Rejected Sago Starch as a Coating Material to Mitigate Urea-Nitrogen Emission

Round 1

Reviewer 1 Report

First of all, the English must be edited in the whole document. There are quite a few grammatical mistakes. I marked just some of them.

In the abstract the objective, method and results are stated summarizing the article quite good.

The introduction has to be improved. More studies with bio-based coatings or coatings based on starch should be cited. The section of the objectives (ll 90 -110) is very confusing. There is no “red line” and there are many duplications. This has to be revised.

Materials and methods: the first two subchapters are sufficient, but it would be good to add the solution in which pH was measured. For a better understanding it would also good to add 1 or 2 main facts for each method to enable the reader to have an idea about the method used without checking all sources. Also no number of replications for each measurement is mentioned. Chapter 2.3 is totally confusing and has to be revised. Do I understand it right that the coating consists of the different RSS slurries/RSS solution (please use just one term to avoid confusions) with different concentrations of RSS plus 50 g of RSS flour (starch powder?). If yes, why should the small amount of slurry should make any difference compared to 50 g of pure RSS in every coated treatment? This would question the whole experiment.

The results are in most cases clearly displayed and described.

In the discussion some results are well explained, some explanations are not clear, sometimes wrong citations were made. A review was cited like a research article.

More detailed comments for all chapters are included in the manuscript.

Comments for author File: Comments.pdf

Author Response

Please see the attachment. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The work presented contains a coherent description of the purpose, the research method used, the presentation of the results achieved and their discussion. The paper deals with a very important research issue on better management of nitrogen fertilization with urea. This is a research problem that is very important worldwide, and the laboratory experiment presented is an attempt to develop a formulation of urea with higher fertilizer efficiency.

The manuscript was developed coherently the discussion presented and the conclusion and conclusion are consistent and accomplish the purpose of the paper as stated in the title.

However, two elements are not clear:

1. In subsection 2.3, row 184-187: ''To obtain the similar size of coated urea, urea granules were weighed (200 g for each formulation), sieved to pass through a 2 mm sieve, and added with 25 g of dried RSS flour 185 after which mixed and rotated in the rotary machine at 42 rpm (revolution per minute) 186 until the urea granules were fully covered with the dried RSS flour''

Was the 200g weight of urea made before or after sieving through a 2 mm mesh sieve? If the sieving was done after the 200g weighing the amount of urea that passed through the sieve could be different for each portion of urea to be encapsulated with RSS, which could affect the different thickness of the pellet because the amount of RSS used for pelleting was a constant 50g and the amount of urea could vary.

2. In subsection 3.4, no statistical analysis in figure 8. The lack of statistical analysis makes it impossible to draw conclusions on how the encapsulation affects daily nitrogen losses.

Author Response

1. Authors appreciate reviewer’s comment. Authors want to clarify that to get similar size and diameter of urea granules, the urea were sieved first through 2 mm sieve and then weighed to get 200 g for each formulation. Thank you very much.

2. Authors appreciate reviewer’s comment. Sorry for not including statistical analysis in figure 7 (formerly written as figure 8). Authors has revised the figure 7 by including standard error (error bars). Thank you very much.

Reviewer 3 Report

Dear Editor and authors:

I've reviewed the manuscript entitled "Rejected sago starch as coating material to mitigate urea-nitrogen emission". It is a well-written manuscript that brings the possibility to improve the nitrogen efficiency from urea fertilizer by coating the granules with sago starch and therefore slowing down their dissolution rate and reducing ammonia volatilization. 

Although the use of sago starch for increasing the value of urea-N isn't a novelty, the authors did a good job in describing the preparation, characterization, and laboratory evaluation of their product.

The significant reduction in ammonia volatilization obtained during a 30 d laboratory incubation, shows that coating urea with sago starch may have merit for increasing fertilizer nitrogen use efficiency.

Unfortunately, I suggest rejecting this manuscript because additional experiments are needed. As presented by most references cited by the authors (4-23) this type of research must include tests involving the use of plants (either greenhouse or field experiments) in order to prove that these materials can actually increase nitrogen use efficiency for a given crop under realistic weather conditions. Agronomic experiments would be essential, especially when considering publishing at Agronomy Journal. 

I suggest to the authors finishing their field experiment involving rice and including the results obtained in the manuscript before resubmitting it. 

 

Author Response

Thank you very much for the comment. Authors would like to clarify that this experiment involved the use of waste from sago starch processing for urea coating and its effect on preliminary study which is to mitigate ammonia volatilization and retain nitrogen in soil in the form of available nitrogen such as ammonium and nitrate.

 

The authors aware on the important of tests involving the use of plants (either greenhouse or field experiments) to support that coating urea with rejected sago starch can increase nitrogen use efficiency for a given crop under realistic weather conditions.

 

Our pot study is on-going, which tested RSS coated urea against uncoated urea on rice cultivation for two planting cycles. The pot experiment has many variables to be explored and consists of huge data to be combined with this study. In this preliminary study, we are targeting on the effects of coated urea on mitigating ammonia loss.

In our pot experiment, we are targeting on the nitrogen recovery in soil and plant interaction. We are looking into nitrogen in soil before planting and after planting as well as nitrogen uptake in plant tissues (using paddy as test crop).

We are planning to use the data of pot experiments to be written as one manuscript.

Round 2

Reviewer 3 Report

Dear editor and authors:

My opinion remains, the authors have not added any results of fertilizer nitrogen uptake efficiency by plants. They are trying the get two publications out of one project.

If you check the citation list of this manuscript (see no. 4-23), the majority of papers in which a novel fertilizer is proposed, also include plant results. 

According to my understanding, it is unacceptable for a manuscript that proposes a novel fertilizer to not include field/pot experiments. As my old advisor from the University of Illinois has always mentioned: it is crucial to test a new fertilizer in field experiments, a given fertilizer can show promising results in controlled environments (such as laboratory incubations), but the plants are the final judge, and must be included. 

Author Response

"Please see the attachment"

Author Response File: Author Response.docx