“独秆”栽培模式下全程氮肥在分蘖中后期施用对旱直播水稻产量和品质的影响

稻麦两熟地区,旱直播水稻生产受前茬小麦收获、全量麦秸秆还田及耕整地质量不高等因素的影响,常采用迟播期、大播量、高基本苗和主茎成穗为主的“独秆”栽培模式,而配套该模式直播稻优质丰产的氮肥管理技术尚缺乏系统的研究。以优质食味粳稻南粳9108为材料,采用机械旱直播方式,基本苗为380×10⁴ hm^-2,设置不同叶龄期(六、七、八、九和十叶龄期)氮肥追施处理及氮肥追施用量(纯氮180 kg hm^-2和225 kg hm^-2)处理,以基本苗380×10⁴ hm^-2和300×10⁴ hm^-2的旱直播精确定量氮肥管理(纯氮270 kg hm^-2,基肥︰分蘖肥︰穗肥=3.5︰3.5︰3.0)为对照,系统比较研究“独秆”栽培模式下,全程氮肥在分蘖中后期施用对旱直播水稻产量和品质的影响。结果表明,随追施叶龄的延后,水稻产量呈先增后降趋势,八叶期追施氮肥水稻产量显著高于其他处理,且追施量增加,水稻产量进一步提高。与2组对照相比,在纯氮180 kg hm^-2,氮肥减量33.3%情况下,不施氮素基肥配合八叶期一次性追施氮肥,可显著提高水稻产量5.10%和8.65%;在纯氮225 kg hm^-2,氮肥减量16.7%情况下,不施氮素基肥配合八叶期及7 d后二次追肥可显著提高水稻产量7.46%和11.09%。不施氮素基肥配合八叶期追施氮肥水稻产量提高的原因是,保障较大穗型的基础上增加有效穗数,显著提高群体颖花量,同时保持较高水平的结实率和千粒重。随追肥叶龄延后,水稻整精米率呈增加趋势,垩白度呈增大趋势,蛋白质含量增加,直链淀粉含量下降,食味值呈降低趋势。与2组对照相比,不施氮素基肥配合八叶期追施氮肥的水稻,加工品质提高,整精米率提高0.67%~2.23%;外观品质变好,垩白度降低3.6%~14.5%;营养品质提升,蛋白质含量增加3.03%~14.08%;蒸煮食味品质呈变优趋势,直链淀粉含量下降4.23%~10.95%;食味值无显著差异。综上所述,“独秆”栽培模式下基肥不施氮肥配合全程氮肥在分蘖中后期适宜叶龄施用可实现稻麦两熟地区旱直播稻迟播期、大播量和高基本苗生产方式的提质增产生产。

Effects of nitrogen fertilizer in whole growth duration applied in the middle and late tillering stage on yield and quality of dry direct seeding rice under“solo-stalk”cultivation mode

In a rice–wheat cropping system,dry direct seeding rice growth was directly affected by harvest dates of the previous crop of wheat,the return of full wheat straw to the field,and the poor quality of tillage and land preparation.A“solo-stalk”cultivation mode with main stem panicles by late sowing dates,large sowing rates and high basic seedlings was commonly used in dry direct seeding.However,the nitrogen fertilizer management of high-quality and high-yield dry direct-seeding rice for the“solo-stalk”cultivation mode was still lacking in systematic research.With high-quality japonica rice Nanjing 9108,380×10⁴ hm^-2basic seedlings were realized by mechanical dry direct seeding method.The leaf age treatments of 6,7,8,9,and 10 leaf age and nitrogen application amount treatments of 180 and 225 kg hm^-2were designed with accurate quantitative nitrogen management(total nitrogen was 270 kg hm^-2,base fertilizer:tiller fertilizer:spike fertilizer=3.5:3.5:3.0)at basic seedlings of 380×10⁴ and 300×10⁴ hm^-2as the control.Then dry direct seeding rice yield and quality were systematically determined and compared with the control and“solo-stalk”cultural method with nitrogen fertilizer in whole growth duration applied in middle and late tillering stage.The results showed that rice yield showed a trend of first increased and then decreased with nitrogen application at bigger leaf age.Rice yield was significantly higher than other treatments when applying nitrogen fertilizer at the 8-leaf stage,and the yield was further improved with the increase of nitrogen application amount.Compare with the controls,nitrogen fertilizer in whole growth duration of 180 kg N hm^-2applied one time at 8-leaf stage could significantly increase rice yield by 5.10%and 8.65%,and reduced nitrogen fertilizer by 33.3%,whereas nitrogen fertilizer in whole growth duration of 225 kg N hm^-2applied two time at 8-leaf stage and 7 days later could significantly increase rice yield by 7.46%and 11.09%,and reduced the nitrogen by 16.7%.The reason was that,compared with the control,seed setting rate and 1000-grain weight,effective panicle number was significantly increased resulting in the increasing total spikelet amount per hectare and yield on the basis of maintaining larger panicle type.With nitrogen applied at bigger leaf age,the head rice rate,chalkiness and protein content of rice revealed an increasing trend,but the amylose content and taste value of rice showed a decreasing trend.Compare to the two controls,the processing quality of rice with the head rice rate was increased by 0.67%–2.23%with nitrogen fertilizer in whole growth duration applied at 8-leaf age;the appearance quality was improved with the chalkiness decreased by 3.6%–14.5%;the nutrition quality was better with protein content increased by 3.03%–14.08%;the cooking and eating quality showed a tendency of getting better with amylose content decreased by 4.23%–10.95%;and there was no insignificant difference in taste value.In conclusion,nitrogen fertilizer in whole growth duration applied at suitable leaf age in the middle and late tillering stage could improve the quality and increase the yield of dry direct seeding rice under“solo-stalk”cultural method caused by late sowing dates,large sowing rate,and high basic seedlings in a rice-wheat cropping system.