Next Article in Journal
Strong Fitness Costs of Fall Armyworm Resistance to Dual-Gene Bt Maize Are Magnified on Less-Suitable Host-Crop Cultivars
Previous Article in Journal
Yielding and Bioaccumulation of Zinc by Cocksfoot under Conditions of Different Doses of This Metal and Organic Fertilization
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Agronomy
Volume 12
Issue 3
10.3390/agronomy12030687
agronomy-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Response of Leaf Senescence, Photosynthetic Characteristics, and Yield of Summer Maize to Controlled-Release Urea-Based Application Depth

by
Xu Guo
1,
Guanghao Li
2,
Xiangpeng Ding
1,
Jiwang Zhang
1,
Baizhao Ren
1,
Peng Liu
1,
Shigang Zhang
3 and
Bin Zhao
1,*
1
State Key Laboratory of Crop Biology, College of Agronomy, Shandong Agricultural University, Tai’an 271018, China
2
College of Agriculture, Yangzhou University, Yangzhou 225009, China
3
Tai’an Municipal Bureau of Agriculture and Rural Affairs, Tai’an 271000, China
*
Author to whom correspondence should be addressed.
Agronomy 2022, 12(3), 687; https://doi.org/10.3390/agronomy12030687
Submission received: 5 January 2022 / Revised: 22 February 2022 / Accepted: 9 March 2022 / Published: 11 March 2022
Browse Figures
Versions Notes

Abstract

:
To explore the response of summer maize leaf senescence, photosynthetic characteristics, and yield to the depth of one-time base application of controlled-release urea, which provides a theoretical basis for the light and simplified production of summer maize. Seven treatments were set up with Zhengdan 958 as the material under field conditions, including no nitrogen fertilizer (CK), surface spreading (DP0), furrow application depth of 5 cm (DP5), 10 cm (DP10), 15 cm (DP15), 20 cm (DP20), 25 cm (DP25). The results showed that under the same nitrogen application rate, there are significant differences in the effects of summer maize leaf senescence and photosynthetic characteristics with the increase of fertilization depth, and DP10 and DP15 have the best effects. The LAI of DP10 and DP15 increased by 5.1% and 5.5% compared to DP0 at tasseling stage, and chlorophyll content increased by 6.8% and 7.3% in 10 days after tasseling. Compared with DP0, superoxide dismutase (SOD) increased by 13.1% and 10.5%, the content of soluble protein increased significantly, while the content of malondialdehyde (MDA) decreased by 9.8% and 10.8%, respectively. In addition, Pn and Gs of the ear-leaf significantly increased by 13.9%, 16.5%, and 26.1% and 31.9% at tasseling stage, respectively, over DP0, while Ci decreased by 22.3% and 26.4%, respectively; meanwhile, the photochemical quenching (qP) and quantum yield (ΦPSII) of the reaction center of photosystem II (PSII) of the ear-leaf were significantly improved, the non-photochemical quenching (NPQ) was significantly reduced. The yield of DP10 and DP15 heightened significantly; two-year average value increased by 5.7% and 6.0% compared with DP0; the kernels per spike and 1000-kernels weight increased by 4.8%, 5.2%, and 4.1%, 5.2%, respectively. Comprehensive analysis of LAI, chlorophyll content, various protective enzyme activities and MDA, soluble protein content showed that 10–15 cm is the appropriate fertilization depth when the nitrogen application rate of controlled-release urea is 225 kg N per hectare. In consequence, optimizing fertilization depth of controlled-release urea as a simplified fertilization mode could improve the nitrogen utilization efficiency and obtain higher yield in summer maize, which provides technical support for large-scale application of controlled-release urea.

1. Introduction

Nitrogen is one of the key nutrients that limit crop growth and yield potential, and the rational application of nitrogen fertilizer is essential for achieving high crop yields [1]. Currently, fertilization in production often adopts the “one-shot bombardment” model. Farmers one-sidedly pursue high yields and apply large amounts of fertilizers [2], resulting in a seasonal utilization rate of only about 30% of nitrogen fertilizers [3], which is a serious waste of resources. Fractional fertilization can reduce nitrogen loss and increase yield and nitrogen use efficiency, but it is inconsistent with the social reality of agricultural labor shortage in China and difficult to promote in actual production [4,5,6]. Therefore, no topdressing became one of the important ways to save cost and improve efficiency of summer maize.
Compared with common urea, controlled-release urea saves more time, labor, and cost. Meanwhile, it can also reduce soil ammonia volatilization and greenhouse gas emissions, thus reducing environmental pollution [7,8]. Studies have shown that under the same nitrogen application rate, one-time basal application of controlled-release urea can significantly improve the nitrogen use efficiency of maize, reduce nitrogen loss; also, controlled-release urea showed stable and increased yield compared to the traditional split fertilization of common urea [9,10,11]. Even if controlled-release urea is about 30% less than that of common urea, it can still achieve stable yield [12]. Therefore, on the premise of not reducing production, one-time base application of controlled-release urea is an effective measure to further simplify agricultural production. The release curve of controlled-release fertilizer in the field matches well with the nitrogen demand of maize plants. Compared with common urea, the nutrient release cycle is longer and the release time is relatively controllable, thereby increasing the nitrogen utilization rate [13], but to improve its fertilizer utilization rate, it needs to be combined with fertilization technology. The nutrient release rate of controlled-release urea is principally affected by the temperature of the external environment, and the release rate increases with the rise of temperature [14]. The surface layer of soil is more susceptible to solar radiation and temperature than the deeper layer [15]. Therefore, different fertilization depths have great differences in the conversion of soil available nutrients and the uptake of nutrients by plants [16].
Compared with surface fertilization, deep fertilizer application technology is an efficient fertilization measure [17]. It has been reported that nitrogen significantly affects the fluorescence characteristics and photosynthetic capacity of plants [18,19]. Adequate soil nitrogen contents are closely related to leaf senescence and maize yield [20]. Relevant studies have found that deep application of nitrogen fertilizer can reduce nitrogen loss and increase soil nitrogen content [21], thereby promoting crop root growth and improving crop yield and nitrogen use efficiency [22]. Surface fertilization or shallow fertilization is easy to cause faster nutrient release, which cannot meet the nutrient requirements of maize in the later stages; while deep fertilization not only involves operation difficulty, but also has an adverse effect on the nutrient supply of seedlings. Therefore, the appropriate depth of fertilization is an important factor to achieve controlled release and sustained release of nutrients in controlled-release urea and to boost yield.
Previous studies have carried out a large number of studies on slowing down leaf senescence and improving maize yield in terms of different fertilizer application amounts, water-nitrogen coupling, and combined application ratio of controlled-release urea [23]. The research on the depth of fertilization is mostly limited to the effect of nitrogen fertilizer on the growth and development of maize and the effect of nitrogen fertilizer management on nitrogen utilization [16]. Systematic studies on yield, leaf senescence, and photosynthetic performance of summer maize under different fertilization depths of controlled-release urea are rarely reported. In this study, through the study of LAI, photosynthetic pigments, leaf protective enzyme activities, and photosynthetic characteristics, the control mechanism of controlled-release urea at different fertilization depths on summer maize leaf senescence and photosynthetic characteristics was deeply explored. The aim is to simplify the fertilization method of controlled-release urea under the premise of ensuring the yield of summer maize and provide a theoretical basis for the efficient utilization of nitrogen fertilizer and increase yield of summer maize.

2. Materials and Methods

2.1. Research Site and Experimental Design

This study was conducted during 2013–2014 at the State Key Laboratory of Crop Biology and Experimental Farm of Shandong Agricultural University, China (36°11′ N, 117°06′ E, 151 m above sea level). Located in the Huang-Huai-Hai Plain, the study area belongs to a semi-humid warm temperate continental monsoon climate zone. Figure 1 shows meteorological data during the growth period of summer maize. The soil used for the two-year experiment is brown loam. Concentrations of organic matter, total N, available nitrogen, rapidly available phosphorous (P), and rapidly available potassium (K) in the upper 20 cm of soil were 11.0 g kg−1, 1.2 g kg−1, 124.4 mg kg−1, 45.2 mg kg−1, and 80.8 mg kg−1, respectively. The pH was 6.0, and field water holding capacity was 22.3%.
The fertilizer used in the experiment was a resin-coated urea independently developed by the College of Resources and Environment of Shandong Agricultural University (N content 42%, controlled-release period of 3 months). The nitrogen application rate of controlled-release urea is 225 kg N per hectare. The experiment was arranged as a randomized block design, with each treatment having three replicate plots, and included the following six fertilization depth treatments: surface spreading (DP0), furrow application depth of 5 cm (DP5), 10 cm (DP10), 15 cm (DP15), 20 cm (DP20), 25 cm (DP25), and no application of nitrogen fertilizer treatment (CK). All treatment fertilizers are applied as base fertilizer at one time when sowing (the depth of fertilization is decided by manually digging trenches between rows and applying controlled-release urea at the corresponding depth and then backfilling, the seed belt and the fertilizer belt are separated by 10 cm). The plot area was 45 m2. The tested maize variety was Zhengdan 958, the planting density was 67,500 plants hm−2, the row spacing was 60 cm, and the plant spacing was 25 cm. Both were sown on 10th June in 2013 and 2014, and harvested on 5th October. When sowing, 120 kg ha−1 of P2O5 and 240 kg ha−1 K2O were both applied as base fertilizer at one time. Other field management is the same as that of high-yield fields.

2.2. Leaf Area Index (LAI)

At the tasseling stage (VT), 10, 20, 30, 40, and 50 days after tasseling, 15 plants with the same growth vigor were selected for each treatment (5 plants for each plot), the length and width of the green leaves of each maize plant were measured, and the leaf area index was calculated.
Single leaf area = length × width × 0.75
Leaf area index (LAI) = (leaf area per plant × number of plants per unit land area)/unit land area

2.3. Chlorophyll Concentration

At the tasseling stage (VT) and 10, 20, 30, 40, and 50 days after tasseling, 5 representative plants with the same vigor were selected for each treatment, and their ear-leaves were put into the liquid nitrogen tank and brought back indoors. Ten 0.7-cm-diameter leaf disks were obtained for chlorophyll extraction from fresh ear leaves of five plants (n = 5). Chlorophyll a and chlorophyll b were extracted by grinding the leaf disks with 80% acetone. Total of 1 g of leaf disks was weighed, and 5 mL of 80% acetone and a small amount of quartz sand were added and the sample was ground. Then the sample was filtered, making the constant volume to 25 mL. Chlorophyll a and b concentrations in the supernatant were determined by measuring light absorbance at 663 and 645 nm, respectively, using an ultraviolet spectrophotometer (UV-2800, UNICO, USA). Chlorophyll concentrations were calculated according to the method of Arnon [24].
Chl a = (12.7A663−2.69A645) × V/W
Chl b = (22.9A645−4.68A663) × V/W
Chl a + b = Chl a + Chl b = (20.2A645 + 8.02A663) × V/W
where A is the absorption at the referenced wavelength, Chl a is concentration of chlorophyll a, Chl b is concentration of chlorophyll b, and Chl a + b is the total chlorophyll concentration. V is volume of extract; W is weight of leaves used for extraction.

2.4. Activities of SOD, POD, and Content of MDA and Soluble Protein

At the tasseling stage (VT), 10, 20, 30, 40, and 50 days after tasseling, five representative plants were selected for each treatment, and their ear-leaves were put into a liquid nitrogen tank and brought back indoors and stored in a refrigerator at −80 °C. Ear-leaves (0.5 g) were homogenized in 50 mM phosphate buffer (pH 7.0) with a small quantity of silica sand (n = 5), and the slurry was moved to centrifuge cubes and centrifuged at 13,000× g for 20 min. All enzyme extractions were performed from 0 to 4 °C, and enzyme assays were performed at room temperature (25 °C). The supernatant was used to determine antioxidant enzymes, MDA, and soluble protein content.
Superoxide dismutase (EC 1.15.1.1) activity was determined as described by Wang et al. [25] with minor revisions. The SOD reaction solution was prepared with 0.05 M phosphate buffer (pH 7.8), 130 mM methionine, 750 µM nitro blue tetrazolium, 100 µM ethylene diamine tetraacetic acid, and 20 µM riboflavin in a ratio of 15:3:3:3:3:2.5. Add 20 µL of enzyme extract to the test tube, and add 3 mL of the prepared SOD reaction solution. The reaction was started by exposing the test tube to a white light tube for 30 min at 4000 lux. The reaction was immediately stopped by switching the light off and covering the tube with a black cloth. The absorbance of the reaction mixture was 560 nm. One unit of SOD activity (U) was defined as the rate of enzyme per gram of fresh leaf sample, causing 50% inhibition of the photochemical reduction of nitro blue tetrazolium.
Peroxidase (EC 1.11.1.7) activity was determined as described by Rao et al. [26]. Reaction mixture contained 50 mL of 0.2 mol L−1 phosphate buffer (pH 6.0), 28 μL of guaiacol, 19 μL of 30% H2O2. Next, 3 mL of reaction mixture was added to 40 μL of enzyme extract and the absorbance was read once at 470 nm wavelength in the next 30 s.
The MDA content was determined following the method of Zhao et al. [27] with minor revisions. The preparation of the MDA reaction solution is as follows: 0.6 g of thiobarbituric acid, first dissolved with a small amount of 1M NaOH, and made up to 100 mL with 10% trichloroacetic acid. The 1 mL of enzyme extract was mixed with 2 mL thiobarbituric acid (0.6%) and incubated at 100 °C for 15 min. The reaction was centrifuged at 2500× g for 10 min after cooling to room temperature. The absorbances of the supernatant at three wavelengths (532, 600, and 450 nm, respectively) were determined.
Determination of soluble protein content followed the method of Bradford [28] with minor revisions. Preparation of reaction solution is as follows: dissolve 0.1 g of G-250 in 50 mL of 90% ethanol, add 100 mL of 85% phosphoric acid, make up to 1000 mL, filter. To 20 µL of enzyme extract add 3 mL G-250 and allow to react for 2 min; the absorbances of the supernatant at 595 nm were determined.

2.5. Blade Gas Exchange Parameters

Using the LI-6400 (LI-COR, USA) portable photosynthesis instrument, the photosynthetic rate of the upper surface of the middle part of the ear-leaf was measured from 10:00 to 12:00 on a clear and cloudless day [29]. Measurement environment: LED light source, and the PAR was 1600 μmol m–2. CO2 concentration was maintained at a constant level of 360 μmol mol–1 using a CO2 injector with a high-pressure liquid CO2 cartridge source. For each treatment, 15 plants with consistent growth were selected for measurement (n = 15).

2.6. Chlorophyll Fluorescence Kinetic Parameters

Total of 15 representative plants are selected for each plot (n = 15). PAM pulse modulation fluorometer (Walz, Germany) was used to measure the chlorophyll fluorescence kinetic parameters. The measurement protocol is as follows: before and after high light treatment, leaves were dark-adapted for 60 min. Measuring light of 0.1 μmol m−2 s−1 was imposed to obtain the minimum fluorescence (Fo), and then a 0.8 s saturating light of 10,000 μmol m−2 s−1 was imposed to obtain the maximum fluorescence in the dark-adapted state (Fm), the leaves were continuously illuminated by 191 μmol m−2 s−1 actinic light for 10 min, and steady-state fluorescence (Fs) was then recorded, and a saturating light intensity of 10,000 μmol m−2 s−1 was then imposed for 0.8 s to obtain the maximum fluorescence in the light-adapted state (Fm′). The actinic light was then turned off, and the minimum fluorescence in the light-adapted state (Fo′) was determined after 10 s illumination with far-red light.
The following fluorescence parameters can be calculated from the measured data [30,31,32]:
Photochemical quenching (qP) = (Fm’−Fs)/(Fm′−Fo′);
Quantum yield (ΦPSII) = (Fm′−Fs)/Fm′;
Non-photochemical quenching (NPQ) = (Fm−Fm′)/Fm′

2.7. Grain Yield

Maize was harvested at maturity. The middle three rows of each plot in the field were harvested, and then 30 ears were randomly selected for testing. The main measures are ear length, ear thickness, bald length, ear rows, row grains, and 1000-kernels weight, and yield is calculated.
Yield (kg) = Number of ears per unit area × Kernel number per × Weight of 1000–kernels (g)/1000/1000 × (1–grain water content (%))/(1–14%)

2.8. Statistical Analysis

The data were processed by Microsoft Excel 2013. SPSS 21.0 was used for testing different treatments by one-way analysis of variance (ANOVA) and the least significant difference (LSD) test at p < 0.05 probability. SigmaPlot10.0 (Systat, Chicago, IL, USA) was used for plotting. The grain yield in this paper is the data of 2013 and 2014, and the other indicators are measured and plotted in 2014.

3. Results

3.1. Effects of Controlled-Release Urea Base Application Depth on Yield and Yield Components of Summer Maize

In 2013 and 2014, the one-time base application of controlled-release urea significantly increased the yield by 14% on average compared to CK (p < 0.05) (Table 1). Compared with DP0, other fertilization treatments increased the yield by 2.9%, 5.7%, 6.0%, 3.8%, −0.9% respectively; the yield of DP15 and DP10 improved significantly, while the yield of DP25 was lower than that of DP0. In addition, the effect of fertilization depth on kernels per spiFike and 1000-kernels weight among the yield components is similar to that of yield. Compared with the two-year average value of DP0, the kernels per spike in the treatments of DP10 and DP15 increased by 4.8% and 5.2%, respectively, and the 1000-kernels weight increased by 4.1% and 5.2% (p < 0.05); however, the kernels per spike and 1000-kernels weight of DP25 decreased by 1.5% and 0.7% compared with DP0. Therefore, deep application of controlled-release urea improves the yield of summer maize by increasing the kernels per spike and the 1000-kernels weight, and the suitable fertilization depth of controlled-release urea is 10–15 cm, which is more conducive to controlled-release urea to exert its effect on increasing yield.

3.2. Effects of Controlled-Release Urea Basal Application Depth on Lai of Summer Maize

After tasseling, the LAI of summer maize in each treatment showed a downward trend as the growth period progressed (Figure 2). LAI of fertilization treatment at different periods was significantly increased compared with CK (p < 0.05), and increased by 15.32% on average at tasseling stage. Compared with DP0, the treatments of DP5, DP10, DP15, and DP20 increased by 0.6%, 5.1%, 5.5%, and 0.8% respectively at the tasseling stage, while the DP25 decreased by 1.3%. From 30 to 50 days after tasseling, DP10 and DP15 were significantly higher than other treatments (p < 0.05) and decreased slowly, while other fertilization treatments decreased rapidly, of which DP25 decreased the fastest.

3.3. Effects of Controlled-Release Urea Basal Application Depth on Chlorophyll Content of Summer Maize

The chlorophyll content of different treatments showed a single-peak curve change, reaching a maximum value of 10 days after tasseling, and then gradually decreasing (Figure 3). The application of controlled-release urea treatments significantly increased the chlorophyll content (p < 0.05), over CK. For different basal application depth treatments, 10 days after tasseling, the chlorophyll content of DP5, DP10, DP15, and DP20 increased by 2.7%, 6.8%, 7.3%, 3.5% compared with DP0, and DP25 decreased by 2.9%. Moreover, 50 days after tasseling, the chlorophyll content of each treatment (except DP25) increased by 2.1%, 23.1%, 22.4%, and 5.8% over DP0, and the chlorophyll content of DP25 decreased by 7.9% (p < 0.05).

3.4. Effects of Controlled-Release Urea Base Application Depth on Senescence Characteristics of Ear-Leaves of Summer Maize

From tasseling to 50 days after tasseling, the SOD activity of ear leaves reached the maximum 10 days after tasseling (Figure 4). Compared with CK, the SOD activity of ear-leaves in the treatment of nitrogen application in each period improved significantly (p < 0.05). For the fertilization treatments, 50 days after tasseling, other treatments increased by 11.8%, 22.6%, 28.1%, 10.5% (p < 0.05), and 1.6% respectively over DP0. From 10 to 50 days after tasseling, the SOD activities of DP0, DP5, DP10, DP15, DP20, and DP25 decreased by 56.2%, 54.9%, 52.5%, 49.2%, 54.3%, and 56.0%, respectively; DP15 had the smallest drop, followed by DP10. The change pattern of POD activity and soluble protein content in ear-leaves of summer maize after tasseling was similar to that of SOD activity.
With the advancement of the growth process, the MDA content in ear-leaves of summer maize showed a gradually increasing trend. Compared with CK, MDA content was significantly decreased by nitrogen application (p < 0.05). In the treatments of nitrogen application, from 10 to 50 days after tasseling, MDA contents in ear-leaves of DP15 and DP10 were significantly lower than other treatments (p < 0.05). Furthermore, 50 days after tasseling, the MDA content of DP5, DP10, DP15, and DP20 ear leaves were 8.2%, 16.3%, 18.6%, and 10.5% lower than that of DP0, respectively, while DP25 increased by 2.0%.

3.5. Effects of Controlled-Release Urea basal Application Depth on Photosynthetic Characteristics of Summer Maize

As the growth period progressed after tasseling, the net photosynthetic rate (Pn) and stomatal conductance (Gs) of ear-leaves of each treatment decreased significantly, while the intercellular CO2 concentration (Ci) showed an opposite trend (Figure 5). Compared with the treatment without fertilization, the one-time base application of controlled-release urea can significantly improve Pn and Gs after tasseling, and reduce Ci (p < 0.05).
The depth of basal application of controlled-release urea had a significant effect on the net photosynthetic rate of ear-leaves. From the tasseling stage to 30 days after tasseling, Pn and Gs of ear-leaves of DP15 and DP10 were significantly higher than other fertilization treatments, and Ci was significantly reduced (p < 0.05). At tasseling stage, Pn and Gs of DP10 and DP15 were significantly increased by 13.9%, 16.5% and 26.1%, 31.9%, and Ci was significantly decreased by 22.3% and 26.4% compared with DP0.

3.6. Effects of Controlled-Release Urea Base Application Depth on Photosystem II (PSII) of Ear-Leaves of Summer Maize

The photochemical quenching (qP) and quantum yield (ΦPSII) of the ear-leaves under different treatments all gradually decreased with the growth period, while non-photochemical quenching (NPQ) gradually increased (Figure 6). Compared with CK, the application of controlled-release urea significantly improved qP, ΦPSII and reduced NPQ (p < 0.05). From the tasseling stage to 30 days after tasseling, the difference between different fertilization depths increases. After tasseling, the qP and ΦPSII of DP10 and DP15 were always significantly higher than those of other treatments, and DP15 always had the lowest NPQ (p < 0.05). The difference between DP10 and DP15 was not significant.

4. Discussion

4.1. Effects of Controlled-Release Urea Base Application Depth on Senescence Characteristics of Ear-Leaves of Summer Maize

Grain formation is closely related with leaf senescence after anthesis, and extending the duration of green leaves and increasing the effective grain filling time are the basis for obtaining high yields [33]. The LAI and chlorophyll content can reflect the photosynthetic performance of plants and leaf senescence process, and are also important factors affecting crop yield [34]. Our study indicated that controlled-release urea could improve LAI and chlorophyll content of summer maize significantly. Deep application of nitrogen fertilizer can promote maize root growth and nutrient absorption, increase chlorophyll content in leaves and dry matter accumulation above ground, and delay leaf senescence [35,36]. Our study showed that increasing the fertilization depth based on the application of controlled-release urea can slow down the decline of post-tasseling LAI and chlorophyll content compared to surface spreading (DP0), which is basically consistent with the results of Wu et al. [37]. The difference between DP25 and DP0 gradually decreased, indicating that when the controlled-release urea basal application reaches a certain depth, continuing to increase the fertilization depth will no longer improve LAI and chlorophyll content of summer maize. On the contrary, it leads to a decrease in nitrogen utilization efficiency [38] and accelerates the process of aging.
SOD and POD are the most important ROS-scavenging systems in plants, which activity indicates the strength of the anti-aging ability of plants; the changes in MDA content and soluble protein content are also one of the physiological and biochemical indicators reflecting leaf senescence [39,40,41]. Application of controlled-release fertilizer can enhance the activity of ROS-scavenging enzymes in the middle and late stages of growth, reduce MDA content, delay leaf senescence, improve the net photosynthetic rate of crops, and significantly increase crop yields and economic benefits [42], which is basically consistent with our results. Dysregulation of ROS metabolism is an important cause of premature crop leaf senescence [43,44]. In our study, the application of controlled-release urea at a depth of 10–15 cm could maintain the physiological activities of higher protective enzymes SOD and POD and the content of soluble protein in leaves, reduce the accumulation of MDA in leaves, and be beneficial to improve the balance between the production and elimination of reactive oxygen species in the cell. Appropriate fertilization depth significantly increases SOD, POD, and CAT activity, reducing MDA content and H2O2, O2- content, thereby leading to increases in CO2 assimilation, the Pn value, and biomass [37,45], which is the same as our results. Enhanced antioxidant enzyme activity and photosynthesis together delay leaf senescence. This may be one of the important physiological reasons that the senescence and photosynthetic decline of summer maize leaves can be significantly delayed by the suitable deep application of controlled-release nitrogen fertilizer.

4.2. Effects of Controlled-Release Urea Base Application Depth on Photosynthetic Characteristics of Summer Maize

Improving the photosynthetic capacity of maize leaves after anthesis and extending the duration of higher photosynthetic capacity are the keys to increasing yield [33,46]. One-time base application of controlled-release urea is beneficial to enhancing nitrogen absorption, delaying leaf senescence, and improving maize photosynthetic performance; at the same time, it still maintains a high leaf area and photosynthetic rate after anthesis, which is conducive to the production of more photosynthetic products [47], which is consistent with our results. As the growth period progresses, the net photosynthetic rate of summer maize leaves decreases. Compared with surface spreading (DP0), increasing the fertilization depth of controlled-release urea within a certain range can further enhance photosynthetic performance. It demonstrates that when controlled-release urea is applied deeply in the 10–15 cm soil layer, adequate nitrogen supply could prolong the duration of photosynthetic functions [48], and lead to higher Pn values in leaves [49], enhance the photosynthetic performance of leaves, and make the photosynthetic rate reach the best condition [50]; meanwhile, providing more photosynthetic products for grain filling, which is an important physiological reason for the significant increase in yield of controlled-release urea base application depth of 10–15 cm.
Changes in the chlorophyll fluorescence-induced kinetics can be used to detect the decreases in the photosynthetic capacity caused by leaves senescence [20]. Photosystem II (PSII) is the primary site of photochemical reactions, which has the important function of sustaining photosynthesis and limiting the utilization of light energy [51,52]. The photochemical quenching (qP), quantum yield (ΦPSII), and non-photochemical quenching (NPQ) can reflect the light energy absorption, light energy conversion, and heat dissipation changes of the PSII [32,53], which are important performance indexes. Studies have shown that the application of controlled-release urea can alleviate the decline of Gs and Pn, and meanwhile improve the maximum light energy conversion efficiency of PSII after anthesis [54]. Deep application of nitrogen fertilizer can significantly enhance the performance of the donor/acceptor side of the PSII of leaves after tasseling, improve the photoelectron transfer rate, and thus enhance the photosynthetic rate [55]. In our study, on the one hand, sufficient chlorophyll content and higher LAI under suitable fertilization depth converted more light energy into chemical energy; on the other hand, through the improvement of photosynthetic function, more absorbed light energy is allowed to enter the photochemical process, and non-photochemical dissipation such as heat dissipation is suppressed, which is consistent with previous research [37,56,57]. On this basis, controlled-release urea is suitable to be applied 10–15 cm deep to further strengthen the conversion of light energy in the reaction center. By increasing the openness of the PSII reaction center, it promotes the improvement of its performance; therefore, enhancing the light energy conversion efficiency of crops, accumulating more energy for dark reaction carbon assimilation, and realizing the improvement of the photosynthetic rate of maize ear-leaves.

4.3. Effects of Controlled-Release Urea Base Application Depth on Yield and Yield Composition of Summer Maize

Reasonable application of controlled-release fertilizers has an important effect on the increase of maize yield [23]. The key to achieving high crop yields requires the coordinated development of crop yield components. Studies have shown that the one-time application of controlled-release urea can significantly increase kernels per spike and 1000-kernels weight of maize, and promote the increase of yield [58]. For the fertilization depth of normal nitrogen fertilizer for summer maize, different fertilization positions have no significant effect on kernels per spike and 1000-kernels weight [59]. Our study found that leaves of DP0 and DP25 have low photosynthetic performance, rapid leaf senescence, and their yield and yield composition are significantly reduced, indicating that surface spreading or exceeding the appropriate fertilization depth is not conducive to the rise in yield. The yield of DP10 and DP15 increased by 5.7% and 6.0%, over DP0; the kernels per spike and 1000-kernels weight increased by 4.8%, 5.2% and 4.1%, 5.2%, respectively. It is proved that the suitable deep application of nitrogen is more in line with the root distribution law [22,60], and fertilization depth of controlled-release urea in the range of 10–15 cm can further enhance the nitrogen supply status of maize. Compared with other treatments, appropriate fertilization depth delays the leaves senescence, prolongs the high-value duration of the photosynthetic function of the leaves, and promotes grain filling [36,61,62], thereby improving kernels per spike and 1000-kernels weight, and ultimately increasing yield [37,60]. In summary, the one-time base application of controlled-release urea combined with fertilization depth within the range of 10–15 cm is the best in increasing yield. In our experiment, the one-time basal application and suitable deep application of controlled-release urea can regulate leaf senescence and photosynthesis of ear-leaves in summer maize after tasseling, which may be related to the promotion of the optimal distribution of maize roots and the improvement of root vigor after tasseling. These need to be further studied and verified.

5. Conclusions

Controlled-release urea basal application can meet the nitrogen demand of summer maize during the growth period, and significantly increase the yield of summer maize. When the one-time base application depth of controlled-release urea is in the range of 10–15 cm, it can effectively improve LAI and chlorophyll content of summer maize leaves after tasseling, enhance SOD and POD activities, and reduce MDA accumulation, thereby delaying leaf senescence; meanwhile, the nutrient release capability of the controlled-release fertilizer leads to enhancing the efficiency of light energy conversion and utilization in summer maize leaves, which enhances photosynthesis performance and promotes the transfer and distribution of photosynthetic products to the grain; then increase the yield, especially the 1000-kernels weight and kernels per spike in the yield constituent factors. Under the conditions of this experiment, when the nitrogen rate of controlled-release urea is 225 kg N per hectare, the one-time base application depth in the range of 10–15 cm is a high-yield, efficient, light, and simplified summer maize cultivation and management technique.

Author Contributions

Conceptualization, X.G. and X.D.; methodology, G.L. and X.G.; investigation, G.L. and B.R.; data analysis, X.G. and X.D.; writing—original draft preparation, X.G. and X.D.; writing—review and editing, B.Z. and J.Z.; supervision, P.L. and S.Z.; project administration, B.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This study was funded by National Key R&D Program of China (2018YFD0300603).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data generated or analyzed during this study are included in this published article.

Conflicts of Interest

The authors declare no conflict of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

References

  1. Yong, X.; Li, T.; Han, Y.L.; Yang, L.; Xie, G.X.; Peng, J.W.; Tian, C.; Zhou, X.; Liu, Q.; Rong, X.M.; et al. Reduction in nitrogen fertilizer applications by the use of polymer-coated urea: Effect on maize yields and environmental impacts of nitrogen losses. J. Sci. Food Agric. 2019, 99, 2259–2266. [Google Scholar]
  2. Zhang, F.S.; Wang, J.Q.; Zhang, W.F.; Cui, Z.L.; Ma, W.Q.; Chen, X.P.; Jiang, R.F. Nutrient use efficiencies of major cereal crops in China and measures for improvement. Acta Petrol. Sin. 2008, 45, 915–924. [Google Scholar]
  3. Peng, S.B.; Buresh, R.J.; Huang, J.L.; Zhong, X.H.; Zou, Y.B.; Yang, J.C.; Wang, G.H.; Liu, Y.Y.; Hu, R.F.; Tang, Q.Y.; et al. Improving nitrogen fertilization in rice by site-specific N management: A review. Agron. Sustain. Dev. 2010, 30, 649–656. [Google Scholar] [CrossRef]
  4. Liu, Z.H.; Wu, X.B.; Tan, D.S.; Li, Y.; Jiang, L.H. Application and Environmental Effects of One-off Fertilization Technique in Major Cereal Crops in China. Sci. Agric. Sin. 2018, 51, 3827–3839. [Google Scholar]
  5. Patil, M.D.; Das, B.S.; Barak, E.; Bhadoria, P.B.S.; Polak, A. Performance of polymer-coated urea in transplanted rice: Effect of mixing ratio and water input on nitrogen use efficiency. Paddy Water Environ. 2010, 8, 189–198. [Google Scholar] [CrossRef]
  6. Wang, Y.L.; Lu, Y.L.; Liu, J.; Su, R.G.; Ma, L.; Tan, J.F.; Bai, Y.L. Effects of special slow-release fertilizer on yield and nutrient absorption and utilization of summer maize. China Soils Fert. 2015, 1, 29–32. [Google Scholar]
  7. Chi, Y.B.; Yang, P.L.; Ren, S.M.; Ma, N.; Yang, J.; Xu, Y. Effects of fertilizer types and water quality on carbon dioxide emissions from soil in wheat-maize rotations. Sci. Total Environ. 2020, 698, 134010. [Google Scholar] [CrossRef]
  8. Ward, D.; Kirkman, K.; Hagenah, N.; Tsvuura, Z. Soil respiration declines with increasing nitrogen fertilization and is not related to productivity in long-term grassland experiments. Soil Biol. Biochem. 2017, 115, 415–422. [Google Scholar] [CrossRef]
  9. An, J.W.; Wang, R.; Bao, H.J.; Xie, Z.J.; Hua, L.M. Effects of basal dressing total fertilizers once with different fertilizer formulas on product and nutrient uptake of maize. Chin. J. Soil Sci. 2008, 39, 874–877. [Google Scholar]
  10. Guo, P.; Huang, K.C.; Li, X.D.; Zhu, C.H.; Long, W.J.; Yuan, J.C.; Kong, F.L. Effect of common and controlled release urea ratio on matter accumulation and yield of maize. J. Soil Water Conserv. 2017, 31, 191–196. [Google Scholar]
  11. Yang, Y.; Tan, D.S.; Jiang, L.H.; Guo, J.H.; Sun, K.G.; Xu, Y.; Shi, J.; Wang, M.; Liu, Z.H. The Effects of One-off Fertilization of Summer Maize in Huang-Huai-Hai Region. Sci. Agric. Sin. 2018, 51, 3909–3919. [Google Scholar]
  12. Geng, J.B.; Chen, J.Q.; Sun, Y.B.; Zheng, W.K.; Tian, X.F.; Yang, Y.C.; Li, C.L.; Zhang, M. Controlled-release urea improved nitrogen use efficiency and yield of wheat and corn. Agron. J. 2016, 108, 1666–1673. [Google Scholar] [CrossRef]
  13. Li, G.H.; Zhao, B.; Dong, S.T.; Zhang, J.W.; Liu, P.; Vyn, T.J. Interactive effects of water and controlled release urea on nitrogen metabolism, accumulation, translocation, and yield in summer maize. Sci. Nat. 2017, 104, 72. [Google Scholar] [CrossRef]
  14. Huang, Q.Y.; Fan, X.L.; Tang, S.H.; Zhang, M.; Huang, X.; Yi, Q.; Pang, Y.W.; Huang, J.F. Seasonal differences in N release dynamic of controlled-released urea in paddy field and its impact on the growth of rice under double rice cropping system. Soil Tillage Res. 2019, 195, 104371. [Google Scholar] [CrossRef]
  15. He, T.T.; Wang, Y.K.; Shi, Z.P. Movement law of soil temperature and soil water under annual film mulching in Loess Hilly Region. Southwest China J. Agric. Sci. 2019, 32, 1314–1322. [Google Scholar]
  16. Hiromu, I.; Yoshifumi, N.; Makoto, H.; Masanori, N.; Takuji, O.; Naoki, H. Suppressive effect of the deep placement of lime nitrogen on N2O emissions in a soybean field. Sci. Total Environ. 2021, 804, 150246. [Google Scholar]
  17. Rochette, P.; Angers, D.; Chantigny, M.H.; Gasser, M.O.; MacDonald, J.D.; Pelster, D.E.; Bertrand, N. Ammonia Volatilization and Ni-trogen Retention: How Deep to Incorporate Urea? J. Environ. Qual. 2013, 42, 1635–1642. [Google Scholar] [CrossRef]
  18. Wei, S.S.; Wang, X.Y.; Shi, D.Y.; Li, Y.H.; Zhang, J.W.; Liu, P.; Zhao, B.; Dong, S.T. The mechanisms of low nitrogen induced weakened photosynthesis in summer maize (Zea mays L.) under field conditions. Plant Physiol. Biochem. 2016, 105, 118–128. [Google Scholar] [CrossRef]
  19. Lin, J.; Wang, Y.; Sun, S.; Mu, C.; Yan, X. Effects of arbuscular mycorrhizal fungi on the growth, photosynthesis and photosynthetic pigments of Leymus chinensis seedlings under salt-alkali stress and nitrogen deposition. Sci. Total Environ. 2017, 576, 234–241. [Google Scholar] [CrossRef]
  20. Wang, L.; Deng, F.; Ren, W.J. Shading tolerance in rice is related to better light harvesting and use efficiency and grain filling rate during grain filling period. Field Crops Res. 2015, 180, 54–62. [Google Scholar] [CrossRef]
  21. Jiang, C.Q.; Lu, D.J.; Zu, C.L.; Zhou, J.M.; Wang, H.Y. Root-zone fertilization improves crop yields and minimizes nitrogen loss in summer maize in China. Sci. Rep. 2018, 8, 15139. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  22. Chen, Y.Y.; Fan, P.S.; Mo, Z.W.; Kong, L.L.; Tian, H.; Duan, M.Y.; Li, L.; Wu, L.J.; Wang, Z.M.; Tang, X.R.; et al. Deep Placement of Nitrogen Fertilizer Affects Grain Yield, Nitrogen Recovery Efficiency, and Root Characteristics in Direct-Seeded Rice in South China. J. Plant Growth Regul. 2020, 40, 379–387. [Google Scholar] [CrossRef]
  23. Li, G.H.; Zhao, B.; Dong, S.T.; Zhang, J.W.; Liu, P.; Vyn, T.J. Impact of controlled release urea on maize yield and nitrogen use efficiency under different water conditions. PLoS ONE 2017, 12, e0181774. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  24. Arnon, D.I. Copper enzymes in isolated chloroplasts. Polyphenoloxidase in Beta vulgaris. Plant Physiol. 1949, 24, 1. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  25. Wang, X.; Cai, J.A.; Jiang, D.; Liu, F.L.; Dai, T.B.; Cao, W.X. Preanthesis high-temperature acclimation alleviates damage to the flag leaf caused by post-anthesis heat stress in wheat. J. Plant Physiol. 2011, 168, 585–593. [Google Scholar] [CrossRef]
  26. Rao, M.V.; Paliyath, G.; Ormrod, D.P. Ultraviolet-B- and ozoneinduced biochemical changes in antioxidant enzymes of Arabidopsis thaliana. Plant Physiol. 1996, 110, 125–136. [Google Scholar] [CrossRef] [Green Version]
  27. Zhao, X.X.; Huang, L.K.; Zhang, X.Q.; Li, Z.; Peng, Y. Effects of heat acclimation on photosynthesis, antioxidant enzyme activities, and gene expression in orchardgrass under heat stress. Molecules 2014, 19, 13564–13576. [Google Scholar] [CrossRef] [Green Version]
  28. Bradford, M.M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem. 1976, 72, 248–254. [Google Scholar] [CrossRef]
  29. Ren, B.Z.; Cui, H.Y.; Camberato, J.J.; Dong, S.T.; Liu, P.; Zhao, B.; Zhang, J.W. Effects of shading on the photosynthetic characteristics and mesophyll cell ultrastructure of summer maize. Sci. Nat. 2016, 103, 67. [Google Scholar] [CrossRef]
  30. Bilger, W.; Björkman, O. Role of the xanthophyll cycle in photoprotection elucidated by measurements of light-induced absorbance changes, fluorescence and photosynthesis in leaves of Hedera canariensis. Photosyn. Res. 1990, 25, 173–185. [Google Scholar] [CrossRef]
  31. Genty, B.; Briantais, J.M.; Baker, N.R. The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence. Biochim. Biophys. Acta Gen. Subj. 1989, 990, 87–92. [Google Scholar] [CrossRef]
  32. Van Kooten, O.; Snel, J.F.H. The use of chlorophyll fluorescence nomenclature in plant stress physiology. Photosynth. Res. 1990, 25, 147–150. [Google Scholar] [CrossRef]
  33. Lv, L.H.; Zhao, M.; Zhao, J.R.; Tao, H.B.; Wang, P. Canopy structure and photosynthesis of summer maize under different nitrogen fertilizer application rates. Sci. Agric. Sin. 2008, 41, 2624–2632. [Google Scholar]
  34. Wang, Y.Q.; Tao, H.B.; Yang, L.H.; Qi, L.P.; Zhang, G.G.; Chen, P.F.; Wang, P. Effects of nitrogen managements on canopy structure and nitrogen absorption utilization of summer maize. J. Maize Sci. 2013, 21, 125–130. [Google Scholar]
  35. Yu, H.Y.; Qian, X.G.; Luo, X.Q.; Zhang, S.S.; Ouyang, J.M.; Zhang, Z.M. Effect of nitrogen application depth on plant growth and nutrient absorption of maize seedlings. Jiangsu Agric. Sci. 2017, 45, 44–48. [Google Scholar]
  36. Pan, S.G.; Wen, X.C.; Wang, Z.M.; Ashraf, U.; Tian, H.; Duan, M.Y.; Mo, Z.W.; Fan, P.S.; Tang, X.R. Benefits of mechanized deep placement of nitrogen fertilizer in direct-seeded rice in South China. Field Crops Res. 2017, 203, 139–149. [Google Scholar] [CrossRef]
  37. Wu, P.; Liu, F.; Chen, G.Z.; Wang, J.Y.; Huang, F.Y.; Cai, T.; Zhang, P.; Jia, Z.K. Can deep fertilizer application enhance maize productivity by delaying leaf senescence and decreasing nitrate residue levels? Field Crops Res. 2022, 277, 108417. [Google Scholar] [CrossRef]
  38. Yang, Y.M.; Sun, Y.M.; Jia, L.L.; Meng, C.X.; Jia, S.L. Effect of base nitrogen application depth on summer maize yield, nitrogen utilization efficiency and nitrogen residue. Plant Nutr. Fert. Sci. 2016, 22, 830–837. [Google Scholar]
  39. Hodges, D.M.; Andrews, C.J.; Johnson, D.A.; Hamilton, R.I. Antioxidant enzyme responses to chilling stress in differentially sensitive inbred maize lines. J. Exp. Bot. 1997, 48, 1105–1113. [Google Scholar] [CrossRef]
  40. Zhao, L.Y.; Deng, X.P.; Shan, L. The response mechanism of active oxygen species removing system to drought stress. Acta Bot. Boreali-Occident. Sin. 2005, 25, 413–418. [Google Scholar]
  41. Ren, B.C.; Zhang, J.W.; Li, X.; Fan, X.; Dong, S.T.; Zhao, B.; Liu, P. Effect of waterlogging on leaf senescence characteristics of summer maize in the field. Chin. J. Appl. Ecol. 2014, 25, 1022–1028. [Google Scholar]
  42. Nie, J.; Zheng, S.X.; Dai, P.A.; Xiao, J.; Yi, G.Y. Physiological basis of controlled release nitrogen fertilizer regulating photosynthetic function and leaf senescence in rice. Chin. J. Rice Sci. 2005, 3, 255–261. [Google Scholar]
  43. Yang, S.S.; Gao, J.F. Reactive oxygen species, free radicals and plant senescence. Acta Bot. Boreali-Occid. Sin. 2001, 21, 215–220. [Google Scholar]
  44. Ahmad, I.; Kamran, M.; Yang, X.N.; Meng, X.P.; Ali, S.; Ahmad, S.; Zhang, X.D.; Bilegjargal, B.; Ahmad, B.; Liu, T.N.; et al. Effects of applying uniconazole alone or combined with manganese on the photosynthetic efficiency, antioxidant defense system, and yield in wheat in semiarid regions. Agric. Water Manag. 2019, 216, 400–414. [Google Scholar] [CrossRef]
  45. Wang, J.; Wen, X.F.; Zhang, X.Y.; Li, S.G.; Zhang, D.Y. Co-regulation of photosynthetic capacity by nitrogen, phosphorus and magnesium in a subtropical Karst forest in China. Sci. Rep. 2018, 8, 7406. [Google Scholar] [CrossRef] [PubMed]
  46. Khan, M.N.A.; Murayama, S.; Ishimine, Y.; Tsuzuki, E.; Nakamura, I. Physio-morphological studies of F2 hybrids in rice (Oryza sativa L.). Plant Prod. Sci. 1998, 1, 231–239. [Google Scholar] [CrossRef]
  47. Zhao, B.; Dong, S.T.; Zhang, J.W.; Liu, P. Effects of controlled-release fertilizer on nitrogen use efficiency in summer maize. PLoS ONE 2013, 8, e70569. [Google Scholar]
  48. Chen, Z.K.; Niu, Y.P.; Ma, H.; Hafeez, A.; Luo, H.H.; Zhang, W.F. Photosynthesis and biomass allocation of cotton as affected by deep-layer water and fertilizer application depth. Photosynthetica 2017, 55, 638–647. [Google Scholar] [CrossRef]
  49. Miner, G.L.; Bauerle, W.L. Seasonal responses of photosynthetic parameters in maize and sunflower and their relationship with leaf functional traits. Plant Cell Environ. 2019, 42, 1561–1574. [Google Scholar] [CrossRef]
  50. Wu, P.; Chen, G.Z.; Liu, F.; Cai, T.; Zhang, P.; Jia, Z.K. How does deep-band fertilizer placement reduce N2O emissions and increase maize yields? Agric. Ecosyst. Environ. 2021, 332, 107672. [Google Scholar] [CrossRef]
  51. Strasser, R.J.; Tsimill-Michael, M.; Srivastava, A. Analysis of the chlorophyll a fluorescence transient. In Advances in Photosynthesis and Respiration; Papageorgiou, G., Govindjee, Eds.; KAP Press: Amsterdam, The Netherlands, 2004; Chapter 12; pp. 1–47. [Google Scholar]
  52. Ren, X.L.; Jia, Z.K.; Chen, X.L.; Han, J. Effects of furrow and ridge rain collection on photosynthetic characteristics and yield of maize in semi-arid area. Acta Agron. Sin. 2008, 5, 838–845. [Google Scholar] [CrossRef]
  53. Maxwell, K.; Johnson, G.N. Chlorophyll fluorescence-a practical guide. J. Exp. Bot. 2000, 51, 659–668. [Google Scholar] [CrossRef] [PubMed]
  54. Li, G.H.; Zhao, B.; Dong, S.T.; Liu, P.; Zhang, J.W.; He, Z.J. Effects of coupling controlled release urea with water on yield and photo-synthetic characteristics in summer maize. Acta Agron. Sin. 2015, 41, 1406–1415. [Google Scholar] [CrossRef]
  55. Dong, Q.L.; Lou, H.C.; Zhang, H.; Zhao, R.L.; Zheng, B.; Li, Z.J.; Li, G.; Ning, T.Y. Improving photosynthetic efficiency of flag leaves at anthesis stage and nitrogen utilization of winter wheat by deep placement of common and control-released urea mixture. Plant Nutr. Fert. Sci. 2019, 25, 1134–1145. [Google Scholar]
  56. Hou, W.H.; Zhang, Y.X.; Wang, H.J.; Zhang, Q.X.; Hou, M.L.; Cong, B.M.; Du, X.Y. Effects of Nitrogen Application Level on Leaf Photosynthetic Characteristics and Chlorophyll Fluorescence Characteristics of Leymus chinensis. Acta Agrestia Sin. 2021, 29, 531–536. [Google Scholar]
  57. Ju, Z.C.; Yu, Z.W. Effects of nitrogen topdressing at different growth stage on chlorophyll fluorescence of winter wheat flag leaves. Chin. J. Appl. Ecol. 2006, 17, 395–398. [Google Scholar]
  58. Hou, Y.P.; Li, Q.; Kong, L.L.; Qin, Y.B.; Wang, M.; Yu, L.; Wang, L.C.; Yin, C.X. Effects of different slow/controlled release nitrogen fertilizers on spring maize nitrogen uptake and utilization, soil inorganic nitrogen and nitrogen balance. Sci. Agric. Sin. 2018, 51, 3928–3940. [Google Scholar]
  59. Jiang, C.Q.; Lu, D.J.; Wang, S.J.; Zhou, J.M.; Zu, C.L.; Wang, H.Y. Research on placement site of urea single application in summer maize. J. Agric. Sci. Technol. 2017, 19, 67–74. [Google Scholar]
  60. Cheng, Y.; Wang, H.Q.; Liu, P.; Dong, S.T.; Zhang, J.W.; Zhao, B.; Ren, B.Z. Nitrogen placement at sowing affects root growth, grain yield formation, N use efficiency in maize. Plant Soil 2020, 457, 355–373. [Google Scholar] [CrossRef]
  61. Murchie, E.H.; Chen, Y.; Hubbart, S.; Peng, S.; Horton, P. Interactions between senescence and leaf orientation determine in situ patterns of photosynthesis and photoinhibition in field-grown rice. Plant Physiol. 1999, 119, 553–564. [Google Scholar] [CrossRef] [Green Version]
  62. Zhu, C.H.; Ouyang, Y.Y.; Diao, Y.; Yu, J.Q.; Luo, X.; Zheng, J.G.; Li, X.Y. Effects of mechanized deep placement of nitrogen fertilizer rate and type on rice yield and nitrogen use efficiency in Chuanxi Plain, China. J. Integr. Agric. 2021, 20, 581–592. [Google Scholar] [CrossRef]
Agronomy 12 00687 g001 550
Figure 1. Rainfall and temperature during summer maize growth period from 2013 to 2014.
Figure 1. Rainfall and temperature during summer maize growth period from 2013 to 2014.
Agronomy 12 00687 g001
Agronomy 12 00687 g002 550
Figure 2. Effect of different basal application depths of controlled-release urea on leaf area index. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 15).
Figure 2. Effect of different basal application depths of controlled-release urea on leaf area index. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 15).
Agronomy 12 00687 g002
Agronomy 12 00687 g003 550
Figure 3. Effects of different basal application depths of controlled-release urea on chlorophyll a + b in leaves of panicle. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 5).
Figure 3. Effects of different basal application depths of controlled-release urea on chlorophyll a + b in leaves of panicle. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 5).
Agronomy 12 00687 g003
Agronomy 12 00687 g004 550
Figure 4. Effects of different basal application depths of controlled-release urea on activity of SOD and POD, content of MDA and soluble protein in panicle leaf after tasseling. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 5).
Figure 4. Effects of different basal application depths of controlled-release urea on activity of SOD and POD, content of MDA and soluble protein in panicle leaf after tasseling. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 5).
Agronomy 12 00687 g004
Agronomy 12 00687 g005 550
Figure 5. Effects of different basal application depths of controlled-release urea on photosynthetic characteristics of panicle leaf. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 15). Different letters in each column indicate significant differences at p < 0.05 (LSD).
Figure 5. Effects of different basal application depths of controlled-release urea on photosynthetic characteristics of panicle leaf. CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 15). Different letters in each column indicate significant differences at p < 0.05 (LSD).
Agronomy 12 00687 g005
Agronomy 12 00687 g006 550
Figure 6. Controlled-release urea depth of different base on summer maize ear lobe photochemical quenching (qP), non-photochemical quenching (NPQ), and quantum yield (ΦPSII). CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 15). Different letters in each column indicate significant differences at p < 0.05 (LSD).
Figure 6. Controlled-release urea depth of different base on summer maize ear lobe photochemical quenching (qP), non-photochemical quenching (NPQ), and quantum yield (ΦPSII). CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15: fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Thin vertical bars are standard errors (n = 15). Different letters in each column indicate significant differences at p < 0.05 (LSD).
Agronomy 12 00687 g006
Table
Table 1. Effects of different basal application depths of controlled-release urea on summer maize yield and yield composition.
Table 1. Effects of different basal application depths of controlled-release urea on summer maize yield and yield composition.
YearTreatmentsRow
Number		Kernels per RowKernel Number per SpikeWeight of
1000–Kernels (g)		Yield
(kg·ha−1)
2013CK14.57a35.57b518.26d271.4b8902.5d
DP014.75a36.67ab540.94c283.7ab9954.0bc
DP514.57a37.39ab544.79bc285.0ab10,137.5b
DP1014.93a38.36a572.71a291.8a10,443.0a
DP1514.87a38.95a579.26a295.6a10,492.5a
DP2014.57a38.64a562.93ab286.4a10,308.3ab
DP2514.50a36.33ab526.83cd280.3b9855.0c
2014CK15.35a34.38b527.73c301.8c9315.0d
DP015.45a36.12a558.13b307.0bc10,122.0c
DP515.65a35.88ab561.53b317.0ab10,406.5b
DP1015.70a36.90a579.33a323.3a10,780.5a
DP1515.67a36.77a576.26a326.2a10,790.5a
DP2015.75a36.03a567.48ab319.6a10,526.2ab
DP2515.65a35.58ab556.75b306.5bc10,040.5c
CK: no fertilizer; DP0: surface application; DP5: fertilization depth 5 cm; DP10: fertilization depth 10 cm; DP15; fertilization depth 15 cm; DP20: fertilization depth 20 cm; DP25: fertilization depth 25 cm. Different letters indicate that the difference has reached a significant level (p < 0.05).
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Guo, X.; Li, G.; Ding, X.; Zhang, J.; Ren, B.; Liu, P.; Zhang, S.; Zhao, B. Response of Leaf Senescence, Photosynthetic Characteristics, and Yield of Summer Maize to Controlled-Release Urea-Based Application Depth. Agronomy 2022, 12, 687. https://doi.org/10.3390/agronomy12030687

AMA Style

Guo X, Li G, Ding X, Zhang J, Ren B, Liu P, Zhang S, Zhao B. Response of Leaf Senescence, Photosynthetic Characteristics, and Yield of Summer Maize to Controlled-Release Urea-Based Application Depth. Agronomy. 2022; 12(3):687. https://doi.org/10.3390/agronomy12030687

Chicago/Turabian Style

Guo, Xu, Guanghao Li, Xiangpeng Ding, Jiwang Zhang, Baizhao Ren, Peng Liu, Shigang Zhang, and Bin Zhao. 2022. "Response of Leaf Senescence, Photosynthetic Characteristics, and Yield of Summer Maize to Controlled-Release Urea-Based Application Depth" Agronomy 12, no. 3: 687. https://doi.org/10.3390/agronomy12030687

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop