Study On Nitrogen Metabolism Characteristic, Regrowth Mechanism After Clipping And High Yield And Quality Of Zea Mexicana

The experiment was carried at the maize Scien-tech zone of ShandongAgricultural University during the year of 2002 and 2003.The new-type foragegrass-annual Zea Mexicana was regarded as the researching object. Twoaspects were researched mainly in the experiment: (1) Effects of differentnitrogen application strategies on yield, forage nutritive quality and thecharacteristic of nitrogen metabolism of Zea Mexicana; (2) Effects of differentcutting system on yield and forage nutritive quality and the mechanism ofregrowth after clipping. Zea Mexicana was cultured in field and pools, and theanalysis of physiology and biochemistry was applied in the lab. The nitrogenmetabolism of Zea Mexicana, the mechanism of regrowth after clipping andthe regulation and control measures of high yield and high quality werestudied. Through two years' research, main results were obtained as follows:1. Effects of nitrogen application strategies on yield of Zea Mexicana Once its natural height was 110cm, the plant was clipped. It was clipped 3times in the whole growth stage (H1, H2 and H3 mean the first, second andthird harvest stage, respectively) and the stubble height was 25cm. Under twonitrogen rate (High-rate N, 600 kg·hm-2; Mid-rate N, 300 kg·hm-2), theapplication rate improved the yield of whole plant at H1 and the leaves at H2only. The stalks at H2and the whole plants at H3 were affected by the dressingfertilizer. The higher total yield was obtained by the treatment of base fertilizerunder the two levels. Yield was higher at the higher nitrogen rate under thesame applied fertilizer way. The yield of leaves was the main component of the total yield. It was themain reason of yield enhanced that nitrogen application increased.2. Effects of nitrogen application strategies on the forage quality of ZeaMexicana The content of CP and EE was increased but ADF and CA was decreasedby different nitrogen application strategies, the results showed that the forage 5王永军:墨西哥玉米氮代谢特性,刈后再生机理及高产优质调控研究nutritive quality and the taste were improved. The influence of nitrogen levelon the CP, EE, CA, NFE and GE yield was greater than the applied wa. Withincreasing of the harvest times, the efficiency of the base fertilizer decreasedbut that of the dressing fertilizer increased. The ADF yield increased as theresult of the harvest biomass increased highly, which was over the degree ofADF content decreased. Leaves were the main factor of the forage nutritive quality, too. As aresult, all nitrogen applied as base fertilizer could harvest the higher biomassand improve the forage nutritive quality for summer Zea Mexicana.3. Effects of nitrogen application strategies on spatial and temporalvariability of NO3 -N concentration in Zea Mexicana - The NO3 -N concentration was the highest in the newly leaves, lowest in -the functional leaves and medium in the old leaves. The concentration ofNO3 -N was lower both in stalks and roots than in leaves at H1 but the results -were contrary at H2 and H3. The concentration of nitrate decreased in the threetype leaves with increasing of harvest times, however, the NO3 -N -accumulation in stalks and roots reduced at H2 and increased at H3. The keyfactors which made NO3 -N accumulation in the same type leaves were high -nitrogen rate and nitrogen addition averagely by three times. The treatment ofN2-3 (600 kg N·hm-2 added at average level by three times) made theconcentration of NO3 -N the highest level in the newly leaves in H2, reached -92.66μg·g-1. The data indicated that the concentration of NO3 -N was still -lower than the potential toxicosis dose for animals when the nitrogen rateranged from 300 kg N·hm-2 to 600 kg N·hm-2.4. Effects of nitrogen application strategi...