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Article

Effect of Combined Application of Chicken Manure and Inorganic Nitrogen Fertilizer on Yield and Quality of Cherry Tomato

by
Yang Tao
1,†,
Tuo Liu
1,†,
Jianyu Wu
1,
Zhuangsheng Wu
2,
Daolong Liao
2,
Farooq Shah
3 and
Wei Wu
1,*
1
College of Tropical Crops, Hainan University, Haikou 570228, China
2
Vegetable Research Institute, Hainan Academy of Agricultural Sciences, Haikou 570228, China
3
Department of Agronomy, Garden Campus, Abdul Wali Khan University Mardan, Mardan 23200, Pakistan
*
Author to whom correspondence should be addressed.
†
Yang Tao and Tuo Liu contributed equally to the paper.
Agronomy 2022, 12(7), 1574; https://doi.org/10.3390/agronomy12071574
Submission received: 4 June 2022 / Revised: 22 June 2022 / Accepted: 28 June 2022 / Published: 29 June 2022
(This article belongs to the Section Horticultural and Floricultural Crops)
Browse Figures
Figure 1
<p>Daily precipitation and mean air temperature during cherry tomato growth seasons in 2020–2021 (<b>A</b>) and 2021–2022 (<b>B</b>).</p> "> Figure 2
<p>The comparisons of plant height (<b>A</b>,<b>B</b>), stem diameter (<b>C</b>,<b>D</b>) and leaves number (<b>E</b>,<b>F</b>) of cherry tomato between the three N rates (0, 160 and 320 kg N ha<sup>−1</sup>) and two different chicken manure rates (0 and 40 t N ha<sup>−1</sup>) during the 2021–2022 growth season. Vertical bars above mean values indicate standard error. Means with different lower-case letters show significant differences between six combination treatments among the three N application rates under and the two chicken manure doses according to the least significant difference method (LSD<sub>0.05</sub>).</p> "> Figure 3
<p>The comparisons of ascorbic acid (<b>A</b>), soluble solid (<b>B</b>), soluble protein (<b>C</b>), soluble sugar (<b>D</b>), titratable acid (<b>E</b>), and sugar-acid ratio (<b>F</b>) of cherry tomato between the three N rates (0, 160 and 320 kg N ha<sup>−1</sup>) and under the two chicken manure rates during the 2021–2022 growth season. Vertical bars above the mean values indicate standard error. Means with different lower-case letters show significant differences between six combination treatments among the three N application rates under and the two chicken manure doses according to the least significant difference method (LSD<sub>0.05</sub>). Means with different capital alphabetical letters show significant differences between the two chicken manure rates according to the least significant difference method (LSD<sub>0.05</sub>).</p> "> Figure 4
<p>The Pearson’s correlation coefficients for fruit yield, single fruit weight, fruit number, shoot dry matter, plant height, stem diameter, leaves number, ascorbic acid content, soluble solid content, soluble protein content, soluble sugar content, and titratable acid content. The color gradient is proportional to the Pearson’s correlation coefficient. Red and blue color denote positive and negative correlations, respectively.</p> ">
Versions Notes

Abstract

:
Unreasonable application of inorganic nitrogen (N) fertilizer on cherry tomatoes (Solanum lycopersicum var. cerasiforme) has resulted in serious environmental threats. The advantages of application of organic manure combined with inorganic N fertilizer for vegetable production systems have been reported widely, but there are still few studies on cherry tomato production. Therefore, this study aims to determine the impact of a combined application of organic manure (in form of chicken manure at different application rate of 0 and 40 t ha−1) with inorganic N fertilizer (in form of urea at various N application rates of 0, 160 and 320 kg N ha−1) on the fruit yield and quality of cherry tomato across two seasons. Results showed that inorganic N application exhibited positive effects on fruit yield and its associated components of cherry tomato. However, there was no significant difference in terms of fruit yield and its associated components between the two N rates of inorganic N (160 and 320 kg N ha−1), indicating that fruit yield is not improved significantly when the N application rate exceeds some threshold. Under chicken manure application treatments, however, an increased N rate did not show a positive effect on fruit yield. Importantly, chicken manure application has greatly increased fruit yield and fruit quality (represented by membership function indicator) by 43% and 23%, respectively in comparison with zero manure application. In particular, the soluble protein and titratable acid were increased by 124% and 118%, respectively. Overall, these results suggested that chemical N fertilizers could be largely replaced with chicken manure. Furthermore, the combined application of organic with inorganic N fertilizers seems to be a promising management practice for reducing the reliance on use of inorganic N fertilizer, while mitigating the environmental burden for cherry tomato production.

1. Introduction

China is the largest producer and consumer of vegetables in the world, with a planting area of ~2.4 × 107 ha1 and annual output of ~5.5 × 108 t, which accounted for 42% and 51% of the world’s planting area and production in 2018, respectively [1]. Because of the shallow root system and the subsequent weaker nutrient uptake capacity of most vegetables, their dependency on the applied inputs is comparatively high and thus they are generally categorized as high-input requiring crops [2]. Judicious management of inorganic N fertilizer is needed for guaranteeing higher yield and quality of vegetables. However, many vegetable farmers recently apply an extremely high dose of inorganic N fertilizer to achieve maximum production. As a result, the existing average inorganic N application rate 388 kg N ha−1 in China is 2.4 times greater than the USA [3]. Such an excessive N rate when coupled with a relatively shorter growth period and excessive irrigation, is expected to reduce N use efficiency (NUE) and greater N loss, which will deteriorate the environment [4,5]. Therefore, identifying an alternate fertilizer application technique that reduces loss of N while ensuring high yield of vegetables is required in northern China [6].
To cope with the environmental hazards posed by non-judicious application of inorganic N fertilizer, a policy of “zero growth of inorganic fertilizer by 2020” has been introduced by the Chinese Ministry of Agriculture in 2015 [7,8,9]. This strategy emphasizes the importance of practically implementing improved inorganic N fertilizer management techniques in the fields, including the replacing organic manure for inorganic N fertilizer [8,9]. So far, extensive research has been carried out to assess the role of organic manures in combination with inorganic N fertilizers on crop productivity and the results suggest that crop productivity can be sustained or even improved in comparison with sole application of inorganic N fertilizer [10,11,12]. In addition, previous studies also have shown that partially substituting inorganic N fertilizer with livestock manures tended to decrease total reactive N losses [8,13]. Nowadays, producing high quality vegetables is becoming a desired goal along with the rising standard of living. A previous study on eggplant (Solanum melongena L.) has shown that application of organic manure also can improve vegetable quality [14]. Hence, it is hypothesized that combined applications of livestock manures with inorganic N fertilizers in agroecosystems can improve crop productivity and quality and reduce reactive N pollution than the sole addition of inorganic N fertilizer.
Cherry tomato (Solanum lycopersicum var. cerasiforme) is one of the common vegetables that are widely grown in China, particularly in Hainan and Guangxi provinces [1,15]. The ripe tomato fruit is full of fiber, and contains all four major carotenoids: α-and β-carotene, lutein, and lycopene along with several vitamins [16], that help to protect against heart diseases and support the human immune system [17,18,19]. Currently, an extremely high amount of inorganic N reaching 410 kg N ha−1 is applied locally that is 53.5% higher than the optimum dose [1]. Such a non-judicious application of inorganic N has not only lowered the resource use efficiency in many cropping systems, but has also added to the environmental threats [1]. The advantages of application of organic manure combined with inorganic N fertilizer for vegetable production systems are extensively reported in many studies [20,21,22]. However, few studies have been conducted focused on tomato production. Thus, whether combined application of organic manure with inorganic N fertilizer can sustain or improve fruit yield of tomato yet remains to be further explored. In addition, up till now, the main focus of research was either crop productivity or loss of the reactive N rather than the nutritional quality [9,23,24,25]. Such an objective is acceptable for the major cereals (i.e., rice, wheat and maize), but, as far as vegetable are concerned, especially for cherry tomato, a nutrient-rich food, it can be argued that the food quality is as important as the caloric supply [26]. Therefore, whether combined application of organic manure with inorganic N fertilizer can synergistically regulate the yield and quality of cherry tomatoes in the cropping system warrants being unleashed.
Here, we hypothesized that combining organic manure with inorganic N fertilizer may not only increase cherry tomato yield, but also ensure good fruit quality. Therefore, a two-season field trial involving different rates of chicken manure and inorganic N fertilizer was conducted to: (a) assess the effect of inorganic N on cherry tomato plant growth, yield and quality under the plot with or without chicken manure application, respectively; (b) analyze the mechanism of interaction between organic manure and inorganic N fertilizer and its effect on cherry tomato cropping system.

2. Materials and Methods

2.1. Experimental Site

Two-year field experiments were carried out in two cropping seasons from 2020–2022 at Ledong Experimental Station of Hainan University (109°17′ E, 18°74′ N), Hainan Province, a tropical island in China. The daily precipitation and mean temperature during the growth seasons in situ, obtained from a local weather station (Hengxing Technology Co. Ltd., Handan, China) installed near the experimental field, are presented in Figure 1. No extreme climate event was observed during the experimental period. Soil samples were taken from 0–20 cm depth and soil chemical characteristics were evaluated before starting the trials, as follows, pH: 6.04; soil organic matter: 17.14 g kg−1; total N content: 0.075 g kg−1; total P content: 5.67 g kg−1; available N: 11.71 mg kg−1; and Olsen-P: 48.95 mg kg−1.

2.2. Field Trials

The field trials were conducted in a split–plot arrangement with four replications. The main plot was assigned with two different organic fertilizers (chicken manure) rates, including 0 and 40 t ha−1. The sub-plot consisted of three different N application rates, including 0, 160, and 320 kg N ha−1. The experiment comprised 24 plots in total, and the area of each plot was 12.0 m2 (4.0 m long by 3.0 m wide). A commercial hybrid of cherry tomato, namely Qianxi, was tested in this study. Chicken manure was collected from a local farm, which contained 348.86 g kg−1, 10.61 mg kg−1, and 236.74 mg kg−1 of organic matter, available N and Olsen-P, respectively. Seedlings at the age of 4 weeks were transplanted in each plot on 24 October 2020 and 6 November 2021, and harvested on 26 January 2021 and 19 February 2022 during the two experimental years, respectively. The row and plant spacings were both 1 m in each plot, which included 12 plants. Chicken manure was applied as basal. Fertilizer-N (urea) was split-applied every 2 weeks after seedling transplanting with a splitting-pattern of 2:2:2:2:2. A basal dose of phosphate (225 kg ha−1 P2O5) and potassium (280 kg ha−1 K2O) was broadcasted and incorporated one day before ploughing at seedling transplantation. The rest of the farming practices were performed according to the cropping practices of the region. Pruning was done artificially to make sure that each plant has four main branches. Diseases and insects were intensively controlled by chemicals (thiophanate methyl and imidacloprid) to avoid biomass and yield losses.

2.3. Measurements and Data Analysis

2.3.1. Soil Physicochemical Measurements

The pH of the topsoil (1:1 soil/water, w/w) was determined directly after shaking for 1 h using a digital pH meter (STEH-200N, Shanghai, China). Soil organic matter content was determined using the potassium dichromate volumetric and the oil bath heating method. Olsen P was determined using the sodium bicarbonate extraction method. Available N (NH4+ and NO3–) were extracted with a 1 M KCl solution. The Olsen P and available N were measured using an automatic discrete analyzer (DeChem-Tech, Hamburg, Germany). Prior to the measurement of total N and P, the soil samples were digested with 5 mL H2SO4 and extracted with ultra-pure water.

2.3.2. Yield Performance and Morphological Parameters

On the harvest period, five plants from each plot were selected and the ripe fruits (with full red color) were manually sampled to record the fruit yield and the associated yield components, i.e., fruits number (no m−2) and single fruit fresh weight (g). Then, three plants were chosen from each plot, and then the stem and leaves were separated subsequently. The samples were heated up to 105 °C for 1 h, and then dried to a constant weight at 75 °C for 48 h and their shoot dry weights were recorded.
At the fruit setting (10 December 2021) and full bearing stages (2 January 2022) of the second growth season (2021–2022), three plants were randomly chosen in each plot for determining their morphological parameters, including plant height, diameter of basal stem and leaves number. Plant height was recorded as the distance between the soil surface and top of the main stem. The basal stem diameter was measured by a digital caliper (Meinaite, Chengdu, China). The number of leaves was counted manually and unexpanded leaves were not included.

2.3.3. Quality Traits Assessment

The quality traits of tomato were only evaluated in the second season (2021–2022). During the harvest period, fifty cherry tomato fruits with full red color were sampled randomly from each plot. Then, the sample was pulverized and homogenized into the juices for further determination of fruit quality. The corresponding assay methods are described as follows. The ascorbic acid (AsA) was assessed using the standard technique devised by the Association of the Official Analytical Chemists (AOAC, Rockville, MD, USA) [27]. Briefly, 10.0 g tomato puree was mixed with 4% oxalic acid solution, squeezed through a muslin cloth, and the volume was made up to 50 mL. AsA content was determined after titration of a known amount of the extract against 2,6-dichlorophenol indophenol and measured as mg of AsA equivalent per 100 g of fruit fresh mass using a standard curve.
The method of total soluble solid (TSS) was in accordance with Mamatha et al. (2014) [28]. A handheld refractometer (Atago, Tokyo, Japan) with a range of 0.0–32.0° Brix and a resolution of 0.2° Brix was used to determine TSS, by placing 1–2 drops of clear juice on the prism. For each sample, the prism of the refractometer was dried after washing it with distilled water. Standardization of the refractometer was performed against distilled water for each measurement.
The soluble protein (SP) was measured by the Coomassie Brilliant Blue G-250 (CBB) method as previously described by Bradford et al. (1976) [29]. Briefly, 2.0 g cherry tomato homogenate was weighed and centrifuged at 5000× g for 20 min. Then, 5 mL Coombe Bright blue G-250 solution was added into the supernatant, and the protein content was recorded at a wavelength of 595 nm by a spectrophotometer.
The titratable acidity (TA) was determined using the NaOH-based titrimetric method [30]. Tomato puree with a weight of 10 g was added to distilled water, squeezed through a muslin cloth, and volume was made up to 50 mL. A known volume of the filtrate (20 mL) was titrated with 0.01 N NaOH using phenolphthalein as an indicator. The final TA was measured as percentage (%) of citric acid equivalents using the standard curve of citric acid.
The total soluble sugar was measured by an anthrone-sulfuric acid method as previously described by Zhang et al. (2017) [31]. The samples were extracted by 80% ethanol (v/v), and an anthrone reagent was added accordingly. The absorbance was measured at 620 nm by a spectrophotometer and then the total soluble sugar was recorded by using the standard curve. Sugar–acid ratio was calculated as a function of the soluble solid contents divided by total titratable acids for each sample [32].

2.3.4. Data Calculation and Statistical Analysis

The effects of different treatments on integrated fruit quality performance of cherry tomato were assessed by membership function method [33], and the related parameters were calculated as follows:
X = x − x m i n / ( x m a x − x m i n )
X = 1 − x − x m i n / ( x m a x − x m i n )
where, X and x are the membership function indicator and mean value calculated for each treatment, respectively; x m i n and x m a x denote the minimum and maximum values respectively. Equation (1) was applied if the individual quality parameter was positively correlated with the calculated membership function indicator, otherwise the Equation (2) was used, as recommended by previous studies [33]. The average membership function indicator was calculated based on all measured quality indicators, which was used as the comprehensive index for fruit quality of cherry tomato. The larger the membership function indicator, the better the overall quality parameter of cherry tomato.
The agronomic efficiency of the N applied (AEN) was selected as the NUE indicator, which was calculated as follows (3):
A E N = ( Y a − Y 0 a ) / N a
where Y 0 a and Y a are the accumulated cherry tomato fruit yields (t ha−1) in the zero N plot and N-treated plot; N a is total N fertilizer supplied under N-treated plot (kg N ha−1).
Two-way analysis of variance (ANOVA) was conducted to determine treatment effects using the SPSS statistics package (19.0, SPSS Inc., Chicago, IL, USA). Once a significant (p < 0.05) treatment effect was determined by the ANOVA, treatment mean comparisons with the conservative letter grouping were made at the 95% level of confidence according to the Least Significant Difference method (LSD0.05). Figures were prepared using Origin 9.0 (OriginLab Inc., Northampton, MA, USA). Pearson simple correlations between the measured parameters were evaluated using R software (version 4.0.0, R Core Team, Vienna, Austria).

3. Results

3.1. Fruit Yield, Yield Components, and NUE

The comparisons of the fruit yield and its associated components of cherry tomato between the three N rates and two chicken manure patterns are shown in Table 1. ANOVA results of all the traits are shown in Table S1. It was noted that the interaction between N application rates and manure application rates was significant for fruit yield and fruit number (Table S1). Under the zero chicken manure treatment, N application at the rates of both 160 and 320 kg N ha−1 exhibited a significant and positive effect on fruit yield and its associated components. For example, compared with zero N rate, N application at the rates of 160 and 320 kg N ha−1 enhanced fruit yield by 59% and 64%, respectively in the first experimental seasons; while 24% and 36% in the second season. Similarly, fruit number, single fruit weight, and shoot dry matter were found to be increased significantly, ranging from 18–111% under N application plot compared to zero N plot across both seasons. There was no significant difference in terms of fruit yield and its associated components between the two N application rates (160 and 320 kg N ha−1), although the highest N rate significantly increased fruit yield by 10% than the moderate N rate in 2021–2022 growth season.
Under chicken manure application treatment, addition of N did not exhibit any positive effect on fruit yield and its associated components (Table 1). For instance, there was no significant difference in terms of fruit number and shoot dry matter among the three N application rates (0, 160, and 320 kg N ha−1). Moreover, N applied treatments decreased fruit number by 9% and 11% compared to zero N rate when averaged across the two growth seasons. Similarly, fruit yield was significantly decreased by 8.7% and 7.6% under the highest N rate compared to zero N rate under two cropping seasons, respectively (Table 1).
Moreover, compared with the zero chicken manure treatment, application of chicken manure had a significantly positive effect on fruit yield, single fruit weight, and shoot dry matter, although there was no obvious change in fruit weight during the second growth season (2021–2022) (Table 1). AEN under the moderate N rate of 160 kg N ha−1 was increased by 59% in comparison with the highest N dose of 320 kg N ha−1 when averaged across the two growth seasons (Figure S1).

3.2. Morphological Parameters

Results of ANOVA for all morphological parameters are shown in Table S1. The interaction between N application rates and manure application rates was significant for plant height, stem diameter, and leaves number under both sampling sages. Under zero chicken manure treatment, inorganic N application exhibited a significant and positive effect on plant morphological parameters at fruit setting and full bearing periods (Figure 2). For example, N application at the rates of 160 and 320 kg N ha−1 resulted in taller plants by 23% and 33% compared to zero N rate when averaged across the two stages, respectively. Similarly, stem diameter and leaves number were found to be increased significantly, ranging from 10–33% under N application compared to zero N (Figure 2). In addition, there were significant differences in terms of morphological traits between the two N application rates (160 and 320 kg N ha−1), although the highest N rate did not markedly influence leaves number during the fruit setting period and plant height at full bearing stage (Figure 2).
Under chicken manure application, inorganic N application did not exhibit positive effect on plant morphological parameters, except for plant height and stem diameter at the full bearing period (Figure 2). For instance, during the full bearing period, height of plant and diameter of stem were increased by 6% and 16% under the highest N rate compared to zero N (Figure 2). In addition, compared with zero chicken manure treatment, applying manure chicken had no effect on plant morphological traits, although there was an obvious change in leaves number during the full bearing period (Figure 2). Nevertheless, under the zero N application rate, applying manure chicken significantly increased plant height, stem diameter, and leaves number compared with zero chicken manure treatment, under both measured stages (Figure 2).

3.3. Fruit Quality Traits

The effect of tested treatments on quality traits of cherry tomato (ascorbic acid, soluble solid, soluble protein, soluble sugar, titratable acid, and sugar-acid ratio) is illustrated in Figure 3. Under zero chicken manure treatment, there was no significant difference in terms of all fruit quality traits between the two N application rates (0 and 160 kg N ha−1). However, N application at the rate of 320 kg N ha−1 exhibited a significant and negative effect on partial quality traits such as ascorbic acid and soluble sugar, which were significantly decreased by 35% and 13% compared to zero N rate in 2021–2022, respectively (Figure 3).
Under chicken manure application condition, there was no significant difference in all fruit quality traits between the two N application rates (0 and 160 kg N ha−1) during the second growth season (2021–2022). However, N application at a rate of 320 kg N ha−1 exhibited a significant and negative effect on soluble sugar and sugar-acid ratio. For example, the highest N application rate (320 kg N ha−1) significantly decreased soluble sugar by 11% compared to zero N rate, which resulted in a lower rate of sugar-acid ratio. Conversely, compared to zero N rate, the highest N rate (320 kg N ha−1) exhibited a positive effect on soluble protein content which was significantly increased by 20% (Figure 3). In addition, compared to the zero-chicken manure treatment, application of chicken waste significantly increased the soluble protein content in the 2021–2022 growth season.

3.4. Comprehensive Evaluation of Cherry Tomato Quality under Different Fertilizer Treatments

In general, it is difficult to assess fruit quality objectively and essentially through an independent evaluation of different fruit quality parameters. Hence, the membership function method was used here to comprehensively evaluate fruit quality cherry tomato under different fertilizer treatments (Table 2). Under zero chicken manure treatment, N application at the rates of 160 and 320 kg N ha−1 both exhibited a negative effect on fruit quality (represented by the membership function indicator); especially in case of high N rate (320 kg N ha−1). For example, N application at the rate of 160 and 320 kg N ha−1 decreased membership function indicator by 3% and 73% compared to zero N rate, respectively (Table 2).
Under chicken manure application condition, the moderate N rate (160 kg N ha−1) significantly increased membership function indicator by 40% compared to zero N rate. However, N application at a rate of 320 kg N ha−1 dramatically decreased the membership function indicator by 54% and 67% compared to zero and moderate N rate, respectively. More importantly, chicken manure application treatment showed 23% higher membership function indicator than zero chicken manure treatment under the same N application rate, only except for the zero N rate.

3.5. Pearson Correlations between the Measured Parameters

The Pearson’s correlation analysis showed that fruit yield was significantly positively correlated with single fruit weight, fruit number, shoot dry matter, plant height, stem diameter, and leaves number (R = 0.64–0.86***; Figure 4); while negatively correlated with ascorbic acid content (R = −0.51*). The quality-related parameters, soluble protein content, and ascorbic acid content illustrated positive and negative correlations, respectively with leaves number, stem diameter, plant height, shoot dry matter, and single fruit weight.

4. Discussion

4.1. Fruit Yields in Resposne to N Application Rates and Chicken Manure Application

Nitrogen plays a key role in growth and development of a cherry tomato, and efficient N management is generally considered as the most important and promising strategy for realizing higher crop yields [34]. In this study, N application at the rates of both 160 and 320 kg N ha−1 exhibited a positive effect on fruit yield and significantly increased yield by more than 40% compared to zero N under zero chicken manure treatment, in both experimental seasons. Furthermore, a linear-plus-plateau or quadratic regression was the best model to predict the relationship between fruit yield and N application rate. This mainly implied that the fruit yield does not increase markedly when the inorganic N fertilizer inputs exceed some threshold (Table 1). Similar results were also reported in previous studies in radish (Raphanus sativus L.) [35,36,37], which suggested excessive application leading to a negative effect on fruit yield, through the exorbitant vegetative growth at the cost of fruit production, as well as soil acidification and soil hardening.
In case of chicken manure application treatments, however, an increased N rate did not show a positive effect on fruit yield and fruit number (Table 1). Moreover, under the zero N application rate, applying manure chicken significantly increased fruit yield and yield components compared to zero chicken manure treatment (Table 1). These results were well agreed with the finding that the interaction between N application rates and manure application rates was significant for fruit yield and fruit number. It further implies that more inorganic N rate is required for improvement of fruit yield under no manure application, while less N is demanded under chicken manure application.

4.2. Environmental Concerns of High N Application Rate and the Possibility of Chicken Manure to Replace Inorganic N Fertilizers

In general, urea is the major N form supplied as fertilizer, which can quickly and efficiently provide N for crop growth [38]. However, excessive amounts of urea applied to fields always cause large N losses into the environment through leaching, ammonia volatilization, surface runoff, or N2O emission, rather than being utilized for plant growth [39]. Thus, beyond a threshold level, adding inorganic N fertilizer does not result in higher yields, and even reduce the NUE conversely. In this study, the AEN, as a NUE indicator, was higher under moderate N rate than that under the highest N rate under zero chicken manure treatment (Figure S1), which is consistent with previous results indicating that NUE decreases with increasing N input [40]. In general, local farmers in present experimental site usually apply up to 410 kg N ha−1 to cherry tomato fields, which is 54% higher than the recommended application rate (communicated with local agricultural extension bureau). Thus, such higher doses of inorganic N in cherry tomato fields have resulted in lower NUE [40]. The existing literature suggests that a large portion of N lost to the environment is the key reason for low NUE, which ultimately results in severe pollution of air and water, especially in China where more than 95% of inorganic N fertilizers are urea and ammonium-N [2,41,42]. Thus, under ever-rising demand of vegetables due to the increasing global population, there is an urgent need for devising efficient N strategies that can guarantee higher yields and NUE and minimize the threats posed to environmental health.
It is believable that substituting chemical N fertilizer with organic manure is an environmentally friendly strategy for reducing environmental pollution while sustaining high fruit yield. Its possibility will be discussed in details below. Compared to inorganic N fertilizers, the N in chicken manure is available in organic form which is released at a slower rate to the crop than inorganic N in urea. Thus, combining organic manure with inorganic N could continuously provide plant-available N to the plant, which can effectively compensate for the inorganic N losses during the plant development process, and meet the increasing requirement of the crop for N at the peak growth period [43]. In addition, organic manure also returns essential macro-elements including P, and K, along with micronutrients including Mg, Ca, S, and Mn to the soil, thus sustaining it fertility [20]. Application of organic manure has been shown to rapidly enhance the availability of plant nutrients for uptake in many studies [44,45]. Moreover, the release of several plant hormones i.e., gibberellin and auxin etc., due to the intensive microbial activities in plant roots raised in organic manure rich fertile soil further enhances the growth and development of a crop [20]. Therefore, the chemical N fertilizers could be partially or completely replaced by organic manure to maintain high fruit yield of cherry tomato. In agreement with this argument, the sole use of chemical N fertilizers has been reported to significantly reduce the exchangeable base cations and pH in soil [20,23]. The present study further suggests that the highest fruit yield was achieved under chicken manure application regardless of N application rates, which suggested that the chemical N fertilizers could be largely replaced with chicken manure. These results implied that chicken manure could be applied to significantly reduce the reliance on use of inorganic N fertilizer, while mitigating the environmental burden for cherry tomato production.

4.3. Fruit Quality in Response to Different Fertilizer Management

In the past, yield has always remained the major focus rather than nutritional quality of fresh vegetable products [9,23,24,25]. Nowadays, producing high quality cherry tomatoes is becoming a desired goal along with the rising standard of living [46]. For cherry tomato, as a super-vegetable rich in several healthy and nutritious metabolites, its fruit quality can be regarded as more important than the caloric supply [26]. Although higher doses of inorganic N fertilizer generally lead to an increased yield, it adversely affects the quality. In the present study, applying 160 and 320 kg of N ha−1 exhibited a negative effect on membership function indicator of cherry tomato under zero chicken manure treatment (Table 2), which was also reflected by the lower content in ascorbic acid and soluble sugar (Figure 3). Bénard et al. (2009) [47] also documented a similar finding.
More importantly, this study suggested that chicken manure application have greatly increased fruit quality (represented by membership function indicator) in comparison with zero manure application. In particular, soluble protein and titratable acid content were increased markedly under chicken manure application, compared with zero manure application (Figure 3). These results indicated that application of organic manure not only can improve fruit yields but is also necessary for improving the fruit quality (Figure 4). Similar findings have been reported by previous studies for eggplant [14] and chili pepper (Capsicum spp.) [48]. In summary, combining organic fertilizer with inorganic N can synergistically regulate the fruit yield and quality of the cherry tomatoes. However, the information on the specific nutritional quality of cherry tomato grown under organic manure is still unclear and warrants further study.

5. Conclusions

The results of the present investigation demonstrated that inorganic N application exhibited positive effects on cherry tomato yield and its associated components under zero chicken manure treatment. However, there was no significant difference in terms of fruit yield and its associated components between the two N rates of inorganic N (160 and 320 kg N ha−1), indicating that fruit yield is not improved significantly when the N application rate exceeds the threshold. In case of chicken manure application treatments, however, an increased N rate did not show a positive effect on fruit yield. Chicken manure application have greatly increased fruit yield and fruit quality in comparison with zero manure application. Overall, these suggested that chemical N fertilizers could be largely replaced with chicken manure. Furthermore, the combined application of organic with inorganic N fertilizers seems to be a promising management practice for reducing the reliance on use of inorganic N fertilizer; while mitigating the environmental burden for cherry tomato production.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy12071574/s1. Figure S1: The agronomic efficiency of applied N (AEN) in the different growth stages of cherry tomato; Table S1: Analysis of variance (ANOVA) for all measured parameters across two growth seasons (Y), two chicken manure application rates (CM), and three N application rates (N) and their interactions (Y × CM, Y × N, CM × N, and Y × M × N).

Author Contributions

Conceptualization, W.W.; methodology, W.W.; software, J.W.; validation, J.W.; formal analysis, Y.T., J.W. and Z.W.; investigation, T.L., J.W., Z.W. and D.L.; resources, W.W.; data curation, Y.T., F.S. and W.W.; writing—original draft preparation, Y.T., F.S. and W.W.; writing—review and editing, Y.T. and W.W.; project administration, W.W.; and funding acquisition, W.W. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by Hainan Provincial Natural Science Foundation of China (No. 322RC575), and Scientific Research Foundation of Hainan University (No. KYQD(ZR)20018).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data are included in tables, figures, and supplementary tables.

Conflicts of Interest

The authors declare no conflict of interest.

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Agronomy 12 01574 g001 550
Figure 1. Daily precipitation and mean air temperature during cherry tomato growth seasons in 2020–2021 (A) and 2021–2022 (B).
Figure 1. Daily precipitation and mean air temperature during cherry tomato growth seasons in 2020–2021 (A) and 2021–2022 (B).
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Agronomy 12 01574 g002 550
Figure 2. The comparisons of plant height (A,B), stem diameter (C,D) and leaves number (E,F) of cherry tomato between the three N rates (0, 160 and 320 kg N ha−1) and two different chicken manure rates (0 and 40 t N ha−1) during the 2021–2022 growth season. Vertical bars above mean values indicate standard error. Means with different lower-case letters show significant differences between six combination treatments among the three N application rates under and the two chicken manure doses according to the least significant difference method (LSD0.05).
Figure 2. The comparisons of plant height (A,B), stem diameter (C,D) and leaves number (E,F) of cherry tomato between the three N rates (0, 160 and 320 kg N ha−1) and two different chicken manure rates (0 and 40 t N ha−1) during the 2021–2022 growth season. Vertical bars above mean values indicate standard error. Means with different lower-case letters show significant differences between six combination treatments among the three N application rates under and the two chicken manure doses according to the least significant difference method (LSD0.05).
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Agronomy 12 01574 g003 550
Figure 3. The comparisons of ascorbic acid (A), soluble solid (B), soluble protein (C), soluble sugar (D), titratable acid (E), and sugar-acid ratio (F) of cherry tomato between the three N rates (0, 160 and 320 kg N ha−1) and under the two chicken manure rates during the 2021–2022 growth season. Vertical bars above the mean values indicate standard error. Means with different lower-case letters show significant differences between six combination treatments among the three N application rates under and the two chicken manure doses according to the least significant difference method (LSD0.05). Means with different capital alphabetical letters show significant differences between the two chicken manure rates according to the least significant difference method (LSD0.05).
Figure 3. The comparisons of ascorbic acid (A), soluble solid (B), soluble protein (C), soluble sugar (D), titratable acid (E), and sugar-acid ratio (F) of cherry tomato between the three N rates (0, 160 and 320 kg N ha−1) and under the two chicken manure rates during the 2021–2022 growth season. Vertical bars above the mean values indicate standard error. Means with different lower-case letters show significant differences between six combination treatments among the three N application rates under and the two chicken manure doses according to the least significant difference method (LSD0.05). Means with different capital alphabetical letters show significant differences between the two chicken manure rates according to the least significant difference method (LSD0.05).
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Agronomy 12 01574 g004 550
Figure 4. The Pearson’s correlation coefficients for fruit yield, single fruit weight, fruit number, shoot dry matter, plant height, stem diameter, leaves number, ascorbic acid content, soluble solid content, soluble protein content, soluble sugar content, and titratable acid content. The color gradient is proportional to the Pearson’s correlation coefficient. Red and blue color denote positive and negative correlations, respectively.
Figure 4. The Pearson’s correlation coefficients for fruit yield, single fruit weight, fruit number, shoot dry matter, plant height, stem diameter, leaves number, ascorbic acid content, soluble solid content, soluble protein content, soluble sugar content, and titratable acid content. The color gradient is proportional to the Pearson’s correlation coefficient. Red and blue color denote positive and negative correlations, respectively.
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Table
Table 1. Fruit number, single fruit weight, shoot dry matter and fruit yield of cherry tomato under the three inorganic N rates (0, 160 and 320 kg N ha−1) and two different chicken manure rates (0 and 40 t ha−1) during the 2020–2021 and 2021–2022 growing seasons.
Table 1. Fruit number, single fruit weight, shoot dry matter and fruit yield of cherry tomato under the three inorganic N rates (0, 160 and 320 kg N ha−1) and two different chicken manure rates (0 and 40 t ha−1) during the 2020–2021 and 2021–2022 growing seasons.
Growth SeasonChicken
Manure Rate (t ha−1)		N ApplicateRate
(kg N ha−1)		Fruit Yield
(t ha−1)		Fruit Number
(No. m−2)		Single Fruit Weight
(g) 		Shoot Dry Matter
(t ha−1)
2020–20210016.33d171c10.18d2.72d
016025.99c214a12.00c4.89c
032026.70bc215a12.56bc5.76bc
Mean23.01B199A11.58B4.46B
40027.65ab211a13.65ab6.30ab
4016028.65a191b14.15a6.60ab
4032025.18c186bc14.30a7.51a
Mean27.16A196A14.04A6.80A
2021–20220013.30d79d16.21a1.88d
016016.45c102c16.87a2.30cd
032018.06a112ab17.74a2.66bc
Mean15.94B98A16.94A2.28B
40018.32a114a16.65a2.77bc
4016017.61ab104bc17.78a2.98ab
4032016.89bc102c17.54a3.37a
Mean17.60A106A17.33A3.04A
Note: Means with different lower-case letters show significant differences between six combination treatments among the three N application rates and the two chicken manure doses according to the Least Significant Difference method (LSD0.05). Means with different capital alphabetical letters show significant differences between the two chicken manure rates according to Duncan’s multiple range test (p < 0.05).
Table
Table 2. The membership function indicator of cherry tomato under the three N rates (0, 160, and 320 kg N ha−1) and under the two chicken manure rates during the 2021–2022 growth season.
Table 2. The membership function indicator of cherry tomato under the three N rates (0, 160, and 320 kg N ha−1) and under the two chicken manure rates during the 2021–2022 growth season.
Chicken Manure Rate
(t ha−1)		N Application Rate
(kg ha−1)		Soluble ProteinAscorbic AcidSoluble SugarTitratable AcidSugar-Acid RatioSoluble SolidMembership Function Indicator
000.00 1.00 0.70 0.45 0.65 0.55 0.478
01600.37 0.83 0.77 0.21 0.60 0.46 0.464
03200.39 0.00 0.23 0.01 0.10 0.15 0.127
Mean0.250.610.570.220.450.390.356
4000.27 0.50 0.29 1.00 0.74 0.46 0.464
401600.42 0.63 1.00 0.43 1.00 1.00 0.640
403201.00 0.50 0.00 0.00 0.000.00 0.214
Mean0.560.540.430.480.580.490.439
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Tao, Y.; Liu, T.; Wu, J.; Wu, Z.; Liao, D.; Shah, F.; Wu, W. Effect of Combined Application of Chicken Manure and Inorganic Nitrogen Fertilizer on Yield and Quality of Cherry Tomato. Agronomy 2022, 12, 1574. https://doi.org/10.3390/agronomy12071574

AMA Style

Tao Y, Liu T, Wu J, Wu Z, Liao D, Shah F, Wu W. Effect of Combined Application of Chicken Manure and Inorganic Nitrogen Fertilizer on Yield and Quality of Cherry Tomato. Agronomy. 2022; 12(7):1574. https://doi.org/10.3390/agronomy12071574

Chicago/Turabian Style

Tao, Yang, Tuo Liu, Jianyu Wu, Zhuangsheng Wu, Daolong Liao, Farooq Shah, and Wei Wu. 2022. "Effect of Combined Application of Chicken Manure and Inorganic Nitrogen Fertilizer on Yield and Quality of Cherry Tomato" Agronomy 12, no. 7: 1574. https://doi.org/10.3390/agronomy12071574

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