Effects Of Supplemental Irrigation On Grain Yield And Water Use Efficency Of Winter Wheat Under Different Soil Moisture Conditions At Planting

The experiment was carried out from 2013 to 2014 in the Shiwang village, Yanzhou and from 2014 to 2015 in the Nanqiu village, Feicheng, Shandong Province. The breed is highyielding winter wheat cultivar Jimai 22. To research the effects of supplemental irrigation(SI) period and target soil relative water content(TSRWC) on water consumption characteristics, carbon and nitrogen metabolism and grain yield, supplemental irrigation was conducted with different period and level, under the same year and field, but different soil moisture conditions at planting(SMCP) of A, B(2013-2014) and C, D(2014-2015). The soil relative water content(SRWC) of 0-100 cm soil layer in the SMCP of A, B, C, D was 52.2%, 68.7%, 82.1% and 85.1%(201.5 mm, 266.3 mm, 317.0 mm, 328.7 mm for soil pandage(SP)), and the RSWC of 0-20 cm soil layer respectively 32.5%, 51.7%, 69.4% and 71.3%, respectively.In 2013-2014 years, with 0-20 cm soil layer set as plan wetting soil layer(PWSL), the TSRWC of sowing stage in A1 treatment were set as 60%, and the TSRWC of sowing, jointing and anthesis stage in A2 treatment were set as 60%, 100% and 100%, and the TSRWC of sowing, winering, jointing and anthesis stage in A3 treatment were set as 60%,100%,100% and 100%, and the TSRWC of sowing, jointing and anthesis stage in A4 treatment were all set as 100%, under SMCP of A.In 2013-2014 years, with 0-20 cm soil layer set as PWSL, the TSRWC of sowing stage in B1 treatment were set as 80%, and the TSRWC of sowing, jointing and anthesis stage in B2 treatment were set as 80%, 100% and 100%, and the TSRWC of sowing, winering, jointing and anthesis stage in B3 treatment were set as 80%,100%,100% and 100%, and the TSRWC of sowing, jointing and anthesis stage in B4 treatment were all set as 100%, under SMCP of B.In 2014-2015 years, with 0-20 cm soil layer set as PWSL, the T1 treatment was no irrigation at all growth stage, and the TSRWC of jointing and anthesis stage in T2 treatment were set as 100% and 100%, and the TSRWC of winering, jointing and anthesis stage in T3 treatment were set as 100%,100% and 100%, and the TSRWC of sowing, jointing and anthesis stage in T4 treatment were all set as 100%, under SMCP of C and D.Meanwhile, in 2013-2014 years, set AS1-AS8 eight SI treatment at sowing stage under SMCP of A. The PWSL of AS1 to AS7 was 0-20 cm, and TSRWC was 40%, 50%, 60%, 70%, 80%, 90%, 100%, respectively; the PWSL and TSRWC of AS8 treatment was 0-30 cm and 100%. At SMCP of B, set BS1-BS6 six SI treatment at sowing stage, the PWSL of BS1 to BS5 was 0-20 cm and TSRWC was 60%, 70%, 80%, 90%, 100%, respectively; the PWSL and TSRWC of BS6 treatment was 0-30 cm and 100%. All treatment was conducted at TSRWC reached 100% of 0-20 cm soil layer at jointing stage and anthesis stage. 1 Effects of supplemental irrigation period on grain yield and water use efficency of winter wheat under different soil moisture conditions at planting 1.1 Effects of supplement irrigation period on water consumption characteristics of winter wheatUnder the SMCP of A, compared with A2 treatment, A3 and A4 treatment which increased SI amount in the early growing stage and promoted the water use of 20-140 soil layers, and the soil water consumption and total water consumption of all wheat growth stage was increased, significantly, the growth of A4 was the biggest. Under the SMCP of B, compared with B2 treatment, B3 and B4 treatment increase SI amount in the early growing stage, which is not conductive for wheat to use soil water, and the soil water consumption and total water consumption of B3 was the lowest. Under the SMCP of C and D, adding SI at sowing or wintering stage based on SI carried out at jointing and anthesis stage, the soil water consumption and total water consumption increased significantly, but the soil water consumption have no significant difference. 1.2 Effects of supplement irrigation period on senescence of wheatUnder the SMCP of A, in the middle and later filling stage, compared with A2 and A3 treatment, A4 treatment significantly increased activities of superoxide dismutate(SOD), catalase(CAT) activity and dissolved protein content, decreased malondialdehyde(MDA) content, which was helpful to delay the senescence of flag leaf, and extend functional photosynthesis period after anthesis. Under the SMCP of B, SOD and CAT activity had no significant difference between B3 and B4 treatment, which were higher than that of B2 treatment. Under the SMCP of C and D, adding SI at sowing or wintering stage based on SI carried out at jointing and anthesis stage, there was no significant effect on SOD, CAT activity and MDA content of flag leaf. 1.3 Effects of supplement irrigation period on carbon metabolicUnder the SMCP of A, compared with A2 and A3 treatment, A4 treatment significantly increased Gs and Pn, decreased Ci after anthesis, and increased ETR and ?PSII at middle and later filling stage. Under the SMCP of B, compared with B2 treatment, B3 and B4 treatment which had no significant difference, were helpful to increased Gs, Pn, ETR and ?PSII after anthesis. Under the SMCP of C and D, adding SI at sowing or wintering stage based on SI carried out at jointing and anthesis stage, the regulation to chlorophyll fluorescent characteristics and photosynthetic function was not different significantly.Under the SMCP of A, compared with A2, A3 and A4 was conductive to increase dry matter accumulation from revival to mature stage, and the distribution of post-anthesis assimilates to grain. The dry matter accumulation at mature stage and distribution of postanthesis assimilates to grain of A4 treatment were significantly higher than that in after these of A3 treatment. Under the SMCP of B, compared with B2 treatment, B3 and B4 treatment were conductive to increase dry matter accumulation of anthesis and mature stage, and increase the the distribution of post-anthesis assimilates to grain. Under the SMCP of C and D, adding SI at sowing or wintering stage based on SI carried out at jointing and anthesis stage, had not significant differences for dry matter accumulation. 1.4 Effects of supplement irrigation period on nitrogen metabolicUnder the SMCP of A, compared with A2 treatment, A3 and A4 treatment was conductive to increase the vegetative organs nitrogen accumulation at anthesis, nitrogen accumulation in grain at mature stage, nitrogen translocation of vegetative organs to grain, and the amplitude of nitrogen distribution to grain at mature stage, and A4 treatment was significantly higher than A3. Under the SMCP of B, compared with B2 treatment, B3 and B4 treatment which had no significant difference, were conductive to nitrogen distribution to grain at mature stage. Under the SMCP of C and D, adding SI at sowing or wintering stage based on SI carried out at jointing and anthesis stage, the regulation of wheat nitrogen accumulation and distribution were not significantly different. 1.5 Effects of supplement irrigation period on grain yield and water use efficiency of wheatUnder the SMCP of A, compared with A2, A3 significantly increased panicle number, however, 1000-grain weight and spike grain number were not changed significantly, and A4 significantly increased 1000-grain weight and spike grain number. The grain yield of diferent treatment were ranked as A4>A3>A2, but A4 treatment is significantly lower than A3 treatment in water use efficiency. Under the SMCP of B, the grain yield and 1000-grain weight of B3 and B4 were significantly higher than B2, and B3 treatment is significantly higher than B2 treatment in water use efficiency. Under the SMCP of C and D, there are no significant differences between all SI treatments. The treatment of adding IS at early growth stage significantly increased water consumption, and decrease the water use efficiency.From what has been discussed above, the SMCP and the IS level affect the result of IS at sowing stage.(1) Under the condition that SRWC of 0-100 and 0-20 cm soil layer was 52.2% and 32.5%(201.5 mm and 13.7mm for SP), the grain yield of the treatment which the TSRWC at sowing, jointing and anthesis stage all was 100% in 0-20 cm soil layers, was significantly higher than that of the TSRWC at sowing, jointing and anthesis stage was 60%, 100%, 100% and 100%, but water use efficiency decreased significantly.(2) Under the condition that SRWC of 0-100 and 0-20 cm soil layer was 68.7% and 51.7%(266.3 mm and 21.9 mm for SP), there are no significant difference of grain yield and water use efficiency between the two treatment, which were the TSRWC at sowing, jointing and anthesis stage all set as 100% and at sowing, wintering, jointing and anthesis stage set as 80%, 100%, 100%, 100%, respectively.(3) Under the condition that SRWC of 0-100 and 0-20 cm soil layer was 82.1-85.1% and 69.4-71.3%(317.0-328.7 mm and 28.9-29.6 mm for SP), the high yield and water use efficiency had obtained only when SI carried out at the jointing stage and the anthesis stage, but adding SI at sowing or wintering stage was unprofitable. 2 Effects of the rate of supplemental irrigation at sowing stage on soil water content and grain yield of wheatUnder the SMCP of A and B with 201.5 and 266.3 mm of soil pondage in 0-100 cm soil layer respectively, and with 554.2 and 586.4 mm of soil pondage in 0-200 cm soil layer respectively. The infiltration depth of irrigation water in field B was larger, but mainly concentrated in 0-60 cm soil layer. The increase of soil water content in 0-10 cm and 0-20 cm soil layer in different treatments was higher than that in the other soil layers. The seedling emergence of wheat was mainly affected by the soil water content in 0-10 cm soil layer at seeding stage, but population development, dry matter accumulation and yield formation is affected by the soil pondage before planting and the level of supplemental irrigation at seeding stage. Too low soil water content in upper soil layer was bad for seedling growth, and decreased the stem number per unit area during winter to jointing stage significantly; too low soil pondage in 0-100 cm soil layer before planting restricted the growth of wheat during the middle and later growth stage, reduced ear number and dry matter accumulation amount, decreased yield, even though irrigation was increased within a certain range at seeding stage, and then supplemental irrigation was conducted at jointing and anthesis stage. Under the same available soil water stored at planting condition, the total water consumption of wheat and grain yield increased with the increase of the target relative water content of supplemental irrigation at seeding stage, but the grain yield was no longer increased, and the water use efficiency was lower, as the irrigation water was too much.