Review Reports - Scenario Analysis of Livestock Carrying Capacity Risk in Farmland from the Perspective of Planting and Breeding Balance in Northeast China

Round 1

Reviewer 1 Report

The study reports a comparative analysis of nitrogen supply of manure of livestock and the ordinary nitrogen requirement for crops in agriculture system in three province of northern China. The time span is from 2008 to 2019. The study also attempts to provide the balance between planting and breeding system at the regional scale. The results show that the scale of husbandry breeding is expanding and the scale of the planting industry has remained basically unchanged. Based on the different nitrogen levels 35%(low level),45%(medium level) and 55%(high level), there were 23 regions where the livestock manure exceed the maximum value that can be absorbed by farmland. The study analyzes the planting model for future. It is very practical study in the agriculture system, but there are some troubling in definition and data is not enough to support the conclusion in the view of readers. Some opinions need to be clarify and logically .

Major points:

The definition for “Regional livestock carrying capacity of farmland accounting”is not accurate. The standard is not clear for this definition. Should you determine the number of livestock based on the area of land? Or should you determine the area of crop by amount of manure from animal? It seems not clear in whole manuscript.

Also carrying capacity is not proper to describe this relationship, I also don’t know which words is better, but authors should think about it.

“The risk coefficient of regional livestock carrying capacity of farmland”, For this concept, the same problem appears for the definition. The problems for manure are two aspects: one is there is not pathway for farmers to utilize the manure from breeding factory; the other is whether the pollutants contained in manure exceed the standard. If the quality is If the quality of manure can be guaranteed, it can be transported to agricultural planting areas outside the area.

In conclusion, “There were 14 regions in general risk area and 14 regions in restricted area, indicating that the livestock manure in these regions exceed the maximum value that can be absorbed by farmland, and ecological environment is facing great challenges.” what is general risk? I think it is very unrealistic idea to seek the balance between planting and breeding in region. The characteristic are different for different county, some counties are suitable for farming, while others have the advantage for breeding. So the authors should focus on how much of the manure could supply to other places in one county, rather than seek the balance in one county.

Author Response

Response to Comments from Reviewer

Reviewer:

Reviewer(1)：

The definition for“Regional livestock carrying capacity of farmland accounting”is not accurate. The standard is not clear for this definition. Should you determine the number of livestock based on the area of land? Or should you determine the area of crop by amount of manure from animal? It seems not clear in whole manuscript.

Also carrying capacity is not proper to describe this relationship, I also don’t know which words is better, but authors should think about it.

Response:

Thank you for your suggestion. We have redefined “the regional livestock carrying capacity of farmland” at the end of the 4^th paragraph of Introduction on the basis of referring to relevant researches. In addition, the content of this paragraph was reorganized to explain the research significance of measuring “the regional livestock carrying capacity of farmland”. We also explained the specific measurement methods and measurement principles, based on “Technical Guidelines for the Measurement of Farmland Carrying Capacity of Livestock Manure” issued by the Ministry of Agriculture and Rural Affairs of the People’s Republic of China in the part of 2.3.3-(1), the revised statement is as follows:

“A large number of studies have shown that livestock manure has useful properties, containing nitrogen, phosphorus, potassium and other nutrients necessary for crop production, and is an important nutrient source for improving soil fertility [17]. However, overuse of manure can also lead to environmental pollution and soil compaction [18-19]. In recent years, governments at all levels have successively issued a series of measures to promote the resource utilization of livestock breeding waste, emphasizing the important role of livestock manure in the high-quality development of agriculture. Thus, relocating the production activities of husbandry to the agricultural ecosystem, reconstructing the combination mode and ecological link between agriculture and husbandry, and ensuring that the breeding waste is digested in the ecological cycle system of agriculture and husbandry will undoubtedly effectively increase soil organic matter content [20-21]. The combination of planting and breeding and the cycle of farming and grazing are considered to be the most effective solutions at present [22]. Therefore, based on the idea of planting and breeding balance, scientifically measuring the nutrient demand of regional crop growth and the nutrient availability of livestock manure has become the key to adjusting regional planting and raising structure, reducing the application of chemical fertilizer, reducing environmental pollution and achieving high-quality agricultural development[23]. In this context, research on the regional livestock carrying capacity of farmland is becoming increasingly abundant[24]. The regional livestock carrying capacity of farmland refers to the maximum stock of livestock and poultry that can be supported by farmland in a given region under the condition of the sustainable operation of the land ecosystem, and it can also be popularly understood as the ability of a farmland to absorb livestock and poultry excrement[25]. ”

And “(1) Regional livestock manure nitrogen nutrient supply accounting

According to the Guide, the regional livestock manure nitrogen nutrient supply accounting was based on the nitrogen nutrient supply of livestock manure and the nitrogen nutrient demand for crop growth. The nitrogen nutrient demand for crop growth was determined according to soil fertility, crop type and yield, and the proportion of manure use. The nitrogen nutrient supply of livestock and poultry manure was determined according to the level of livestock breeding and manure nutrient production. Moreover, for ease of calculation and analysis, other major livestock and poultry were converted into the number of pigs (pig equivalent) according to the relationship in the Guide, as follows: ”

Reviewer(2)：

“The risk coefficient of regional livestock carrying capacity of farmland”, For this concept, the same problem appears for the definition. The problems for manure are two aspects: one is there is not pathway for farmers to utilize the manure from breeding factory; the other is whether the pollutants contained in manure exceed the standard. If the quality of manure can be guaranteed, it can be transported to agricultural planting areas outside the area.

Response:

Thank you for your suggestion. Firstly, we also redefine A, in section 2.2.3-(4). Secondly, regarding “the risk coefficient of regional livestock carrying capacity of farmland”, we refered to the research of Fu et al (2020). We just hope to use this coefficient to illustrate the environmental load pressure faced by this region. Obviously, if the number livestock breeding far exceeds the carrying capacity of the farmland, it will inevitably threaten the ecological environment of the region. As for the two aspects mentioned by reviewer, we think that even small-scale farmers can realize the resource utilization of livestock manure through the planting and breeding cycle, not necessarily by using the manure from the factory. The free-range mode under the traditional farming system is to realize the cycle of planting and breeding within the farmers. Guo et al（2020）also pointed that, farmers operating more than 3 hectares of farmland can realize the combination of farming and breeding within the farmer, and can establish a scale of 100-200 live pigs for slaughtering. And “it can be transported to agricultural planting areas outside the area.” is really a good suggestion, we have added this in the part of conclusion, as “Additionally, the potential areas were mostly located in Heilongjiang Province, while the restricted areas were mostly located in Liaoning Province, which means that Liaoning province faces greater threats in the aspect of environmental pollution from livestock breeding. Moreover, in the case of mature organic fertilizer technology, the cross-regional deployment of organic fertilizers (from restricted area to potential area) is also an important way to resolve the environmental pollution of livestock and poultry manure.” However, some studies have pointed out that the long-distance transportation of organic fertilizers will lead to the loss of total nitrogen and total phosphorus, thereby increasing the risk of eutrophication. We have also revised this part, the revised statement is as follows:

“(4)The risk coefficient of regional livestock carrying capacity of farmland

This paper referred to Fu et al. (2020) and selected the risk coefficient of regional livestock carrying capacity of farmland by r, which was used to quantitatively describe the risk of overloading of regional livestock breeding. If r ≤1 (potential area), it means that the livestock breeding in this region has not exceeded the upper limit of farmland carrying capacity, and the breeding scale can be appropriately expanded; if 1<r<2 (general risk area), it means that the livestock manure has exceeded the upper limit of farmland absorption, which will have a negative affect on the regional ecological environment, if r >2 (restricted area), it means that the livestock manure has far exceeded the upper limit of farmland absorption, and if left unchecked, there will be irreversible effects on the environment. The higher r is, the greater risk of environmental pollution is. This paper defines three risk levels: low, medium and high, corresponding to the potential zone, general risk zone, restricted zone (Table 2)[33], as follows:”

Reviewer(3)：

Response:

Thank you for your suggestion. As for the “potential area”, we added some contents to describe like “ if 1<r<2 (general risk area), it means that the livestock manure has exceeded the upper limit of farmland absorption, which will have a negative affect on the regional ecological environment”. As for the conclusion, we agree that it is unrealistic to achieve a balance of planting and breeding, but we can use the balance of planting and breeding as a standard to measure whether the scale of breeding in this region is reasonable or not, can it continue to scale up or needs to be scaled down, and where input is needed and where output is needed, so as to provide decision-making reference for regional planting and breeding structure and layout regulation. We have almost rewritten this part to make the conclusions more easier to understand, the revised statement is as follows:

“In this paper, we selected the northeast region as the study area from the perspective of soil nutrient demand; calculated the livestock carrying capacity of farmland under three scenarios where nitrogen nutrient accounts for 35% (low level), 45% (medium level) and 55% (high level) of fertilization; and carried out a risk analysis. We found that the scale of husbandry breeding is expanding while the scale of the planting industry has remained basically unchanged. Compared with 2008, the livestock carrying capacity risk has displayed a significant improvement, but some regions still show a decline compared with 2014. In the 35% scenario, the scale of livestock breeding in 29 out of 36 regions exceeded the actual carrying capacity level, and 15 of them belonged to restricted areas in 2019, which means that livestock waste in these regions far exceeds the capacity of farmland absorption, causing serious environmental problems in the long term. Additionally, the potential areas were mostly located in Heilongjiang Province, while the restricted areas were mostly located in Liaoning Province, which means that Liaoning province faces greater threats in the aspect of environmental pollution from livestock breeding. Moreover, in the case of mature organic fertilizer technology, the cross-regional deployment of organic fertilizers (from restricted area to potential area) is also an important way to resolve the environmental pollution of livestock and poultry manure. ”

In addition, we have thoroughly revised the sentences of the full paper through the English editing service provided by MDPI.

Author Response File: Author Response.doc

Reviewer 2 Report

The paper is interesting, however some important issues has been detected in order to be accepted for publication and consider well written

Add some comment about the negative effect of overgrazing among other to soil erosion. Also, mention that under climate change the erosion threat seems to increase [1,2]

Establishing a regulatory framework for grazing could be an effective erosion mitigation measure that also improves its quality. The degraded rangelands can be restored by moderating grazing pressures rather than completely banning livestock grazing [3-5]

Stefanidis, S.; Alexandridis, V.; Chatzichristaki, C.; Stefanidis, P. Assessing soil loss by water erosion in a typical Mediterranean ecosystem of northern Greece under current and future rainfall erosivity. Water 2021, 13(15), 2002.
Li, Y., Li, J., Are, K. S., Huang, Z., Yu, H., & Zhang, Q. (2019). Livestock grazing significantly accelerates soil erosion more than climate change in Qinghai-Tibet Plateau: Evidenced from 137Cs and 210Pbex measurements. Agriculture, Ecosystems & Environment, 285, 106643.
Papanastasis, V.P.; Bautista, S.; Chouvardas, D.; Mantzanas, K.; Papadimitriou, M.; Mayor, A.G.; Koukioumi, P.; Papaioannou; Vallejo, R.V. Comparative assessment of goods and services provided by grazing regulation and reforestation in degraded Mediterranean rangelands. Land Degrad. Dev. 2015, 28(4), 1178-1187
Kaltsas, D., Panayiotou, E., Kougioumoutzis, K., & Chatzaki, M. (2019). Overgrazed shrublands support high taxonomic, functional and temporal diversity of Mediterranean ground spider assemblages. Ecological Indicators, 103, 599-609.
Panagopoulos, Y.; Dimitriou, E.; Skoulikidis, N. Vulnerability of a Northeast Mediterranean Island to Soil Loss. Can Grazing Management Mitigate Erosion? Water 2019, 11, 1491.

In the last paragraph of the introduction clearly mention the novelty of the current approach according to similar studies based on the author knowledge. It is important to state the research gap in a clear context.

Chapter 2.2.2. Methdology correct to methodology

The discussion part is rather sort. Additionally, there is no reference as the results did not discussed in comparison with the results of other researches (differences, similarities ect)

Author Response

Response to Comments from Reviewer

Reviewer:

The paper is interesting, however some important issues has been detected in order to be accepted for publication and consider well written.

Reviewer(1)：

Add some comment about the negative effect of overgrazing among other to soil erosion. Also, mention that under climate change the erosion threat seems to increase [1,2]

Response:

Thank you for your suggestion. We have added some comment about the negative effect of overgrazing among other to soil erosion, and also mentioned that under climate change the erosion threat seems to increase, we also added some content about “Establishing a regulatory framework for grazing could be an effective erosion mitigation measure that also improves its quality. The degraded rangelands can be restored by moderating grazing pressures rather than completely banning livestock grazing” in the part of discussion, and applied the corresponding references, the revised statement is as follows:

“and resulting problems such as overgrazing will also lead to ecological problems such as soil erosion and land desertification. Especially with the intensification of the global climate change process, soil erosion and other problems are becoming more serious[14-15].” And “Moreover, establishing a regulatory framework for grazing could also be an effective mitigation measure that also improves farmland quality. The degraded land can be restored by moderating grazing pressures rather than completely banning livestock grazing [44-46].”

Reviewer(2)：

Response:

Thank you for your suggestion. We have modified the expressions to make the research gap more clearly, the revised statement is as follows:

“The existing research generally studies the livestock carrying capacity of farmland from the perspective of meeting the nutrient requirements of crops, through constructing the farmland consumption model of livestock breed waste based on the soil nitrogen and phosphorus nutrient-balance method[26-30]. If the regional crops can absorb the livestock breeding waste in an equal proportion, the balance between planting and breeding in the region can be considered to be achieved[30]. In 2018, the Ministry of Agriculture and Rural Affairs of the People’s Republic of China issued the "Technical Guidelines for the Measurement of Farmland Carrying Capacity of Livestock Manure"(hereinafter referred to as the Guide), which requires that the livestock carrying capacity should be calculated based on the balance between the nitrogen supply of manure and the nitrogen demand of plants. Subsequently, Nitrogen Nutrient Balance Method (NNBM) has been widely used in the field of analyzing the carrying capacity of livestock breeding[31-32]. However, farmland consumption of livestock manure is mainly via absorption by crops of nitrogen, phosphorus and other elements emitted by livestock. Clearly, the ability to absorb livestock manure of farmland varies under different fertilization intensities, and the corresponding livestock carrying capacity of farmland will also be significantly different, and the existing research has not considered the effect of different fertilization intensities[33]. Therefore, calculating the carrying capacity of livestock breeding under different fertilization intensities is helpful for providing references for determining the reasonable livestock breeding scale and adjusting the industrial layout within the region.”

Reviewer(3)：

Chapter 2.2.2. Methdology correct to methodology

Response:

Thank you for your suggestion. We have corrected Methdology to Methodology.

Reviewer(4)：

The discussion part is rather sort. Additionally, there is no reference as the results did not discussed in comparison with the results of other researches (differences, similarities ect)

Response:

Thank you for your suggestion. We have revised this part, added comparisons with existing research and references, so that to make the discussion more in-depth, ,the revised statement is as follows:

“In recent years, with the continuous transformation of northeast China’s residents' dietary structure, the demand for animal products had been increasing, so the production scale of husbandry in this area has expanded significantly [42]. With the rise of modern large- and medium-sized husbandry enterprises, large-scale production has been realized in the breeding industry with intensive and factory-like characteristics. Large-scale breeding enterprises have achieved spatial concentration, but the degree of integration with agricultural production is becoming lower and lower. More and more manure is being produced, but the path for manure to return to farmland is becoming narrower and narrower. Zheng et al. (2019) also pointed that these changes can achieve large-scale economic growth in agricultural production and livestock manure treatment, but it often results in environmental pollution and waste of resources due to the uncoordinated structure of planting and breeding and the mismatch of planting and breeding spaces [43]. Behind this alienation, another important problem derived is that a large amount of manure that is difficult to digest in farmland is discharged into the ground and rivers in various ways, which seriously pollutes the environment and water resources, and this then evolves into an important environmental problem. Therefore, relocating the production activities of husbandry to the agricultural ecosystem, reconstructing the combination mode and ecological link between agriculture and husbandry, and ensuring the breeding waste is digested in the ecological circulation system of agriculture and husbandry are important ways to realize the sustainable utilization of farmland.

As for the changes in the livestock carrying capacity of farmland and risk coefficient, from the results we can see that although compared with 2008 the risk coefficient shows a significant improvement, some regions still have a decline compared with 2014, indicating that the relevant policies issued by governments to promote the adjustment of planting and breeding structure and the utilization of livestock manure resources have achieved certain results. However, it cannot be ignored that there were still 28 regions where the livestock manure exceed the maximum value that can be absorbed by farmland in 2019. The regional ecological environment is facing huge challenges. Compared with the scenario where the proportion of nitrogen nutrient in fertilization is 35%, the 55% scenario can absorb more livestock manure, and the corresponding risk level will be lower. However, from the perspective of agricultural production law, it is not the case that more fertilization is more beneficial to farmland protection and crop production. Excessive nitrogen elements may cause soil salinization, which is also not conducive to the sustainable use of farmland. Fu et al. (2020) also pointed that we cannot rely on excessive fertilization to improve farmland's absorption of livestock manure [33]. Additionally, from the regional distribution of the livestock carrying capacity, most of the restricted areas are concentrated in Liaoning Province, while most of the potential areas are concentrated in Heilongjiang Province. This also indicates that Liaoning Province urgently needs to take more scientific and effective measures in strengthening the adjustment of the planting and breeding structure and the utilization of livestock and poultry waste. Moreover, establishing a regulatory framework for grazing could also be an effective mitigation measure that also improves farmland quality. The degraded land can be restored by moderating grazing pressures rather than completely banning livestock grazing [44-46].”

In addition, we have thoroughly revised the sentences of the full paper through the English editing service provided by MDPI.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

The revised version is better, and good enough for this journal.

Reviewer 2 Report

The authro's adressed all the reviewer comments. In the current form the article could be accepted for presentation.