Effects Of Long-term Fertilization On Photosynthesis And Nitrogen Flow Of Winter Wheat

The experiment was conducted in 2012-2014 at the Maize Technological Innovation Center of the north China plain(NCP) and State Key Laboratory of Crop Biology of Shandong Agricultural University. The winter wheat(Triticum aestivum L.) variety was Shimai15, the source of organic nitrogen was cow manure, and the fertilizer was applied as four different treatments: no N fertilizer application, single application of urea, single application of cow manure, and mixed application of urea and cow manure.In order to clarify the effects of mixed application of inorganic and organic nitrogen on photosynthetic capacity, assimilate distribution, nitrogen flow and grain yield of winter wheat, then aimed to seek rational fertilizing methods and reference for the yield improvement of winter wheat, the main results were as follows:1 Effects of different fertilizer treatments on photosynthesis andsenescence characteristics of winter wheat At the early growth period, the CAP, Pn and LAI of U treatment were the highest, which was followed by the U+M treatment and finally the M treatment. However, 10 days after anthesis, M and U+M treatments delayed the leaf senescence process when compared with the U treatment. This could be due to the two treatments having higher anti-oxidant enzyme activity and promoting a longer green leaf duration, which could maintain a higher photosynthetic capability. Consequently, U+M treatment could delay leaf senescence and maintain a better canopy structure and higher photosynthesis capability at the late grain filling stage, which resulted in a higher grain yield.2 Effects of different fertilizer treatments on distribution of 13C-assimilates of winter wheat Most of the 13C-assimilates were distributed to the stem and sheath at flag leaf stage and anthesis stage, while the 13C-assimilates of early grain filling stage were mainly distributed to the grains. At the mature period, about 87.5% of the 13 C assimilated at early grain filling stage distributed to mature grains, about 75.4% of the 13 C assimilated at anthesis stage distributed to mature grains, and only 15.2% of the 13 C assimilated at flag leaf stage distributed to mature grains, hence the assimilation of grain filling stage contributed most to the grain yield. In addition, among the four treatments, CK and U+M treatments, all distributed more 13 Cassimilates of flag leaf stage and anthesis stage to the mature grains, however, U treatment retained more 13C-assimilates in the stem and sheath. What’s more, M and U+M treatments distributed more 13C-assimilates of grain filling stage to the mature grains,and finally U+M treatment distributed more 13C-assimilates of all the three stages to the mature grains compared to the other treatments. Consequently, U+M treatment was conducive to distribute more photosynthates to grains.3 Effects of different fertilizer treatments on nitrogen flow and nitrogen balanceof winter wheat Most of the nitrogen applied in the soilwas sucked up by wheat plants, the crop absorption ratio were namely 75.21%-102.91% and 129.48%-149.34% between two years. The grain nitrogen accumulation amount between the two years were significantly different, U and U+M treatments were the highest in the first year, however, U+M treatment had the highest grain nitrogen accumulation amount in the second year. The four treatments had little effects on the grain nitrogen distribution ratio.The proportion of ammonia volatilization loss to total nitrogen applied, were namely 6.93%-16.84% and 6.65%-20.11% between two years. After applied basal fertilizer, the ammonia volatilization rate of the four treatments first increased and then decreased rapidly, the peak value appeared at 4-5 days after fertilization. After applied top dressing, the ammonia volatilization rate tended to drop off in 2012-2013, however, the ammonia volatilization rate of the four treatments first increased and then decreased rapidly in 2013-2014, and the peak value appeared at 4-5 days after fertilization. Moreover, U and U+M treatments had the highest ammonia volatilization rate between the two years, and the ammonia volatilization rate of basal fertilizer was higher than top dressing. The cumulation of ammonia volatilization and total ammonia volatilization loss both were: U>U+M>M. Applying cow manure could significantly reduce the ammonia volatilization loss. The proportion of nitrate leaching loss to total nitrogen applied was relatively the least, the nitrate leaching loss mainly appeared at sowing period and wintering period. The nitrate was leached seriously in 2012-2013, 4% of the nitrate was leached to the soil layer deeper than 2m. However, as the higer temperature at sowing period in 2013-2014, the volume of leacheate and nitrate amount of leacheate were significantly decreased. The nitrate leaching loss of U treatment was the most and U+M treatment was the least. Among the four treatments, applying nitrogen fertilizer was conducive to maintain a surplus nitrogen balance. The U treatment had higher ammonia volatilization and leaching loss, however, M treatment was conducive to reduce ammonia volatilization and leaching loss but not conducive to crop absorb, also was conducive to fertility betterment. The U+M treatment could reduce ammonia volatilization and leaching loss, and got the highest crop absorption.4 Effects of different fertilizer treatments on soil enzymes of winter wheat As the soil layer getting deeper, the activity of soil urease, invertase and phosphatase tended to drop off, however the activity of catalase first increased and then decreased. U treatment was not conducive to improve the activity of soil enzymes, and the urease activity of U was lower than CK treatment. Moreover, M and U+M treatments were more conducive to improve the activity of soil urease, invertase, phosphatase and catalase in the 0-40 cm soil layer.5 Effects of different fertilizer treatments on yield and yield components of winter wheat The yield of three fertilization treatments were significantly higher than CK treatment, and U, M and U+M treatments were namely 81.38%, 76.98% and 89.88% higher than CK treatment. Among them U+M treatment got the highest yield, followed by the U treatment, and M treatment was the third. Moreover, the grains per spike of the four treatments had little difference. U treatment had a higher spike numbers but got a lower grain weights, however, M treatment had a higher grain weights but got a lower spike numbers. What’s more, the U+M treatment got both higher grain weights and higher spike numbers, and finally got the highest grain yield. The yield of U+M treatment was 3.5% and 11.0% higher than M treatment between two years, and 3.9% and 5.5% higher than U treatment between two years.