[目的]研究西南丘陵旱地小麦、玉米轮作系统中秸秆覆盖后小麦根系构型与根尖氮素转运的过程,阐明秸秆覆盖与施氮促进小麦氮素高效吸收利用的生理基础.[方法]试验于2020-2022年在四川仁寿现代农业试验站进行,采用原位土柱试验与大田定位试验相结合,试验设计为二因素裂区试验,秸秆覆盖(SM:秸秆覆盖;NSM:秸秆不覆盖)为主区,副区为施氮量(N0:0;N1:120 kg·hm-2).针对西南丘陵旱地土壤干旱抑制根系伸长、导致小麦生物量和养分利用效率低的现状,分析秸秆覆盖和氮素对土壤理化性状、小麦根系构型、根尖氮吸收、植株生物量和地上部氮素积累与利用的影响.[结果]2020-2021年度和2021-2022年度秸秆覆盖处理较不覆盖处理土壤硝态氮含量分别增加43.1%和30.8%,铵态氮增加21.8%和 18.8%;秸秆覆盖提高了小麦拔节期、孕穗期和开花期 0-10 cm 土层的根长、根表面积和根体积,且施氮也显著增加 0-10 cm 土层根长、根表面积和根体积.同时秸秆覆盖与施氮均可显著提高小麦根尖 H+、NO3-的吸收速率和净吸收速率,降低 0-20 cm土层根尖的H+外排速率;秸秆覆盖与施氮显著提高根系硝酸还原酶和谷氨酰胺合成酶活性,且地上部氮素积累量和生物量两年度分别平均提高25.8%和35.8%.H+吸收速率、NO3-吸收速率、硝酸还原酶活性、谷氨酰胺合成酶活性、氮素积累量与0-10 cm土层根长、根表面积和根体积呈显著正相关(P＜0.05).[结论]在西南丘陵旱地小麦、玉米轮作系统中,玉米秸秆覆盖与施氮能够增加小麦季土壤无机氮含量,表层根系分布和根尖H+、NO3-吸收速率,促进氮素吸收与根尖氮素转运进而促进地上部氮素同化与积累;秸秆覆盖配合 120 kg N·hm-2 是适用于四川丘陵旱地小麦高产、氮素高效利用的绿色生产模式.
Effects of Straw Mulching and Nitrogen Application on the Improvement of Wheat Root Architecture and the Absorption and Utilization of H+ and NO3-in Hilly Dry Land
[Objective]In order to further study the root architecture and root tip nitrogen transport process of wheat after straw mulching in the wheat-maize rotation system in the dry land of southwest China,and to elucidate the physiological basis of straw mulching and nitrogen application to promote the efficient absorption and utilization of wheat nitrogen.[Method]The experiment was a two-factor split plot experiment of straw mulching(SM:straw mulching;NSM:no straw mulching)and nitrogen application(N0:0;N1:120 kg·hm-2),which was conducted at Sichuan Renshou Modern Agricultural Test Station from 2020-2022.The effects of straw mulching and nitrogen application on soil physicochemical properties,wheat root architecture,nitrogen absorption in root tips,plant biomass and aboveground nitrogen accumulation and utilization were analyzed according to the current situation that soil drought inhibited root elongation in dry land of southwest hills,resulting in low wheat biomass and nutrient use efficiency.[Result]The soil nitrate nitrogen content of straw mulching treatment increased by 43.1%and 30.8%,and the ammonium nitrogen content increased by 21.8%and 18.8%,respectively,in 2020-2021 and 2021-2022 compared with the no straw mulching treatment.Straw mulching increased the root length,root surface area,and root volume of the 0-10 cm soil layer at jointing stage,booting stage and anthesis stage of wheat,and nitrogen application significantly increased the 0-10 cm soil root length,root surface area and root volume.In addition,straw mulching and nitrogen application could significantly increase the absorption rate and net absorption rate of H+ and NO3-at the root tips of wheat,and reduce the H+ efflux rate at the root tips of 0-20 cm soil layer.Straw mulching and nitrogen application significantly increased the activities of nitrate reductase and glutamine synthetase in roots,and the nitrogen accumulation and biomass in the aboveground part of wheat increased by 25.8%and 35.8%on average,respectively,in two years.H+ absorption rate,NO3-absorption rate,nitrate reductase activity,glutamine synthetase activity,and nitrogen accumulation were positively correlated with root length,root surface area and root volume of 0-10 cm soil layer(P＜0.05).[Conclusion]In the southwest hilly dry land wheat-maize rotation system,maize straw mulching and nitrogen application can increase the content of inorganic nitrogen in the soil during the wheat season,the root distribution in the soil surface and the absorption rate of H+ and NO3-at the root tips,promote nitrogen uptake and root tip nitrogen transport,and then promote aboveground nitrogen assimilation and accumulation;Under the conditions of this experiment,straw mulching combined with 120 kg N·hm-2 is a green production mode suitable for high yield and high nitrogen use efficiency in Sichuan hilly dry land.
winter wheatstraw mulchingroot architecturenitrogen flux in root tipnitrogen uptake and utilization
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