Keywords

1 Introduction

N, P, and K are the major elements restricting the growth and yield formation of maize [1]. The amount absorbed by maize affects the utilization rate of N, P, and K fertilizers. At present, the excessive application of chemical fertilizer not only causes a waste of resources but also poses a potential threat to the environment. There is a certain space for saving fertilizer when applying N, P, and K fertilizers [2]. The Sanjiang Plain is the main production area of spring corn in Heilongjiang province [3]. Maintaining the maize yield is of great significance for food security and stability in China [4]. However, to pursue high yield, the Sanjiang Plain has a high amount of fertilization and a serious phenomenon of blind fertilization, resulting in an imbalance in the proportion of soil N, P, and K, and limiting corn yield [5]. In the northeast black soil area, the yield will not be reduced by reducing the application of P fertilizer by 20%, and the partial productivity of P fertilizer will increase by 17.0%-21.6% [6]. There is no significant difference in corn yield when the straw is used to replace 30% and 60% K fertilizer [7]. Optimizing fertilization can reduce fertilizer input, stabilize production and increase production, reduce environmental pollution, and improve the utilization rate of N, P, and K fertilizers. Studies have shown that reasonable fertilization is conducive to improving the photosynthetic rate of plant leaves [8], prolonging the photosynthetic time, and significantly improving the yield and its indicators [9]. Under the wheat-maize rotation system, the maize yield of optimized fertilization increased by 5.3% [10]. Winter wheat of optimal fertilization in Weibei dryland increased wheat yield, reduced nitrate nitrogen accumulation in the soil profile, and improved nitrogen utilization rate [11].

How to effectively maintain the yield and control the amount of fertilizer is an urgent problem to be solved in agricultural production. This study recommended fertilization according to the nutrient expert system, and on this basis, weight loss, and clear the impact of different fertilizer elements on soil and corn yield, to provide basic data for the gradual realization of cost reduction and efficiency increase in agriculture.

2 Materials and Methods

2.1 Overview of the Test Site

The test site is located in the Agricultural Extension Center of Friendship Farm in Sanjiang Plain, (46.7548° N, 131.8498° E). The soil type is typical black soil, belonging to the continental monsoon climate of the cold temperate zone. The annual average temperature is 2.8 ℃, the effective accumulated temperature is 2 170-2 700 ℃, the annual precipitation is 512.4 mm, and the frost-free period is 120–130 days. The soil type is black soil, with organic matter content of 20.8 g kg−1, an available phosphorus content of 23.86 mg kg−1, an alkali hydrolyzed nitrogen content of 64.0 mg kg−1, a pH of 6.16, an ammonium nitrogen content of 11.86 mg kg−1, the nitrate nitrogen content of 8.42 mg kg−1, and available potassium content of 169.60 mg kg−1.

2.2 Experimental Design

The optimization fertilization experiment in 2021 and 2022 adopted the random block arrangement design, and a total of five treatments are set: nutrient expert-recommended fertilization system (NE), N deficiency treatment (NE-N), P deficiency treatment (NE-P), K deficiency treatment (NE-K) and conventional fertilization (FP). The fertilizer amount were shown in Table 1. The maize variety was Tianhe 2, and the sowing date was in the middle of May. During the whole growth period of maize, natural precipitation was the main irrigation practice.

Table 1. Effect of different fertilization treatments on nitrogen fertilizer utilization rate
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2.3 Sample Collection and Determination Method

Soil sample collection: Five points were selected in different treatments according to the “S” shape before corn harvest, using a soil drill to collect 0–20 cm and 20–40 cm soil layers and mixed totally into a sample respectively. Picked out straw residues and small stones. The air-dried soil samples were extracted with 1 mol L−1 potassium chloride solution (the ratio of soil to liquid is 1:10) by shaking for 1 h. After filtering, use a continuous flow analyzer to determine nitrate nitrogen and ammonium nitrogen. Other soil nutrients were determined by conventional methods.

Yield measurement: in the mature period, the sampling area of each plot was 13 m2, and another 10 plants were taken for indoor planting to calculate the yield.

2.4 Data Analysis

N utilization rate (NUE,%) = (N accumulation amount of plants in N application area at maturity - N accumulation amount in non N application area)/N application amount × 100；

The utilization rate of P fertilizer (PUE,%) = (P accumulation amount of plants in P application area at maturity – P accumulation amount in non-P application area)/P application amount × 100；

Utilization rate of K fertilizer (KUE,%) = (K accumulation of plants in K application area at maturity - K accumulation in non K application area)/K application amount × 100；

The SPSS 17.0 (SPSS, Inc., Chicago, IL, USA) analytical software package was used for all the statistical analyses. Single-factor analysis of variance (ANOVA) and least significant range (LSD) was used to test the different significance at the 5% level. Pearson correlation coefficients of maize yield and other indexes.

3 Results

3.1 Maize Yield and Its Components

The yield was more sensitive to any deficit in N, P, and K fertilizer, especially the fertilizer N. As shown in Table 2, the ear length of maize in the NE-N treatment was the shortest and the FP treatment was the longest, the ear length of NE-N was 41.7% lower than that in the NE treatment (P < 0.05), while NE-P and NE-K were slightly lower than NE treatment. The bald tip value of NE-N was 2.15 cm at the highest level and NE treatment was 0.2 cm at the lowest level, while the value of NE-P, NE-K, and FP treatments did not reach a significant difference higher than NE. In terms of yield, the yield of the NE-N treatment was the lowest one which was significantly different from other treatments, only 3 156 kg ha−1, and the FP, NE-P, and NE-K treatments were lower than NE at 9.3%, 78.0%, and 6.4%, respectively. The NE-N treatment showed the lowest yield, the highest bald tip length, and the ear length the lowest which indicated that the yield and its indicators were seriously affected by fertilizer N deficiency, and the yield reduction of fertilizer P deficiency was the minimum, following by fertilizer K deficiency.

Table 2. Effect of different fertilization treatments on nitrogen fertilizer utilization rate
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3.2 Effect of Different Treatments on Soil Nutrients, Nitrate Nitrogen, and Ammonium Nitrogen

It was shown in Fig. 1 that the nitrate nitrogen content of NE-N was the lowest at 0–20 cm and 20–40 cm soil layers, only 1.57 mg L−1 and 1.79 mg L−1, and FP treatment was the highest at 6.56 and 5.67 mg L−1, which had significant differences from other treatments. However, it was not different among NE-P, NE-K, and NE treatments. Nitrate nitrogen content was closely related to the amount of nitrogen fertilizer applied, for which N deficiency had a lower nitrate nitrogen content. Ammonium nitrogen is mostly adsorbed and fixed by soil particles, with less leaching in soil. Ammonium nitrogen content in NE was the highest at 0–20 cm and 20–40 cm layers. With the deeper of the soil layer, ammonium nitrogen content decreased slightly. At 0–20 cm, the content of ammonium nitrogen of NE-K was the lowest, 28.6% lower than NE while 18.6% of NE-N was lower than NE. At 20–40 cm, the content of ammonium nitrogen in NE was 24.5% higher than that in FP, with no significance.

Fig. 1.
figure 1

Ammonium nitrogen and nitrate nitrogen under different treatments (Different lowercase letters indicate the significance analysis at the level of 0.05 between different treatments at the same level)

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Fertilizer deficiency could decrease organic matter content at 0–20 cm soil layer, except for K deficiency which showed in Fig. 2. All the treatments had no obvious effect at the 20–40 cm soil layer. The content of organic matter of NE-N was the lowest and had a significant difference with NE (P < 0.05). The content pH did not fluctuate heavily, and NE treatment increased the pH value of both 0–20 cm and 20–40 cm soil layer, followed by NE-P as the lowest. There was no significant difference among NE-P, NE-K, and FP treatments.

The content of available nutrients in all treatments was higher at 0-20cm than in the 20–40 cm soil layer (Fig. 2). AN of NE-K and FP treatments were the highest at 0–20 cm soil layer, and the NE-N was the lowest one. The content of AP in FP was the highest at 0–20 cm and 20–40 cm, and the NE treatment was the lowest. The NE-N, NE-P, NE-K, and FP were 3.3%, 10.6%, 26.1%, and 46.6% higher than the NE treatment, respectively.

Fig. 2.
figure 2

Soil nutrient under different treatments (Different lowercase letters indicate the significance analysis at the level of 0.05 between different treatments at the same level)

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3.3 The Relationship Between Yield and Other Indicators

It could be seen from Table 3 that the yield had a positive correlation with AN and organic matter. Nitrate nitrogen had a very significant positive correlation with AP, and a significant positive correlation with AN.

Table 3. Person correlation among yields and other indicators
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4 Discussion

4.1 Effects of Optimized Fertilization on Soil Nutrients, Yield, and Fertilizer Utilization

Optimal fertilization can promote the matching of nutrient demand and supply of crops to promote high yield. N, P, and K are all essential nutrients for crop growth [12]. N is the material basis for plant growth and physiological metabolism. The net photosynthetic rate of maize can be improved by increasing the amount of synthetic chlorophyll and enzymes. P participates in the energy metabolism of maize. K can promote protein synthesis and carbohydrate transfer [13]. In this experiment, the optimized fertilization could increase the content of AN, AP, AK, soil organic matter, and pH in the soil. NE-N did not significantly reduce the content of AN, although no sufficient N fertilizer supply, the growth of plants was reduced due to N deficiency, and the ability to absorb N was significantly weakened. The optimized fertilization had the longest ear length, the shortest bald tip, and the highest yield in all treatments, and the NE-N treatment was the lowest. One of the reasons for the P deficiency without reducing yield was the amount of phosphorus applied in the local custom was higher than that in the optimized fertilization, and a large amount of phosphorus was fixed in the soil.

The fertilizer utilization rate is a representation of the situation in that the fertilizer input in crop production is absorbed and utilized by crops. In 1998, the utilization rate of N, P, and K fertilizers for major grain crops in China ranged from 30% to 35%, from 15% to 20%, and 35% to 50%, respectively [14]. Twenty years later, the utilization rate of N, P, and K fertilizers for major grain crops in China has gradually declined, and the utilization rates of N, P, and K fertilizers range from 10.8% to 40.5%, 7.3% to 20.1% and 21.2% to 35.9%, respectively. In recent years, it has become a common understanding to reduce the amount of fertilizer and improve the practice of fertilization. According to the survey of corn fields in many cities and counties in Heilongjiang Province in recent 20 years, the utilization rates of N, P, and K fertilizers have been improved to varying degrees, 22.3%-50.7%, 5.1%-37.6%, and 26.3%-76.4%, respectively [15]. In this experiment, the utilization rate of N, P, and K in NE was higher than that of FP. Similarly, in Heilongjiang Province, the optimized fertilization of maize carried out in Shuangcheng was 41.8%, 15.5%, and 48.8% of N, P, and K application [9], and the utilization rate of N is significantly higher than the results of this experiment, which may be because the AN content in Shuangcheng was three times that of this experiment. The optimized fertilization treatment with light simplified one-time fertilization can significantly increase the yield of maize, and at the same time improve the utilization rate of nitrogen, phosphorus, and potassium fertilizer, which was 12.8%, 1.8%, and 2.9% higher than the farmers’ conventional fertilization. More importantly, it was a reasonable and effective practice to reduce nitrogen according to the local climate, soil, and production conditions, and to conFig.feasible fertilization technology so that the applied nitrogen fertilizer can be fully absorbed and utilized by crops [16].

4.2 Effects of Optimized Fertilization on Nitrate Nitrogen and Ammonium Nitrogen

Nitrate nitrogen was a former of nitrogen loss in soil moved down with water which tends to increase with the increasing amount of nitrogen [17]. Here, we described the NE treatment and applied a small amount of N fertilizer repeatedly to avoid the loss of water and fertilizer caused by too much N fertilizer. On the other hand, it could also supply N continuously, effectively avoiding the leaching loss of N caused by the one-time mass application and high rainfall intensity [18]. Zheng et al. studied how to reduce N and apply different proportions of organic fertilizer at the same time to ensure maize yield in Shanxi Loess and found that the content of nitrate nitrogen was lower after applying slow-release fertilizer, reducing the amount of potential leaching nitrogen [19]. Under the same amount of nitrogen fertilizer application, coated urea could slowly and continuously release nitrogen. Nitrate nitrogen tends to be low first, then high, and then low throughout the growth period, and remains at an environmentally friendly level. In this experiment, the nitrate nitrogen content of the local farmers used to apply fertilizer was the highest, and the NE-N content was the lowest. Reducing the application of nitrogen fertilizer can significantly reduce the nitrate nitrogen content of the soil. P and K deficiency had little impact on nitrate nitrogen. The soil ammonium nitrogen in NE treatment was the highest in 0–40 cm, and most of it was adsorbed and fixed in soil particles after entering the soil. Only when the amount of nitrogen fertilizer was high, the soil adsorption of ammonium nitrogen reached saturation.

5 Conclusion

The application of fertilizer has a significant impact on the growth and yield formation of maize, especially the application of N fertilizer. A significant correlation between maize yield and AN, organic matter. The optimized fertilization treatment had a good effect on the growth indicators and yield components of maize, which could significantly reduce the bald tip length, increase the ear length of maize, and increase the yield. N deficiency could affect maize yield and its indicators seriously while P and K deficiency was not significant. Based on reducing the application of chemical fertilizer, the optimized fertilization could also improve the utilization rate of N, P, and K, and the yield increase effect was obvious. In summary, it was a reasonable practice to reduce fertilizer by combining local climate conditions and production conditions with fertilizer application technology, then and improving fertilizer utilization.