Estimation of Watermelon Nutrient Requirements Based on the QUEFTS Model

Round 1

Reviewer 1 Report

Comments:

In the present study authors have made an interesting estimation of watermelon yield using a modification of QUEFTS model from an older method of Janssen et al, 1990. Since watermelon cultivation in China seems to be important, I think this study is a nice and useful research idea to predict fertilization-based production. Authors using QUEFTS model make a quantification and evaluation of N, P, and K uptake of watermelon plantation through field experiments, a crop that has not yet been studied using the initial model or any modified one. Model of this study can provide guidance about conventional fertilization.

My comments are:

• Authors discuss extensively in introduction and generally inside the whole text the interactions among N, P, and K which have been considered in this model. They don’t discuss the field fertilization in general. They could add a few lines in introduction and in discussion the importance of fertilization balance concerning soil type, soil microbial population and possible biofertilization additionally with conventional fertilizing and how this approach could affect N, P, and K uptake and final crop yield.
• They can also discuss the correlation between pH 8.66 and the high P-Olsen 22.2 (table 2), namely the bioavailability of P in the specific field.
• Line 30-34: too many numbers and details on an abstract. It is better to describe the whole QUEFTS model crop prediction in relation to  N, P, K balance in general

 

Author Response

Question #1：They don’t discuss the field fertilization in general.

Response: Thanks for the reviewer’s suggestion. We discuss the field fertilization of watermelon as “In this study, some observations of N, P, and K uptake were not close to the balanced nutrient uptake thresholds …… including farmers’ practices, nutrient omission treatments from field experiments in the watermelon database [60].” in line 275-282, “The nutrient HI calculated by the QUEFTS model (Table 7) …… were therefore provide practical guidance for the appropriate fertilization and avoiding of fertilizer waste[30] in line 297-303, and have added more detailed writings as follows: “In validation trials, organic fertilizer combined with synthetic …… to achieve robust production and economic returns in the future, according to these balanced nutrient requirements for watermelon production.” in line 316-327.

 

Question #2：They could add a few lines in introduction and in discussion the importance of fertilization balance concerning soil type, soil microbial population.

Response: Thanks for the reviewer’s suggestion. These contents have been supplemented as “Moreover, nutrient uptake (especially N, P) is affected by many factors, such as soil type, pH, organic matter, and soil microbes and their activity, and all of them are closely related to the bioavailability of nutrients, further causing the difference of nutrient supply in different regions [21].” in line 71-74 and “However, a few of such N, P, and K uptake values were not close to the 1:1 threshold (Figure 5), which might be attributed to the diversities of soil properties, soil microbial population and fertilizer type (organic or synthetic fertilizer) [61]” in line 314-316.

 

Question #3：They could add the possible bio-fertilization additionally with conventional fertilizing and how this approach could affect N, P, and K uptake and final crop yield.

Response: Thanks for your valuable suggestion, although “bio-fertilization” or “microbial fertilizers” has not been applied in watermelon plantations in China. On the other hand, “manures or other organic fertilizers, etc.” should be combined with inorganic fertilizers, if we understand your comments correctly. As a result, in the revised manuscript we have added to the writings as follows: “In validation trials, organic fertilizer combined with synthetic or inorganic fertilizer application significantly increased nutrient uptake and fruit yield compared to conventional fertilization (Table 3). This was due to the fact that organic or inorganic fertilization changed soil physic-chemical properties, especially pH, which affected the availability of nutrients [62]. This interpreted well for the low available phosphorus in alkaline soil (Table 2) [63]. Meanwhile, the results also indicated the applicability and feasibility of bio-fertilization additionally with conventional fertilizing in watermelon production.” in line 316-322.

 

Question #4：They can also discuss the correlation between pH 8.66 and the high P-Olsen 22.2 (table 2), namely the bioavailability of P in the specific field.

Response: Thanks for the reviewer’s suggestion. In line 316-322 we have added more detailed writings as follows: “In validation trials, organic fertilizer combined with synthetic or inorganic fertilizer application significantly increased nutrient uptake and fruit yield compared to conventional fertilization (Table 3). This was due to the fact that organic or inorganic fertilization changed soil physic-chemical properties, especially pH, which affected the availability of nutrients [62]. This interpreted well for the low available phosphorus in alkaline soil (Table 2) [63].”. What needs to be explained is that the content of P-Olsen in fluvo-aquic soil is in a low level, lower than that of the whole country（24.7 mg/kg）, and fluvo-aquic soil is a typical soil in North China Plain.

 

Question #5：Line 30-34: too many numbers and details on an. It is better to describe the whole QUEFTS model crop prediction in relation to N, P, K balance in general.

Response: Thanks for the reviewer’s suggestion. The balanced nutrient requirements of N, P and K of watermelon predicted by the QUEFTS model have been listed in the abstract, which are principal and important parameters to fertilization management. In line 30-35 we have revised those sentences as “To produce 1000 kg fruit of watermelon, 2.11 kg N, 0.27 kg P, and 2.69 kg K were required in shoot, and the corresponding internal efficiencies (IE) were 475, 3682, and 372 kg fruit per kg N, P, and K, respectively. The modified QUEFTS model also simulated that a balanced N, P, and K removal by fruit (accounting for 50.9%, 58.2%, and 66.4% of these nutrient accumulations in shoots, respectively).”

 

In addition

1. Authority on Latin binomial of watermelon has been revised as “Citrullus lanatus (Thunb.) Matsum. et Nakai” in line 43.

 

2. In line 311-313 we have added more detailed writings as follows: “The P values for N, P, and K were 0.574, 0.156, and 0.654, respectively (Figure 5), suggesting that there were no significant differences between observed and model values and they fitted well with each other.”

 

In addition, numerous minor corrects, modifications and language edits with tracking have been substantially revised taken throughout the whole manuscript.

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

only few not fundamental suggestions:

line 23....."where" (delete), perhaps better "which"

line 24....."global watermelon" (delete), perhaps better "world's watermelons"

line 49 - 50......"global production" (delete), perhaps better "world values"

line 64......addict "use for" after "are hard to"

line 107...."indexes (HIs)", perhaps better "indexes (HI)"

Tab. 3 2th line..."NE-N ^1" (delete) perhaps better "NE-N"

line 142.......not "¹ N" but "N"

line 200......."Red" (delete)

line 222......."few" (delete), perhaps better "only one"; delete "were" and add "was" after "HI observation"

line 228 add "maximum" before "diluition"

 

What is the main question addressed by the research? Is it relevant and interesting? The main question addressed by the research is to test a method to drive the mineral fertilization of watermelon in China environments. It is relevant because China is absolutely the first world watermelons producer (62% and 60% of the world surfaces and tons produced) and the first world utilizer of mineral fertilizers with about the 25% of the total. It is interesting because actually in China the mineral fertilization is a big question not so controlled. How original is the topic? What does it add to the subject area compared with other published material? The argument is not so original because the method QUEFTS is already been tested on other cultivated plants and the new contribution to the subject area is moderate, but overall significant. Is the paper well written? Is the text clear and easy to read? For me the paper is sufficient well written, but the text in not so easy and clear to read above all in the case of "material and methods". Are the conclusions consistent with the evidence and arguments presented? Do they address the main question posed? Overall yes.

Author Response

Question #1：line 23....."where" (delete), perhaps better "which"

Response: Thanks for the reviewer’s suggestion. “where” has been replaced by “which” in line 23.

 

Question #2：line 24....."global watermelon" (delete), perhaps better "world's watermelons"

Response: Thanks for the reviewer’s suggestion. “global watermelon” has been replaced by “world's watermelons” in line 24.

 

Question #3：line 49-50......"global production" (delete), perhaps better "world values"

Response: Thanks for the reviewer’s suggestion. “global production” has been replaced by “world values” in line 50.

 

Question #4：line 64......add "use for" after "are hard to"

Response: Thanks for the reviewer’s suggestion. “use for” has been added after “are hard to” , and “estimate” has been replaced “estimating” in line 64.

 

Question #5：line 107...."indexes (HIs)", perhaps better "indexes (HI)"

Response: Thanks for the reviewer’s suggestion. “indexes (HIs)” has been replaced by “indexes (HI)” in line 110.

 

Question #6：Tab. 3 2th line..."NE-N 1" (delete) perhaps better "NE-N"

Response: Thanks for the reviewer’s suggestion. “NE-N 1” has been replaced by “NE-N” in Table 3.

 

Question #7：line 142.......not "1 N" but "N"

Response: Thanks for the reviewer’s suggestion. “1 N” has been replaced by “N” in line 145.

 

Question #8：line 200......."Red" (delete)

Response: Thanks for the reviewer’s careful comment, we are really sorry for our carelessness. “Red” has been deleted in line 203.

 

Question #9：line 222 "few" (delete), perhaps better "only one"; delete "were" and add "was" after "HI observation"

Response: Thanks for the reviewer’s suggestion. “few” has been replaced by “only one” and “were” after "HI observation" has been replaced by “was” in line 226.

 

Question #10：line 228 add "maximum" before "dilution"

Response: Thanks, and done as suggested in line 233.

 

 

In addition, numerous minor language edits with tracking have been taken throughout the whole manuscript.

 

 

Author Response File: Author Response.docx