Carbon budget of diversified cropping systems in southwestern China: Revealing key crop categories and influencing factors under different classifications.

Cropping systems are considered the largest source of agricultural GHG emissions. Identifying key categories and factors affecting cropping systems is essential for reducing these emissions. Most studies have focused on the carbon budget of cropping systems from the perspective of a single crop or crop category. Comprehensive studies quantifying the carbon budget of diversified cropping systems, including farmland and garden crops, are still limited. This study aims to fill this gap by quantifying the carbon budget of diversified cropping systems, clarifying their carbon attributes, and identifying key crop categories and influencing factors within different classifications of the system. This study analyzed the carbon budget of a diversified cropping system consisting of 19 crops in Yunnan Province, southwestern China, using a crop-based net greenhouse gas balance methodology based on the "cradle-to-farm" life cycle idea. Crops were categorized into three levels of categories to assess the potential impact of categorization within the cropping system on its carbon balance. Results showed that Yunnan's diversified cropping system is a significant carbon sink, with net sequestration of 33.1 Mt CO2 eq, total emissions of 37.4 Mt CO2 eq, and total sequestration of 70.5 Mt CO2 eq. Cereals, vegetables, and hobby crops were the main contributors to carbon emissions, accounting for 41.61%, 21.87%, and 15.37%, respectively. Cereal crops also made the largest contribution to carbon sequestration at 53.18%. Bananas had the highest emissions per unit area (11.45 t CO2 eq ha-1), while walnuts had the highest sequestration (20.64 t CO2 eq ha-1). In addition, this study highlights effective strategies to reduce greenhouse gas emissions, such as reducing nitrogen fertilizer use, minimizing reactive nitrogen losses, and controlling methane emissions from rice fields. By elucidating the impact of carbon dynamics and crop categories, this study provides insights for sustainable agricultural practices and policies.

Organic management increases beneficial microorganisms and promotes the stability of microecological networks in tea plantation soil.

Introduction: Organic agriculture is highly regarded by people for its commitment to health, ecology, care, and fairness. The soil microbial community responds quickly to environmental changes and is a good indicator for evaluating soil microecology. Therefore, from the perspective of soil microbial communities, elucidating the impact of organic management on soil microecology in tea plantations has great significance for improving local tea plantation systems. Methods: The study collected bulk soil from organic management (OM) and conventional management (CM) tea plantations in Pu'er City, a major tea-producing area in China, and analyzed their species diversity, structural composition, and co-occurrence networks using metagenomics technology. Results: Compared with CM, the diversity index (Shannon) and evenness index (Heip) of soil fungi increased by 7.38% and 84.2% in OM tea plantations, respectively. The relative abundance of microorganisms related to the nitrogen cycle increased. Specifically, there was a significant increase in Rhodobiales, a 2-fold increase in Nitrospirae, and approximately 1.95 and 2.03 times increases in unclassified genera within Betaproteobacteria and Deltaproteobacteria, respectively. The relative abundance of plant residue degradation species, Gemmatimonadetes, Ascomycota, and Basidiomycota, increased by 2.8, 1, and 1.4 times, respectively. The OM was conducive to the establishment of collaborative relationships among bacterial species and increased the diversity and complexity of species relationships in fungal communities. The network stability of soil ecosystems was promoted. The organic tea plantations' keystone taxa contained mycorrhizal fungi (Pezoloma_ericae, Rhizophagus_irregularis, Rhizophagus_clarus), as well as species involved in soil nitrogen metabolism (Acidobacteria_bacterium, Acidobacteriia_bacterium_AA117, Sphingomonas_sp._URHD0007, Enhydrobacter_aerosaccus), pathogen (Erysiphe_pulchra), and parasites (Paramycosporidium saccamoeba). The partial least squares method (PLS-SEM) indicated that OM affected N-NH4+ negatively, increasing the abundance of fungi, and thereby positively affecting the Shannon index. Conclusion: In brief, reasonable organic management can improve the diversity of soil microorganisms, increase the relative abundance of beneficial bacteria in tea plantation soil, and promote the stability of the soil microbial ecological network.

Knowledge domain and research progress in the field of crop rotation from 2000 to 2020: a scientometric review.

As one of the most fundamental and prevalent agronomic practices, crop rotation is of great significance for the optimization of regional planting structure and sustainable agricultural development. Therefore, crop rotation has attracted continuous attention from both researchers and producers worldwide. In recent years, many review articles have been published in the field of crop rotation. However, since most reviews usually focus on specialized directions and topics, only few systematic quantitative reviews and comprehensive analysis can fully determine the state of research. To address this knowledge gap, we present a scientometric review to determine the current research status of crop rotation by using CiteSpace software. The main findings were as follows: (1) From 2000 to 2020, five knowledge domains were identified as representing the intellectual base of crop rotation: (a) synergism and comparison of conservation agriculture measures or other management measures; (b) soil microecology, pest control, weed control, and plant disease control; (c) soil carbon sequestration and greenhouse gases (GHGs) emissions; (d) organic crop rotation and double cropping patterns; and (e) soil properties and crop productivity. (2) Six notable research fronts were identified: (a) plant-soil microbial interactions under crop rotation; (b) integrated effect with minimum soil disturbance and crop retention; (c) carbon sequestration and GHG emission reduction; (d) impact on weed control; (e) heterogeneity of rotation effects under different weather and soil conditions; and (f) comparison between long-term and short-term rotation. Overall, this study provides a comprehensive overview of crop rotation and proposes some future development trends for the researchers.

Nitrogen Footprint of a Recycling System Integrated with Cropland and Livestock in the North China Plain.

Nitrogen-based pollution from agriculture has global environmental consequences. Excessive use of chemical nitrogen fertilizer, incorrect manure management and rural waste treatment are key contributors. Circular agriculture combining cropland and livestock is an efficient channel to reduce the use of chemical nitrogen fertilizers, promote the recycling of livestock manure, and reduce the global N surplus. The internal circulation of organic nitrogen resources in the cropland-livestock system can not only reduce the dependence on external synthetic nitrogen, but also reduce the environmental impacts of organic waste disposal. Therefore, this study tried to clarify the reactive nitrogen emissions of the crop-swine integrated system compared to the separated system from a life cycle perspective, and analyze the reasons for the differences in nitrogen footprints of the two systems. The results showed that the integrated crop production and swine production increased the grain yield by 14.38% than that of the separated system. The nitrogen footprints of crop production and swine production from the integrated system were 12.02% (per unit area) and 19.78% lower than that from the separated system, respectively. The total nitrogen footprint of the integrated system showed a reduction of 17.06%. The reduction was from simpler waste manure management and less agricultural inputs for both chemical fertilizer and raw material for forage processing. In conclusion, as a link between crop planting and pig breeding, the integrated system not only reduces the input of chemical fertilizers, but also promotes the utilization of manure, increases crop yield, and decreases environmental pollution. Integrated cropland and livestock is a promising model for agriculture green and sustainable development in China.

Mitigating Groundwater Depletion in North China Plain with Cropping System that Alternate Deep and Shallow Rooted Crops.

In the North China Plain, groundwater tables have been dropping at unsustainable rates of 1 m per year due to irrigation of a double cropping system of winter wheat and summer maize. To reverse the trend, we examined whether alternative crop rotations could save water. Moisture contents were measured weekly at 20 cm intervals in the top 180 cm of soil as part of a 12-year field experiment with four crop rotations: sweet potato→ cotton→ sweet potato→ winter wheat-summer maize (SpCSpWS, 4-year cycle); peanuts → winter wheat-summer maize (PWS, 2-year cycle); ryegrass-cotton→ peanuts→ winter wheat-summer maize (RCPWS, 3-year cycle); and winter wheat-summer maize (WS, each year). We found that, compared to WS, the SpCSpWS annual evapotranspiration was 28% lower, PWS was 19% lower and RCPWS was 14% lower. The yield per unit of water evaporated improved for wheat within any alternative rotation compared to WS, increasing up to 19%. Average soil moisture contents at the sowing date of wheat in the SpCSpWS, PWS, and RCPWS rotations were 7, 4, and 10% higher than WS, respectively. The advantage of alternative rotations was that a deep rooted crop of winter wheat reaching down to 180 cm followed shallow rooted crops (sweet potato and peanut drawing soil moisture from 0 to 120 cm). They benefited from the sequencing and vertical complementarity of soil moisture extraction. Thus, replacing the traditional crop rotation with cropping system that involves rotating with annual shallow rooted crops is promising for reducing groundwater depletion in the North China Plain.

Recharge and groundwater use in the North China Plain for six irrigated crops for an eleven year period.

Water tables are dropping by approximately one meter annually throughout the North China Plain mainly due to water withdrawals for irrigating winter wheat year after year. In order to examine whether the drawdown can be reduced we calculate the net water use for an 11 year field experiment from 2003 to 2013 where six irrigated crops (winter wheat, summer maize, cotton, peanuts, sweet potato, ryegrass) were grown in different crop rotations in the North China Plain. As part of this experiment moisture contents were measured each at 20 cm intervals in the top 1.8 m. Recharge and net water use were calculated based on these moisture measurement. Results showed that winter wheat and ryegrass had the least recharge with an average of 27 mm/year and 39 mm/year, respectively; cotton had the most recharge with an average of 211 mm/year) followed by peanuts with 118 mm/year, sweet potato with 76 mm/year, and summer maize with 44 mm/year. Recharge depended on the amount of irrigation water pumped from the aquifer and was therefore a poor indicator of future groundwater decline. Instead net water use (recharge minus irrigation) was found to be a good indicator for the decline of the water table. The smallest amount of net (ground water) used was cotton with an average of 14 mm/year, followed by peanut with 32 mm/year, summer maize with 71 mm/year, sweet potato with 74 mm/year. Winter wheat and ryegrass had the greatest net water use with the average of 198 mm/year and 111 mm/year, respectively. Our calculations showed that any single crop would use less water than the prevalent winter wheat summer maize rotation. This growing one crop instead of two will reduce the decline of groundwater and in some rain rich years increase the ground water level, but will result in less income for the farmers.

[Nitrogen cycling in rice-duck mutual ecosystem during double cropping rice growth season].

Raising duck in paddy rice field is an evolution of Chinese traditional agriculture. In May-October 2010, a field experiment was conducted in a double cropping rice region of Hunan Province, South-central China to study the nitrogen (N) cycling in rice-duck mutual ecosystem during early rice and late rice growth periods, taking a conventional paddy rice field as the control. Input-output analysis method was adopted. The N output in the early rice-duck mutual ecosystem was 239.5 kg x hm(-2), in which, 12.77 kg x hm(-2) were from ducks, and the N output in the late rice-duck mutual ecosystem was 338.7 kg x hm(-2), in which, 23.35 kg x hm(-2) were from ducks. At the present N input level, there existed soil N deficit during the growth seasons of both early rice and late rice. The N input from duck sub-system was mainly from the feed N, and the cycling rate of the duck feces N recycled within the system was 2.5% during early rice growth season and 3.5% during late rice growth season. After late rice harvested, the soil N sequestration was 178.6 kg x hm(-2).

[Integrated evaluation of circular agriculture system: a life cycle perspective].

For the point of view that recycling economy system is one of ways to achieve the low-carbon economy, we have made an evaluation on a typical circular agriculture duck industry in Hunan Province, China, through improving the framework of life cycle assessment (LCA). The analysis indicated that the consumption of non-renewable resources, land and water were 48.629 MJ, 2.36 m2 and 1 321.41 kg, while the potential greenhouse gas (GHGs), acidification, eutrophication, human toxicity, freshwater ecotoxicity and terrestrial ecotoxicity were 11 543.26 g (CO2 eq), 52.36g (SO2eq), 25.83g (PO4eq), 1.26, 60.74 and 24.65 g (1,4-DCBeq), respectively. The potential damage of aquatic eutrophication, freshwater ecotoxicity and terrestrial ecotoxicity was more serious than that of GHGs. Main results were following: i. the circular agricultural chain promoted the principle of "moderate circulation", which based on the traditional production methods; ii. circular agriculture could not blindly pursue low carbon development. Instead, soil and biological carbon sequestration should be considered, in addition to reducing carbon emissions; iii. circular economy and circular agriculture should take other potential environmental impacts into account such as acidification, eutrophication and ecotoxicity,with the exception to carbon emissions,to developed integrated system assessment; iv. LCA could provide a comprehensive assessment of circular agriculture, and it was worth of further study.

[Investigation and analysis of China residents' environmental conservation desire].

From the viewpoints of country's safety and residents' desire, this paper investigated and analyzed the factors affecting China residents' attitudes on environmental protection policies, and the implementing results of these polices. It was indicated that people have an enhanced consciousness on environmental protection, and the relations between this consciousness and economic growth fit Kuznets curve, because most of the poor people are living in the suburban or remote regions with bad or seriously degraded environment, while the fast development of urbanization accelerates the deterioration of urban environment. People are more concerned about environment deterioration, and support the governments' policies of environmental conservation. The environment policy-making should put more emphasis on developing economics, strengthening education, and improving residents' livelihood.

[Research progress on ecological footprint analysis].

Ecological footprint (EF) model, as an indicator of sustainability, has received broad attention and wide use. With the development and refinement of the research work on EF theory and methodology, it appeared various methods which can be applied at different scales. Ecological footprint analysis has been combined with material flow analysis, life cycle assessment or input-output analysis, and especially, the newest progress in EF methods called allocating EF to final consumption categories with input-output analysis helps to develop a "standardized" EF. In this paper, the underlying causes of these methods were interpreted theoretically, and the research methods were classified into progress analysis and input-output analysis (IOA). In addition, the compound and component-based methods as well as IOA were introduced, with their respective features, application, and development progress discussed. A prospect on the development of EF in term of the tendency and application of EF methods in China and abroad was given, i. e. , the common framework should be built at the national and regional scales by using compound analysis, IOA and component-based analysis are expected to develop their application

[Soft-ridged bench terrace design in hilly loess region].

Reconfiguration of hillside field into terrace is regarded as one of the key techniques for water and soil conservation in mountainous regions. On slopes exceeding 30 degrees, the traditional techniques of terracing are difficult to apply as risers (i.e., backslopes), and if not reinforced, are so abrupt and easy to collapse under gravity alone, thus damaging the terrace. To improve the reconfiguration of hillside field into terrace, holistic techniques of soft-ridged bench terrace engineering, including revegetation, with trees and planting grasses on riser slopes, were tested between 1997 and 2001 in Xiabiangou watershed of Yan' an, Shaanxi Province. A "working with Nature" engineering approach, riser slopes of 45 degrees, similar to the pre-existing slope of 35 degrees, was employed to radically reduce gravity-erosion. Based on the concepts of biodiversity and the principles of landscape ecology, terrace benches, bunds, and risers were planted with trees, shrubs, forage grasses, and crops, serving to generate a diverse array of plants, a semi-forested area, and to stabilize terrace bunds. Soft-ridged bench terrace made it possible to significantly reduce hazards arising from gravity erosion, and reduce the costs of individual bench construction and maintenance by 24.9% and 55.5% of the costs under traditional techniques, respectively. Such a construction allowed an enrichment and concentration of nutrients in the soils of terrace bunds, providing an ideal environment for a range of plants to grow and develop. The terrace riser could be planted with drought-resistant plants ranging from forage grasses to trees, and this riser vegetation would turn the exposed bunds and risers existing under traditional techniques into plant-covered belts, great green ribbons decorating farmland and contributing to the enhancement of the landscape biology.

[Main affecting factors of soil wind erosion under different land use patterns--a case study in Wuchuan County, Inner Mongolia].

Field investigation, laboratory analysis and wind tunnel simulation showed that in Wuchuan County of Inner Mongolia, low precipitation, frequent and high wind velocity, coarse soil texture, and thawing and freezing were the main causes of soil wind erosion happened very easily in spring. In late winter and early spring, the vegetation coverage was in order of shrub-land>natural grassland>rainfed farmland, and thus, increasing the surface cover of rainfed farmland should be an urgent need to control the wind erosion in Wuchuan County. The soil wind erosion rate decreased exponentially with increasing soil moisture content, and 6% soil moisture content was a turning point from severe to light. The topsoil moisture content under different land use patterns was in order of natural grassland> rainfed farmland >shrub-land. With increasing wind velocity, soil wind erosion rate increased by power function, and 18 m x s(-1) wind velocity was a switching point to aggravate the wind erosion.

[Effect of crop-residue incorporation on soil CO2 emission and soil microbial biomass].

In a wheat-corn cropping system, the crop residues were crushed and incorporated into soil after harvest. The soil respiration and soil microbial biomass were compared one year later with soil that had doubled amount of residues incorporation or had no incorporated residues. The soil respiration was increased by the residue incorporation and the effect was more apparent when the incorporated residue amount was doubled. The soil microbial biomass was also increased by the residue incorporation. But the effect of the incorporated residue quantity was not significant. Seasonally, the maximum soil respiration appeared earlier than the maximum microbial biomass, but soon turned to decrease. The microbial biomass maintained the high level for a longer period, indicating there was maintenance respiration and biosynthetic respiration as well. The residue incorporation was suggested as a measure to increase the soil fertility, but doubling the amount of residue incorporation seems not necessary.