Plant Gene and Trait 2025, Vol.16, No.3, 133-141 http://genbreedpublisher.com/index.php/pgt 138 and quality of tomatoes (Fan et al., 2022; Bello et al., 2024; Fidler et al., 2025). For instance, when the temperature is high or evaporation is fast, nitrogen fertilizer may be more prone to loss or have a lower utilization rate. Therefore, fertilization plans should be determined based on local weather and soil conditions in different places (Li et al., 2020; Ayankojo and Morgan, 2021). 8 Case Study: Greenhouse Trials on Split Nitrogen in Indeterminate Tomatoes 8.1 Trial design and nitrogen allocation schedules In greenhouse experiments, a randomized block design is usually adopted, and several different time schedules for nitrogen fertilizer application are set. The more common practices include applying all nitrogen fertilizer at once during transplanting and using the nitrogen fertilizer in two separate applications. For instance, use half of it when transplanting and the other half after the plant has grown to a certain stage. Apply 25% of the nitrogen fertilizer at the time of transplanting, and the remaining 75% should be applied when the plants enter their growth peak period. In addition, a control group without nitrogen fertilizer application was also set up (Wabela, 2018; Wang et al., 2025). Some experiments also incorporated different irrigation methods (such as total irrigation, water-saving irrigation or controlled irrigation) to observe the effects of the combination of irrigation methods and nitrogen fertilizers (Zhou et al., 2020; Ayankojo and Morgan, 2021; Sun et al., 2023). In the experiment, the total dosage of nitrogen fertilizer was generally determined based on soil testing or recommended values, and was reasonably allocated according to the growth stage, with a focus on the fertilizer requirements at the seedling stage, flowering stage and fruiting stage (Zhou et al., 2020; Wang et al., 2025). 8.2 Measured outcomes: fruit set, yield, and nitrogen use efficiency The test results revealed that applying nitrogen in batches could significantly increase the fruit setting rate and total yield of tomatoes. The treatment of using half of the nitrogen fertilizer during transplanting and the other half in the later stage achieved the highest yield, reaching 39.33 tons per hectare. The combined yield of 25%+75% was 33 tons per hectare, which was also better than one-time fertilization (Wabela, 2018). In a greenhouse environment, choosing an appropriate total amount of nitrogen fertilizer (such as N60-N80, corresponding to 93-128 kilograms of nitrogen per hectare) not only leads to high yields but also enables more efficient utilization of nitrogen fertilizer. If too much is applied, it will instead cause waste (Wang et al., 2025). Because tomatoes use less fertilizer during the seedling stage, they mainly rely on nitrogen in the soil during the flowering stage, and by the fruiting stage, they are even more dependent on nitrogen in the fertilizer. Therefore, applying nitrogen fertilizer in stages is more in line with the growth requirements of tomatoes (Zhou et al., 2020; Sun et al., 2023; Wang et al., 2025). If combined with appropriate irrigation methods at the same time, such as moderate and less watering, the utilization rates of fertilizers and water can be further improved, making the root system more developed and the fruits better (Zhou et al., 2020; Ayankojo and Morgan, 2021; Sun et al., 2023). 8.3 Economic analysis and farmer adoption potential In addition to increasing the yield, applying nitrogen in several installments can also make nitrogen fertilizer less likely to be wasted, have higher fertilizer efficiency, and reduce the impact on the environment (Du et al., 2020; Wang et al., 2025). Economic analysis reveals that if the amount of nitrogen fertilizer is appropriately reduced and the fertilization time is properly arranged, not only is the output not reduced, but the input-output ratio is also higher and the profit is better (Du et al., 2020; Fan et al., 2022). For instance, one approach is to irrigate the entire process with one-third of the water volume, combined with two-thirds of the recommended amount of nitrogen fertilizer. The result is excellent in terms of yield, fruit quality and economic benefits, and is highly suitable for promotion to farmers (Fan et al., 2022). In addition, the operation of stepwise nitrogen application is not complicated and can be matched with the current irrigation system. It is easy for farmers to master and use (Du et al., 2020; Fan et al., 2022). Overall, this phased nitrogen application management approach can help the unlimited-growth tomatoes in greenhouses achieve the goals of high yield, high efficiency and environmental protection.
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