Photosynthesis Characteristics of Flag Leaf and Dry Matter Accumulation and Allocation in Winter Wheat under Supplemental Irrigation after Measuring Moisture Content in Different Soil Layers

Abstract

This study aimed to propose a suitable soil layer depth used in determining the irrigation amount.A field experiment was conducted in the 2011–2012 and 2012–2013 wheat growing seasons to study the effects of supplemental irrigation based on the measurement of soil moisture contents on photosynthesis of flag leaf and dry matter accumulation and allocation.Four irrigation treatments were designed with target soil moisture of 65% at jointing and 70% at anthesis in 0–20(D1),0–40(D2),0–60(D3),and 0–140 cm(D4)soil layers.Zero-irrigation(D0)was used as the control.D2 was superior to other treatments with higher values of leaf area index(LAI)and flag leaf area on one square meter land at anthesis,photosynthetic rate(Pn)and actual photochemical efficiency(ΦPSII)at seven and fourteen days after anthesis; whereas,the stomatal limitation(Ls)of D2 was lower than those of other treatments.Compared with other treatments,D2 had larger dry matter accumulation at maturity,more dry matter allocated in grains,and higher contribution ratio of dry matter from vegetative organs to grain after anthesis.The grain yield in D2 was 9367.4 kg ha–1 in 2011–2012 growing season and 9727.5 kg ha–1 in 2012–2013 growing season,which were significantly higher than those in other treatments.The water use efficiency of D2 was significantly higher than those of D0,D3,and D4,but with out significant difference to that of D1.To obtain both high yield and high water use efficiency,we suggest the optimal soil layer for measuring moisture content is 0–40 cm,and supplementary water should be given at jointing and anthesis based on measured soil moisture.