Optimal Fertilization Strategies for Winter Wheat Based on Yield Increase and Nitrogen Reduction on the North China Plain

Abstract

In practice, most Chinese farmers usually apply excessive fertilizers to ensure wheat (Triticum aestivum L.) yield, resulting in environmental impacts. How to maintain an even increase wheat yield with less fertilizers is still not clear. This study evaluated the yield, quality, nutrient accumulation, and environmental costs of winter wheat under optimal fertilization management strategies. A field trial was set up with a randomized block design, constituted of eight different fertilization management strategies and four replicate plots. The results showed that optimal fertilization management strategy increased wheat yield and net benefit, and increased N, P, K accumulation, N and P fertilizer partial productivity and N and P uptake efficiency. Compared with the farmers’ practice, the yield in the different optimal fertilization management strategies was increased by 2.21–8.42% through improving the spike number or the grain number per spike. Meanwhile, the net benefit increased by 6.83–11.29% in different optimal fertilization management strategies. Furthermore, NO₃⁻ leaching and nitrous oxide (N₂O) emission in the different optimal fertilization managements were reduced by 25.50–35.15%, 48.80–60.26%, and 29.60–38.36%, respectively. In conclusion, CF3, CF1, 90%CF1 fertilization management can not only achieve high yield of wheat, but also improve economic benefits and reduce environmental costs, which are effective fertilization management strategies.

1. Introduction

The global population is expected to reach at least 9 billion by the year 2050, requiring up to 70% more food [1]. Over the past five decades, Chinese grain production has increased fourfold. Meanwhile, more than half of the increased crop production can be attributed to a rapid increase in the consumption of chemicals, particularly chemical fertilizers [2]. Over the past 50 years, the widespread use of chemical fertilizers has contributed greatly to the huge increase in global food production, and modern agriculture feeds 6000 million people [3,4]. The extensive use of various chemical fertilizers in high-input, high-yield agricultural production leads to low resource efficiency and a number of environmental problems, including aquatic eutrophication, groundwater pollution, soil degradation and greenhouse gas emissions [5,6,7,8].

Wheat (Triticum aestivum L.) is one of the three major grains in the world and the main food crop in China. More than 80% of wheat yield is produced from the North China Plain [9]. Laoling is a typical winter wheat planting city, planted with about 5.8 × 10⁴ ha⁻¹ winter wheat in 2020. Excessive fertilization has become a serious phenomenon due to farmers’ excessive pursuit of high yield and super high yield in winter wheat in Laoling City, Shandong province. In the North China Plain, the yield of winter wheat was only 5.76 t ha⁻¹ when nitrogen application was as high as 325 kg N ha⁻¹ [10]. Liu et al. [11] reported that 208–230 kg N ha⁻¹ was the best nitrogen application rate in winter wheat–summer maize rotation region. There is no simple linear correlation between the intensity of chemical fertilizers application and grain yield [12]. A certain amount of chemical fertilizers can ensure a high grain yield, but the grain yield declines rapidly when the chemical fertilizers amounts are over-dosed [13], resulting in the reaction of chemical fertilizers’ application. Although fertilizers are an integral part of agricultural production, excessive fertilization results in the waste of fertilizers. Discharge to air and water results in the loss of active nitrogen, including nitrous oxide (N₂O) direct and indirect emissions, nitrous oxide (N₂O) indirect emissions through nitrate (NO₃⁻) leaching, and ammonia (NH₃) volatilization [14]. Meanwhile, the accumulation of soil nutrients and inefficiency of fertilizer use may cause several negative environmental impacts [13,15]. For a sustainable food security future, it needs a huge balancing act to achieve high yields and high fertilizer use efficiency while significantly reducing its environmental footprint in China [14,16].

In China, there are problems of uneven distribution and low utilization rate of fertilizer in the main wheat-producing areas [17]. Nitrogen is the first nutrient that restricts wheat yield, followed by phosphorus and potassium [18]. Nitrogen (N) is the most important nutrient element for plant growth and grain quality, but its utilization efficiency is very low in wheat [19]. Lu et al. [20] found that rational N management can improve N use efficiency without compromising yield in winter wheat. Zhao et al. [21] found that the simulated yield of winter wheat was first increased and then decreased with the increase in N input. N application that meets but does not exceed crop N requirements is critical for achieving maximum food yield and minimizing environmental risks [22]. Cereal production also depends greatly on the application of phosphorus (P) fertilizer to achieve food security [23], such as P nutrition of plants improved yield by increasing fertile spike formation in wheat [24]. The effect of potassium deficiency on wheat yield was obvious with the decrease in available potassium (K) content in soil [25]. It is very difficult for farmers to apply fertilizers in different stages according to the growth and development of winter wheat because of lacking fertilization knowledge and input cost; thus, more and more new fertilizers are emerging. Previous studies showed that the application of compound microbial fertilizer in wheat planting could increase the content of soil available phosphorus and potassium, and improve soil fertility [26]. Manure application can effectively reduce soil acidification caused by fertilizer application [27]. The application of organic amendments can effectively alleviate soil salinization, increase the diversity of soil bacterial community and promote crop growth [28]. Compared with common fertilizers, new fertilizers may reduce the loss of fertilizer nutrients in the soil and improve the utilization rate of fertilizers [29]. To optimize the fertilizer application structure of farmers, and disseminate scientific and technological knowledge to farmers on the front line of agricultural production, the Science and Technology Backyard (STB) was built in the Nanxia village, Laoling City in 2014.

In this study, the yield, quality, and nutrient accumulation of winter wheat were analyzed. Meanwhile, the input and environmental costs of different fertilization management strategies were compared. The scientific question of this paper is whether optimized new compound fertilizer management strategies can synchronously achieve nutrient use efficiency, environmental loss mitigation and wheat yield maintenance increasing in wheat production systems in Northern China. We hypothesized that suitable fertilizer type and dosage are effective strategies to improve wheat yield, nutrient efficiency, and reduce nitrogen pollution. The purpose of this study was to understand the most effective way to apply fertilizer for stabilizing yield and quality of winter wheat, reduce input cost and environmental pollution.

2. Materials and Methods

2.1. Experimental Site

Field experiment was conducted in 2019–2020 in Laoling (37°40′ N, 117°4′ E), Shandong province, China. The climate in this region is warm temperate, continental, subhumid, and monsoonal [30]. The preceding crop in these fields was summer maize. The soil at the experiment site is Fluvo-aquic soil and the soil textural class is loam with an organic matter content of 16.55 g kg⁻¹; Total N, 1.15 g kg⁻¹; Olsen-P, 21.12 mg kg⁻¹; Available K, 146.52 mg kg⁻¹; and pH 7.3.

2.2. Experimental Design

The field experiment had a randomized block design with eight treatments and four replicate plots (11 m × 6 m) per treatment. In this study, the winter wheat variety, Ji Mai 22, was sown from early to mid-October and harvested in early June of the following year. Urea, superphosphate and potassium chloride were bought from local agricultural dealers. Sea flower seaweed compound fertilizer, oligosaccharides compound fertilizer and compound fertilizer of wheat king meal were supplied by Worldfull Agricultural Technology Co., Ltd. (German roller granulation equipment, Germany). Weed removal and insecticide spraying are performed exactly as local farmers do.

Through a questionnaire survey on the fertilization situation of 100 local farmers, the input amount of nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer for winter wheat in Laoling area was determined (Table S1. Survey information). Based on the actual survey (Table S1), the following eight treatments were used (

Table 1. Nitrogen, phosphorus and potassium fertilizers application amounts of different fertilization managements.

Treatment	Before Planting (kg ha−1)			At Stem Elongation Stage (kg ha−1)			Total (kg ha−1)
	N	P2O5	K2O	N	P2O5	K2O	N	P2O5	K2O
CK	0	0	0	0	0	0	0	0	0
FPT	114	134	40	170	0	0	284	134	40
OPT	108	120	48	108	0	0	216	120	48
CF1	108	120	48	108	0	0	216	120	48
90%CF1	97	108	43.2	97.2	0	0	194.2	108	43.2
CF2	108	120	48	108	0	0	216	120	48
90%CF2	97	108	43.2	97.2	0	0	194.2	108	43.2
CF3	90	78	30	126	0	0	216	78	30

CK = Control; FPT = Farmers’ nitrogen practice treatment; OPT = Optimal practice treatment; CF1 = Compound fertilizer 1; 90%CF1 = 90% compound fertilizer 1; CF2 = Compound fertilizer 2; 90%CF2 = 90% compound fertilizer 2; CF3 = Compound fertilizer 3.

); control (CK), no fertilizer was applied in the soil; Farmers’ practice treatment (FPT), N (Nitrogen), phosphorous (P), and potassium (K) fertilizers rates were according to the traditional amount of fertilizers applied by local farmers; optimal practice treatment (OPT), N, P and K fertilizers rates were according to the results of the soil testing and target yield; compound fertilizer 1 (CF1), sea flower seaweed compound fertilizer; 90% compound fertilizer 1 (90%CF1); compound fertilizer 2 (CF2), oligosaccharides compound fertilizer; 90% compound fertilizer 2 (90%CF2); compound fertilizer 3 (CF3), compound fertilizer of wheat king meal. N, phosphorous (P), and potassium (K) fertilizers were applied as urea, superphosphate, and potassium chloride, respectively in the FPT and OPT treatments. All the P and K fertilizers were applied into the soil as basal fertilizers at sowing in each treatment. Both 40% and 60% of N fertilizer were applied as basal fertilizer and the other half was applied at the jointing stage in the FPT treatment. Half of the N fertilizer was supplied by sea flower seaweed compound fertilizer in the CF1 and 90%CF1 treatment, oligosaccharides compound fertilizer in the CF2 and 90%CF2 treatment as basal fertilizer, and the other half was used as urea at the jointing stage. A total of 40% of N fertilizer was supplied by compound fertilizer of wheat king meal as basal fertilizer and 40% of N fertilizer was used as urea at the jointing stage. In this study, the new compound fertilizer contains ammonium nitrogen, which is easily adsorbed by soil colloid and can be directly absorbed by crops. The medium nutrient component is amide nitrogen, the lasting supply of nutrients.

2.3. Sampling and Measurements

At harvest, plants in a 1 m² area of each treatment were harvested. Threshed and grains were dried to determine grain yield (14% of water content). The grain number per spike was determined by counting the grains on each spike from 30 randomly selected plants in each plot before harvest. The 1000-grain weight was determined using the weights of three sets of 500 kernels from each plot.

Plants at the maturity stages were separated into leaves, stalks, and grains. All plant samples were heated at 105 °C for 30 min and dried at 70 °C for constant weight, weighed to obtain dry matter. The plant and soil nitrogen concentration were obtained using the Kjeldahl method; the total phosphorus concentration was measured using the colorimetric method based on extraction with NaHCO_3; and the total potassium concentration was determined using a flame photometer. The amino acid content of grain was determined with a hydrochloric acid hydrolysis method and Hitachi L-8900 amino acid analyzer. The soluble sugar concentration was determined via a anthrone colorimetric method. The N, P, and K content were calculated as dry matter multiply N, P, and K concentration, respectively.

N (P, K) fertilizer partial productivity is defined as the yield per unit of N (P, K) input amount.

$$\mathrm{PFPN} \left(\mathrm{P}, \mathrm{K}\right), \mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{fertilizer} \mathrm{partial} \mathrm{productivity} \left({\mathrm{kg} \mathrm{kg}}^{-1}\right)= \mathrm{Grain} \mathrm{yield}/\mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{application} \mathrm{rate}$$

(1)

N (P, K) uptake efficiency refers to the above-ground N (P, K) accumulation per unit of N (P, K) input amount.

$$\mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{upE}, \mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{uptake} \mathrm{efficiency} \left({\mathrm{kg} \mathrm{kg}}^{-1}\right)= \mathrm{Total} \mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{uptake} \mathrm{by} \mathrm{plant}/\mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{application} \mathrm{amount}$$

(2)

N (P, K) utilization efficiency refers to the yield per unit of the above-ground N (P, K) accumulation.

$$\mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{utE}, \mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{utilization} \mathrm{efficiency} \left({\mathrm{kg} \mathrm{kg}}^{-1}\right)= \mathrm{Grain} \mathrm{yield}/\mathrm{Total} \mathrm{N} \left(\mathrm{P}, \mathrm{K}\right) \mathrm{uptake} \mathrm{by} \mathrm{plant}$$

(3)

2.4. Environmental Cost and Economic Benefit Calculation

Active nitrogen losses (including nitrous oxide (N₂O) emission, nitrate (NO₃⁻) leaching, and ammonia (NH₃) volatilization) were used to assess the associated environmental impacts. The calculation formula of N₂O emission, NO₃⁻ leaching, and NH₃ volatilization was derived from Cui [14].

$${\mathrm{N}}_2\mathrm{O} \mathrm{emission} =0.50\times e^{0.0032\times Nrate}$$

(4)

$${\mathrm{NO}}_3^{-} leaching=3.63\times e^{0.0080\times Nrate}$$

(5)

$${\mathrm{NH}}_3 \mathrm{volatilization}=2.69+0.069\times Nrate$$

(6)

$$\mathrm{Net} \mathrm{benefit} \left({\mathrm{CNY} \mathrm{ha}}^{-1}\right)=\mathrm{Total} \mathrm{output} \mathrm{value}-\mathrm{total} \mathrm{cost}$$

(7)

$$\mathrm{Total} \mathrm{cost} \left({\mathrm{CNY} \mathrm{ha}}^{-1}\right)=\mathrm{material} \mathrm{cost} + \mathrm{labor} \mathrm{cost} + \mathrm{mechanical} \mathrm{operation} \mathrm{cost}$$

(8)

$$\mathrm{Total} \mathrm{output} \mathrm{value} \left({\mathrm{CNY} \mathrm{ha}}^{-1}\right)=\mathrm{Grain} \mathrm{yield} \times \mathrm{wheat} \mathrm{unit} \mathrm{price}$$

(9)

According to the local price of wheat in 2020, the purchase price of wheat is CNY 2.3 kg⁻¹. Material cost: the unit price of wheat seed is CNY 2.4 kg⁻¹, the unit price of ordinary urea (46%) is CNY 2 kg⁻¹, the unit price of superphosphate (12%) is CNY 1.2 kg⁻¹, the unit price of potassium chloride (60%) is CNY 3.1 kg⁻¹, the unit price of sea flower seaweed compound fertilizer, oligosaccharides compound fertilizer, and compound fertilizer of wheat king meal is CNY 5.1, 5.1, 5.2 kg⁻¹, respectively. The cost of disease, insect, and grass control is CNY 700 kg⁻¹. The labor cost is CNY 1500 kg⁻¹. Mechanical operation cost: the operation cost of rotary tillage sowing and fertilization machine is CNY 1200 kg⁻¹, and the wheat mechanical harvesting operation cost is CNY 750 kg⁻¹.

2.5. Statistical Analysis

Microsoft Excel 2019 was used for data processing and Origin 2019b assisted in drawing. All analyses were performed through variance analysis using DPS v.7.05 software [31]. Multiple comparisons were performed after a preliminary F-test. Means were tested based on the least significant difference at p < 0.05.

3. Results

3.1. Yield

Significant differences were found in yield, spike number, grain number, and 1000-grain weight among different fertilization management treatments (

Table 2. Grain yield and its components in different fertilization managements.

Treatments	Yield	Spike Number	Grain Number	1000 Grain
	(kg ha−1)	(104 ha−1)	Per Spike	Weight (g)
CK	5933 c	308 d	23.0 e	39.6 b
FPT	7654 b	527 c	29.2 cd	42.0 ab
OPT	7824 ab	597 b	31.1 ab	42.6 ab
CF1	8210 a	671 a	30.0 bc	41.0 ab
90%CF1	8067 ab	641 a	30.5 bc	41.0 ab
CF2	8077 ab	597 b	29.4 bcd	41.7 ab
90%CF2	7907 ab	538 c	27.8 d	42.6 a
CF3	8299 a	534 c	32.5 a	42.7 a

Means followed by the different lowercase letters indicate significant differences among different treatments (p < 0.05) according to LSD test.

). The yield, spike number, grain number and were all significantly higher in the fertilization management treatments than in the CK treatment. Compared to the FPT, the yield in OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was increased by 2.21%, 7.26%, 5.39%, 5.52%, 3.30%, and 8.42%, respectively. Compared to the FPT, the spike number of the OPT, CF1, 90%CF1, and CF2 treatments was significantly increased by 13.29%, 27.39%, 21.70%, and 13.30%, respectively. There was no significant difference in spike number among the 90%CF2, CF3 treatments, and FPT. The number of grains per spike in the CF3 and OPT treatments was the highest, which was significantly increased by 10.97% and 6.38% compared with FPT, respectively. There was no significant difference between other fertilizers treatments and the FPT. Compared to the FPT, the 1000-grain weight was no different among fertilization management treatments.

3.2. Nutrient Accumulation and Use Efficiency

There were significant differences in N, P, and K concentrations and dry matter accumulation among the different fertilization treatments (Table S2). Compared to the FPT, the accumulation of dry matter in the stalk in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was increased by 7.22%, 22.94%, 22.32%, 14.63%, 7.32% and 18.93%. Meanwhile, the accumulation of dry matter in the grains in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was increased by 5.75%, 15.06%, 14.85%, 6.36%, 9.83% and 18.04%, respectively. In contrast, the concentrations of soluble sugar, calcium, and magnesium in the fertilization treatment were higher than those in the CK treatment, but there was no significant difference among treatments (Figure S1). Moreover, compared to the FPT, the essential and nonessential amino acid content were not different among fertilization management treatments (Table S3).

The N, P, and K accumulation were all significantly higher in fertilization management treatments than the CK treatment (Figure 1). However, no significant difference in the concentrations of total N, P, K in the stalk, leaves and grain in the different fertilization managements was observed. The accumulation of N, P, K in different organs was higher in the different optimized fertilization management than that in the FPT. This may be caused by the different dry matter accumulation in different fertilization management treatments. Compared to the FPT, the total N accumulation in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was increased by 0.91%, 18.79%, 21.18%, 7.34%, 2.74%, and 11.16%, respectively. Meanwhile, the P accumulation in the CF1, 90%CF1, CF2, 90%CF2 and CF3 treatments was increased by 21.79%, 22.40%, 17.96%, 7.96% and 11.46%, respectively. Moreover, the K accumulation in OPT, CF1, 90%CF1, CF2 and CF3 treatments was increased by 4.89%, 12.35%, 15.42%, 11.65% and 10.06%, respectively. Soil nutrient content gradually decreased as soil depth increased. In the 0–20 cm soil layer, soil total nitrogen content under different fertilization management measures was significantly higher than that under CK treatment, while in the 20–40 cm soil layer, soil total nitrogen content under FPT treatment was the highest (Figure S2A). In the 20–40 and 40–60 cm soil layers, soil available P content applied with the new compound fertilizer management strategy was higher than that under FPT treatment (Figure S2B).

Significant differences were found in PFPN, PFPP, PFPK, NupE, PupE, KupE, and NutE, PutE, KutE among different fertilization management treatments (

Table 3. Nitrogen, phosphorous and potassium use efficiency of plant at physiological maturity in different fertilization managements.

Treatments	PFPN	NupE	NutE	PFPP	PupE	PutE	PFPK	KupE	KutE
FPT	26.95 f	0.82 e	33.07 a	57.12 f	0.15 d	376.31 ab	191.36 a	4.73 ab	40.87 ab
OPT	35.72 e	1.07 d	33.53 a	65.20 e	0.17 cd	393.98 a	162.99 e	4.13 b	39.88 ab
CF1	38.01 c	1.28 b	29.74 bc	68.42 cd	0.21 ab	330.95 c	171.04 cd	4.42 ab	39.22 ab
90%CF1	41.50 a	1.45 a	28.68 c	74.69 a	0.23 a	324.34 c	186.73 b	5.05 a	37.12 b
CF2	36.88 d	1.14 cd	32.35 ab	67.30 d	0.20 b	335.98 bc	168.26 d	4.40 b	38.37 b
90%CF2	40.68 b	1.23 bc	33.08 a	73.22 b	0.20 b	360.74 abc	183.04 b	4.11 b	44.72 a
CF3	38.42 c	1.20 bc	32.14 ab	69.16 c	0.19 bc	367.84 abc	172.89 c	4.33 b	40.17 ab

Means followed by the different lowercase letters indicate significant differences among different treatments (p < 0.05) according to LSD test.

). PFPN, PFPP, and NupE were all significantly higher in fertilization management treatments than the CK treatment. Compared to FPT, PFPN in the the OPT, CF1, 90%CF1, CF2, 90%CF2, CF3 treatments was increased by 32.55%, 41.02%, 53.96%, 36.83%, 50.92% and 42.55%, respectively. Compared to the FPT, PFPP in the OPT, CF1, 90%CF1, CF2, 90%CF2, CF3 treatments was increased by 14.14%, 19.77%, 30.76%, 17.83%, 28.17% and 21.07%, respectively. Compared to the FPT, NupE in the OPT, CF1, 90%CF1, CF2, 90%CF2, CF3 treatments was increased by 30.87%, 56.18%, 77.03%, 39.20%, 50.09% and 46.16%, respectively. Compared to the FPT, PupE in the CF1, 90%CF1, CF2, 90%CF2, CF3 treatments increased by 36.00%, 51.87%, 31.72%, 33.95%, and 24.46%, respectively. Compared with FPT, the NutE, PutE, PFPK, KupE, KutE were not different among fertilization management treatments.

3.3. Economic Benefit and Reactive Nitrogen Loss

Compared with FPT, the total output value in OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was increased by 2.21%, 7.26%, 5.39%, 5.52%, 3.30%, and 8.42%, respectively (

Table 4. Output, input and net benefit of different fertilization managements.

Treatments	Total Output Value	Total Input Cost	Net Benefit
	(CNY ha−1)	(CNY ha−1)	(CNY ha−1)
CK	13,646	4690	8956
FPT	17,605	7471	10,134
OPT	17,994	7090	10,904
CF1	18,883	7750	11,133
90%CF1	18,553	7444	11,109
CF2	18,576	7750	10,826
90%CF2	18,187	7444	10,743
CF3	19,088	7810	11,278

). Since labor cost was the same as mechanical operation cost, the material cost had the greatest impact on total input cost. Compared with FPT, the total input cost in the CF1, CF2, and CF3 treatments was increased by 3.73%, 3.73%, and 4.53%, respectively. Compared with FPT, the net benefit in the OPT, CF1, 90%CF1, CF2, 90%CF2, and CF3 treatments was increased by 7.60%, 9.86%, 9.63%, 6.83%, 6.01%, and 11.29%, respectively.

In the active N loss, NH₃ volatilization and NO₃⁻ leaching were the main factors, andN₂O emission was the smallest (Figure 2). Among different fertilization management treatments, the largest active N loss was found in the FPT while the lowest active N loss occurred in the 90%CF1 and 90%CF2 treatments. Compared with FPT, the NH₃ volatilization in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was reduced by 21.05%, 21.05%, 27.80%, 21.05%, 27.80%, and 21.05%, respectively. Meanwhile, the NO₃⁻ leaching in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was reduced by 41.96%, 41.96%, 51.25%, 41.96%, 51.25%, and 41.96%, respectively. Moreover, the N₂O emission in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was reduced by 19.56%, 19.56%, 24.98%, 19.56%, 24.98% and 19.56%, respectively. Furthermore, there were no significant differences among different fertilization treatments in different soil layers (Figure S2). FPT treatment had the highest total nitrogen in all soil layers, and different fertilization management treatments had similar effects on available P and available K in all soil layers (Figure S2B,C). In the 20–40 cm soil layer, soil available P under CF1, 90%CF1, CF2 and 90%CF2 treatments increased by 45.39%, 41.17%, 44.88% and 35.05%, respectively, compared with the FPT treatment.

4. Discussion

4.1. Yield Components

In practice, most Chinese farmers do not know the appropriate amount of N fertilizer and usually apply excessive N fertilizer to ensure wheat yield [32]. In Laoling city, the N, P, and K fertilizers were input more than 300 kg ha⁻¹, 120 kg ha⁻¹, and 64 kg ha⁻¹, accounting for 54%, 44%, and 22%, respectively (Table 2). Xu et al. [17] reported that the average seasonal N requirement for wheat was just 175 kg ha⁻¹ with a yield of 8.0 Mg ha⁻¹ in North-central China, while the seasonal N application rate of wheat is 279 kg ha⁻¹ with a yield of 7.9 Mg ha⁻¹ in the Hebei, Henan, Shandong, and Shanxi provinces in the North China Plain [33]. In this study, the N application rate of optimal practice treatment was set at 216 kg ha⁻¹ according to the results of the soil testing and target yield (Table 1). This suggested that the amount of nitrogen applied to wheat is determined by the availability of soil nutrients, the climatic conditions of the area and the target yield of wheat [34,35].

The coordination of wheat yield consists of three elements (spike number, grain number per spike, and 1000-grain weight) necessary for a high yield of winter wheat [36]. However, a negative correlation was also found among the components of three elements’ yield [37,38,39]. Compared with FPT, the yield in the OPT, CF1, 90%CF1, CF2 and 90%CF2, CF3 treatments was increased by 2.21%, 7.26%, 5.39%, 5.52%, 3.30%, and 8.42%, respectively. Meanwhile, the spike number of the OPT, CF1, 90%CF1, and CF2 treatments was significantly increased by 13.29%, 27.39%, 21.70%, and 13.30%, respectively. The number of grains per spike in the CF3 treatment was the highest, and significantly higher by 10.97% than the FPT. There was no significant difference between other fertilizers treatments and the FPT. Compared with the FPT, the 1000-grain weight was not different among fertilization management treatments (Table 2). This suggested that the increase in wheat yield is largely due to the increase in the spike number in the OPT, CF1, 90%CF1, CF2, and 90%CF2 treatments and the increase in the grain number per spike in the CF3 treatment. The spike number of winter wheat was determined from seeding to the elongation stage and was affected by seeding rate, seedtime, and effective tiller number [19]. The seeding rate and seedtime were the same for the different treatments, indicating that the effective tiller number was improved in the OPT, CF1, 90%CF1, CF2, and 90%CF2 treatments. The grain number per spike was determined from the elongation stage to anthesis and was affected by nutrient supply [40]. The compound fertilizer of wheat king meal (CF3) had a full amount of nutrients, which may stimulate the increase in grain number per spike.

4.2. The Different Fertilization Strategies Affect Nutrient Accumulation and Utilization

The yield of winter wheat depended on dry matter and nutrient accumulation and was affected by the balance of energy, water, carbon, and N assimilations [41]. N is one of the essential nutrients required for wheat growth and 90% of leaf N was reserved in the chloroplast for photosynthesis to produce carbohydrates (dry matter) [42]. In this study, however, the N fertilizers input amount was reduced by 23.9% in the different optimal management compared to the FPT. The N concentrations and accumulation amount of leaves were not significantly declined in the OPT and CF3 treatments and even significantly increased in the CF1, 90%CF1, CF2 and 90%CF2 treatments (Table 4), which might help to increase the photosynthetic rate of leaves, hence the dry matter accumulation [43]. The higher dry matter accumulation increased the absorption of N, P, and K [44], and then it improved the PPFN, NutE, PPFP, and PutE (Table 3). This was in accordance with [45] who showed that there would be no negative impact on grain yield and improved the N use efficiency by reducing the amount of N applied. Many studies have shown that optimal use of nitrogen fertilizer can stabilize crop yield, improve nitrogen efficiency and reduce environmental impact [46,47,48,49]. In addition, the efficiency of crop use of phosphorus fertilizer is closely related to soil factors and fertilization factors [50]. P is responsible for the transport of carbohydrates from the source (leaf) to the sink (grain) [51]. The higher P concentrations and accumulation amount of leaves might contribute to the transport of carbohydrates from leaves to grain, which resulted in the higher yield in the different optimal managements than FPT treatment (Table S3 and Table 4; Figure 1). Compared to the blended fertilizer, the controlled release fertilizer can effectively control the release rate of nutrients, promote the absorption of nitrogen nutrients, and meet the needs of crops at the later stage of growth, so as to improve the yield and fertilize utilization efficiency [52,53]. Studies have shown that the new fertilizers can extend their availability in the soil and thus improve utilization efficiency [54].

4.3. The Different Fertilization Strategies Affect Active Nitrogen Loss

Chemical fertilizers are an indispensable part of agricultural production, and their application has increased greatly in the past thirty years. Crop yields cannot be increased or sustained indefinitely by increasing fertilizer investment [55,56]. The amount of nitrogen applied by farmers is much higher than the amount of nitrogen uptake in the ground part of the maximum crop yield, and even the amount of nitrogen applied by farmers in some areas is twice the amount of nitrogen needed by crops [57]. Excessive fertilization not only causes fertilizer waste and a negative impact on the environment but also leads to soil nutrient accumulation and low nutrient utilization efficiency [15]. A large amount of nitrogen fertilizer is lost, resulting in the direct emission of N₂O and the indirect emission of N₂O caused by ammonia volatilization and NO₃⁻ leaching.

A large number of fertilizer inputs cause N loss, including NO₃⁻ leaching, NH₃ volatilization, and N₂O emission, which has caused a lot of environmental problems [58]. In the intensive wheat production in North China Plain, with the increase in N application rate, the response of direct N₂O emission and nitrate leaching increased exponentially, while NH₃ volatilization increased linearly [14]. The maximum decrease in Nr losses and greenhouse gas emissions through optimal management measures was 24% and 28%, respectively [59]; the optimal nutrient management measures can reduce the total N₂O emission by 54.8% and the total GHG emission by 44.8% [33]. In this study, compared with FPT, the NH₃ volatilization, NO₃⁻ leaching, and N₂O emission in the different fertilization managements were reduced by 21.05–27.80%, 41.96–51.25%, and 19.56–24.98%, respectively (Figure 2). This is in line with [60], who found that greenhouse gas emission intensity and active N loss intensity can be further reduced under optimal N application management. Zhang et al. [61] further found that applying controlled release urea at an appropriate N application rate could not only achieve a high yield but also improve the economic benefits of the ecosystem and alleviate the negative impact on the environment. Similar results were also found in the higher yield, net benefit, and lower NH₃ volatilization, NO₃⁻ leaching, and N₂O emission in the different fertilization managements in the present study (Table 2; Figure 2). This indicated which precise fertilization management, including suitable fertilizer type and dosage, was an effective strategy for sustainable wheat production.

5. Conclusions

CF3 and CF1 treatments have the highest yield and good economic benefits; therefore, they are attractive to farmers. However, in terms of environmental benefits, 90%CF1 and 90%CF2 produced less reactive nitrogen loss, although CF3 and CF1 had higher reactive nitrogen loss than the above two fertilization management measures, which was 39.24% lower than FPT treatment. In nitrogen utilization, the 90%CF1 and 90%CF2 treatments had the best effect, while the FPT treatment had the worst effect. In conclusion, CF3, CF1, 90%CF1 fertilization management can not only achieve high yield of wheat, but also improve economic benefits and reduce environmental costs, which is an effective fertilization management strategy. In addition, fertilization management strategies are different in different regions, and appropriate management strategies should be further studied according to the soil and climate of different regions.