was moved north,while both mean daily temperature and effective accumulative temperature decreased,but the cumulative radiation increased.As a result,the yields at Donghai County were 0.01–0.39 t ha–1lower than those of Jianhu County for the six sowing dates.The effective accumulative temperature and cumulative radiation both had significant positive correlations with yield.The average temperature was significantly negatively correlated with the yield.The decrease in grain yield was mainly due to the declines in grains per spike and 1 000-grain weight caused by the increase in the daily temperature and the decrease in the effective accumulative temperature.

Effects of Transplanting Date on Growth, Development, Yield and Quality of Flue-cured Tobacco in Western Henan

With Yunyan 87 as an experimental material, the effects of different transplanting dates on the growth and development of tobacco plants and the yield and quality of cured tobacco leaves were studied in Lingbao City, Sanmenxia City. With the postponement of transplanting date, the growth period in field was prolonged, and the plant height and leaf area both increased at first and decreased then. TMV, weather fleck and brown spot all showed an incidence and a disease index decreased with the postponement of transplanting date. The total sugar and reducing sugar contents of the cured tobacco leaves from the upper and middle part increased at first and decreased then with the postponement of transplanting date. The main nitrogenous compounds decreased at first and increased then. The economic traits and leaf class were on the decrease.

Influence of Date of Transplanting on Growth and Yield Attributes and Resultant Seed Quality of Davana

A field experiment was conducted at TamilNadu agricultural university, Coimbatore during rabi 2011 to study the effect of time transplanting on growth, yield attributes and resultant seed quality of davana. The experiment was laid out with five different dates of transplanting viz., October 15th, November 1st, November 15th, December 1st and December 15th with the spacing of 15 × 7.5 cm and 125:125:75 NPK kg/ha were adopted in a randomized block design with four replications. The results revealed that the seedlings transplanted at 15th November recorded the maximum number of branches/plant, seed yield/plant, seed yield/plot, resultant seed germination and vigour index.

Effect of Dates and Methods of Sowing with and without Hydropriming on Growth,Phenology and Yield of Sorghum under Semi Arid Conditions of Eritrea

A study was carried out at the research farm of Hamelmalo Agricultural College during summer 2015 to study the effect of dates and methods of sowing with and without hydro-priming on growth,development and yield of sorghum.The experiment consisted of 2 factors-three dates of sowing viz.D0(Sowing before the onset of first summer rain,June 30),D1(Sowing with the onset of first summer rains,July 7)and D2(Sowing after the onset of summer rains,July 14)and three methods of sowing viz.SP(Direct sowing with hydro seed priming),TR(Transplanting)and DS(Direct sowing without hydro seed priming).The experiment was conducted in split plot design with 4 replications by keeping dates of sowing in the main plots and methods of sowing in the sub plots.The data on growth parameters,crop phenology,yield components and yield were recorded.The data were analysed using GENSTAT software and inferences were drawn by using LSD at 5%level of significance.Sowing methods significantly affected leaf area and leaf area index but sowing dates and their interaction with sowing methods did not show significant difference.Stand count,plant height,phenological parameters,thousand grain weight,grain and biomass yield were significantly affected by the sowing dates and methods but no significant difference in their interaction on all the parameters except in stand count and phenological parameters.Sowing before the onset of first summer rains(D0)resulted in significantly highest grain yield.Among the sowing methods,transplanting resulted in significantly higher grain yield seconded by direct sowing with hydro seed priming.Transplanting is less profitable and practicable as it is more laborious and difficult to apply in larger areas.

播期对不同熟期组大豆品质的影响

为明确不同播期对大豆品质的影响,本研究以东北地区不同熟期组(早、中、晚)的20个大豆品种为试材,探讨了不同播期(5月13日、5月23日、6月2日、6月12日和6月22日)条件下大豆蛋白质含量、脂肪含量、蛋脂总量等品质指标的变化规律。结果表明:整体而言,播期推迟在10 d以内,对大豆品质影响较小,推迟10~20 d,对蛋白质含量的影响大于对脂肪含量影响,推迟20 d以上,各项品质指标与第1期差异达到显著或极显著水平,推迟40 d时,蛋白质含量和脂肪含量均极显著下降,达到最低值。本研究进一步分析了不同熟期组大豆品质对播期推迟的响应。结果表明:大豆品质指标随播期推迟而变化的趋势与品种的生育日数(即熟期)密切相关,不同熟期组间存在较大差异,播期推迟越晚导致早熟组大豆平均蛋白质含量降低的幅度越大,第3期(6月2日)及以后各期蛋白质含量较第1期(5月13日)下降达到显著、极显著水平,中熟组和晚熟组大豆的蛋白质含量分别在6月2日和6月12日前,差异不显著;晚熟组大豆脂肪含量随播期推迟显著下降,且下降幅度逐渐扩大,早熟组和中熟组大豆的脂肪含量分别在6月2日和6月12日下降未达显著水平;不同熟期组的大豆蛋脂总量总体上随播期的推迟而下降,其下降趋势与蛋白质含量的变化规律基本一致,即早熟组大豆在晚播10 d以上时,蛋脂总量显著下降,而中熟组、晚熟组大豆蛋脂总量分别在6月12日和6月2日播种,蛋脂总量相对稳定;不同熟期组大豆晚播30 d以上时,各项品质指标均会出现严重下降。本研究为沈阳地区晚播大豆的品质预测提供重要参考依据。

不同播期对油葵农艺性状及品质的影响

本研究探索播期对不同油葵品种开花习性、经济性状、产量和品质的影响,旨在为我国中部省区向日葵栽培提供参考。结果表明,早春育苗移栽较早春直播极大地缩短了播种到初花的时间;除早熟品种6K132外,各播期处理的成熟时间均随着播期推迟而缩短,夏秋播的成熟期较早春播种缩短9~25 d,较春季播种缩短9~11 d。早春直播和育苗移栽对籽粒产量的影响在不同年份间存在差异,且与品种存在互作效应。不同播期对油葵脂肪酸组分含量影响明显,夏秋播收获的籽粒中亚油酸含量显著增加,2021年和2022年分别比春播增加13.2%~39.1%和16.0%~35.4%;亚油酸/油酸比从春播的0.39~0.65和0.26~0.67分别升高到夏秋播的1.47~3.42和0.65~2.11。此外,夏秋播收获的种子发芽力最好,2021年和2022年出苗率分别为92.2%~97.8%和60.0%~93.3%。综上所述,在武汉等中部省区,可通过选择不同播期来生产不同亚油酸/油酸比的葵花籽,春播可提高向日葵籽油酸含量,而夏秋播可提高亚油酸含量;可实现一年两季向日葵生产和多季观花需求,并具备通过品种选择和适宜的栽培措施来提高产量的潜力;通过播期调控可躲避花期和灌浆期的高温高湿从而获得高质量的种子,夏秋播种有利于提高种子质量。

播期和密度对精量穴直播水稻产量和抗倒伏性的影响

为探究渝西地区播期与密度互作对精量穴直播水稻产量和抗倒伏的影响,以渝香优8133和泰优粤禾丝苗为试验材料,设置2个播期(B1:3月29日、B2:5月25日)和5个播种密度(D1:每1 hm^(2)1.50×10^(5)穴、D2:每1 hm^(2)1.95×10^(5)穴、D3:每1 hm^(2)2.40×10^(5)穴、D4:每1 hm^(2)2.85×10^(5)穴、D5:每1 hm^(2)3.30×10^(5)穴),分析茎秆力学、茎秆形态及器官干物质积累与茎秆抗倒伏性和产量的关系。结果表明,与早播处理(B1)相比,迟播处理(B2)可显著提高精量穴直播水稻产量水平;同时,B2播期处理较高的叶面积指数(LAI)和有效穗数导致茎秆倒伏指数显著提高。随着播种密度增加,2个水稻品种的产量均呈先增加后降低趋势,B1播期下D3处理产量最高,B2播期下D4处理产量最高,但与D3处理差异不显著;而倒伏指数呈持续增加趋势,2个水稻品种趋势一致。与D1处理相比,B1和B2播期的D2、D3处理倒伏指数增幅较小,D4、D5处理显著升高,以渝香优8133表现明显。在B1和B2播期下,D2、D3处理的单株茎鞘干重、基部节间茎粗、壁厚及茎鞘充实度与D1处理相当,而D4、D5处理大幅降低。综合分析认为,在B1和B2播期下,D3处理是精量穴直播水稻产量、抗倒伏协同较好的适宜播种密度。

播期调整对华北北部冬小麦、夏玉米产量和品质的影响

【目的】基于田间分期播种试验,研究华北北部冬小麦、夏玉米播期调整,其生长发育、光合生理特性、籽粒灌浆和产量形成及品质对气候变暖的不同响应,为华北平原农业生产采取措施应对气候变化提供科学依据。【方法】采用分期播种方法,于2017—2023年在华北北部的河北固城农业气象国家野外科学观测研究站开展冬小麦和夏玉米的大田分期(早播10 d、正常播期、晚播10 d、晚播20 d)播种试验,获取冬小麦和夏玉米的生育进程、地上干物质累积和分配、叶片光合特性、籽粒灌浆速率以及产量农艺性状和籽粒营养成分等资料。【结果】冬小麦全生育期随播期推迟而缩短,主要原因在于冬前幼苗期缩短;夏玉米全生育期与播期呈抛物线关系,播期每推迟10 d,幼苗期缩短1.3 d,花粒期和籽粒形成-灌浆期分别延长1.5和1.6 d。冬小麦、夏玉米籽粒灌浆过程对播期调整的响应完全不同,冬小麦籽粒灌浆特征在播期间反应并不敏感,夏玉米籽粒灌浆速率在播期间差异较小,但籽粒形成期、灌浆结束日期和峰值日期因播期推迟顺次延后,且灌浆持续日数因播期每推迟10 d,灌浆持续日数缩短4 d。北方麦区在秋暖和冬暖背景下,冬小麦播种期界限延宽,播期对产量的影响明显减弱,播期推迟配套增加播种量,产量不减且会小幅增产;夏玉米产量随播期推迟明显递减,理论产量播期每推迟10 d递减率1381.50 kg·hm^(-2),但冬小麦和夏玉米晚播20 d产量都凸显跳跃变小。播期每推迟10 d,冬小麦籽粒分配率递增1.67%,夏玉米则递减1.57%,冬小麦收获指数提高0.017,而夏玉米降低0.016。冬小麦和夏玉米叶片光合速率(Pn)对播期的响应亦不同,冬小麦播期间的Pn较为相近,而夏玉米播期每推迟10 d Pn递减率1.21μmol·m^(-2)·s-1。播期调整对华北北部冬小麦、夏玉米籽粒品质不会产生明显影响。【结论】气候变暖背景下我国北方冬小麦延迟播种,延宽适宜播种期是适应气候变暖的积极有效措施,华北平原夏玉米适期早播可避免高温热害影响,有助于稳产增产。

基于SWAP模型分析青铜峡灌区春小麦播期优化及其对灌溉需水量的影响

以宁夏青铜峡灌区春小麦为研究对象,基于2a田间观测试验和率定后的SWAP模型,构建旱作区春小麦模型参数集,以偏差校正后的7个大气环流模式(General Circulation Models,GCMs)数据驱动模型,评估未来不同气候情景下(SSP2-45和SSP5-85)春小麦产量和灌溉需水量变化,定量分析播期调整对青铜峡灌区春小麦生长和耗水过程的影响。结果表明:参数校正后的SWAP模型能有效模拟青铜峡灌区春小麦生长过程;SSP2-45情景下未来两个时期(2021-2050年和2051-2080年)青铜峡灌区多模式平均最高温度相对于历史基准期(1991-2020年)分别增加1.6℃和2.6℃,两个时期SSP5-85情景下最高温度将分别增加1.8℃和3.6℃。在不改变播期和品种条件下,未来春小麦全生育期长度将随温度升高而缩短,最大缩短天数达14.2d,出现在SSP5-85情景下2051-2080年。SSP2-45情景下未来两个时期春小麦多模式平均产量将分别下降9.6%和12.9%,SSP5-85情景下则分别下降12.1%和17.2%;不同情景不同时期春小麦灌溉需水量变化幅度相对较小,均不超过3.5%;提前播种可有效减少青铜峡灌区春小麦产量损失,但不能完全抵消气候变化的负面影响,其中,SSP2-45情景下未来两个时期分别提前23d和33d播种,产量损失可控制在1.5%和5.3%,在SSP5-85情景下分别提前30d和42d播种,产量损失可分别控制在2.9%和5.4%。优化播种日期后,青铜峡灌区春小麦收获日期平均提前5d左右。未来不同情景不同时期下春小麦灌溉需水量增加明显,增加比例在4.0%~8.0%。