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Article

Application of Nitrate–Ammonium Nitrogen Fertilization Reduced Nitrogen Loss in Surface Runoff and Infiltration by Improving Root Morphology of Flue-Cured Tobacco

by
Chengren Ouyang
,
Kang Yang
and
Zhengxiong Zhao
*
College of Tobacco Science, Yunnan Agricultural University, Kunming 650201, China
*
Author to whom correspondence should be addressed.
Agronomy 2024, 14(11), 2532; https://doi.org/10.3390/agronomy14112532
Submission received: 8 September 2024 / Revised: 19 October 2024 / Accepted: 23 October 2024 / Published: 28 October 2024
(This article belongs to the Section Plant-Crop Biology and Biochemistry)
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Abstract

:
Nitrogen loss in water from farmland has become an environmental issue. Nitrogen fertilizer is the main cause of agricultural non-point source pollution in the Lake Basin, Yunnan. However, it is unclear how different nitrogen fertilizer forms affect water loss from farmland and how the root systems of crops respond. We established five nitrogen fertilizer treatments (100–0% [T1], 75–25% [T2], 50–50% [T3], 25–75% [T4], and 0–100% [(T5)] nitrate–ammonium) and performed an investigation to determine nitrogen loss in water and root morphological parameters of tobacco in Mile County and Chengjiang County. Compared with in the T1, T4, and T5 treatments, the total nitrogen loss in surface runoff was reduced by 4.67%, 11.85% and 9.56% in the T2 treatment and 27.32%, 23.20%, and 31.43% in the T3 treatment, respectively. Similar results were observed for the nitrogen loss due to infiltration. The root biomass was negatively correlated with nitrogen loss. There was greater root biomass, root surface area, and root spatial distribution in T2 and T3 compared with in T1, T4, and T5. These results indicate that 50–50% nitrate–ammonium nitrogen fertilizer can facilitate the root growth of tobacco and reduce nitrogen loss, which provides a reference for agricultural sustainable development.

1. Introduction

Lake eutrophication is a major environmental problem to be solved that requires urgent attention for water environments globally [1,2]. In China, more than 60% of lakes have eutrophication issues, and more than 50% of the nitrogen and phosphorus in lakes originates from non-point source pollution [3]. In recent years, the Lake Basin of Yunnan has been polluted by nitrogen fertilizer runoff from farmland, which has increased the eutrophication risk from runoff into river and lake basins [4]. This can cause serious ecological problems and threaten the safety of drinking water. Thus, there is an urgent need to effectively prevent and reduce nitrogen pollution from farmland to protect water resources and ecology [5,6,7].
Various studies have investigated nitrogen reduction and degradation measures in water bodies, attracting wide attention in water resource research and environmental management [7,8]. Hou et al. (2021) found that controlled-release fertilizer application, conventional urea, and conventional urea as an environmental fertilizer were observed to be used in 29%, 47%, and 46% of cases, respectively, and these resulted in lower total nitrogen loading in surface and percolating water than conventional fertilizer practices [3]. For agricultural production, nitrogen fertilizer application to soil is an important measure to increase crop yields [9]. In recent decades, large amounts of nitrogen fertilizer have increased crop yields to ensure national food security [10]. However, continuous overapplication of nitrogen fertilizer leads to the loss of nitrogen nutrients from farmland, releases a large amount of surplus nitrogen pollutants to the environment, and increases the risk of eutrophication in water bodies [11]. Therefore, appropriate nitrogen fertilizer application is needed to reduce agricultural nitrogen nutrient loss in terms of surface runoff and infiltration and is an effective method to reduce non-point source pollution in lake basins [12].
In fact, nitrogen in the forms of ammonium and nitrates found in river and lake drainage areas are consistent with those in nitrogen fertilizer, indicating that fertilizer entered these areas with rainwater [13]. Studies have shown that nitrate nitrogen is the main cause of lake water pollution [14]. Nitrate nitrogen can cause the rapid reproduction of algae and other plankton and decrease dissolved oxygen in water, resulting in water pollution [15]. The nitrate–ammonium ratio can affect the growth of algae and other plankton by affecting the nutrient structure of river and lake basins, indicating that different nitrogen forms in water are important factors for the eutrophication and the aggravation of non-point source pollution in lake basins [11]. Therefore, changing the type of nitrogen fertilizer used could reduce nitrogen loss into water bodies [16].
Crops absorb nutrients through their root system [17]. Root length, root surface area, root tip number, root activity, and other morphological and physiological indicators are affected by the nitrogen form in the soil environment, which in turn affect the nitrogen absorption ability of roots [18,19]. A single application of nitrate nitrogen or ammonium nitrogen can inhibit root elongation and growth [20,21]. In contrast, a combined application of nitrate and ammonium nitrogen can promote root growth [22]. Root growth is affected by nitrogen form and nitrogen use efficiency [23]. However, knowledge of the response of crop roots to nitrogen forms for the protection of water resources and ecological security is still lacking.
Tobacco (Nicotiana tabacum L.) is one of the main cash crops in Yunnan, including in the Honghe watershed and the Fuxian Lake Basin [24]. Nitrogen fertilizers, including ammonium and nitrate nitrogen, are applied to improve tobacco plant growth and increase tobacco yield [25,26]. However, the different forms of nitrogen fertilizer will inevitably affect the ecology of a watershed. Whether different forms of nitrogen fertilizer can reduce nitrogen loss in lake basins and ensure tobacco yield and quality is unclear. Therefore, in this study, we collected runoff in real-time and infiltration water samples during tobacco plant growth in the Honghe watershed and the Fuxian Lake Basin to study the effect of different forms of nitrogen fertilizer on the soil environment. The results of this study will be useful for the protection of water quality.

2. Materials and Methods

2.1. Experimental Site

The experiment was conducted from April to September 2020 in the Mile County and Chengjiang County, Yunnan. The experimental site in Mile County was located in the basin of the Red River (103°45′46″ E, 24°37′34″ N, 1451 m a.s.l.), which has a south-central subtropical or mid-subtropical monsoon climate with an average annual temperature of 19.7 °C, annual rainfall of 800–1100 mm and annual sunshine duration of 2176 h. The experimental site in Chengjiang was located in the basin of Fuxian Lake (102°52′39″ E, 24°38′29″ N, 1767 m a.s.l.), which has a subtropical plateau monsoon climate with an average annual temperature of 17.5 °C and an average annual rainfall of 900–1200 mm. The total sunshine duration is 2172 h, and the sunshine rate is 50%. The soil is red soil in Mile County and paddy soil in Chengjiang County (Chinese Classification system).

2.2. Experimental Design

Five nitrogen fertilizer treatments were used: 100–0% nitrate–ammonium nitrogen fertilizer (T1), 75–25% nitrate–ammonium nitrogen fertilizer (T2), 50–50% nitrate–ammonium nitrogen fertilizer (T3), 25–75% nitrate–ammonium nitrogen fertilizer (T4), and 0–100% nitrate–ammonium nitrogen fertilizer (T5). A randomized complete block design (RCBD) was used in this study. Each treatment was replicated three times. Each plot was set up with a collection tank at the bottom of the plot.
K326, a flue-cured tobacco variety that is widely planted in Yunnan, was used at the two field experimental sites. The plot size was 12 × 3.6 m2, and the plant row spacing was 1.2 m × 0.6 m, resulting in a density of 13,890 plants ha−1 (60 plants in each plot) when the tobacco seedlings were transplanted into the soil, which was consistent with the cultivation customs in Yunnan. The fertilizer was applied as follows: 75  kg∙ha−1 annual pure nitrogen (N), 75 kg∙ha−1 pure phosphorus (p) as P2O5, and 150  kg∙ha−1 pure potassium (K) as KR2RO, with the same total amount of nitrogen, phosphorus, and potassium fertilizer in each treatment. The N fertilizer input was applied according to the form of the nitrogen fertilizer. All fertilizer was provided by a local tobacco company. The cultivation management practices were carried out following local high-quality tobacco production protocols.

2.3. Data Collection

2.3.1. Meteorological Data Collection

At the field experimental sites, movable automatic weather stations Vantage Pro 2 (Davis Instruments, Sunnyvale, CA, USA) were used to collected precipitation data every 10 min.

2.3.2. Water Sample Collection and Measurement

In a field experiment, runoff and infiltration are important parameters for evaluating nitrogen loss.
Surface runoff water collection: Tobacco was cultivated in single rows with double ridges, and a runoff collection tank was used each plot. Following rainfall, runoff flowed along the ridges and entered into the collection point, and then flowed through PVC pipes into the collection tank. These PVC pipes underwent strict waterproofing treatment to ensure uniform specifications for all runoff tanks, preventing leakage or seepage. Within the runoff tank, connecting pipes extended to the soil surface, allowing for the extraction and volume recording of runoff liquid using a vacuum pump (Figure 1).
Infiltration water collection: A simple leaching pond was installed per plot to collect the leachate, which was 120 cm wide and 100 cm high. In the field experiments, the soil within the pond was excavated into layers separated by 20 cm intervals, and then refilled with soil at its original bulk density. The soil mass was surrounded by a plastic sheet barrier. A leachate collection barrel was placed beneath the soil, and covered with two layers of 80 mesh nylon net and a 3 cm layer of quartz sand. All water that leached to a depth of 80 cm was entirely entered the collection tank. A connecting pipe within the barrel extended to the soil surface. Finally, a vacuum pump was used to extract and record the volume of leaching water within the tank (Figure 1).
Samples (250 mL) of runoff and infiltration water were sampled, stored at −4 °C, and used to determine total nitrogen, nitrate nitrogen, and ammonium nitrogen content. The test was carried out using the midline of the plot ridge as a reference to calculate the catchment area of the test plots. The measurements were conducted following the national standard using the alkaline potassium persulfate digestion method to determine total nitrogen, a UV spectrophotometer to determine nitrate nitrogen, and the alkaline potassium persulfate digestion method to determine ammonium nitrogen. The nitrogen loss was calculated by multiplying the water volume by the concentration, and was converted to yield loss per hectare [27].

2.3.3. Biomass and Root Index of Tobacco

At the two field experimental sites, the biomass of tobacco was used to extrapolate the yield per unit ground area in each plot. When tobacco plants were picked (90 d after transplanting), four plants were randomly selected and cut at the ground level in each plot; the roots, stems, and leaves of tobacco were separated, weighed fresh, oven-dried at 80 °C to a constant weight, and weighed separately to determine the dry matter weight.
When tobacco plants were picked (90 d after transplanting), four plants were randomly selected to observe the spatial distribution of roots in each plot. The 3D monolith stratified spatial sampling method was used. In summary, a small cubic in situ root and soil sampler was used to sample the roots of tobacco; nine soil blocks were taken in each layer centered on the tobacco plant; soil blocks with a volume of 10 cm × 10 cm × 20 cm were sampled; and a total of 27 root samples were collected from each plant. The root samples were used to measure the root morphological parameters such as the root length density and root surface area. The root length density and root surface area were measured using a root scanning system Win RHIZO (Regent, Gatineau, QC, Canada).

2.4. Data Analysis

All metrics were statistically analyzed, and ANOVA was performed using IBM SPSS Statistics 23.0. The LSD method was used for two-way comparisons. The significance level was p < 0.05 for all analyses.

3. Results

3.1. Rainfall and Average Temperature in the Experiment Site

Meteorological data was collected from January to December to match with the period of crop growth, and the rainfall and mean temperature each day at the experimental site in 2020 are shown in Figure 2. In Mile County, monthly rainfall from April to September was 57.3, 49.0, 210.5, 91.6, and 198.4 mm, respectively. The average monthly temperature from April to September was 17.73, 20.98, 19.98, 20.02, and 18.95 °C, respectively. In Chengjiang County, rainfall from April to September was 38.5, 92.4, 332.4, 178.7, and 91.9 mm, respectively. The average temperature from April to September was 16.32, 19.15, 18.59, 18.28, and 17.50 °C, respectively. In summary, the average temperature at the Mile experimental site was higher than that at the Chengjiang experimental site, but the rainfall followed the opposite trend.

3.2. Nitrogen Loss from Tobacco Fields with Different Forms of Nitrogen Fertilizer

3.2.1. Nitrogen Loss in Surface Runoff

The nitrogen loss in surface runoff from tobacco fields with different forms of nitrogen fertilizer is shown in Figure 3. Nitrogen loss in surface runoff in T2 and T3 was significantly lower than that in the T1, T4, and T5 in terms of the total nitrogen, nitrate nitrogen, and ammonium nitrogen contents in the two field experiments. Nitrogen loss in surface runoff in the Mile experimental site was higher than that in the Chengjiang experimental site.
At the Chengjiang experimental site, the total nitrogen loss in surface runoff in T2 and T3 was significantly lower than that in T1, T4, and T5 (p < 0.05), but the difference between T2 and T3 was not significant (p > 0.05). Nitrate nitrogen loss of in surface runoff in T1 and T2 was significantly lower than that in T3, T4, and T5 (p < 0.05), but there were no significant differences among T3, T4, and T5 (p > 0.05). Ammonium nitrogen loss in surface runoff in T4 and T5 was significantly higher than that in T1, T2, and T3 (p < 0.05), but there were no significant differences among T1, T2, and T3 (p > 0.05).
At the Mile experimental site, the total nitrogen loss of in surface runoff in the T2, T3, and T4 treatments was significantly lower than that in the T1 and T5 treatments (p < 0.05), but there were no significant differences among the T3, T4, and T5 treatments (p > 0.05). Nitrate nitrogen loss in surface runoff in the T1 and T2 treatments was significantly higher than that in the T3, T4, and T5 treatments (p < 0.05), but there were no significant differences among the T3, T4, and T5 treatments (p > 0.05). Ammonium nitrogen loss in surface runoff in the T4 and T5 treatments was significantly higher than that in the T1, T2, and T3 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T3 treatments (p > 0.05).
The results from the two experimental sites suggested that 50–50% nitrate–ammonium nitrogen fertilizer results in a lower total nitrogen loss, which may promote the root growth of tobacco plants and the absorption of soil nutrients.

3.2.2. Nitrogen Loss in Infiltration Water

The characteristics of nitrogen loss due to infiltration in tobacco fields with different forms of nitrogen fertilizer are shown in Figure 4. Nitrogen loss due to infiltration in the T2 and T3 treatments was significantly lower than that in the T1, T4, and T5 treatments in terms of the total nitrogen, nitrate nitrogen, and ammonium nitrogen contents in the two field experiments. Nitrogen loss due to infiltration in the Mile experimental site was higher than that in the Chengjiang experimental site.
At the Chengjiang experimental site, the total nitrogen loss due to infiltration in the T1 and T5 treatments was significantly higher than that of in the T2, T3, and T4 treatments (p < 0.05), but there were no significant differences among the T2, T3, and T4 treatments (p > 0.05). Nitrate nitrogen loss due to infiltration in the T1 and T2 treatments was significantly lower than that in the T3, T4, and T5 treatments (p < 0.05), but there were no significant differences among the T3, T4, and T5 treatments (p > 0.05). Ammonium nitrogen loss due to infiltration in the T4 and T5 treatments was significantly higher than that in the T1, T2, and T3 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T3 treatments (p > 0.05).
At the Mile experimental site, the total nitrogen loss due to infiltration in the T1, T2, and T3 treatments was significantly lower than that of in the T4 and T5 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T3 treatments (p > 0.05). Nitrate nitrogen loss due to infiltration in the T3 and T5 treatments was significantly lower than that in the T1, T2, and T4 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T4 treatments (p > 0.05). Ammonium nitrogen loss due to infiltration in the T4 and T5 treatments was significantly higher than that in the T1, T2, and T3 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T3 treatments (p > 0.05). The results from the two experimental sites result suggested that 50–50% nitrate–ammonium nitrogen fertilizer results in less total nitrogen loss, which may contribute to promoting the root growth of tobacco plants and the absorption of soil nutrients.

3.3. Root Spatial Distribution of Tobacco Roots with Different Forms of Nitrogen Fertilizer

3.3.1. Root Biomass of Nitrogen-Fertilized Tobacco

The characteristics of root biomass of tobacco grown with different forms of nitrogen fertilizer are is shown in Table 1. At the Chengjiang experimental site, the root biomass of tobacco in the T1, T2, and T3 treatments was significantly higher than that in the T4 and T5 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T3 treatments (p > 0.05). At the Mile experimental site, the root biomass of tobacco in the T1, T2, and T3 treatments was significantly higher than that in the T4 and T5 treatments (p < 0.05), but there were no significant differences among the T1, T2, and T3 treatments (p > 0.05). Compared to in the T5 treatment, the root biomass of tobacco in the T1, T2, T3, and T4 treatments increased by 15.49–18.32%, 11.74–14.87%, 18.99–22.36%, and 0.02–4.02%, respectively. The root biomass of tobacco in the T3 treatment was significantly higher than that of in the T1, T2, T4, and T5 treatments in the two field experiments, indicating that 50–50% nitrate–ammonium nitrogen fertilizer could promote the root growth of tobacco after transplanting. The root biomass of tobacco can facilitate nutrient absorption, which may contribute to improved nutrient utilization efficiency in the tobacco.

3.3.2. Root Surface Area of Nitrogen-Fertilized Tobacco

The root surface area of tobacco given different forms of nitrogen fertilizer is shown in Table 1. At the Mile experimental site, the root surface area in T2 and T3 was significantly higher than that in T1, T4, and T5 in the 0–20 cm soil layer (vertical direction), and the same result was observed in the 20–40 cm soil layer. The root surface area followed the order T1 > T2 > T3 > T4 > T5 in the 40–60 cm soil layer. At the Chengjiang experimental site, the root surface area in T2 and T3 was significantly higher than that in T1, T4, and T5 in both the 0–20-cm soil layer and the 20–40 cm soil layer. The root surface area followed the order T4 > T2 > T3 > T1 > T5 in the 40–60 cm soil layer, indicating that 50–50% nitrate–ammonium nitrogen fertilizer could promote the root growth of tobacco after transplanting.
At the Mile experimental site, the root surface area followed the order T2 > T1 > T3 > T5 > T4 in the 0–10 cm soil layer (horizontal direction), T3 > T2 > T1 > T4 > T5 in the 10–20 cm soil layer, and T4 > T3 > T1 > T5 > T2 in the 20–30 cm soil layer. At the Chengjiang experimental site, the root surface area followed the order T3 > T2 > T4 > T1 > T5 in the 0–10 cm, 10–20 cm, and 20–30 cm soil layers. The root surface area in T2 and T3 was higher than that in T1, T4, and T5.
These results suggest that a high nitrate nitrogen content in fertilizer is beneficial for root elongation both longitudinally and laterally, and both 50–50% and 75–25% nitrate–ammonium nitrogen fertilizer facilitate root growth and promote nutrient uptake in the soil layers.

3.3.3. Root Distribution of Nitrogen-Fertilized Tobacco

The root distribution in the 0–60 cm soil layer is shown in Figure 5. The roots were mainly distributed in the 0–40 cm soil layer at the two experimental sites. The root distribution in T2 and T3 was greater than that in T1, T4, and T5. The root distribution in T1, T2, and T3 was both wider and deeper compared with that in T4 and T5. These results suggest that the 50–50% nitrate–ammonium nitrogen fertilizer treatment promotes greater root distribution, which may contribute to a reduction in nutrient loss.

3.4. Relationship Between the Root System of Tobacco and Nitrogen Loss Under Different Forms of Nitrogen Fertilizer

The relationship between the root system of tobacco and nitrogen loss under different forms of nitrogen fertilizer is shown in Figure 6. The two experimental sites showed that the nitrogen loss was closely related to the root system under different forms of nitrogen fertilizer. The nitrogen loss decreased and the root length density (root biomass) increased when the proportion of nitrate nitrogen fertilizer increased. By contrast, the nitrogen loss increased and the root length density (root biomass) decreased when the proportion of ammonium nitrogen fertilizer increased. These results suggest that root morphology plays an important role in reducing nitrogen loss given different forms of nitrogen fertilizer.

3.5. Plant Biomass Under Different Forms of Nitrogen Fertilizer

The biomass of tobacco plants under different forms of nitrogen fertilizer is shown in Table 2. The biomass of tobacco plants in T3 was higher than that in T1, T2, T4, and T5 in both experimental sites. The biomass of tobacco plants followed the order T3 > T4 > T2 > T1 > T5 at the Mile experimental site and T3 > T2 > T4 > T1 > T5 at the Chengjiang experimental site. The biomass of tobacco plants in T1, T2, T4, and T5 was 48.00%, 25.57%, 37.48%, and 70.66%, respectively, at the Mile experimental site and 39.63%, 29.33%, 26.84%, and 57.53%, respectively, at the Chengjiang experimental site. This indicates that 50–50% nitrate–ammonium nitrogen fertilizer can increase root absorption.

4. Discussion

4.1. Nitrate–Ammonium Nitrogen Fertilizer Can Improve Root Morphology and Increase Flue-Cured Tobacco Biomass

The nitrate–ammonium nitrogen fertilizer significantly affected the root spatial distribution and biomass accumulation of flue-cured tobacco under the same nitrogen input. Tobacco roots are highly plastic and thus able to adapt to the spatial heterogeneity of soil nutrients. Nitrogen form can significantly affect root morphology. Numerous studies have shown that flue-cured tobacco prefers nitrate, and some studies have also shown that it is a nitrate–ammonium-balanced crop [28]. The results of this study showed that the root system of flue-cured tobacco is farthest distributed in the horizontal direction with nitrate ammonium nitrogen fertilizer. As a pair of cations and anions, the two forms of nitrogen help regulate intracellular charge and pH balance, increase nitrogen storage, and enhance root expansion in horizontal and vertical directions [29]. In addition, nitrate-dominant fertilization resulted in more root dispersal in specific horizontal directions than ammonium dominance. This is consistent with numerous studies showing that local nitrate supply can stimulate lateral root elongation, whereas local ammonium supply can induce the formation of branched short roots [30,31]. In both Mile and Chengjiang County, the application of balanced ammonium and nitrate fertilization or more nitrate fertilization resulted in higher shoot stem and leaf biomass than more ammonium fertilization. This is because balanced nitrate ammonium and more nitrate fertilization could increase the activities of enzymes required at the different stages of plant physiology, thereby increasing plant biomass [32]. These enzymes include those involved in the synthesis of chlorophyll during photosynthesis and nitrate reductase, glutamine synthetase, and glutamate synthetase in plant nitrogen metabolism [33,34]. In conclusion, nitrate ammonium nitrogen fertilizer and nitrate-preferred fertilization can improve root morphology, expand the horizontal and vertical distribution area of flue-cured tobacco, and improve stem and leaf biomass above the ground.

4.2. Nitrate–Ammonium Nitrogen Fertilizer Can Reduce Total Nitrogen Runoff and Infiltration Loss

The nitrate–ammonium nitrogen fertilizer significantly affected the nitrogen runoff loss and infiltration loss. The results of this study show that runoff had more total nitrogen loss than infiltration under the same nitrate–ammonium ratio of fertilization. Flue-cured tobacco is a crop grown in the rainy season in the subtropical monsoon climate zone, which is characterized by short time and high rainfall intensity [22]. Therefore, runoff production is much greater than infiltration, and the total nitrogen loss caused by runoff is much higher than infiltration. From 0%:100% to 100%:0%, total nitrogen runoff and infiltration showed a “V” shape. Nitrate–ammonium nitrogen fertilization increases nitrogen uptake and indirectly reduces nitrogen runoff and infiltration in flue-cured tobacco. Whether runoff or infiltration loss, nitrate nitrogen loss was much higher than ammonium nitrogen under the same nitrate–ammonium ratio fertilizer application. The main reason is that nitrate carries a negative charge and is not easily adsorbed by negatively charged soil particles; it exists in soil solutions and is easily absorbed by plants, but it is also easily lost with rainfall. Ammonium nitrogen carries a positive charge and is easily adsorbed by soil particles. It can not only adsorb on the surface of soil particles, but also enter the crystal of clay minerals and become a fixed ammonium ion [35,36]. Therefore, it has less mobility and is easily stored by soil particles. In conclusion, nitrate–ammonium nitrogen fertilizer could effectively reduce the contents of total nitrogen, ammonium, and nitrate in runoff and infiltration.

4.3. Nitrate–Ammonium Nitrogen Fertilizer Can Reduce Nitrogen Loss by Improving Root Morphology

Crop root length density refers to the total length of roots per unit volume of soil. The results showed that root length density was negatively correlated with nitrogen loss in runoff and infiltration [37]. The increase in root length density improved the accessibility between roots and distant nitrogen, enabling flue-cured tobacco to absorb more available nitrogen in soil, thereby indirectly reducing the loss of nitrogen in runoff and infiltration. Correlation analysis suggested that roots played an important role in nitrogen loss, that is, the loss of nitrogen was closely related to the root system under different forms of nitrogen fertilizer. The nitrate–ammonium nitrogen fertilizer treatment had higher root length density, root surface area, and root weight than that of 100% nitrate and ammonium nitrogen fertilizer. These results indicate that the root plays an important role in nitrogen uptake and plant growth when fertilizer with different nitrogen forms is added, which consistent with Ranjan’ result [17]. Xu’s result suggests that nitrate–ammonium nitrogen fertilizer facilitated root growth and increased root weight for nitrogen absorption [37]. Furthermore, this study also found that the root spatial distribution of nitrate–ammonium nitrogen fertilizer treatment changed the deep root system distribution, with more access to more of the soil volume, thus improving the roots under deep-soil nitrogen and other nutrient absorption use, improving the use efficiency of nitrogen in the soil. That is, nitrogen loss of surface runoff and infiltration water in the nitrate–ammonium nitrogen fertilizer treatment was lower than 100% nitrate and 100% ammonium nitrogen fertilizer.
One reason is that nitrate–ammonium nitrogen fertilizer in the soil can decrease the pH and increase the nitrogen supply in the soil under nitrification in agricultural soils. The absorption of nitrogen by the root system improves, and nitrogen use efficiency increases, in tobacco farmland [38,39]. Wang showed that allowing roots to “extend vertically” reduces root crowding in the upper soil, making tobacco plants more efficient at absorbing nutrients from fertilizers [40]. In this study, high nitrate nitrogen content of fertilizer was beneficial to root elongation both longitudinally and laterally. Furthermore, studies reported that nitrate does not adhere well to negatively charged soil particles and easily leaches into the soil. That is, nitrate nitrogen in the soil is the most active in the process of soil nitrogen migration and transformation of nitrogen forms, which is difficult for soil to adsorb. Then, large amounts of nitrate nitrogen entered the water, resulting in water pollution with the rapid reproduction of algae and other plankton and decreased dissolved oxygen in water, which clarified that nitrate nitrogen is the main cause of lake water pollution [15]. On the contrary, ammonium nitrogen is adsorbed easily and more efficiently by soil because ammonium is directly used to synthesize glutamine and subsequently other amino acids as well. The study suggested that ammonium nitrogen application resulted in higher chlorophyll, starch, monosaccharide, and amino acid levels, all important crop growth parameters when compared with nitrate nitrogen fertilizer [38]. However, when 100% ammonium nitrogen is used as a nitrogen fertilizer, it leads to short roots due to plants being prevented from absorbing cations [40]. In this study, the roots of plants given 100% ammonium nitrogen fertilizer were short and root elongation was difficult both longitudinally and laterally. The root activity decreased when a small number of lateral roots developed, there were more negatively charged suspended soil particles, and root activity decreased with the generated rainfall runoff [41].
Nitrogen-form fertilizer application is an important measure taken to facilitate plant growth and increase crop yield when the fertilizer is added to the soil layer [8,9]. Many studies clarified have focused on crops’ absorption and utilization of nitrogen forms (nitrate and ammonium) and their effects on tobacco plant growth [26,42]. However, the unreasonable and continuous input of nitrogen-form fertilizer leads to the loss of nitrogen nutrients from farmland, releases a large amount of surplus nitrogen pollutants to the environment, and increases the risk of eutrophication in water bodies. Thus, nitrogen loss in water is one of the key factors causing the eutrophication of lake water, which is urgent and of great significance to effectively prevent and reduce agricultural non-point source pollution from farmland and protect water resources and ecological security [43]. In this study, results from two experimental sites suggested that the loss of total nitrogen, nitrate nitrogen, and ammonium nitrogen in surface runoff and infiltration was significant when different forms of nitrogen fertilizer were added to the soil layer. That is, the nitrogen loss in water in the 50–50% nitrate–ammonium nitrogen fertilizer treatment was lower, which may contribute to reducing agricultural non-point source pollution and providing a basis for fertilizer management in the watershed. In this study, nitrate–ammonium nitrogen fertilizer not only guaranteed the nitrate nitrogen active degree but also guaranteed fertilizer adsorption. Thus, the root length density, root surface area, and spatial distribution was beneficial to root elongation both longitudinally and laterally. Pan’s result suggested that nitrate–ammonium nitrogen fertilizer promoted root growth and development, and improved fertilizer utilization efficiency [20]. The improvement of fertilizer use efficiency further reduced the amount of ammonium and nitrate nitrogen entering river and lake drainage areas through rainwater and decreased the risk of eutrophication in lake basins [6].

5. Conclusions

This study suggested that the 50–50% nitrate–ammonium nitrogen fertilizer treatment had a smaller nitrogen loss than the 100% nitrate nitrogen fertilizer treatment and the 100% ammonium nitrogen fertilizer treatment, which contributed significantly to reducing agricultural non-point source pollution. An important reason is that flue-cured tobacco roots (root length density, root surface area, and spatial distribution) play an important role in the regulation of nitrogen loss with the roots in the 50–50% nitrate–ammonium nitrogen fertilizer treatment being the most developed. The root systems in the 50–50% nitrate–ammonium nitrogen fertilizer treatment was widely distributed in the different soil layers, maximizing the use of soil nutrients and reducing the entry of soil nitrogen nutrients into lake basins. The findings demonstrated that nitrogen form affected nitrogen loss by regulating growth of root morphology in the tobacco fields, which provides a theoretical basis for the prevention and control of agricultural non-point source pollution. Future studies can further improve this study by enhancing the agricultural non-point source pollution into similar fertilizer application management practices.

Author Contributions

C.O. and Z.Z. conceived and designed the experiments. K.Y. performed the experiments and analyzed the data and performed the analysis. K.Y. and C.O. wrote and revised the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Program for the Key Research and Development Program of Yunnan, China (No. 202202AE090034), National Key R&D Program Projects (No. 2022YFD1901504), Basic Application Research Project of Yunnan Province, China (No. 2019YD096).

Data Availability Statement

Data is the authors’ own original work, which has not been previously published elsewhere and has no conflict of interest. Data will be made available upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Tan, C.; Ma, M.; Kuang, H. Spatial-temporal characteristics and climatic responses of water level fluctuations of global major lakes from 2002 to 2010. Remote Sens. 2017, 9, 150. [Google Scholar] [CrossRef]
  2. Yang, C.-H.; Yang, P.; Geng, J.; Yin, H.-B.; Chen, K. Sediment internal nutrient loading in the most polluted area of a shallow eutrophic lake (Lake Chaohu; China) and its contribution to lake eutrophication. Environ. Pollut. 2020, 262, 114292. [Google Scholar] [CrossRef] [PubMed]
  3. Hou, P.; Jiang, Y.; Yan, L.; Petropoulos, E.; Chen, D.-L. Effect of fertilization on nitrogen losses through surface runoffs in Chinese farmlands: A meta-analysis. Sci. Total Environ. 2021, 793, 148554. [Google Scholar] [CrossRef] [PubMed]
  4. Husain, A.; Muneer, M.-A.; Fan, W.; Yin, G.-F.; Shen, S.-Z.; Wang, F.; Li, Y.; Zhang, K.-Q. Application of optimum n through different fertilizers alleviate NH4+-N, NO3−N and total nitrogen losses in the surface runoff and leached water and improve nitrogen use efficiency of rice crop in Erhai Lake Basin; China. Commun. Soil Sci. Plant Anal. 2019, 50, 716–738. [Google Scholar] [CrossRef]
  5. Barcellos, D.; Queiroz, H.-M.; Nóbrega, G.-N.; de Oliveira Filho, L.-R.; Santaella, S.-T.; Otero, X.-L.; Ferreira, T.-O. Phosphorus enriched effluents increase eutrophication risks for mangrove systems in northeastern Brazil. Mar. Pollut. Bull. 2019, 142, 58–63. [Google Scholar] [CrossRef]
  6. Liu, X.; Zhang, G.; Sun, G.; Wu, Y.; Chen, Y. Assessment of lake water quality and eutrophication risk in an agricultural irrigation area: A case study of the Chagan Lake in northeast China. Water 2019, 11, 2380. [Google Scholar] [CrossRef]
  7. Tang, X.; Li, R.; Han, D.; Scholz, M. Response of eutrophication development to variations in nutrients and hydrological regime: A case study in the Changjiang River (Yangtze) Basin. Water 2020, 12, 1634. [Google Scholar] [CrossRef]
  8. Zhang, X.-C.; Razavi, B.; Liu, J.-X.; Wang, G.; Zhang, X.-C.; Li, Z.-Y.; Zhai, B.-N.; Wang, Z.-H.; Zamanian, K. Croplands conversion to cash crops in dry regions: Consequences of nitrogen losses and decreasing nitrogen use efficiency for the food chain system. Land Degrad. Dev. 2021, 32, 1103–1113. [Google Scholar] [CrossRef]
  9. Diao, Y.; Li, H.; Jiang, H.; Li, H. Effects of changing fertilization since the 1980s on nitrogen runoff and leaching in rice–wheat rotation systems; Taihu Lake Basin. Water 2020, 12, 886. [Google Scholar] [CrossRef]
  10. Cai, A.; Xu, M.; Wang, B.; Zhang, W.; Liang, G.; Hou, E.; Luo, Y. Manure acts as a better fertilizer for increasing crop yields than synthetic fertilizer does by improving soil fertility. Soil Till. Res. 2019, 189, 168–175. [Google Scholar] [CrossRef]
  11. Lu, Y.-X.; Li, C.-J.; Zhang, F.-S. Transpiration, potassium uptake and flow in tobacco as affected by nitrogen forms and nutrient levels. Ann. Bot. 2005, 95, 991–998. [Google Scholar] [CrossRef] [PubMed]
  12. Li, W.-H.; Cheng, X.-J.; Yu, Z.; Cheng, G.-L.; Zhao, L.-W. Response of non-point source pollution to landscape pattern: A case study in mountain-rural region, China. Environ. Sci. Pollut. Res. 2021, 28, 16602–16615. [Google Scholar] [CrossRef] [PubMed]
  13. Zhao, L.-S.; Hou, R.; Wu, F.-Q.; Keesstra, S. Effect of soil surface roughness on infiltration water; ponding and runoff on tilled soils under rainfall simulation experiments. Soil Till. Res. 2018, 179, 47–53. [Google Scholar] [CrossRef]
  14. Xue, L.; Hou, P.; Zhang, Z.; Shen, M.; Yang, L. Application of systematic strategy for agricultural non-point source pollution control in Yangtze River basin; China. Agric. Ecosyst. Environ. 2020, 304, 107148. [Google Scholar] [CrossRef]
  15. Monchamp, M.-E.; Pick, F.-R.; Beisner, B.-E.; Maranger, R. Nitrogen forms influence microcystin concentration and composition via changes in cyanobacterial community structure. PLoS ONE 2014, 9, e85573. [Google Scholar] [CrossRef]
  16. Ying, J.; Li, X.; Wang, N.; Lan, Z.; He, J.; Bai, Y. Contrasting effects of nitrogen forms and soil pH on ammonia oxidizing microorganisms and their responses to long-term nitrogen fertilization in a typical steppe ecosystem. Soil Biol. Biochem. 2017, 107, 10–18. [Google Scholar] [CrossRef]
  17. Ranjan, R.; Yadav, R. Genetics of root traits influencing nitrogen use efficiency under varied nitrogen level in spring wheat (Triticum aestivum L.). Cereal Res. Commun. 2022, 50, 755–765. [Google Scholar] [CrossRef]
  18. Martínez-Dalmau, J.; Berbel, J.; Ordóñez-Fernández, R. Nitrogen fertilization. A review of the risks associated with the inefficiency of its use and policy responses. Sustainability 2021, 13, 5625. [Google Scholar] [CrossRef]
  19. Elsalam, H.-E.-A.; Sharnouby, M.-E.-E.; Mohamed, A.-E.; Raafat, B.-M.; El-Gamal, E.-H. Effect of sewage sludge compost usage on corn and faba bean growth; carbon and nitrogen forms in plants and soil. Agronomy 2021, 11, 628. [Google Scholar] [CrossRef]
  20. Pan, S.-G.; Liu, H.-D.; Mo, Z.-W.; Bob, P.; Duan, M.-Y.; Tian, H.; Hu, S.-J.; Tang, X.-R. Corrigendum: Effects of nitrogen and shading on root morphologies; nutrient accumulation; and photosynthetic parameters in different rice genotypes. Sci. Rep. 2017, 7, 45611. [Google Scholar] [CrossRef]
  21. Chen, J.-T.; Li, J.-H.; Li, W.-F.; Li, P.; Zhu, R.; Zhong, Y.-X.; Zhang, W.-F.; Li, T.-Y. The optimal ammonium-nitrate ratio for various crops: A Meta-analysis. Field Crops Res. 2024, 307, 109240. [Google Scholar] [CrossRef]
  22. Kurt, D.; Kinay, A. Effects of irrigation; nitrogen forms and topping on sun cured tobacco. Ind. Crops Prod. 2021, 162, 113276. [Google Scholar] [CrossRef]
  23. Thorup-Kristensen, K.; Dresbøll, D.-B.; Kristensen, H.-L. Crop yield; root growth; and nutrient dynamics in a conventional and three organic cropping systems with different levels of external inputs and N recycling through fertility building crops. Eur. J. Agron. 2012, 37, 66–82. [Google Scholar] [CrossRef]
  24. Kakar, K.-U.; Nawaz, Z.; Cui, Z.-Q.; Ahemd, N.; Ren, X.-L. Molecular breeding approaches for production of disease-resilient commercially important tobacco. Brief. Funct. Genom. 2020, 19, 10–25. [Google Scholar] [CrossRef] [PubMed]
  25. Zia, A.; Berg, L.D.; Riaz, M.; Arif, M.; Ahsmore, M. Nitrogen induced DOC and heavy metals leaching: Effects of nitrogen forms; deposition loads and liming. Environ. Pollut. 2020, 265 Pt B, 114981. [Google Scholar] [CrossRef]
  26. Suyala, Q.; Liguo, J.; Qin, Y.-L.; Chen, Y.; Fan, M.-S. Effects of different nitrogen forms on potato growth and development. J. Plant Nutr. 2017, 40, 1651–1659. [Google Scholar]
  27. Xu, Y.; Huang, G. A Risk-Based interval two-stage programming model for agricultural system management under uncertainty. Math. Probl. Eng. 2016, 7438913, 1–13. [Google Scholar] [CrossRef]
  28. Chen, X.; Mao, A.; Alice, Z.; Zhang, Y.; Chang, L.; Gao, J.; Thompson, H.-J.; Michael, L. Carbon and nitrogen forms in soil organic matter influenced by incorporated wheat and corn residues. Soil Sci. Plant Nutr. 2017, 63, 377–387. [Google Scholar] [CrossRef]
  29. Hachiya, T.; Sakakibara, H. Interactions between nitrate and ammonium in their uptake, allocation, assimilation, and signaling in plants. J. Exp. Bot. 2017, 68, 2501–2512. [Google Scholar] [CrossRef]
  30. Bisseling, T.; Scheres, B. Nutrient computation for root architecture. Science 2014, 346, 300–301. [Google Scholar] [CrossRef]
  31. Li, K.; Guo, Y.; Liu, C.; Lu, X.; Liao, H. Effects of different NH4+/NO3 ratios on soybean growth, nodulation and biological N fixation. Chinese. J. Oil Crop Sci. 2014, 36, 349–356. [Google Scholar]
  32. Cesco, S.; Mimmo, T.; Tonon, G.; Tomasi, N.; Pinton, R.; Terzano, R.; Neumann, G.; Weisskopf, L.; Renella, G.; Landi, L.; et al. Plant-borne flavonoids released into the rhizosphere: Impact on soil bio-activities related to plant nutrition. A review. Biol. Fertil. Soils. 2012, 48, 123–149. [Google Scholar] [CrossRef]
  33. Ashraf, M.; Shahzad, S.M.; Imtiaz, M.; Rizwan, M.-S. Salinity effects on nitrogen metabolism in plants—Focusing on the activities of nitrogen metabolizing enzymes: A review. J. Plant Nutr. 2018, 41, 1065–1081. [Google Scholar] [CrossRef]
  34. Urban, A.; Rogowski, P.; Wasilewska-Dębowska, W.; Romanowska, E. Understanding maize response to nitrogen limitation in different light conditions for the improvement of photosynthesis. Plants 2021, 10, 1932. [Google Scholar] [CrossRef]
  35. Bhambri, A.; Karn, S.-K. Biotechnique for nitrogen and phosphorus removal: A possible insight. Chem. Ecol. 2020, 36, 785–809. [Google Scholar] [CrossRef]
  36. Xia, Y.; Zhang, M.; Tsang, D.C.W.; Geng, N.; Lu, D.; Zhu, L.; Igalavithana, A.D.; Dissanayake, P.D.; Rinklebe, J.; Yang, X.; et al. Recent advances in control technologies for non-point source pollution with nitrogen and phosphorous from agricultural runoff: Current practices and future prospects. Appl. Biol. Chem. 2020, 63, 8. [Google Scholar] [CrossRef]
  37. Xu, G.; Jiang, M.; Lu, D.; Wang, H.; Chen, M. Nitrogen forms affect the root characteristic; photosynthesis; grain yield; and nitrogen use efficiency of rice under different irrigation regimes. Crop Sci. 2020, 60, 2594–2610. [Google Scholar] [CrossRef]
  38. Beeckman, F.; Motte, H.; Beeckman, T. Nitrification in agricultural soils: Impact, actors and mitigation. Curr. Opin. Biotech. 2018, 50, 166–173. [Google Scholar] [CrossRef]
  39. Schortemeyer, M.; Feil, B.; Stamp, P. Root morphology and nitrogen uptake of maize simultaneously supplied with ammonium and nitrate in a split-root system. Ann. Bot. 1993, 72, 107–115. [Google Scholar] [CrossRef]
  40. Wang, J.-F.; Zhu, C.-Y.; Weng, B.-S.; Mo, P.-W.; Xu, Z.-J.; Ping, T.; Cui, B.-S.; Bai, J.-H. Regulation of heavy metals accumulated by Acorus calamus L. in constructed wetland through different nitrogen forms. Chemosphere 2021, 281, 130773. [Google Scholar] [CrossRef]
  41. Wang, J.-L.; Fu, Z.-S.; Chen, G.-F.; Zou, G.-Y.; Song, X.-F.; Liu, F.-X. Runoff nitrogen (N) losses and related metabolism enzyme activities in paddy field under different nitrogen fertilizer levels. Environ. Sci. Rollut. Res. 2018, 25, 27583–27593. [Google Scholar] [CrossRef] [PubMed]
  42. Kamel, H.; Khawla, I.; Selma, F.; Tarek, S.; Chedly, A.; Kadambot, S.; Cristina, C. Interactive effects of salinity and nitrogen forms on plant growth; photosynthesis and osmotic adjustment in maize. Plant Physiol. Biochem. 2019, 139, 171–178. [Google Scholar]
  43. Bergstrom, A.-K.; Jansson, M. Atmospheric nitrogen deposition has caused nitrogen enrichment and eutrophication of lakes in the northern hemisphere. Global Chang. Biol. 2006, 12, 635–643. [Google Scholar] [CrossRef]
Agronomy 14 02532 g001
Figure 1. Schematic of the devices used to collect surface runoff and infiltration.
Figure 1. Schematic of the devices used to collect surface runoff and infiltration.
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Figure 2. Meteorological data from the two experimental sites.
Figure 2. Meteorological data from the two experimental sites.
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Figure 3. Characteristics of nitrogen nutrient loss of runoff under different nitrogen form conditions. Different small letters indicate significant differences among treatments at p < 0.05; LSD test by one-way ANOVA.
Figure 3. Characteristics of nitrogen nutrient loss of runoff under different nitrogen form conditions. Different small letters indicate significant differences among treatments at p < 0.05; LSD test by one-way ANOVA.
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Figure 4. Characteristics of nitrogen nutrient loss of infiltration given different nitrogen forms. Different small letters indicate significant differences among treatments at p < 0.05; LSD test by one-way ANOVA.
Figure 4. Characteristics of nitrogen nutrient loss of infiltration given different nitrogen forms. Different small letters indicate significant differences among treatments at p < 0.05; LSD test by one-way ANOVA.
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Figure 5. Characteristics of root spatial distribution of flue-cured tobacco given different nitrogen forms.
Figure 5. Characteristics of root spatial distribution of flue-cured tobacco given different nitrogen forms.
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Figure 6. Relationship among fertilizer nitrogen forms, root, and nitrogen and phosphorus loss in the two field experiments.
Figure 6. Relationship among fertilizer nitrogen forms, root, and nitrogen and phosphorus loss in the two field experiments.
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Table 1. Characteristics of root surface area of flue-cured tobacco given different nitrogen forms.
Table 1. Characteristics of root surface area of flue-cured tobacco given different nitrogen forms.
Experimental SiteTreatmentsVertical Distance (cm)Horizontal Distance (cm)
0−20 cm 20−40 cm40−60 cm0−10 cm10−20 cm20−30 cm
Mile CountyT1601.79 ± 20.24 b309.27 ± 13.29 b381.93 ± 36.21 a293.38 ± 23.13 a708.5 ± 62.11 bc291.1 ± 19.20 a
T2637.22 ± 11.89 a342.41 ± 20.76 a333.59 ± 20.28 b300.05 ± 31.11 a725.63 ± 27.66 b286.54 ± 23.28 a
T3642.76 ± 20.11 a356.06 ± 26.98 b315.33 ± 30.19 b247.61 ± 27.00 b764.95 ± 33.29 a301.59 ± 17.55 a
T4604.29 ± 10.59 b306.08 ± 18.36 c303.29 ± 29.10 b159.27 ± 16.14 c649.12 ± 49.01 c325.27 ± 18.02 a
T5569.41 ± 30.41 c254.87 ± 30.23 d301.29 ± 19.28 b185.32 ± 12.18 c641.09 ± 38.44 c299.06 ± 20.00 a
Chengjiang CountyT1586.71 ± 18.20 b321.58 ± 21.48 a166.27 ± 10.15 b143.21 ± 17.77 a812.36 ± 12.09 b139.62 ± 12.98 b
T2607.34 ± 32.17 ab333.17 ± 19.00 a217.87 ± 17.00 a156.44 ± 13.00 a837.25 ± 19.00 a165.23 ± 15.00 a
T3621.00 ± 28.29 a346.57 ± 23.33 a174.20 ± 27.19 b163.87 ± 10.38 a840.76 ± 16.44 a167.14 ± 12.87 a
T4589.91 ± 20.17 b308.33 ± 15.29 b220.73 ± 20.19 a149.64 ± 12.67 a822.90 ± 16.20 ab146.32 ± 14.23 b
T5663.14 ± 30.10 a299.31 ± 19.20 b111.31 ± 15.25 c137.41 ± 11.19 b795.43 ± 10.99 b141.10 ± 11.11 b
Values represent means ± standard errors. Different lower-case letters indicate significant differences at p < 0.05 (LSD).
Table 2. Characteristics of agronomic traits of flue-cured tobacco given different nitrogen forms.
Table 2. Characteristics of agronomic traits of flue-cured tobacco given different nitrogen forms.
TreatmentsBiomass (g plant−1)
RootsStemsLeaves
Mile County Chengjiang County Mile County Chengjiang CountyMile County Chengjiang County
T193.15 ± 6.00 b99.90 ± 5.76 ab87.30 ± 5.89 b93.15 ± 5.21 ab204.00 ± 12.88 b205.50 ± 6.55 ab
T297.65 ± 6.02 b105.75 ± 7.77 a105.30 ± 7.00 a100.80 ± 7.00 a205.50 ± 9.21 b201.50 ± 7.08 ab
T3106.65 ± 11.28 a107.10 ± 8.32 a97.20 ± 6.54 ab103.50 ± 5.30 a238.00 ± 10.09 a212.50 ± 6.32 a
T4110.70 ± 9.02 a96.30 ± 4.20 ab94.05 ± 5.30 ab94.95 ± 3.02 ab184.00 ± 8.21 c200.50 ± 10.21 ab
T596.30 ± 5.98 b94.50 ± 5.29 b90.90 ± 6.42 b90.45 ± 4.98 b203.50 ± 14.90 b199.50 ± 5.08 b
Values represent means ± standard errors. Different lower-case letters indicate significant differences at p < 0.05 (LSD).
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Ouyang, C.; Yang, K.; Zhao, Z. Application of Nitrate–Ammonium Nitrogen Fertilization Reduced Nitrogen Loss in Surface Runoff and Infiltration by Improving Root Morphology of Flue-Cured Tobacco. Agronomy 2024, 14, 2532. https://doi.org/10.3390/agronomy14112532

AMA Style

Ouyang C, Yang K, Zhao Z. Application of Nitrate–Ammonium Nitrogen Fertilization Reduced Nitrogen Loss in Surface Runoff and Infiltration by Improving Root Morphology of Flue-Cured Tobacco. Agronomy. 2024; 14(11):2532. https://doi.org/10.3390/agronomy14112532

Chicago/Turabian Style

Ouyang, Chengren, Kang Yang, and Zhengxiong Zhao. 2024. "Application of Nitrate–Ammonium Nitrogen Fertilization Reduced Nitrogen Loss in Surface Runoff and Infiltration by Improving Root Morphology of Flue-Cured Tobacco" Agronomy 14, no. 11: 2532. https://doi.org/10.3390/agronomy14112532

APA Style

Ouyang, C., Yang, K., & Zhao, Z. (2024). Application of Nitrate–Ammonium Nitrogen Fertilization Reduced Nitrogen Loss in Surface Runoff and Infiltration by Improving Root Morphology of Flue-Cured Tobacco. Agronomy, 14(11), 2532. https://doi.org/10.3390/agronomy14112532

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