One-Time Nitrogen Fertilizer Application Using Controlled-Release Urea Ensured the Yield, Nitrogen Use Efficiencies, and Profits of Winter Wheat

Round 1

Reviewer 1 Report

The aim of the paper „One-time nitrogen fertilizer application using controlled-release urea ensured the yield, nitrogen use efficiencies, and profits of winter wheat” was to evaluate the effectiveness of one-time nitrogen fertilizer application and to investigate is it possible to simplify fertilization methods with minimal labor input in different soil types. Wheat is a staple crop, and China is among the world's largest producers, so even a small increase in average yield, could bring significant economic gain, which outlines the importance of the results presented in this paper. This article falls within the scope of this journal, and I believe that it will be interesting to readers.

 

The experiment is well designed, results are properly analyzed and presented. Authors used ANOVA to test a hypothesis, they noted that they used year, wheat variety, fertilizer, and their interactions as sources of variation. I wonder, why they didn’t use location as a source of variation too? And it would be interesting to see the effect size of each source of variation and their significance.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer:

Thank you for your comments concerning our manuscript entitled “One-time nitrogen fertilizer application using controlled-release urea ensured the yield, nitrogen use efficiencies, and profits of winter wheat” (ID agronomy-1821507). Those comments are valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and have made correction which we hope meet with your approval. All revisions are marked up in the MS Word document by the "Track Changes" function. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

Point 1: Line 22 split instead of spilt

Response 1: The misspelling has been revised.

Point 2: Line 35 and 36 Wheat grain yield in China has reached 5.74 tons per hectare 35 in 2020, which is 65% higher than that of the world average - According to FAO STAT average wheat yield in China in 2020 was 5.74, and average World yield was 3.47 t/ha. The difference is not 65% as it is stated in line 35 and 36.

Response 2: We apologized for not describing the yield data precisely. We modified this sentence into: “China has achieved a wheat grain yield of 5.74 tons per hectare in 2020, which is 1.65 times the world average.”

Point 3: Line 143 The reference is not written in accordance to instructions

Response 3: The wrong citation format has been revised.

Point 4: Line 235 3.2 subtitle is under the table 2, I guess that something has moved during saving the document as pdf. It should be corrected.

Response 4: The position of the table has been re-arranged.

Point 5: The experiment is well designed, results are properly analyzed and presented. Authors used ANOVA to test a hypothesis, they noted that they used year, wheat variety, fertilizer, and their interactions as sources of variation. I wonder, why they didn’t use location as a source of variation too? And it would be interesting to see the effect size of each source of variation and their significance.

Response 5: Thank you for your suggestion! Initially, we tried to perform ANOVA analysis considering the experiments at different sites as two independent experiments. We realized that the role of locations is also very interesting and needs further analysis. We reincorporated location as a variable in the ANOVA analysis and present the results in Table S1.

Reviewer 2 Report

Abstract

 

What is CRF-60/80?

Please, check this sentence. It is confused. “One-time fertilization with controlled released fertilizer (CRF) is a promising way for reducing labor cost, increasing nitrogen use efficiency (NUE) and alleviating environmental pollution in winter wheat (Triticum aestivum L.) cultivation. However, further study is needed in developing suitable fertilizer formulas due to the complex relationship among CRF release characteristics, soil  properties, temperature and precipitation of wheat growing regions.”

 

Introduction

Explain, N world consumption

Explain, N consumption of wheat

Explain, the difference between the N sources (urea (SCU), polymer-coated urea (PCU), polymer coating of sulfur-coated urea)

 

Materials and Methods

Add information of are cultivation in the last 5 years

Add soil classification (soil taxonomy or FAO)

Give more explanation about the fertilizers (i.e., process)

Add average of precipitation and temperature in both years and areas

Add Figure with treatments

 

Results

 

Figure 1: Explain the difference between 40 and 60, for example.

Explain, the soil N decreasing with N fertilizers. Try to explain the plant absorption

The authors could use some multivariate analysis to explain the data. I think that will help to understand the Results. For example, which site presented the better result.

Demonstrate the difference between sites and years.

How was the effect of climate conditions?

Why CRF-60 and CRF-80 treatments were the better options?

 

 

Author Response

Dear Reviewer:

Thank you for your comments concerning our manuscript entitled “One-time nitrogen fertilizer application using controlled-release urea ensured the yield, nitrogen use efficiencies, and profits of winter wheat” (ID agronomy-1821507). Those comments are valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and have made correction which we hope meet with your approval. All revisions are marked up in the MS Word document by the "Track Changes" function. The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

Point 1: (Abstract) What is CRF-60/80?

Response 1: Due to the word limit of the abstract, we abbreviate CRF-60 and CRF-80 as CRF-60/80. We apologize for the confusing expression and have revised the text to “CRF-60 and 80 treatments”.

Point 2: (Abstract) Please, check this sentence. It is confused. “One-time fertilization with controlled released fertilizer (CRF) is a promising way for reducing labor cost, increasing nitrogen use efficiency (NUE) and alleviating environmental pollution in winter wheat (Triticum aestivum L.) cultivation. However, further study is needed in developing suitable fertilizer formulas due to the complex relationship among CRF release characteristics, soil properties, temperature and precipitation of wheat growing regions.”

Response 2: We apologize for the confusion caused by the expression. This sentence has been revised to: “One-time fertilization with controlled released fertilizer (CRF) is a promising way for reducing labor cost, increasing nitrogen use efficiency (NUE) and alleviating environmental pollution in winter wheat (Triticum aestivum L.) cultivation. However, CRF release characteristics were related to various factors such as soil properties, temperature and precipitation, further study is needed in developing suitable fertilizer formulas adapting to local conditions.”

Point 3: (Introduction) Explain, N world consumption

Response 3: In my humble opinion, “N world consumption” indicates “total nitrogen fertilizer consumption all around the world”.

Point 4: (Introduction) Explain, N consumption of wheat

Response 4: In my humble opinion, “N consumption of wheat” stands for “the total amount of nitrogen required by wheat from both soil and fertilizer during the whole growth period”.

Point 5: (Introduction) Explain, the difference between the N sources (urea (SCU), polymer-coated urea (PCU), polymer coating of sulfur-coated urea)

Response 5: Three kinds of CRU mentioned in the text were SCU, PCU and PSCU.

SCU, indicating “sulfur coated urea”, is a controlled release fertilizer (CRF) with sulfur or modified sulfur coated on urea granule. SCU was initially an attractive CRF for farmers. The price is cheap, and sulfur is a secondary plant nutrient and fungicide. But its mechanism comprises two steps: the burst of its coating and the continual release by core fertilizer diffusion.

PCU, which is “polymer-coated urea”, is to cover the fertilizer core with polymer coating. There are different types of polymer coatings. Unlike sulfur coatings, polymer coatings are not easily disrupted by microorganisms. Its diffusion mechanism has three steps: 1. water penetrates into the coating and the core granule; 2. fertilizer dissolves, the osmotic pressure increases; 3. the nutrient releases gradually through swollen coating membrane.

PSCU, known as the polymer coating of sulfur-coated urea, which is to coat another polymer material outside the sulfur-coated urea granule. It has better controlled release characteristics than SCU, but the manufacturing cost is cheaper than PCU, since it has a thinner polymer coat.

Point 6: (Materials and Methods) Add information of are cultivation in the last 5 years

Response 6: Do you mean information of area cultivation in the last 5 years? Thanks for the advice, we have added “… and in both areas the cultivation system has been rice-wheat rotation for more than five years.” in line 107-108.

Point 7: (Materials and Methods) Add soil classification (soil taxonomy or FAO)

Response 7: We apologize for not specifying the soil classification in the text. Soil type information has been added in table 1.

Point 8: (Materials and Methods) Give more explanation about the fertilizers (i.e., process)

Response 8: Thank you for your advice! We have added some details about the fertilizers in line 120-123.

Point 9: (Materials and Methods) Add average of precipitation and temperature in both years and areas

Response 9: Thank you for your advice! We have added precipitation and temperature data in both years and areas in line 112-115.

Point 10: (Materials and Methods) Add Figure with treatments

Response 10: Thank you for your advice! We have added a table (Table 2) to better clarify the nitrogen fertilizer used in the treatments.

Point 11: (Results) Figure 1: Explain the difference between 40 and 60, for example.

Response 11: The coating thickness of fertilizer granules differs for CRFs with different controlled release longevity, and the rate of water absorption and expansion of fertilizer granules differs, resulting in different time durations for them to enter the “nutrient release phase”. For example, CRF-40 has a thinner coating than CRF-60, so it has a shorter time span for the initial stage of water absorption. Its N accumulative release rate reached to 20% at about 11 days after incubation, while for CRF-60, this time point is about 20 days after incubation. That makes the difference in release longevity between different CRFs.

Point 12: (Results) Explain, the soil N decreasing with N fertilizers. Try to explain the plant absorption.

Response 12: Soil inorganic nitrogen content shows the dynamic results of nitrogen in the soil under the head action of nitrogen release from nitrogen fertilizer and nitrogen uptake by wheat. When nitrogen fertilizer is applied to the field, it is decomposed into inorganic nitrogen, part of which is stored in soil particles or converted into organic nitrogen, another part is absorbed by crops, and some is lost into the environment, such as ammonia volatilization. So soil N content decreased soon after the fertilization. It is generally assumed that there are two peaks of N demand for winter wheat: at the seedling stage and after jointing, and the demand is much higher in the latter. Therefore, the rate of soil inorganic nitrogen decline will be lower in the earlier stages of fertility than in the later stages.

Point 13: (Results) The authors could use some multivariate analysis to explain the data. I think that will help to understand the Results. For example, which site presented the better result.

Response 13:

Thank you for your suggestion!

Initially, we consider the main objective of the study was set to select the best fertilizer application formulations at different trial sites (with different soil types, weather conditions). So we tried to perform ANOVA analysis considering the experiments at different sites as two independent experiments. We reincorporated location as a variable in the ANOVA analysis and present the results in Table S1.

We also tried to perform multiple regression analysis of indicators such as soil inorganic N content with wheat grain yield or plant N accumulation, but did not obtain the satisfying results. We believe that there are different CRF formulas that suited to local conditions in different locations. The effects of different locations on CRF fertilizer release in relation to temperature, precipitation and soil type, and cultivation practices deserve further in-depth exploration, and we are already conducting chamber and field trials in this regard.

Point 14: (Results) Demonstrate the difference between sites and years.

Response 14:

The ANOVA results indicated that, wheat grain yield in 2017-2018 was lower than 2018-2019, while the yield at YZ site was lower than that at JY site. The number of spikes, grain per spike  and thousand grain weight showed the same trend, which could be due to the low precipitation at the beginning of the growth season in 2017-2018, which was not suitable for CRFs to absorb water and releasing N, while higher precipitation and rainy weather during the filling period were not conducive for grain-filling.

When it comes to the differences of the experimental sites, the grain yield at JY site was higher than that at YZ site, and the thousand grain weight and spike number showed the same trend with the yield. The soil organic matter and total N content of JY site was higher, and the soil inorganic N content was also higher, which was more adequate for the N supply of wheat.

Point 15: (Results) How was the effect of climate conditions?

Response 15:

Since the temperature and precipitation conditions were relatively close between the two sites, the differences in weather conditions were mainly between the different experimental years. Overall, less precipitation in the early stage in 2017-2018 was unfavorable for CRF to absorb water and release nutrients, which was slightly less effective in the tiller formation stage compared to the 2018-2019 years, so fewer spikes were formed. More precipitation in May 2018 was unfavorable for the formation of high grain weight in the seed filling stage. So the experiment in the 2018-2019 showed a higher number of spikes and higher thousand grain weight.

In terms of temperature, the overwintering period in 2017-2018 was cooler, but during the rest of the year, there was little difference. Little difference in temperature were observed between locations, so the impact of temperature on wheat growing was small.

Point 16: (Results) Why CRF-60 and CRF-80 treatments were the better options?

Response 16: In treatments of CRF-60 in Yangzhou and CRF-80 in Jiangyan, soils provided appropriate N to produce adequate tillers, wheat stored sufficient dry matter for translocating to grains after anthesis, which also improved the post-anthesis photosynthesis, promoted the accumulation of photosynthates in wheat grains.