氮肥對玉米氮素吸收、同化與根活性的影響

Effects of Nitrogen Fertilization on Nitrogen Uptake, Assimilation and Root Activity of Maize (Zea mays L.)

宋珂(Lamin B. Sonko)

指導教授 ： 蔡秀隆 ； 謝清祥

國立屏東科技大學/農學院/熱帶農業暨國際合作系所/碩士(2012年)

https://doi.org/10.6346/NPUST.2012.00154

摘要

玉米需要施用高量氮肥以穫得高產，當水分、溫度等氣象條件適當時，氮素的有效性成為玉米生產力的主要限制因子。氮素是蛋白質、核酸、葉綠素等物質的組成分，並且在許多植物生理過程扮演重要的角色。氮素可建構足夠的葉面積與葉面積持續期以有效地利用陽光，增進光合作用效率。瞭解影響玉米吸收與利用氮素的生理與生化的機制是增加氮素利用效率、增加產量與減少環境污染的有效策略。本論文的主要目的在探討土壤施予不同氮肥對玉米氮素吸引、生理與生化以及生長和產量的影響。
本研究以糯玉米(玉美珍)為試驗材料，進行兩次田間試驗與一次盆栽試驗，完全逢機設計(CRD)，四個氮素肥料等級(0、90、180、270 kg N ha-1)。取樣玉米植株測定硝酸鹽還原酵素(NRA)、脫氫酵素活性、葉綠素含量與植株氮素含量。並量取株高、葉數、綠葉面積、生物質量與產量構成成分。研究結果顯示硝酸鹽還原酵素(NRA)、脫氫酵素活性與植株氮素含量顯著受到氮肥施用量的影響，玉米根部NRA活性比葉部的更容易受到土壤氮素量的影響，根部脫氫酵素活性於玉米生長初期較高，之後，隨著植株成長與土壤氮素量減少而下降。植株氮素含量亦隨著植株成長而下降。玉米植株所吸收的氮素大部分累積在葉片。
玉米營養器官的氮素含量顯著受到氮肥施用量的影響，但是穀粒的氮素含量於四個氮肥施用量處理間並無顯著差異，這意味著營養器官的氮素可以再運移至繁殖器官的積儲部位以供應積儲部位對氮素的需求。無論如何，玉米植株總氮素含量仍然以施用高量氮肥的處理比對照處理高，因為施用氮肥可促進生物質量的累積與提高植株氮素濃度。
株高於生育初期，氮肥施用量處理間並無顯著差異，至營養生長後期，則以高氮肥施用量處理比低量氮肥的處理高，其它所有植株生長介量亦均受到氮肥施用的促進。玉米產量構成成分顯著受到氮肥施用量的影響，第一次田間試驗的結果以施用180 kg N ha-1 的產量最高(10.72 tons ha-1)，於第二次田間試驗的結果則以施用270 kg N ha-1 的產量最高(10.66 tons ha-1)。
由本研究的結果顯示增加氮肥施用量由0 、 90 到 180 kg N ha-1 的處理可以顯著增加玉米產量構成成分，但是當氮肥施用量由180增加到 270 kg N ha-1 之時，即無法顯著增加玉米產量構成成分。高的玉米產量藉由施用氮肥可提高玉米植株生理與生化活性與促進生長，提高生物質量的累積，這些因子之間具有相關的關係。

關鍵字

玉米 ； 氮素 ； 硝酸鹽還原酵素活性 ； 氮素濃度

並列摘要

Maize is one of the cereal crops that require higher amounts of nitrogen (N) to attain higher growth and yield. When water and temperature conditions are ideal, productivity of maize is mainly limited by availability of nitrogen. Nitrogen is a component of a number of compounds, e.g. proteins, nucleic acids and chlorophyll; and plays important role in many of the plants physiological processes. In particular, it is important in the efficient capture and use of solar radiation; it is fundamental to establish the plant's photosynthetic capacity and prolongs the effective leaf area duration. Understanding the physiological and biochemical mechanisms that influence the capacity of maize to take up and efficiently utilize nitrogen is a useful strategy for increasing its nitrogen utilization efficiency, increasing yield and reducing environmental problems. The main aim of this study was to investigate the physiological and biochemical mechanisms which determine nitrogen uptake and metabolism in maize at different soil nitrogen levels, and their implications on maize growth and yield. In this study, two field experiments and one pot experiment were conducted. Glutinous white maize (White pearl) was used as the test variety in all the experiments. The experimental design was a complete randomized design (CRD), consisting of four N fertilizer rates treatments: 0, 90, 180 and 270 kg N ha-1. The physiological parameters assessed were nitrate reductase activity (NRA), dehydrogenase enzyme activity and total nitrogen content and concentration of plant samples. NRA and dehydrogenase enzyme activity were determined only at the pot experiment at 11 and 18 days after emergence. Total N content and concentration in plant tissues was determined using the micro-kjeldahl procedure. Plant growth parameters measured include plant height, leaf number, green leaf area, leaf chlorophyll content and biomass accumulation. Leaf chlorophyll was measured using SPAD-502 meter. Grain yield components were also measured. The results showed that nitrate reductase activity, dehydrogenase activity and total N content and concentration were all significantly influenced by N fertilizer rates. Data obtained indicated that NRA in maize roots was more affected by variations in soil N levels than in leaves. Dehydrogenase activity of maize roots was higher when the plants were younger and was found to decrease as the plants grow and soil N levels started to go down. Nitrogen concentration in plant tissues was higher at early growth stage and decreases as the plants mature. In terms of concentration of N in plant parts, data indicated that a greater proportion of N taken up by maize was concentrated in the leaves. Whiles nitrogen concentration in vegetative parts was significantly affected by N rates, grain N concentration showed no significant difference between all the four treatments in both field experiments. This was due to the potential of maize to maintain a stable supply of N in the reproductive parts by remobilizing N from the vegetative parts. Total N content of the shoot of plants in N fertilized treatments were also significantly higher than those in the control plots because the two factors that determines N content i.e. nitrogen concentration and biomass accumulation were both enhanced by N fertilizer application. All the plant growth parameters assessed in this study were significantly enhanced by N application. Plant height was similar for all the treatments at early growth stage, but at late vegetative stage, significant differences were observed between the higher and the lower N treatments. Maize yield components such as ear weight per plant, number of grain rows per ear and ear weight were all significantly affected by N rates. The highest yield in field experiment one (10.72 tons ha-1) was obtained at 180 kg N ha-1 treatment. In experiment two, the highest yield (10.66 tons ha-1) was obtained at 270 kg N ha-1 treatment. In this study, increasing N rates from 0 to 90 kg N ha-1 and from 90 kg N ha-1 to 180 kg N ha-1 in most cases resulted in an increment in grain yield components; but adjusting from 180 kg N ha-1 to 270 kg N ha-1 did not show any significant increment for all the grain yield components. Higher maize yields recorded in the higher N treatments was as a result of the positive effects that N application had on plants physiological and growth factors.

並列關鍵字

Maize ； nitrate reductase activity ； dehydrogenases ； nitrogen concentration

參考文獻

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