General comments

The authors performed an extensive study on maize growth at two distinct soil textures with different water regimes for a normal and extremely dry weather year. During the growing season, they collected a comprehensive dataset on root length, soil water potential, sap flow, leaf water potential, leaf transpiration, stomatal conductance, net photosynthesis and maize growth observations. These data were used to derive hydraulic conductances for the soil-root system, the plant stems and the entire plant system, to describe the maize reaction to dry weather and soil conditions and the determine the maize water use efficiency.

The paper addresses very relevant scientific questions related to the growth and management of one of the most important staple crops. The methods are clearly described and valid. The experimental results are well presented in 14 informative graphs and supplementary material and are objectively in detail described. The discussion is systematic and justified. Both the introduction and discussion are embedded in current scientific literature. The conclusions are sound and very useful for state-of-the-art crop-soil modeling.

In general, the used language is fluent and precise. Below I listed some minor text errors.

Specific comments

Line 66: Omit “of”

Line 117: Add space in “genotypesduring”

Line 134: “it” should be “it’s”

Line 178: “and 2018F1P3” should be “and 2018F2P3”

Line 180: omit “in”

Line 187: “form” should be “from”

Line 593-596: rewrite sentence

Line 649: “effects” should be “effect”

Line 650: “which based” should be “which was based”

Line 667-669: rewrite sentence

Review of the paper « Responses of field-grown maize to different soil types, water regimes, and contrasting vapor pressure deficit « 

The paper reports the results of two experiments in which a maize genotype is grown under two soil types, i.e. a stony soil type and a silty soil type, and under two water treatment, i.e. a rainfed treatment that suffers water stress and a fully irrigated treatment. The authors then perform a number of measurement on the stomatal conductance, transpiration, sap flow rate, and assimilation rate, together with a number of water potential measurements at different levels. They also measured the root:shoot ratio in this factorial. One of the important results is the large variation between soil, but also between water treatment, in the root:shoot ratio. This has consequences for the hydraulic conductance of the soil-root-leaf-atmosphere continuum, where the main result is the demonstration that root system and soil-plant hydraulic conductance depended strongly on the soil texture. This is an important result that confirms other recent findings.

The results of the paper are very important, especially in showing the important role of the soil in shaping up plant physiological responses related to the plant hydraulic properties, and as such need to be published. That said, I find that the paper is quite long and with too many figures (14). It has a discussion that I think is too long (11 pages) and contains complex elements of the results and does not make enough effort of summarizing, part by part, what are the key messages that need to come up. Therefore, I think the papers needs to be made more concise, may be less technical in some parts of it, before it can be published. It gives at times the impression that it was written as a long report about a series of results, lacking in focus sometimes. As it stands, it does not pay justice to the results that are presented and to the work that was done.

Minor comments:

L108: Replace ‘that’ by ‘because they’

L117: Space

L128: Insert ‘.’ After ‘conductance’

L134: replace ‘it’ by ‘its’

L138: replace ‘includes’ by ‘including’

L146-147: may be replace ‘different components  (root, stem and whole soil-plant hydraulic conductance)’ by ‘different components of the hydraulic conductance (root, stem, whole soil-plant)’

L155-157: Does each of these “rhizitrone facilities” represent what you call later “a site”??

L187: replace ‘form’ by ‘from’

L198: Do you mean to say that over the 7m length of each of these 54 horizontal tubes, 20 measurements (images) were taken in each of them??

L206: replace ’of’ by ‘in’

 L210-211: Do you mean to say that you harvested five subplots, each of a 1m2, in each replication?? If that is the case, how did you treat the data? You averaged them?

L304-305: The question is whether you measured such root cracks. And also what was the size of these putative crack as, if too large, roots may not be able to grow through such air-filled gaps. So, may be clarify whether you had any kind of indication of such cracks, and about their size (in Vertisol you could have cracks that would be 10 cm wide and surely no roots would go through that, so, it is important to know more about soil cracks in that silty soil).

L312-328 and Figs 4-6: I wonder if you should group the three figures by showing the continuation of these 4 types of measurements on the same graph, indicating when irrigation would begin and stop. It would much better allow to compare different days, and compare soil and soil-by-water treatment combinations among them for these different factors. The way the figures are laid out and given the relatively small differences it is a bit difficult to do that.

L377-378: Here you switch to DOY, whereas in earlier figures you used the calendar dates. This may be a detail but the data presented are sufficiently complex that it would be good to harmonize what can be. So either choose DOY or calendar dates but stick to it.

L389-399: I see the graph of Fig 11, but the end of the paragraph makes an important interpretation on the data that I have difficulties to follow, possibly because the data that are presented are not adequate for the reader to easily understand that interpretation. Could you clarify?

L440: Instead of saying that rooting depth was sensitive to the presence of crack, it would be clearer to say if presence of cracks increased/decreased rooting depth.

L455: you mention root:shoot ratio but then talk about 200-1000 cmg-1, which is a density and not a ratio, please correct.

L435-478: This part of the discussion is too long, repeats a number of result part, and then brings elements of literature in a rather scattered and unrelated way (for instance talking about the soil nutrient effects on root length). And finally, it does not give a tangible conclusion of what we should retain about these root length differences between soil texture and between water treatment.

L481: as affected by ?

L484: replace ‘lower’ by ‘less’

L482-489: you comment your results, then earlier results from others. And these are different. But you leave the reader hanging here: what is your interpretation/explanation for that?

L482-522: Here also is a fairly long piece of complex discussion that would need to end with a kind of message. I guess the message is that while Welcker and other have show genotypic differences earlier, here you show the soil influence on minimum psi Leaf.

L525: Stomatal conductance?

L528: replace ‘estimate’ by ‘estimation’

L533-539: Here I think it would be better to stick to the units of mm h-1 MPa-1 and then convert the values in 10-5 h-1  from  the citations into that mm h-1 MPa-1 unit which has been used in your graphs.

L540-541: That sentence is not understandable

L649: contrasting

L666: …. and decreased at more negative…

L667: remove ‘plant’

L668: replace ‘that’ by ‘and’