**5. Impacts of conventional tillage on soil health**

Since the origins of agriculture, tillage has been used to prepare seedbeds, control weeds, and incorporate amendments. However, conventional intensive tillage using frequent disturbance through implements like moldboard plowing and heavy disking can seriously impair soil health over time. Tillage breaks up soil structure, disrupts biological communities, and exposes soil organic matter to decomposition, resulting in a cascade of physical, chemical, and biological degradations.

#### **5.1 Physical impacts**

One of the most prominent physical impacts of intensive tillage is increased soil compaction and degradation of soil structure [2, 14]. Frequent tractor passes and inversion by moldboard plowing form plow pans and destroys soil aggregation, reducing macroporosity for drainage, aeration, and root growth [7, 15]. With poor structure, tillage also leaves soil much more vulnerable to compaction and wheel traffic effects [16]. Loss of stable aggregation from organic binding agents and disruption of soil biology impair soils' ability to regain structure [10].

In addition, conventional tillage leaves soil nearly bare between crops, dramatically increasing susceptibility to erosion from wind and rainfall. Intensive tillage

pulverizes surface aggregates and residues that protect soil from raindrop impact and overland flow [17]. Erosion removes fertile topsoil and organic matter, reduces infiltration, and causes further structural decline. Tillage also speeds evaporation of soil moisture, requiring more frequent passes for seedbed preparation that perpetuates compaction issues.

Formation of surface crusts is another common physical impact in conventionally tilled soils. Destruction of surface aggregates combined with loss of protection from residues and minimal biological activity near the surface often causes crusting and poor seedling emergence [7]. Hard crusts reduce infiltration and increase runoff and erosion. Emerging seedlings can be cut off or plants may expend crucial energy breaking through crusted layers.

Overall, intensive conventional tillage degrades the fundamental physical properties needed for soil functionality. The resulting problems with compaction, structure loss, erosion risks, and crusting diminish root growth, drainage, and plant establishment which are critical for agricultural productivity and soil sustainability.

#### **5.2 Chemical impacts**

Tillage also substantially alters key chemical properties and processes in soil systems. Most notably, conventional intensive tillage generally causes significant declines in soil organic matter and overall carbon stocks [3, 11]. Frequent inversion and disturbance expose previously protected organic matter to microbial decomposition and release CO2 into the atmosphere [17]. Reduced carbon inputs from less residue return also deplete organic matter over time. Lower organic matter negatively impacts structure, reduces nutrient and water-holding capacities, and decreases soil biology.

Nutrient balances and availability dynamics are also disrupted by conventional tillage regimes. Native soil nutrient reserves become depleted over years of crop removal without adequate replenishment from organic cycling or additions of fertilizers and amendments [1]. Nutrients like nitrogen and phosphorus can be rapidly lost through leaching and gas emissions when bound up in soil organic matter that is decomposed through tillage exposure. Soluble nutrients are also readily lost when tillage causes erosion. More intensive fertilizer inputs are thus needed to maintain crop nutrition in degraded tilled soils. However, fertilizer use efficiency is often impaired by poor soil structure and biological activity as well.

Improper pH levels resulting from conventional tillage may further impact soil chemical processes and crop growth. Acidification is common, stemming largely from greater nitrate leaching when ammonium fertilizers are rapidly converted to nitrate, and reduced liming due to minimal surface residue incorporation [18]. Lower pH substantially influences nutrient availability, solubility of heavy metals and aluminum, and microbial communities (**Table 1**).

#### **5.3 Biological impacts**

Soil biology represents a foundational component of overall soil health that is significantly altered by frequent conventional tillage [19]. The extensive physical disturbance and changing soil environmental conditions under intensive tillage regimes reduce soil biological diversity, activity, and community resilience [20]. Fungal communities are particularly affected due to their sensitivity to disturbance, while bacteria increase in dominance [21].


#### **Table 1.**

*Comprehensive analysis of the impacts of conventional tillage on soil health.*

Biomass, abundance, and diversity of soil fauna including protozoa, nematodes, earthworms, and arthropods generally decline with tillage intensity, which removes surface residues and kills organisms directly through mechanical disruption [22, 23]. Declines in mycorrhizal associations further impact plant and root ecology. Reduced soil macrofauna and fungal activity negatively affect soil structure development and stabilization. Lower organic matter under tillage also cuts off the energy source driving soil food web integrity and function.

Overall biological activity including nutrient mineralization and immobilization, carbon transformations, and pest suppression suffers under intensive tillage regimes [24]. For example, earthworms and arbuscular mycorrhizal fungi play key roles in soil carbon storage; their reduction with tillage decreases soil carbon sequestration [10, 25]. Impaired biology diminishes critical services like nutrient cycling, water regulation, and disease suppression.

In essence, conventional tillage degrades soil biological function at many levels, from microbial communities and soil fauna diversity to critical services that support agricultural productivity and ecological health. Regenerating soil biology requires a systemic approach including reduced tillage, increased plant diversity, and enhanced organic matter inputs.
