秸秆覆盖温度效应对冬小麦农艺和生理性状的影响

Temperature effects of straw mulching on the agronomic and physiological characteristics of winter wheat

秸秆覆盖是一项有效的节水保墒技术,广泛应用于农业生产。而对于凉季生长的作物,秸秆覆盖引起的温度效应对作物生长发育的影响大于秸秆覆盖的保墒效应,会导致作物减产。利用大田试验研究秸秆覆盖冬小麦的温度效应对冬小麦生理和农艺性状的影响,探明秸秆覆盖引起冬小麦减产的机理。试验设置4个秸秆覆盖量处理:不覆盖(CK)、低覆盖量(2450 kg∙hm^(−2),LM)、中覆盖量(3675 kg∙hm^(−2),MM)和高覆盖量(7350 kg∙hm^(−2),HM),调查不同处理对土壤温度、冬小麦内源激素含量、茎伤流液离子浓度、农艺性状[植被指数(NDVI)、比值植被指数(RVI)、地上部干物质积累、根长]及产量的影响。结果表明:秸秆覆盖提高了冬季土壤温度,降低了春季返青期土壤温度。由于冬季冬小麦生长发育停止,秸秆覆盖的增温效应对冬小麦生长影响较小。春季返青期,冬小麦开始快速生长,秸秆覆盖对根区土壤温度的降低效应显著抑制了冬小麦的生长发育。返青期冬小麦茎生长素(IAA)含量在低、中和高覆盖量下分别是不覆盖处理的1.7倍、2.5部和2.7倍,较高的IAA含量抑制了冬小麦的生长。覆盖处理茎中生长素和玉米素核苷比值(IAA/ZR)增加,抑制了分蘖的生长。秸秆覆盖下冬小麦农艺性状如根长密度、NDVI和RVI、密度和地上部生物量显著低于CK。至拔节期随着秸秆覆盖对土壤温度影响减弱,覆盖处理茎中的IAA含量显著降低,并低于CK处理,IAA/ZR比值也迅速下降,与CK间差异减小,茎中伤流液中离子浓度覆盖处理均高于CK,均表明覆盖处理下小麦的生理功能加强,但至拔节期覆盖处理下的冬小麦各农艺性状仍然低于CK,秸秆覆盖下的冬小麦抽穗和扬花期比不覆盖晚2 d,最终覆盖处理的冬小麦产量低于CK。秸秆覆盖对土壤温度、生理性状和农艺性状的影响随着覆盖量的增加而增加。综上研究表明,秸秆覆盖引起的返青期土壤温度偏低延缓冬小麦生理过程,是导致冬小麦产量降低的主要原因,消减返青期秸秆覆盖层的温度效应是解决秸秆覆盖影响冬小麦产量的有效途径。

Straw mulching is a popular water-saving technology that is widely used in dry farming areas.However,the negative effects of straw mulching on soil temperature should be avoided when it is used on crops grown in cool seasons.Field experiments were conducted to investigate the temperature effects of straw mulching on the physiological and agronomic properties of winter wheat and to find solutions to reduce the negative effects of straw mulching on winter wheat production.An experiment consisting of four treatments was set up at the Luancheng Agro-Ecosystem Experimental Station,Chinese Academy of Sciences in 2019–2020,which were no mulching(CK),low-rate straw mulching(2450 kg∙hm^(−2),LM),medium-rate straw mulching(3675 kg∙hm^(−2),MM),and high-rate straw mulching(7350 kg∙hm^(−2),HM).The physiological characteristics(endogenous hormones,concentration of stem bleeding ions)and agronomic traits(NDVI,RVI[ratio vegetation index],dry matter accumulation,root length density,and winter wheat yield)were monitored.The results showed that straw mulching increased the soil temperature during winter dormancy and decreased the soil temperature in spring when winter wheat entered the recovery stage.The warming effects of mulching did not affect winter wheat growth during the winter dormancy period because the crop was inactive.When winter wheat entered the recovery stage after winter dormancy,the effects of straw mulching on soil temperature inhibited the growth and development of winter wheat.At the recovery stage,the stem auxin(IAA)contents in the LM,MM,and HM treatments were 1.7,2.5,and 2.7 times that of CK,respectively.The higher IAA content inhibited the growth of winter wheat.The ratio of IAA to zeatin riboside(ZR)increased in the stems of mulched plants,which inhibited tiller growth.Agronomic characteristics,such as root length,NDVI,RVI,plant density,and aboveground biomass of winter wheat at the recovery stage,were all significantly lower than those of CK.At the jointing stage,when the effects of straw mulching on soil temperature were weaker,the IAA content in wheat stems in mulching treatments significantly decreased and was even lower than that of CK treatment.The IAA/ZR ratio also rapidly decreased,and its difference from that of the CK also decreased.The ion concentrations in the stem sap in mulching treatments were higher than those in CK,indicating that the physiological properties of winter wheat under straw mulching were strengthened;however,the increased growth could not compensate for growth loss during the long recovery stage.The values for the agronomic characteristics under straw mulching were lower than those under CK at the jointing stage.The growth of winter wheat under straw mulching was delayed by 2 days at heading and anthesis.The yield of winter wheat under the straw mulching treatments was lower than that under CK.The results showed that the decrease in soil temperature at the recovery stage caused by straw mulching delayed the growth of winter wheat and was the main reason for the decrease in winter wheat production.The effects of straw mulching on soil temperature and the physiological and agronomic properties increased with the increased straw amount.Therefore,breaking the straw layer to reduce the negative effects of straw mulch on soil temperature during the recovery stage would be an effective measure to promote the positive effects of straw mulching on winter wheat.