Energy Balance and Energy Use Efficiency of Annual Bioenergy Crops in Field Experiments in Southern Germany

Round 1

Reviewer 1 Report

The manuscript is generally well written, but I have several suggestion for improvement. The study is limited to annual crops, and this is a pity because there is much interest in comparing maize with perennials grasses like Miscanthus.  The is much interest on comparing maize with no-till perennial crops. The fact that the study is limited to annual crops and arable soil should be better indicated in the title and in the introduction. Yet, not only energy balance is important for energy crops but also the improvement greenhouse gas balance and the accrual of soil carbon storage. So the authors should better clarify that this study compares only a set of annual arable crops. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

your manuscript deals the energy efficiency of energy crops from a multi-site and multi-year field experiment in southern Germany.

The manuscript is well structured and written. The experiments-data are analysed in well known-energy process analyses. The scientific findings are valuable for publication.

The weakness point of the “mineral N fertilization of maize as energy crop” is well discussed in the Methodology chapter 4.1.

From the statistical point of view, I suppose that a 3-factorial ANOVA of your orthogonal dataset could differentiate the three factors (site, catch crop/main crop system) more clearly for the total DM yield (catch and main crop), total net energy output and total energy use efficiency. It would be also easier to interpret the effect of the three factors.

Some aspects for improvement:

Line 137: Was the fuel consumption measured or modelled? Please specify.

Table 3: EUE (energy use efficiency) instead of Eeff of energy efficiency. Consistency in the manuscript.

Line 166: Energy use efficiency instead of energy efficiencies.

Line 195: Please specify the catch crop, where the energy input was higher than in the main crop.

Table 4: Please specify the crop: winter barley => Winter barley (catch crop)/Maize (main crop), etc.

Table 5: What is game browsing?

Comment for the Table 5 and 6:

I suppose a 3-way ANOVA could differentiate the factors (site, catch crop/main crop system and year) more clearly for the total DM yield (catch and main crop).

Line 362-363: What are the reasons for the lower energy input (average - 10 GJ/ha) for ryegrass in Ansbach than in Freising and Straubing?

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf