Effects Of Nitrogen Management On Yield, Quality And Relative Physiological Characteristics Of High Yield Summer Maize (Zea Mays L.)

The experiment was carried out in Shandong Agriculture University experimental farm, Wenkou town of Taian city, Daan town of Yanzhou city and the State Key Laboratory of Crop Biology from 2008 to 2009. The analysis included field and ¹⁵N isotopic dilutions for pot experiments. Two maize cultivars, DH661 and ZD958 were used as experimental materials. The effects of nitrogen application rates on yield, quality and physiological characteristics were studied in order to find out the most optimal nitrogen fertilizer rate at the first year. The effects of nitrogen application stage on on yield, quality and physiological characteristics were studied at the second year. The main results as followed:1 Effects of nitrogen management on grain yield.The grain yield was increased at first and then decreased with the increase of nitrogen application rates. The grain yields of DH661 and ZD958 reach to 12172-15080 kg·ha^-1 and 12011-15360 kg·ha^-1, NPFP inproved on 40 kg·kg^-1 under nitrogen rate of 240-360 kg·ha^-1. Under this field experiment conditions, it could increase grain yield significantly and get great economic benefits with nitrogen rate of 240-360 kg·ha^-1.Grain yield was not increased significantly with the single nitrogen application at the jointing stage. Grain yield of two cultivars were increased significantly with the increase of nitrogen application times. Nitrogen application at grain filling stage could increase weight significantly. The grain yield of DH661 was highest, when the nitrogen application stages were jointing stage, male tetrad stage and grain filling stage and the ratio was 2:4:4. The grain yield of ZD958 was highest, when the nitrogen application stages were base fertilizer, jointing stage, male tetrad stage and grain filling stage and the ratio was 1:2:5:2. 2 Effects of nitrogen management on grain quality.With the increase of nitrogen application rates, the content of free amino acids increased significantly and the content of protein increased at first and then had no increased significantly. The proteins synthesis was stunted under excessive nitrogen. Supplying nitrogen could increase the content of soluble sugars and exther extract. After increased the nitrogen application, the content of exther extract had no increased significantly.With increased nitrogen application times and nitrogen application at grain filling stage, the content of protein was increased significantly and the free amino acids decreased significantly. The effect on gliadin was the most significant. The effects on the amino acids components and content were different with the kind of amino acids.increased supplying nitrogen times could increase the content of soluble sugars and exther extract, decreased the content of starch. With nitrogen application times and nitrogen application at grain filling stage the quality of grain increased significantly. But this nitrogen management decreased the glutenin/gliadin ratio, increased amylose/amylopectin ratio. It made against improving the components of protein and starch.3 Effects of nitrogen management on nitrogen uptake.Amount of total nitrogen accumulation in whole plant corn and nitrogen recovery efficiency were increased at first, and then decreased with the increase of nitrogen application rates. Under the 240-360 kg/ha nitrogen fertilizer application rates, total nitrogen accumulation, nitrogen recovery efficiency and nitrogen agronomic efficiency of DH661 were the highest. Under those nitrogen fertilizer application rates, translocation efficiency and nitrogen contribution proportion of DH661 and ZD958 after the flowering stage could be regulated effectively.Nitrogen accumulation amount in whole plant corn and grain, nitrogen harvest index, nitrogen agronomic efficiency, nitrogen recovery efficiency, nitrogen partial factor productivity were increased significantly with nitrogen application times and nitrogen application at grain filling stage. It also could prolong active nitrogen accumulation period. Nitrogen application several times before flowering could increase nitrogen translocation amount and nitrogen translocation efficiency, nitrogen application at silking could increase the assimilating amount of nitrogen after anthesis in grain. Through the ratio 2:4:4 and 3:5:2, the fertilizer-derived recovery rates were 67.5% and 78.1%, respectively, and the fertilizer-derived recovery rates of nitrogen supplied after anthesis were 90.3% and 83.4%. These methods of nitrogen application increased the using of fertilization through increased the fertilizer-derived recover of nitrogen supplied after anthesis. N uptake for different organs of the plant in the mature period was the highest in the grains, and then decreased through leaves, stems sheath, root and earaxis. N uptake was lowest in bract.4 Effects of nitrogen management on the related physiological characteristics.Nitrogen application could increase the enzyme activities related to nitrogen metabolism, the net photosynthesic rate of leaf. It also could increase the activities of internal source protective enzyme. The bottom leaves were caducity in grain filling stage under excessive nitrogen. As a result, the leaf index decreased significantly. It made again improving photosynthetic characteristics and increasing grain yield.Nitrogen application times before anthesis could increase the NR activity significantly. Nitrogen application at grain filling stage could increase the enzyme activities related to carbon and nitrogen metabolism at the same time. And it could keep the enzyme activities stay a high level. Nitrogen application times and nitrogen application at grain filling stage could also increase the net photosynthesic rate of leaf, LAI and the enzyme activities related to photosynthetic characteristics. It increasedΦPSII, NPQ and ETR. Nitrogen application at grain filling stage increased the activities of inherent protection system, decreased MDA content. As a result, it could delay plant senility significantly.