The impact of long-term mulching cultivation on soil quality, microbial community structure, and fruit quality in “Wanzhou Red Mandarin” citrus orchard – Frontiers

Report on the Impact of Grass Mulching on Sustainable Citrus Cultivation and the Achievement of Sustainable Development Goals (SDGs)

Executive Summary

This report details the findings of a study comparing grass mulching with clean tillage in a red mandarin orchard. The research demonstrates that grass mulching is a highly effective agricultural practice for advancing several key United Nations Sustainable Development Goals (SDGs). The practice significantly improves soil health, enhances microbial biodiversity, increases carbon sequestration, and boosts fruit quality. These outcomes directly contribute to SDG 2 (Zero Hunger), SDG 3 (Good Health and Well-being), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), and SDG 15 (Life on Land). The findings strongly support the adoption of grass mulching as a standard for sustainable citrus cultivation.

Research Findings: A Pathway to Sustainable Agriculture

Enhancing Soil Health and Fertility (SDG 2, SDG 15)

The implementation of grass mulching resulted in substantial improvements in soil physicochemical properties, directly addressing the targets of SDG 2 (Zero Hunger) by promoting sustainable agriculture and SDG 15 (Life on Land) by halting and reversing land degradation. Compared to clean tillage, mulching led to a healthier and more fertile soil environment.

• Surface Soil (0-20 cm) Nutrient Enhancement:
  1. Alkali-hydrolyzable Nitrogen (AN): Increased by 105.5%
  2. Available Phosphorus (AP): Increased by 144.4%
  3. Available Potassium (AK): Increased by 102.1%
  4. Soil Organic Matter (SOM): Increased by 42.5%
• Enhanced Soil Enzyme Activity:
  1. Alkaline Phosphatase: Increased by 60.1%
  2. Urease: Increased by 39.3%

These improvements create a robust foundation for long-term crop productivity, reducing the reliance on synthetic fertilizers and supporting sustainable food production systems.

Climate Action and Biodiversity (SDG 13, SDG 15)

The study highlights the role of grass mulching in climate change mitigation and the preservation of terrestrial ecosystems, aligning with SDG 13 (Climate Action) and SDG 15 (Life on Land).

• Carbon Sequestration: A significant increase in Total Organic Carbon (TOC) was observed in both soil layers, representing a direct contribution to climate action by sequestering atmospheric carbon in the soil.
  • Surface Layer (0-20 cm): TOC increased by 93.1%
  • Deep Layer (20-40 cm): TOC increased by 101.9%
• Microbial Community Enhancement: Grass mulching fostered a more diverse and beneficial soil microbiome, a key indicator of a healthy ecosystem.
  • The abundance of Proteobacteria, a phylum crucial for nutrient cycling, increased in both surface (36% to 39%) and deep soil layers (33% to 37%).
  • Fungal community composition was altered, indicating a shift towards a more complex and functional ecosystem.
  • Distinct microbial clustering between mulched and tilled plots confirms that the practice fundamentally reshapes the soil’s biological architecture.

Improving Nutrition and Production Patterns (SDG 2, SDG 3, SDG 12)

The benefits of grass mulching extend beyond the soil to the final agricultural product, contributing to SDG 2 (Zero Hunger) by improving food quality, SDG 3 (Good Health and Well-being) by enhancing nutritional value, and SDG 12 (Responsible Consumption and Production) by demonstrating a sustainable production method.

• Enhanced Fruit Quality: The practice led to measurable improvements in red mandarin fruits.
  1. Vitamin C content increased by 24.5%, contributing to improved public health and nutrition.
  2. Pericarp thickness decreased by 27.1%, improving the desirability and marketability of the fruit.
• Correlation with Soil Health: The study established a stronger correlation between bacterial communities and fruit quality than fungal communities, underscoring the critical role of a healthy soil microbiome in producing nutritious food.

Conclusion and Recommendations for SDG Advancement

The research unequivocally demonstrates that grass mulching is a superior agricultural practice compared to clean tillage for achieving sustainability in citrus orchards. By enhancing soil fertility, boosting carbon sequestration, fostering biodiversity, and improving fruit quality, this practice provides a tangible and effective strategy for advancing multiple Sustainable Development Goals.

It is recommended that grass mulching be widely promoted and adopted as a key component of sustainable agricultural policies, particularly within citrus cultivation, to help meet global targets for food security, climate action, and environmental protection.

Analysis of Sustainable Development Goals in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

   The research on grass mulching in citrus orchards directly addresses and connects to the following Sustainable Development Goals (SDGs):

   • SDG 2: Zero Hunger – By focusing on improving agricultural practices, soil fertility, and fruit quality, the article contributes to sustainable food production.
   • SDG 12: Responsible Consumption and Production – The study promotes a sustainable agricultural practice (grass mulching) that enhances natural resources (soil) and represents a move towards more sustainable production patterns.
   • SDG 15: Life on Land – The core of the article is about improving soil health, restoring land quality, and understanding the impact on soil biodiversity (microbial communities), which are central themes of this goal.

2. What specific targets under those SDGs can be identified based on the article’s content?

   Based on the article’s focus, the following specific targets can be identified:

   • Under SDG 2 (Zero Hunger):
     • Target 2.4: “By 2030, ensure sustainable food production systems and implement resilient agricultural practices that increase productivity and production, that help maintain ecosystems… and that progressively improve land and soil quality.” The article’s conclusion that grass mulching supports “sustainable citrus cultivation” by enhancing “soil fertility” and “soil properties” directly aligns with this target.
   • Under SDG 12 (Responsible Consumption and Production):
     • Target 12.2: “By 2030, achieve the sustainable management and efficient use of natural resources.” The study demonstrates how grass mulching is a method for the sustainable management of soil, a critical natural resource for agriculture.
   • Under SDG 15 (Life on Land):
     • Target 15.3: “By 2030, combat desertification, restore degraded land and soil… and strive to achieve a land degradation-neutral world.” The research provides a practical method for improving soil quality, as evidenced by significant increases in soil nutrients and organic matter, which is a direct action towards restoring soil health.
     • Target 15.5: “Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity…” The article analyzes the impact on the soil’s “microbial community structure,” noting changes in “Proteobacteria abundance” and “fungal dominance,” which relates to the biodiversity within the soil ecosystem.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

   Yes, the article provides several direct and implied indicators for measuring progress:

   • For Target 2.4 (Sustainable food production and resilient agricultural practices):
     • Soil Organic Matter (SOM): The article explicitly measures and reports a 42.5% increase in SOM, a key indicator of soil health and sustainable agriculture.
     • Soil Nutrient Levels: The study quantifies increases in “alkali-hydrolyzable nitrogen (AN, 105.5%)”, “available phosphorus (AP, 144.4%)”, and “available potassium (AK, 102.1%)”, which are direct measures of improved soil fertility.
     • Food Quality: The improvement in “fruit quality,” specifically the 24.5% increase in “vitamin C” and 27.1% decrease in “pericarp thickness,” serves as an indicator of enhanced production quality.
   • For Target 15.3 (Restore degraded land and soil):
     • Soil Organic Carbon (SOC): The article measures “total organic carbon (TOC)” and finds a 93.1% increase in the surface layer and a 101.9% increase in the deep layer. SOC is a primary indicator for monitoring land degradation neutrality.
   • For Target 15.5 (Halt biodiversity loss):
     • Microbial Community Composition: The study uses beta diversity analysis to show “distinct microbial clustering between treatments” and measures changes in the abundance of specific phyla like “Proteobacteria” (increased from 36% to 39%). These are direct indicators of shifts in soil biodiversity.

4. Table of SDGs, Targets, and Indicators

   SDGs	Targets	Indicators Identified in the Article
   SDG 2: Zero Hunger	Target 2.4: Ensure sustainable food production systems and implement resilient agricultural practices that improve land and soil quality.	Increase in Soil Organic Matter (SOM): +42.5% Increase in soil nutrients (AN: +105.5%, AP: +144.4%, AK: +102.1%) Improvement in fruit quality (Vitamin C: +24.5%)
   SDG 12: Responsible Consumption and Production	Target 12.2: Achieve the sustainable management and efficient use of natural resources.	Adoption of sustainable practices (grass mulching) Enhanced soil enzyme activities (urease, alkaline phosphatase)
   SDG 15: Life on Land	Target 15.3: Restore degraded land and soil.	Increase in Total Organic Carbon (TOC): +93.1% (surface), +101.9% (deep)
   SDG 15: Life on Land	Target 15.5: Halt the loss of biodiversity.	Change in microbial abundance (Proteobacteria increased from 36% to 39%) Shift in fungal dominance (from unclassified_Agaricomycetes to Mortierella) Beta diversity analysis showing distinct microbial clustering

Source: frontiersin.org