Abstract
Nitrogen (N) is the most limiting nutrient for maize, and appropriate N fertilization can promote maize growth and yield. The effect of N fertilizer rates and timings on morphology, antioxidant enzymes, and grain yield of maize (Zea mays L.) in the Loess Plateau of China was evaluated. The four N levels, i.e., 0 (N0), 100 (N1), 200 (N2), and 300 (N3) kg ha−1, were applied at two timings (T1, one-third N at sowing and two-thirds at the six-leaf stage of maize; T2, one-third applied at sowing, six-leaf stage, and eleven-leaf stage of maize). The results show that N2 and N3 significantly increased the plant height, stem and leaf dry weight, and leaf area index of maize compared with a non-N-fertilized control (N0). The net photosynthetic rate, transpiration rate, stomatal conductance, and leaf chlorophyll contents were lower, while the intercellular carbon dioxide concentration was higher for non-fertilized plants compared to fertilized plants. The activities of peroxidase (POD) and superoxide dismutase (SOD) increased with N rate, but the difference between 200 and 300 kg ha−1 was not significant; further, the isozyme bands of POD and SOD also changed with their activities. Compared with a non-N-fertilized control, N2 and N3 significantly increased grain yield by 2.76- and 3.11-fold in 2018, 2.74- and 2.80-fold in 2019, and 2.71- and 2.89-fold in 2020, and there was no significant difference between N2 and N3. N application timing only affected yield in 2018. In conclusion, 200 kg N ha−1 application increased yield through optimizing the antioxidant enzyme system, increasing photosynthetic capacity, and promoting dry matter accumulation. Further research is necessary to evaluate the response of more cultivars under more seasons to validate the results obtained.
Highlights
Nitrogen (N) is typically a limiting nutrient for the production of most of the cereals, and most importantly for maize (Zea mays L.) [1]
Our research showed that the variation in dry matter under different N rates was a result of differences in plant height, which had significant linear relationships with dry matter [35]
Our research found photosynthetic rate (Pn) showed an increasing trend with increased N application, which eventually led to an increase in production
Summary
Nitrogen (N) is typically a limiting nutrient for the production of most of the cereals, and most importantly for maize (Zea mays L.) [1]. The demand for N fertilizer in cropping systems has substantially increased and N fertilizer is the most expensive external input in maize production [2]. The Loess Plateau in China is a typical rainfed agricultural region and main area for maize planting, which is approximately equal to 17.9% of the total area used for crop production [3,4]. Nutrient deficiency and insufficient rainfall are the key factors limiting maize yield [5]. To achieve a higher yield, excessive application of. Excessive N fertilization does not increase grain yield, reducing economic efficiency and disrupting the environment [6]
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