Effect Of Last Year’s Film Mulch With Reduced Water And Nitrogen On Physio-ecological Indicators Of Wheat

The effect of using combined water and nitrogen management for one year and two years to improve water use efficiency of wheat has been verified by experiments and production practices.However,there is still no theoretical basis for how this measure affects water use efficiency and how to further tap its technical potential.From 2019 to 2020,set up two farming methods:no-tillage for one and two years（NT）and traditional farming（CT）,two irrigation levels:traditional irrigation(I2,2400 m³·hm^-2)and traditional irrigation reduction20%(I1,1920 m³·hm^-2),3 nitrogen application levels:pure N 225 kg?hm^–2（N3）,180 kg?hm^–2（N2）and 135 kg?hm^–2（N1）,composed of a three-factor split area experiment to explore the effects of different treatments on the main physiological and ecological characteristics of wheat population,leaf and cell level water,and analyze the internal mechanism of different treatments to improve wheat water use efficiency.The main conclusions are as follows:（1）The use of no-tillage for one and two years（NT）significantly improved the photosynthetic capacity of wheat compared with traditional tillage（CT）.Compared with traditional irrigation and nitrogen（I2N3）treatments,traditional irrigation combined with reduced nitrogen application was 20%（I2N2）treatment also significantly improved wheat photosynthesis.Compared with CT,NT increased the average leaf area index,photosynthetic potential,relative chlorophyll content,photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO2 concentration in wheat growth period by 29.3%,14.8%,8.2%,19.4%,respectively,4.7%,6.1%,4.1%;the actual photochemical efficiency and photochemical quenching coefficient of wheat increased by 13.4%and 6.8%,respectively.Reduced irrigation and reduced nitrogen application made the photosynthetic rate of wheat show a decreasing trend,I1 decreased by 10.1%compared with I2,and N1 and N2 decreased by 9.7%and 12.5%,compared with N3,respectively.However,the photosynthetic rate of wheat under NTI1N2 treatment and control（CTI2N3）treatment had no significant difference.It shows that the photosynthetic rate of wheat decreases when irrigation and nitrogen application are reduced,and the use of no-tillage film for one year or two years can alleviate this negative effect.（2）Compared with CT,NT significantly reduces wheat canopy light transmittance,population CO2 concentration and population relative humidity.Compared with CT treatment,the CO2 concentration of wheat population during the whole growth period,the relative humidity of wheat population,and the light transmittance of wheat canopy were reduced by5.4%,6.4%,and 21.8%,respectively.Reduced irrigation has no significant effect on it,but reduced nitrogen application has a significant effect on it.This shows that compared with the control treatment,combined water and nitrogen management with no-tillage for one and two years can significantly improve the population structure of wheat and increase wheat yield by coordinating the relationship between various factors.（3）NT significantly increases the soil water content of wheat farmland,while irrigation and nitrogen application have no significant effect on it.Compared with CT,the soil water content of wheat under NT conditions increased by 4.3%from the seedling stage to the jointing stage;the filling stage increased by 7.5%,and there was no significant difference in water consumption during the whole growth period.However,NT significantly reduced the evapotranspiration（E）and the evapotranspiration ratio（E/ET）between trees in farmland,and the treatment with a 20%reduction in both water and nitrogen further strengthened its effect of reducing E and E/ET.Compared with the control（CTI2N3）,NTI1N2 treatment reduced E and E/ET in the whole growth period by 25.3%and 26.1%,respectively.（4）Compared with CT,NT has obvious advantages in increasing yield,and the water use efficiency is significantly improved;while reducing irrigation and nitrogen application results in a decrease in wheat yield,but reducing irrigation volume improves water use efficiency.Compared with CT wheat,NT increased by 13.4%,and WUE increased by 9.2%.Compared with I2,I1 reduced production by 5.9%,but WUE increased by 5.8%;N1 reduced production by 16.0%compared with N3.There was no significant difference between N2 and N3,and the difference in WUE between the three was not significant.Compared with the control（CTI2N3）treatment,the NTI1N2 treatment not only maintained comparable grain yields,but also significantly reduced water consumption,resulting in higher WUE.