Effect Of Nitrogen Levels On Photosynthesis Rate And Yield Of Soybean

Soybean（Scientific name：Glycine max）is a kind of legume which is enriched in protein andwas called beans in the ancient China. Soybean cultivation has been going for5,000years sinceancient times. Photosynthetic rate is an important indicator of photosynthesis, which represents theability of light energy can be converted to chemical energy. For photosynthetic rate, there remainsdiscrepancy among different varieties. Increasing net photosynthetic rate is an important way toraise soybean yield and nitrogen level directly affects each link of photosynthesis. Studying oneffect of nitrogen level on photosynthetic characteristics and yield of soybean systematically hastheoretical and practical significance. This work was conducted with frame tests and field tests inthe experimental station of Northeast Agricultural University (NEAU) in2012. The soybeanvarieties that were used for test were HH49、HN40、SN28with different maturity. Four types oftreatments were set in the frame tests, which were divided into N0, N5, N10and N15. In order toensure that the difference of the whole growth period of available nitrogen, the method of nitrogenapplication by stages was applied. Studying on effect of nitrogen level on photosynthetic rate, leafarea index and carbon dioxide absorption rate of HN40systematically. Studying on effect ofdifferent nitrogen levels on soybean yield by comparing three soybean varieties in harvest time. Acomparison of fertilization treatments and without fertilization treatment in field tests couldshowed effect of fertilizer on yield of soybean. The results showed that:（1）Carbon dioxide absorption rate of soybean plant at low nitrogen level was relatively highin seedling stage. But that of soybean plant in low nitrogen treatment and without fertilizationtreatment maintained at a relatively high level at the late growth period. Carbon dioxide absorptionrate was at a relatively low level in middle and high nitrogen treatment and that presented abimodal peak curve with nitrogen levels in the whole growth stage of soybean.（2）Thephotosynthetic rate of soybean plant at different nitrogen levels showed a gradual decline trendwith advancement of growth. And that of soybean plant in low nitrogen treatment and withoutfertilization treatment maintained at a relatively high level in the whole growth stage of soybean.（3）It could be gathered from tests, the leaf area of soybean plant in fertilization treatments waslarger than that of without fertilization treatment. And nitrogen fertilizer could promote increase ofsoybean leaf area so as to keep leaf area index maintain a higher level at the whole growth period.（4）The dry matter accumulation of soybean plant without fertilization treatment maintained at a relatively low level in the whole growth stage of soybean. There was no obvious rule amongtreatments at different growth stages. The application of nitrogen fertilizer could significantlyincrease the accumulation of dry matter of soybean plant.（5）Leaf was the nitrogen accumulationcenter of soybean plant before podding-seed filling period. With the advancement of growth, podbecame the center of nitrogen accumulation and nitrogen distribution. Nitrogen in vegetativeorgans, namely, leaf, stem, root, petiole was transferred to pod and the nitrogen accumulation ofpod reached a peak in harvest time.（6）Moderate nitrogen could increase yield of soybean. For early-maturing and medium varieties,yield of soybean presented an increasing trend with fertilizer application amount rising. For latevariety, yield of soybean in fertilization treatments was higher than that of soybean withoutfertilization treatment. For early-maturing and late varieties, plant height and nodes of soybean infertilization treatments were higher than that of soybean without fertilization treatment. The plantheight and nodes of medium variety did not showed regularity. Fertilizer application amount hadlittle influence on seeds number and100-seed weight. The yield and the components of yield ofsoybean in fertilization treatments were higher than that of soybean without fertilization treatmentin field test.