Studies On The Interactive Effects Of Irrigration And Topdressing Nitrogen On Yield And Water Use Efficiency Of Winter Wheat

This experiment was carried out under the automatic control canopy at the Henan Agricultural University Science and Education Garden Area in 2007-2008 year. The effects of topdressing nitrogen and irrigation on soil moisture, photosynthesis characters, stress indicators, yield and water use efficiency were investigated under the same conditions of based nitrogen and irrigation at anthesis using pot and pit experiments. The main results were as below:(1) The soil water content of Yunong202 in different treatmens presented different wave peaks. It decreased with the growth period.under the same condition of nitrogen applying, The soil water content showed: W3>W2>W1.Under the same condition of irrigation,with the increasing of nitrogen topdressing amount, The soil water content showed: N3>N2>N1.Under the condition of water and nirogen treatment at the jointing stage, the teatment of N3W3 (nitrogen is 180 kg/ha, irrigation 1 050 m~3/ha) was highest and N1W1 (topdressing nitrogen is 0 kg/ha, irrigation is 450 m~3/ha) was the lowest.The soil water content in 0-20 cm soil layer changed greatly and in 60-120 cm soil layer was stable. The soil water rate in 60-120 cm soil layer decreased with the reducing of irrigation quantity at he jointing stage, Its time of reduction was ahead. The soil water rate in 80-100 cm layer was highest in different treatments at the jointing stage.(2) The net photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll a, chlorophyll b and the total of chlorophyll of winter wheat rised with the increasing of irrigation and nitrogen topdressing amount, there was a coupling interaction effect between water and nitrogen.The net photosynthetic rate of the treatment N3W3 was highest in the pond culture, the net photosynthetic rate of the treatment N3W1(topdressing nitrogen is 180 kg/ha, water content is 80-85% of yield capacity) was highest in the pot culture.With the increasing of irrigation and topdressing nitrogen, the ETR and NPQ of the winter wheat flag decreased, It can't improve the rate of Fv/Fm through increasing irrigation quantity without topdressing nitrogen at the jointing stage.(3) With the increasing of irrigation and nitrogen at the jointing stage, the content of MDA and the activity of SOD in the leaves of the two wheat varieties decreased, there was a remarkable coupling interaction between water and nitrogen, MDA and SOD in the treatment N3W3 of the leaves of the two wheat varieties were lowest in the pond culture, the treatment N1W1were highest.The content of MDA and the activity of SOD in the treatment N3W1 of the leaves of the two wheat varieties were lowest in the pot, the N1W2(topdressing nitrogen is 0 kg/ha, water content is 55-60% of yield capacity) were highest.(4) The plant biomass of winter wheat increased, with the increasing of irrigation quantity and topdressing nitrogen at the jointing stage, the dry weight of root, shoot, leaf and sheath appeared single peak changing line, the peak value occurred in the period of heading to flowering. That the dry weight of leaf, shoot, sheath and wheat ear proportion occupied by total dry weight increased with the increasing of irrigation quantity and topdressing nitrogen at the jointing stage.the root decreased. The teatment of N3W3 was highest and N1W1was the lowest in pond culture, the teatment of N3W1 was highest and N1W2 was the lowest in pot culture. The maximum filling rate occurred from May 9 to May 14. With the increasing of irrigation quantity and topdressing nitrogen at the jointing stage, the time of maximum filling rate was late.The plant height, ear length and seed setting number increased with the increasing of irrigation quantity and topdressing nitrogen at the jointing stage, infertility spikelets decreased. The spike number, grain number per spike, grain weight and yield increased with the increasing of irrigation quantity and topdressing nitrogen, at the jointing stage, the yield of two varieties difference reached significant level among the different treatmens of irrigation quantity and topdressing nitrogen. The yield did not improve significantly over the irrigation 1 050 m~3/ha and topdressing nitrogen 90 kg/ha.There were significant coupling effect among different irrigation and nitrogen treatmens, the teatment of N3W3 was highest and N1W1was the lowest in pond culture, the teatment of N3W1 was highest and N1W2was the lowest in pot culture.(5) Topdressing nitrogen increased the WUE of leaf significantly. Irrigation qantity reached W2 (750 m~3/ha) at the jointing stage, it could improve the WUE of leaf. Increasing the irrigation quantity at the jointing stage was useful to improve the WUE of leaf under the topdressing nitrogen condition of N1 (0 kg/ha) and N2 (90 kg/ha). Increasing irrigation quantity was not useful to enhance the WUE of leaf under the level of N3 (180 kg/ha). There were interaction effect significantly between water and nitrogen.The maximum of Pn was the treatment N3W3 (topdressing nitrogen 180 kg/ha, irrigation 1 050 m~3/ha), the maximum of leaf WUE was the treatment N2W3 (topdressing 90 kg/ha, irrigation 1 050 m~3/ha). Path analysis showed that photosynthetic character contribute to the leaf WUE from maximun to minimum was Pn>Gs>ch a >Ci>chl b>Tr.This study showed that the high production and high efficiency method of irrigation quantity and topdressing nitrogen.under the condition of low entropy water, the same fundamental topdressing nitrogen and irrigation quantity at flowering stage, it is the best method of irrigation quantity 750 kg/m3 and topdressing nitrogen 180 kg/ha to improve the WUE of yield under condition of yield stable.