Effect of Tillage Mode on Diurnal Variations of Water Potential and Chlorophyll Fluorescence Characteristics of Flag Leaf after Anthesis and Water Use Efficiency in Wheat

Abstract

Water resource shortage has become the urgent problem limiting wheat(Triticum aestivum L.) production in Yellow-Huaihe-Haihe Rivers Plain of China.A crucial target of wheat production is to develop water-saving agriculture to reduce irrigation water and increase the water use efficiency(WUE).The objective of this study was to understand the effects of tillage practices on soil moisture content,water potential and consumption in plants,diurnal variation of chlorophyll fluorescence characteristic in flag leaf after anthesis,and grain yield in wheat under flexible irrigation conditions.A high-yielding wheat cultivar,Jimai 22,was continuously planted in the same plot across two growing seasons from 2007 to 2009.Five tillage modes were established with flexible irrigation after measuring soil moisture,which were strip rotary tillage(SR),strip rotary tillage after subsoiling(SRS),rotary tillage(R),rotary tillage after subsoiling(RS),and plowing tillage(P).The moisture contents of soil layers within 0-200 cm were measured at sowing,jointing,anthesis,and maturity stages.In the 2008-2009 growing season,the diurnal variation of water potential and chlorophyll fluorescence characteristic in flag leaf were measured at 22 d and 24 d after anthesis.The SRS and RS treatments had the lowest moisture content in different soil layers of 60-200 cm below surface.The result indicated that subsoiling had the effect to promote water absorption of wheat in deep soil layers.From anthesis to maturity,the water consumption of SRS treatment exhibited the highest amount and ratio from soil and the lowest ratio from precipitation and irrigation.Compared with SR treatment,SRS treatment had higher water potential from 6:00 to 18:00 and larger values of Fv/Fm and ΦPSII of flag leaf from 8:00 to 14:00.Clearly,subsoiling was favorable to keep high physiological activity from mid to late filling stage.The positive effect of subsoiling was confirmed by the comparison between RS and R treatments.Among the five tillage treatments,SRS produced the highest grain yield of 9 516.48 kg ha-1 in 2007-2008 growing season and 8 957.92 kg ha-1 in 2008-2009 growing season.The yield level of RS had no significant difference from that of SRS treatment.In contrast,SR and R treatments showed the lowest yields in all treatments.As for WUE,the ranking sequence of treatments was SRS RS P SR or R.Therefore,we recommend SRS as the best tillage practice for high yield and water saving in wheat producing areas with similar ecological conditions to the experiment.