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Article

Chemical Fertilizer Reduction Potential Estimation and Fertilization Optimization Strategy Based on a 10-Year Application Summary and Status Questionnaires in a Typical Yellow River Irrigated Area

by
Yunpeng Sun
1,2,
Jingtian Xian
1,
Xiaobing Chen
1,*,
Dan Cao
1,
Rongjiang Yao
2,
Yongming Luo
2 and
Xin Zhang
2,*
1
Key Laboratory of Coastal Environmental Processes and Ecological Restoration, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China
2
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
*
Authors to whom correspondence should be addressed.
Agronomy 2023, 13(8), 2047; https://doi.org/10.3390/agronomy13082047
Submission received: 12 July 2023 / Revised: 23 July 2023 / Accepted: 24 July 2023 / Published: 1 August 2023
(This article belongs to the Special Issue Sustainable Water-Fertilizer Management for Soil Salinization Amendment and Crop Production in Salt-Affected Agroecosystems)
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Versions Notes

Abstract

:
The Yellow River Delta is an important grain production base in China, and it is a typical Yellow River irrigated area. Chemical fertilizer overuse has seriously affected grain production safety, and understanding the fertilizer application situation is useful for scientific agronomy management. In this study, we collected the data of the N, P, K fertilizers for crop cultivation in Donging City from 2011 to 2020, and we collected 185 investigating questionnaires to gather information on the fertilizer application rate for small farmers. The results showed that the amount of total fertilizer used has decreased from the year 2015, but the macro element fertilizer rate for crop cultivation exceeded the recommended dosage. The application of compound fertilizer increased during the investigated 10 years, and its proportion in 2020 was 1.65 times higher than in 2011. For obtaining an ideal grain yield, the N and P2O5 had relative reduction rates of 67.8% and 69.6% for wheat planting. Furthermore, the relative reduction rates of N, P2O5, and K2O were 25.9%, 69.6%, and 59.7%, respectively, for maize cultivation when compared to the recommended dosage. During wheat growth, the potassium fertilizer was needed to increase the dosage, although the K element content in the soil was high. Furthermore, the medium and trace elements are all important nutrients for improving crop yield and quality which need to be studied. More scientific measurements should be conducted to match chemical fertilizer reduction to constructing healthy and sustainable agriculture in the Yellow River irrigated area.

1. Introduction

With the increase in population, the demand for food is up around the globe. Although food is supplied by various sources throughout the world [1], the global food security issue is closely related to limited resources [2]. The climate is changing, affecting us all, and it will have an obvious effect on global food supply. This situation has accelerated the exploration of faster methods of obtaining more food in soil or water. It has been determined that about 95% of food is obtained from soil, so soil fertility is crucial to ensuring crop production all around the world [3]. Chemical fertilizers have been widely used to obtain the highest productivity in conventional agricultural systems. The application of chemical fertilizers for improving soil fertility during crop cultivation season has apparently increased crop yields to satisfy the global need for food [4]. However, the sole application of fertilizers cannot satisfy the need for food for a very long time in the future, as the long-term excessive application of chemical fertilizer, causing soil degradation, has been reported in many areas [5]. The soil degradation caused by the use of inorganic fertilizer causes fertility decline [6], soil compaction [7], microbial diversity reduction [8], soil layer loss [9], and so on. Furthermore, the excessive application of chemical fertilizers may not only cause a decrease in soil quality, but also may produce many environmental problems. Uncontrolled N fertilizer addition could bring about soil acidification [10], P fertilizer loss could cause water blooms [11], and excess K fertilizer use could cause decreased crop quality [12]. In the past fifty years, China has supplied 22% of the world’s population with about 9% of its lands, but its agriculture has consumed almost 35% of the world’s inorganic fertilizers [13]. Agriculture in China has been characterized by small-scale farms, and the overuse of inorganic fertilizers is also widespread and not controlled [14]. The ideal cultivation situation is producing more with fewer fertilizers. Although chemical fertilizer application could increase crop yields at a reasonable range, the production of chemical fertilizer is a high-energy consumption and high-pollution industry [15]. On the other hand, the lower price and application process of chemical fertilizers were the primary reasons that brought about its overuse in China [16]. The decrease of chemical fertilizers is a vital method to improve the sustainable and healthy development of saline agriculture [17]. The imbalanced use of inorganic fertilizers under intensive planting practices over many years has caused a variety of problems, especially with regard to nutrient availability [18]. China had proposed the “zero growth” plan for the reduced application of chemical fertilizers. For maintaining food security, it is of critical importance to develop a reasonable fertilization strategy. The urgent requirement for food prompted the development of marginal lands to plant crops, such as the large area of saline soils. The saline soils are mainly distributed in coastal and inland areas, and were generated by sea water intrusion or water evaporation. Coastal saline agriculture has been developed in many countries for hundreds of years [19,20], but its sustainable development still meets many obstacles, including seawater intrusion, climate change [21], lower fertility conditions, and so on [22]. So, developing the coastal salt-affected lands needs scientific improvement, with proper strategies and planning.
The Yellow River Delta, a typical Yellow River irrigated area, is an important production base in China. It is the fastest growing delta all over the world. It has huge potential in food production and plays an ecological function with its large area of saline soils. The Yellow River Delta coastline along the Gulf of Bohai has always experienced constant changes, and its land area is growing every year. Although fertilizers have been used in this region for increasing or maintaining crop productivity, many fertilizers are lost because of microbial activity and climate effects [23]. The fertilizer losses into the air or water will contaminate the coastal environment and threaten the ecological security of the coastal zone [24]. The average organic matter content was at a low level in the Yellow River Delta, so it needs a greater addition of fertilizer to facilitate more food production [25]. Nitrogen fertilizer was used extensively in the Yellow River Delta, and it was easy to lose after fertilizing the soil [26]. In coastal areas, potassium fertilizer was used less than nitrogen and phosphorus fertilizers, because the soil also contains a high quantity of K+ [27]. In addition, the recommended fertilizer usage for crop planting is varied in different areas. And the higher fertilizer rate utilization may result in crop yield decline [28]. Except for the macro fertilizer, the medium and trace elements need to be paid more attention to as well. The increasing application of macro element fertilizers could decrease soil and crop quality. And the addition and regulation of medium and trace elements may be a practical method. To increase the crop yield, this cannot rely on the three primary nutritional elements alone. The addition of medium and trace element fertilizers can satisfy the demand for crops for necessary nutrient elements, thus achieving the purpose of improving the yield. The contradiction between fertilizer demand and supply in the Yellow River Delta restricts the crop yields in this area. Nitrogen is essential for life on Earth, but in excess it is a pollutant and poisons water and plants while driving climate change through emissions of the greenhouse gas nitrous oxide. In the coming decades, agriculture will cope with food security for the increasing world population without affecting environmental security. It is very influential in formulating suitable fertilization strategies to alleviate fertilizer use and improve crop yields [29].
More and more studies have proven that with the reduction of chemical fertilizer usage, high yields can also be obtained [30]. The Yellow River Delta is not only a big crop production base, but also an important ecological shelter. Thus, the reduction of chemical fertilizer usage in the vast area of the Yellow River Delta plays huge direct and indirect functions in agricultural development. Based on the above analysis, the aim of this study is to summarize the chemical fertilizer usage information from the last 10 years and then analyze the potential for its reduced application. We hope that the research can supply scientific guidance for the rational utilization of fertilizer in the typical Yellow River irrigated area.

2. Materials and Methods

2.1. Study Area

The study area, Dongying City, is the core region of the Yellow River Delta, and it is located on the bank of the Bohai Sea (Figure 1). The climate in the study location is temperate continental monsoon. The temperature changes differently in the four seasons and the mean annual rainfall is 630 mm. About 80% of the rainfall occurs between June and September, and most of the rain flows into the sea. The average soil organic matter in this area is 11.13 g/kg, and the average salt content is 5.84 g/kg [31]. The total land area of Dongying City is 0.83 million ha, and the agricultural land accounts for 57.85% of the land. The farmland area is 0.22 million ha. The crops in the Yellow River Delta are mainly cultivated with a maize–wheat rotation system. In the year 2022, the maize cultivation area was 0.09 million ha, and the sown area of the wheat was 0.11 million ha. Trial soil testing to determine appropriate fertilizer formulas is the major fertilization method promoted by the city government. The nitrogen (N) fertilizer is also applied twice during wheat cultivation and once during the maize planting period. Phosphorus (P) and potassium (K) fertilizers are applied only once as base fertilizers during soil preparation.

2.2. Data Collection

The data of the crop sown area, grain yield, fertilization content, fertilizer application rate, population, and fertilizer composition in the years from 2011 to 2020 were collected from the Dongying Statistical Yearbook and the Shandong Province Statistical Yearbook. Furthermore, the climate data were collected from the National Meteorological Science Data Center “http://data.cma.cn (accessed from 2011 to 2020)”. The recommended fertilizer dosage was obtained from Wu [32,33]. For obtaining the fertilization method, fertilizer dosage, and fertilizer composition of the wheat and maize of the ordinary farmer household, 200 questionnaires were conducted from July 2021 and August 2022. And finally, 185 questionnaires were recovered.

2.3. Data Calculation

2.3.1. Active Fertilizer Dosage

Since the fertilizer used by ordinary farmers was not unique, the active fertilizer application rate was more effective for analyzing the status of fertilizer application. The calculation formula is as follows.
A F kg / ha =   F ( kg )   ×   PAF ( % ) / FAA ( ha )
AF is the active fertilizer dosage; F, the fertilizer dosage; PAF, the proportion of active fertilizer dosage; and FAA, the fertilizer application area.

2.3.2. Potential Reduction of Fertilizer Application

The yield targets of wheat and maize were 7.5 t/ha and 8.3 t/ha, respectively. The recommended fertilizer dosages of N, P2O5, and K2O of wheat in the study area were 184 kg/ha, 88 kg/ha, and 59 kg/ha, respectively [33]. The recommended fertilizer dosages (RF) of N, P2O5, and K2O during maize cultivation were 178 kg/ha, 46 kg/ha, and 63 kg/ha, respectively [32]. The absolute reduction rate of active fertilizer (AAF) and the relative reduction rate of active fertilizer (RAF) were calculated as follows.
AAF ( kg / ha ) = AF ( kg / ha )   −   RF ( kg / ha )
RAF ( kg / ha ) = AAF ( kg / ha )   −   RF ( kg / ha )
AAF is the absolute reduction rate of active fertilizer; AF, the active fertilizer dosage; RF, the recommended fertilizer dosage; and RAF, the relative reduction rate of active fertilizer.

2.4. Statistical Analysis

The descriptive statistical analysis of the data was conducted with Excel 2020 (Microsoft Company, Washington, DC, USA). The data figures were created using Origin 2021 (OriginLab Company, Massachusetts, USA).

3. Results

3.1. Crop Sown Area and Yield

The total crop sown area maintained a stable level, and the food crops account for 41~87% of the sown area (Figure 2a). The sown area of food crops increased year after year. The sown area of oil crops and melons increased for the first two years and decreased during the following years. The downward trend existed for the cotton and vegetables among the investigated years. Contrary to the trend of the crop sown area, the grain yield per unit area decreased every year from 2011 (Figure 2b). The grain yield per unit area in 2020 was 23% less than that of 2011. The per unit area yield of oil crop, cotton, and melon showed no obvious change from 2011 to 2020. But the vegetable yield per unit area increased to its highest level in 2014, with a yield of 6.85 t/ha, then decreased until 2020.

3.2. Fertilization Application Characteristics

The N/P/K fertilizer application dosage increased from 2011 to 2015, then continually decreased until the year 2020, and its change tendency was similar to that of the agricultural chemical fertilizers (Figure 3a). But the application amount of compound fertilizer increased to a stable level from 2011, and it showed no great change until 2020. As shown in Figure 3b, the relative ratio of the N/P/K active content in fertilizers stayed at the range of 1:(0.34~0.52):(0.19~0.21). The ratio of compound fertilizers occupied was higher every year. It was highest in 2020, when it was 1.64 times bigger than in 2011. Although the fertilizer application density went up first and then went down, it was still higher than the international recommended safe carrier of 225 kg/ha.

3.3. Population and Weather

Figure 4 shows that the population in Dongying City increased from 2.06 million in 2011 to 2.19 million in 2020. The higher population requires more food. The precipitation changed variously during the 10 years. The sunlight increased slightly from 2011, and it was beneficial for crops to take more time for photosynthesis. Longer photosynthetic duration is an important factor for obtaining high yields and can be used for the improving of crop yields. So, the longer sunlight and stable precipitation were important guarantees for crop production during the period of population growth.

3.4. Status of Fertilizer Application

The data collected from questionnaires showed that the average nitrogen fertilizer application dosage was 243 kg/ha as a base fertilizer, and 328 kg/ha was added in the topdressing stage during wheat cultivation (Table 1). The base fertilizer amount of N fertilizer was bigger than the recommend dosage of 61 kg/ha for wheat planting. The nitrogen fertilizer topdressing content was 2.7 times higher than the recommended dosage. The average N fertilizer amount was 3.1 times bigger than the recommended 184 kg/ha for wheat growth. The available P base fertilizer was 502 kg/ha, which was 5.7 times higher than the recommended dosage. The topdressing was 16 kg/ha, but the recommended tip was no fertilizer application. The K fertilizer was added only once as a base fertilizer, and its dosage was 38 kg/ha, which was lower than the recommended dosage for wheat fertilization.
For maize cultivation, according to the results of the questionnaires, the N fertilizer was solely applied once as a base fertilizer with the amount of 243 kg/ha, which was 1.35 times larger than the recommended dosage (Table 1). The P and K fertilizers in the available dosages were 148 kg/ha and 38 kg/ha, respectively, during maize growing. There was no topdressing supplied for maize fertilization. The P2O5 and K2O dosages were 3.3 and 2.5 times bigger than the recommended dosages for maize planting. The fertilizer application showed excessive amounts during wheat and maize planting, especially for wheat cultivation. Although the N fertilizer was the largest dosage, the P fertilizer actual usage was the highest above its recommended dosage.
As illustrated in Table 2, the ratio between N, P2O5, and K2O, the available fertilizer content, in the base fertilizer section for wheat cultivation was 1:2.07:0.16. The corresponding proportion in the topdressing was 1:0.05:0. The ratio of N, P2O5, and K2O of base fertilizer and topdressing during wheat planting was 0.43:0.57, 0.97:0.03, and 1:0, separately. For the fertilizer used only as a base fertilizer for maize cultivation, the ratio of the available main elements fertilizer amount was 1:0.61:0.59.
As shown in Table 3, the absolute reduction rates of N, P2O5, and K2O fertilizers for wheat planting were 182, 414, and −13 kg/ha in the base fertilizer and 205, 16, and 0 kg/ha in the topdressing, respectively. The relative reduction rates of N, P2O5, and K2O fertilizers for wheat planting were 74.9%, 82.5%, and −34.2% in the base fertilizer and 62.5%, 100%, 0% in the topdressing, respectively. The absolute reduction rates of N, P2O5, and K2O fertilizers for maize planting were 63, 103, and 86 kg/ha, respectively. And the relative reduction rates of N, P2O5, and K2O fertilizers for maize planting were 25.9%, 69.6%, and 59.7%, respectively.

4. Discussion

4.1. Chemical Fertilizers and Crop Cultivation

Chemical fertilizers have been invented and applied for agricultural production for hundreds of years all over the world. Since the technology of superphosphate was made in the early 19th century and nitrogen transformed into fertilizer was developed in 1913, chemical fertilizer has improved mass crop production and accelerated population growth worldwide [34]. However, the excessive use of chemical fertilizers may have little effect on increasing production, but also lead to the decline of production, runoff of nutrients, increase of greenhouse gases [35], and heavy metal pollution. For example, in this study, although the crop sown area changed little during the ten years, the food crop yield per unit area decreased every year. This is consistent with a number of studies. For instance, Moreno et al. reported that when N fertilizer was added at more than 383 kg/ha, the broccoli yield decreased [36]. And long-term application of chemical fertilizers decreased organic carbon and soil pH, accelerating the runoff of beneficial cations [37]. Zhao et al. conducted a meta-analysis showing that the long-term application of inorganic phosphate fertilizers added Cd and other toxic elements to the soil [38]. Chemical fertilizers are specifically made to target the nutrient levels of plants, and their main goal is to supply the plant with primary nutrients at a controlled amount. However, this situation does not control in a reasonable range. Through our questionnaires, small farm holders also used many types of fertilizers during crop cultivation, and they were used only based on experience, without taking into account scientific recommendations. Few farmers even made use of the relevant department release announcement about the recommended fertilizer composition before sowing. The conflict between practical production and scientific guidance needs to be solved. Except for the amount of chemical fertilizer application, the composition of the fertilizers has important effects on crop yields. The N/P/K fertilizer in this research showed an average ratio of 1:0.44:0.2, and it maintained a stable structure during the investigated ten years (Table 2). Most of the food we eat every day is in the form of biological molecules, and plants absorb little molecules consisting of nitrogen, phosphorus, and potassium to build bigger molecules such as sugars, oils, and proteins. The macro element N/P/K fertilizers were the most-used during crop planting in China, but a missing single nutrient will not be able to produce all of the large molecules in plants [39]. The fertilizer ratio affects crop yield, quality, and nutrition composition [40]. Compared to the nitrogen and potassium elements, phosphorus is easily fixed in soil. The long-term stable fertilizer ratio will disturb the nutrition balance of the soil and thus affect crop yield [41]. In addition, the base/topdressing ratio at an appropriate range could improve plant growth and improve crop quality and yield [42], so the fertilizer application should be conducted with reasonable guidance. Furthermore, application methods are important for improving the fertilizer utilization rate, because the chemical fertilizer will quickly decompose into useless fertilizer after fertilization [43]. Except for the macro element chemical fertilizer with simple element additions, the compound fertilizer application rate increased year to year (Figure 3). In the current study, about 70% of small farmers used ammonium secondary phosphate with a compound fertilizer for wheat cultivation, and approximately 98% of respondents were used to applying compound fertilizer during maize planting. Although the chemical fertilizers have some advantages, for example, high effective components [44], low production cost [45], and various nutrient types [46], their application rate was still above the recommended dosage. Furthermore, to improve the production of crops, farmers also focus only on the large chemical fertilizers, and the lack of medium and trace elements may lead to a poor quality and quantity of crops. The application of medium and trace element fertilizers maintained the balance composition of nutrients, not only increasing the crop yield, but also improving the quality of agricultural products.

4.2. Chemical Fertilizer Reduction Application

The development of more sustainable agriculture for increasing and maintaining food production has received more and more attention in recent years [47]. But the population increased year by year, requiring more crop production to feed it (Figure 4). Soil salinization is the typical type of land degradation in the Yellow River Delta, and it dramatically affects the sustainable development of agriculture in this region [48]. The reduction of chemical fertilizer shows great potential for healthy agricultural development in the Yellow River Delta. Our previous study had shown that grain yields had the highest production levels with increases in the addition of N and then decreased with the fertilizer dosage [49]. The reduction amount of available N and P fertilizers for wheat planting was up to 387 and 430 kg/ha, and this indicated the serious situation of excessive chemical fertilizer in this area. Although the K fertilizer needs to be added for wheat cultivation, this was in conflict with earlier findings, which reported applying little K fertilizer for crop planting in this area [50]. Potassium (K) is an essential element for performing plant physiological functions, and it acts as a transporter for photosynthetic substances (from source to sink) and regulates osmotic pressure [51]. So, it is very important to supply enough potassium nutrition for wheat seedlings to be resistant to the cold in winter [52]. But the fertilization rate for maize planting was still above the standard. The fertilizer nutrition absorbed by plants is not only affected by its composition, but also by the temperature [53], soil moisture content [54], microbial activity [55], and the growth period [56]. In addition, underground water in coastal areas is a dynamic and complicated system with the threat of seawater intrusion [57]. Hydro-meteorological aspects and human activities also affect the seasonal change of coastal groundwater, and they could alter the water distribution of tillage soils and then influence the fertility efficiency [58]. Fertilizer reduction is not only related to the macro element fertilizer dosage, but it is also associated with soil fertility, soil salinity, irrigation management, and policies. Higher soil basic fertility could decrease fertilizer usage, so improving soil longer-term fertility such as by planting green manure [59] could save chemical fertilizers. Moreover, compared with the sole addition of chemical fertilizers, combined fertilizers of organic and inorganic fertilizers could cause more and longer stable crop production [60]. Some organic material has been proved useful for crop growth with chemical fertilizer reduction. Organic materials used for soil remediation and fertilization improvement include green manure, wastewater sludge, grass, agricultural or forestry waste, and so on. For example, milk vetch with a 20% chemical fertilizer reduction improved crop growth and yield compared to the traditional fertilization practice [61]. The soil salt content accelerated N fertilizer losses as the salinity increased, so soil desalination was beneficial for fertilizer reduction in the Yellow River Delta [62,63]. During crop growth, water was an important factor affecting plant nutrition absorption. The scientific management of water through plant cultivation could decrease fertilizer dosages [64]. The government policies were also a neglected point, for they could absolutely affect the cultivation methods. The primary planting measure involves small farmers with small-area farms in China. If the combination of those small farms could be achieved, it would be beneficial for the accurate control of fertilization [65]. In addition, nano-fertilizers are a sustainable technology for increasing crop nutrition with lower fertilizer usage [66]. Crop rotation is another practice proven to increase yield potential from available soil nutrients [67]. While considering macro element fertilizer reduction, the medium and trace elements are important nutrients for crop production as well. Whether the medium and trace fertilizers need to be reduced needs further study in the future. So, more effective and scientific measures need to be developed for fertilizer reduction to build sustainable agriculture in the Yellow River Delta.

5. Conclusions

Soil and fertilizer are important components of supplying sustainable food production in the Yellow River Delta. The crop sown area maintained a stable situation during the 10 years from 2011 to 2020 in the Yellow River Delta. But the increased chemical fertilizer dosage did not result in higher grain yields. For the main food crops of wheat and maize, N and P fertilizer dosages should be reduced and K fertilizer usage should be increased during wheat cultivation, and the use of N, P, and K fertilizers should be decreased during maize cultivation. The P fertilizer showed the highest relative reduction rate, which was 69.6% for maize and wheat planting. But the absolute reduction rate was in wheat cultivation, where the N and P fertilizers had 387 kg/ha and 430 kg/ha reduction potentials compared to the current dosage. Moreover, more attention should be paid to the soil’s inherent productivity, salinity decrease, and water management when conducting fertilizer reduction strategies. Future research should focus on the accurate optimum fertilization rate of different crops. For establishing sustainable saline agriculture in the Yellow River Delta, more scientific studies should be conducted to reduce fertilizer rates and improve fertilizer use efficiency.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy13082047/s1, Supplementary-questionnaires.

Author Contributions

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

Funding

This research and the APC were funded by the National Natural Science Foundation of China, grant numbers U1906221 and 42077084; and the National Key Research and Development Program, grant numbers 2021YFC3201201 and 2021YFD1900602.

Data Availability Statement

Supplementary-questionnaires.

Acknowledgments

The authors would like to acknowledge the Dongying Experimental Base of Shandong Academy of Agricultural Sciences and the Science and Education Integration Base of Ludong University.

Conflicts of Interest

The authors declare no conflict of interest.

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Agronomy 13 02047 g001
Figure 1. Location of the study area and design of the research.
Figure 1. Location of the study area and design of the research.
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Figure 2. The sown area of different crops in Dongying City from 2011 to 2020 (a); the yield per unit area of crop in Dongying City from 2011 to 2020 (b).
Figure 2. The sown area of different crops in Dongying City from 2011 to 2020 (a); the yield per unit area of crop in Dongying City from 2011 to 2020 (b).
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Figure 3. The fertilizer application dosage (a) and application density (b) in Dongying City from 2011 to 2020.
Figure 3. The fertilizer application dosage (a) and application density (b) in Dongying City from 2011 to 2020.
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Figure 4. The population (a) and weather data (b) in Dongying City from 2011 to 2020.
Figure 4. The population (a) and weather data (b) in Dongying City from 2011 to 2020.
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Table 1. Actual dosage and recommended application of N/P/K fertilizers.
Table 1. Actual dosage and recommended application of N/P/K fertilizers.
CropsBase Fertilizer (kg/ha)Topdressing (kg/ha)Total (kg/ha)
Actual
Dosage		Recommended
Dosage		Actual DosageRecommended DosageActual DosageRecommended Dosage
NP2O5K2ONP2O5K2ONP2O5K2ONP2O5K2ONP2O5K2ONP2O5K2O
Wheat2435023861885132816012300571518381848851
Maize2431481441804558 2431481441804558
Total48665018224113310932816012300814666182364133109
Table 2. Fertilizer application structure in Dongying City.
Table 2. Fertilizer application structure in Dongying City.
CropsBase FertilizerTopdressingTotal
Relative RatioProportion of the Total DosageRelative RatioProportion of the Total DosageRelative RatioProportion of the Total Dosage
Wheat1:2.07:0.160.43:0.97:11:0.05:00.57:0.03:01:0.91:0.071:0.91:0.07
Maize1:0.61:0.591:1:1--1:0.61:0.591:0.61:0.59
Table 3. The absolute and relative reduction rates of fertilizers in Dongying City.
Table 3. The absolute and relative reduction rates of fertilizers in Dongying City.
The Absolute Reduction Rate of Available Fertilizer (kg/ha)
CropsBase FertilizerTopdressingTotalAverage
NP2O5K2ONP2O5K2ONP2O5K2O
Wheat182414−13205160387430−13268
Maize6310386---631038684
The relative reduction rate of available fertilizer (%)
CropsBase fertilizerTopdressingTotalAverage
NP2O5K2ONP2O5K2ONP2O5K2O
Wheat74.982.5−34.262.5100067.869.6−34.234.4
Maize25.969.659.7---25.969.659.751.7
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Sun, Y.; Xian, J.; Chen, X.; Cao, D.; Yao, R.; Luo, Y.; Zhang, X. Chemical Fertilizer Reduction Potential Estimation and Fertilization Optimization Strategy Based on a 10-Year Application Summary and Status Questionnaires in a Typical Yellow River Irrigated Area. Agronomy 2023, 13, 2047. https://doi.org/10.3390/agronomy13082047

AMA Style

Sun Y, Xian J, Chen X, Cao D, Yao R, Luo Y, Zhang X. Chemical Fertilizer Reduction Potential Estimation and Fertilization Optimization Strategy Based on a 10-Year Application Summary and Status Questionnaires in a Typical Yellow River Irrigated Area. Agronomy. 2023; 13(8):2047. https://doi.org/10.3390/agronomy13082047

Chicago/Turabian Style

Sun, Yunpeng, Jingtian Xian, Xiaobing Chen, Dan Cao, Rongjiang Yao, Yongming Luo, and Xin Zhang. 2023. "Chemical Fertilizer Reduction Potential Estimation and Fertilization Optimization Strategy Based on a 10-Year Application Summary and Status Questionnaires in a Typical Yellow River Irrigated Area" Agronomy 13, no. 8: 2047. https://doi.org/10.3390/agronomy13082047

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