Influence of the Physical Properties of Samples in the Use of NIRS to Predict the Chemical Composition and Gas Production Kinetic Parameters of Corn and Grass Silages

Round 1

Reviewer 1 Report

The study tries to use the NIRS to predict the chemical composition and gas production kinetic parameters of corn and grass silages. Many data were presented and meaningful, whereas there are some questions and the manuscript cannot be accepted at this form. The following is the specific points:

Line 126 the reference and methods of pH and Ammoniacal Nitrogen should be added, the same as Line 130-134.

Table the min and max DM contents were 14.38 and 84.68, respectively. Please check.

Author Response

The study tries to use the NIRS to predict the chemical composition and gas production kinetic parameters of corn and grass silages. Many data were presented and meaningful, whereas there are some questions, and the manuscript cannot be accepted at this form.
-I am very thankful for all your feedback. Your suggestions have helped improve the article greatly.

The following is the specific points:
Line 126 the reference and methods of pH and Ammoniacal Nitrogen should be added, the same as Line 130-134.
Thank you for your feedback. The change was made in the text, (now line 142, 143)

Table the min and max DM contents were 14.38 and 84.68, respectively. Please check.
-The dry matter limit values presented are correct, since in the Azores archipelago, due to the climatic conditions (high rainfall and humidity) it is difficult to lower the moisture content of the pasture to make silage. Therefore, it is necessary to harvest the grass at a more advanced stage of maturation, increasing the dry matter content of the silage.
It should be noted that the main challenge to the use of NIR spectroscopy is the establishment of reliable calibration equations. This implies that a large calibration set with heterogeneous and representative samples of the application domain is identified and collected beforehand, so that in the future a reliable prediction of unknown samples is possible in the target agroclimatic area.

Reviewer 2 Report

The paper is interesting and well structured, however the materials and methods must be revised and the discussion seems confused. I suggest to revise and remodulate it in differente section to better understand the different analysis performed.

2.2 Experimental design

I suggest to report in a table che climatic condition of the studied area.

The materials and methods must be rewritten, in particular the paragraph 2.6. Non-destructive method -NIR spectroscopy must be improved. 

The data concerning the procedures utilized for the analysis (i.e. quantity of samples, the length of the materials, the replications….)

In addition for the calibration and validation a table with RMSECV; R2 and RMSEP must be added.

Also, the characteristic of corn and the others grasses must be added (i.e. hybrid, time of harvest, month of cultivation….)

In the discussion are reported the calibration data but these must be reported in materials and methods. In particular see lines 295-308 and 472-486.

2.4.2. Determination of biological parameters 

The description of gas production must be improved adding information concerning the:

- replication for each sample

• The measurement of gas ha been done manually or with automatic system?
• Which kind of buffer has been utilized?
• How long was the incubation time?

The discussion must be divided in to three section:

-Traditional methods vs. Non-destructive method -NIR spectroscopy 

-Fresh vs. dry samples

-Gas production 

I suggest to improve the discussion concerning the NIRS analysis of corn with this paper Zicarelli et al. 2023  Nutritional Characteristics of Corn Silage Produced in Campania Region Estimated by Near Infrared Spectroscopy (NIRS). Agronomy 2023, 13, 634.

In conclusion no results of gas production are reported. Please add it.

Author Response

The paper is interesting and well-structured, however, the materials and methods must be revised and the discussion seems confused. I suggest revise and remodulate it in different sections to better understand the different analysis performed.
-I am very thankful for all your feedback. Your suggestions have helped improve the article greatly.

2.2 Experimental design

I suggest reporting in a table the climatic condition of the studied area.
-Thank you so much for your suggestion. The change was made in the text (line 97).

The materials and methods must be rewritten, in particular paragraph 2.6. Nondestructive method -NIR spectroscopy must be improved.
The data concerning the procedures utilized for the analysis (i.e. quantity of samples
-This information is in the text (Line 108-114).

, the length of the materials, the replications….)
-This information is in the text (Line 189-198).

In addition for the calibration and validation a table with RMSECV; R2 and RMSEP must be added.
The spectrophotometer did not have any preset factory calibration that can be reported in the material and methods section. The goal of this work was to calibrate it from scratch for the agroclimatic area of the Azores, with the 400 samples that were collected for this purpose, and test the quality of the calibration.
Also, the characteristic of corn and the other grasses must be added (i.e. hybrid, time of harvest, month of cultivation….)
-This information was added in the text (Line 108-114).

In the discussion are reported the calibration data but these must be reported in materials and methods. In particular see lines 295-308 and 472-486.
-The change was made in the text (now Line 206-237).

2.4.2. Determination of biological parameters
The description of gas production must be improved adding information concerning the:
- replication for each sample
The measurement of gas has been done manually or with automatic system?
Which kind of buffer has been utilized?
How long was the incubation time?
-This information was added in the text (Line 148-159).

The discussion must be divided into three sections:
-Traditional methods vs. Non-destructive method -NIR spectroscopy
-Fresh vs. dry samples
-Gas production
-Thank you for your feedback. I have adjusted the discussion accordingly. I do believe it helps.

I suggest to improve the discussion concerning the NIRS analysis of corn with this paper Zicarelli et al. 2023 Nutritional Characteristics of Corn Silage Produced in Campania Region Estimated by Near Infrared Spectroscopy (NIRS). Agronomy 2023, 13, 634.
-Thank you for your feedback. I added the article to the discussion.

In conclusion no results of gas production are reported. Please add it.
-This information was added in the text.

Round 2

Reviewer 2 Report

The paper can be accepted in the current form.