Effects of Water and Nitrogen Conditions on the Photosynthetic Characteristics and Yield of Maize in Slightly Salted Soil

Through investigated the characteristic of maize leaves' diurnal variation of photosynthetic rate and the relationship between yield and them in mild salinization area by field test which would find the reasonable ratio of water and nitrogen in planting maize and prevent the secondary salinization.Set ten treatments with the different water and nitrogen condition in mild salinization soil and investigated the maize leaves' photosynthetic characteristics and the yield of maize.The results showed that the soil salt content increased with the condition of salinity soil and low moisture.The chlorophyll relative content,photosynthetic rate and WUE of maize leaf decreased significantly.The effect of applying additional nitrogen was not obvious.With the condition of middle and high moisture,increasing application of the nitrogenous fertilizer could increase the chlorophyll relative content,photosynthetic rate and WUE of maize leaf.When the nitrogen amount was more than 225kg/hm2,the chlorophyll relative content,photosynthetic rate and WUE of maize leaf did not increase any more.The appropriate water-saving and fertilizer-saving did not reduce the photosynthetic rate and WUE of maize leaf and had no significant influence on yield.The irrigation amount of T5was 2 250m3/hm2 which saved the 30percent of water compared with the local irrigation amount which was 2 925m3/hm2.The fertilizing amount of T5was 225kg/hm2 which saved 30.8percent of fertilizer compared withthe local fertilizing amount which was 325kg/hm2.But the photosynthetic rate and WUE of maize leaf increased by 4.83%and 3.76%compared with the photosynthetic rate and WUE of maize leaf of T9.The yield just decreased by 1.32%compared with the yield of T9.The path analysis showed that the treatment with no irrigation and nitrogen and the treatment with different fertilization in the condition of low moisture of photosynthesis were mainly limited by non-stomatal factor(TL,PAR).The treatments with different fertilization in the condition of middle moisture of photosynthesis were mainly limited by stomatal factors(GS,Ci,Ls).And the treatments with different fertilization in the condition of high moisture of photosynthesis were limited by stomatal factors(Ci,Ls)and non-stomatal factors(TL,PAR).In conclusion,T5was a reasonable ratio of water and nitrogen in mild salinization area.