Integrated Management of Weeds in Direct-Seeded Rice in Cambodia
, Joel Janiya 3, Ratha Rien 4, Sophea Yous 4, Sokunroth Chhun 4 and Chariya Korn 4
Round 1
Reviewer 1 Report
Dear authors,
I was glad to read your paper, which I find interesting and well written. Suggestion that could make your work even better are presented in the text of the manuscript.
Comments for author File: 
Comments.pdf
Author Response
Lines 15 & 16:
We inserted "application" but are not sure where to insert "weed management"
Line 44: Please mention Figure 1 in the text, indicate in the figure that the red line shows temperatures and the blue columns show precipitation.
Figure 1 is already referenced in the text. We added text to Figure 1 caption: (blue columns represent monthly rainfall and the red line, maximum temperature oC).
Line 157: This is not exactly understandable. If the main treatment (main plot) is post-emergence application, how than sub-treatment (subplot) can be pre-emergence?
Split –plot designs were implemented to minimise edge effects. In 2018, main plots were seeding rate to avoid excessive tractor movements in the experiment. In 2019, pre-emergence herbicide was chosen as the main plot to minimise edge effects because pre-emergence herbicides were the main focus of the experiment.
Line 246: Methods for determining rice yield components are not listed in materials and methods, they need only be briefly described.
Additional text has been added as per below:
2.3. Sampling procedures in 2018 and 2019
Plant density of rice and weeds (grasses, broadleaves, sedges) was determined from three 60 * 60 cm quadrats per plot. At rice physiological maturity, samples for determination of yield components were taken from three 60 * 60 cm quadrats in each plot. After counting panicles, two sub-samples of three panicles were taken for counts of spikelets per panicle. Paddy moisture content was recorded and 100 grain weight was determined from two samples per plot. Following sampling for yield components, whole plots were harvested for determination of rice paddy yield and weed biomass. Paddy yield was corrected to 14% moisture content.
Line 259. So I don't understand the design of the experiment, if pre-emergence treatment has been performed at 17 DAS (and this is sub-treatment or subplot) then you treated the main plot at the same time because in split plot design the main treatment (main plot) is divided on subplots.
In 2019, the main plots (post-emergence herbicide) and sub-plots (pre-emergence herbicide) were marked out at commencement of the experiment and pre-emergence herbicides were applied to sub-plots on 25th June. Post-emergence herbicide was applied to main plots on 22nd July. See also above line 157 comment.
Line 337: I suggest authors to add a few more references to the discussion and try to comment more on their results by comparing them with other results of similar research.
We have considered this suggestion and have added the following additional passage in the discussion
Pendimethalin was found to effectively control weeds in both years this benefit was not carried through to significant increases in paddy yield and this implies the potential for phytotoxicity to rice. This result is consistent with other findings [21] where pendimethalin effectively controlled weeds but reduced paddy yields especially at higher application rates. Never-the-less, pendimethalin is a potentially valuable post-sowing pre-emergence herbicide for dry direct-seeded rice in North-West Cambodia but further evaluation is required to enable reliable recommendations to be made.
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Author Response File: 
Author Response.docx
Reviewer 2 Report
This is a sound piece of work which deserves to be published with some small improvements. The following are my suggestions:
1. Lines 62 & 70. 'Practice' is the noun and 'Practise' is the verb. In UK English, these should read: 'now practise' and 'been practised'.
2. Line 89. Eleusine indica, also according to...
3. Line 103. costs and benefits
4. Line 129. quadrats. Weeds from...
5. Line 168. Consider adding a line or two of explanation of the concept of orthogonal contrasts.
6. Line 173. Consider explaining what In (y + 1) means.
7. Figs 2. 3, 7c, the axis legends are very difficult to read.
8. Line 233. tillers plant-1.
9. Fig 5a. SQRT in full.
10. Line 248. 80 kg ha-1 resulted...
11. Line 308. non-weedy...
12. You need to add a short Conclusions section.
Author Response
Response to suggestions:
1. Lines 62 & 70. Change accepted and made.
2. Line 89. Change accepted and made.
3. Line 103. Change accepted and made.
4. Line 129. qChange accepted and made.
5. Line 168. We included "planned". Single degree of freedom orthogonal contrasts are commonly used and referenced (Steele & Torrie, 1980) and we feel there is no need to provide any more detail.
6. Line 173. Text revised: "The variance increased with the mean for weed density and biomass data. Therefore a logarithmic transformation, ln (y + 1), was performed on these dependent variable data [13]."
7. Figs 2. 3, 7c, the axis legends are very difficult to read. All figures have been enlarged to make it easier to read the axis legends.
8. Line 233. Change accepted and made.
9. Fig 5a. Change accepted and made.
10. Line 248. Change accepted and made.
11. Line 308. Change accepted and made.
12. Conclusions section added:
Seeding rates in direct-seeded rice can be reduced from 200 kg ha-1 to 80 kg ha-1 or less with row or drill seeding and improved weed control. The use of post-sowing pre-emergence herbicides such as butachlor or oxadiazon can improve weed control in dry direct-seeded rice in North-West Cambodia. However, further research is required to determine if pendimethalin is also a pre-emergence herbicide option for dry direct-seeded rice in the region.
Author Response File: Author Response.docx
