**7. Strategic tillage effects on soil nutrients**

In addition to overall soil physical and biological properties, strategic tillage can influence key chemical processes in soils related to plant nutrition. These include impacts on nutrient stratification, availability, fertilizer efficiency, and nutrient cycling.

### **8. Impacts on nutrient stratification and availability**

One common effect of long-term no-till systems is increased stratification of nutrients like phosphorus and potassium at the soil surface, since inputs are not mixed through tillage [1]. While this can facilitate early crop access, it can also lead to localized depletion over time. Occasional strategic tillage may modify these stratified layers and move surface nutrients into the active rooting zone, increasing availability during later growth stages [29]. For example, Abdollahi and Munkholm [3] found that periodic deep loosening of no-tilled soils redistributed potassium down the profile. Similarly, Reicosky and Archer [30] showed that tillage incorporation of composted swine manure reduced surface phosphorus accumulation compared to no-till.

However, excessive disturbance through aggressive strategic tillage could quickly deplete surface nutrient reserves. More moderate vertical tillage may provide a balance, with Schomberg et al. [31] finding that strip tillage increased phosphorus deeper in the root zone compared to no-till, likely improving access during grain filling. In general, occasional strategic tillage shows potential to modify stratified nutrient layers favorably but should be constrained to prevent over-mixing.

Stratified nutrient layers can also influence overall mineralization and nutrient availability for crop uptake. For instance, Franzluebbers [32] found that tillage incorporation of cover crop residues, which contained high N and P concentrations, nearly doubled plant availability of these nutrients compared to surface-retained residues. This illustrates how strategic tillage augmenting buried organic matter decomposition could supplement crop nutrition when coordinated with key growth stages.

### **9. Interactions with fertilizers and residues**

Strategic tillage approaches generally increase fertilizer use efficiency compared to no-till, through better incorporation with soil [1]. For example, Reider et al. [33] found that deep banding of phosphorus fertilizer under strip tillage increased nutrient uptake and yields compared to broadcast fertilizer under no-till, likely due to placement in moist subsurface zones with higher biological activity. However, excessive disturbance could expose nutrients to leaching or gaseous losses before crop utilization.

Occasional tillage can also encourage decomposition of surface residues and release of nutrients like nitrogen for crop use. Wright et al. [34] showed that strip tillage increased nitrogen mineralization from previous cover crop residues compared to no-till, synchronized with peak corn demand. Strategic tillage must balance mineralization and nutrient uncovering with preventing excess loss through disturbance.

## **10. Maximizing nutrient cycling**

By fostering a more active and diverse soil biological community while limiting soil degradation, strategic tillage can enhance internal nutrient cycling [24]. Periodic tillage aerates soils, mixes crop residues, and incorporates amendments to stimulate microbial activity and soil fauna critical to decomposition and nutrient release [3]. For example, Plaza et al. [35] found that occasional chisel plowing increased soil nematode populations and nitrogen mineralization compared to untilled soils under conservation agriculture.

Strategic tillage also encourages development of soil structure and permeability to water flows that facilitate cycling and prevent nutrient losses [26]. Combined with practices like cover cropping, manuring, and reduced chemical inputs, strategic tillage could make soils more self-sufficient through enhanced biological nutrient transformations [1]. However, over-intensive disturbance risks accelerating organic matter and nutrient depletion.

#### **10.1 Implementing strategic tillage in farming systems**

While the concepts behind strategic tillage are straightforward, real-world implementation requires integrating it effectively within diverse crop rotations, soil types, and climates. Key considerations include combining strategic tillage with other conservation practices, selecting suitable equipment, and evaluating impacts through soil and crop monitoring.

#### **10.2 Integration with other conservation practices**

Rather than a stand-alone approach, strategic tillage should be viewed as one potential tool within a diversified soil health management system [17]. Combining occasional strategic tillage with practices like cover cropping, diverse rotations, and reduced surface disturbance is key to realizing benefits without compromising longterm productivity and resilience [3].

For example, including deep-rooted cover crop mixes can help fracture compaction and improve infiltration between cash crops. This could reduce the intensity and frequency of subsoiling or deep ripping required for the same purposes [7]. Leaving corn or bean residues intact with zone or strip tillage maintains surface cover for erosion control. Rotational diversification disrupts pest and disease cycles improved by occasional full-width tillage. Overall, the goal is to address all aspects of soil function and health using strategic tillage only where other practices are unable to resolve priority limitations.

#### **10.3 Appropriate equipment and techniques**

Selecting suitable tillage implements is crucial for focused soil disruption and residue management rather than broad inversion or disturbance [17]. Equipment like strip tillage tools, shallow disk cultivators, specialty plows, and deep rippers allow targeted intervention. Matching implement capabilities like tillage depth, width, and inversion intensity to specific limitations enables sufficient yet minimal soil disturbance.

Proper setup and operation of equipment is also key, for example, using guidance systems for precise subsurface tillage at optimal speeds and depths. Successfully avoiding compaction from excess equipment passes requires caution. Integrating equipment use into controlled traffic patterns can help restrict soil compaction effects [26]. Overall, the mindset must focus on disturbing only the minimal soil volume needed to address verified limitations.

### **10.4 Evaluation and monitoring**

Ongoing assessment through soil testing and crop yield monitoring provides critical feedback for improving strategic tillage implementation over time. Baseline soil samples prior to adopting strategic tillage establish reference conditions for physical, chemical, and biological indicators of soil function [3]. Periodic retesting then helps gauge impacts on organic matter, compaction, fertility, biology, etc. Post-harvest crop yields correlated to strategic tillage actions provide additional real-world measures of agronomic value from addressing soil constraints.

For example, Raper et al. [28] combined deep tillage and in-row subsoiling based on soil resistance profiling and crop yields showing compaction-limited root growth and water infiltration. Zone sampling over years tracked soil carbon changes showing no significant difference between strategic tillage and continuous no-till [4]. This empirical evidence helps refine decisions on which limitations to address, proper tillage types, depths, timing, and frequency for local conditions. In summary, strategic tillage is not a universal prescription but rather one possible tool integrated through systematic soil health management. Combining it with practices enriching soil biology, structure, and nutrient cycling maximizes the potential for strategic tillage to address priority limitations without degrading soils through excessive disturbance. Matching equipment capabilities and operation to pinpointed soil needs minimizes disturbance. Ongoing monitoring via soil testing and crop yield response provides real-world evidence to refine site-specific implementation over time. When integrated using a goal-oriented systems approach, strategic tillage offers opportunities to balance soil function improvements with practical farming needs.
