Long-term conservation agriculture with optimum nitrogen fertilization improves soil phosphorus availability

Area of Science:

• Soil Science
• Agronomy
• Nutrient Management

Background:

• Sustainable nutrient management requires understanding soil phosphorus (P) dynamics under conservation agriculture (CA).
• Long-term data on P pools under combined CA practices and nitrogen (N) fertilization are limited.
• This study investigates the interactive effects of CA and N on soil P fractions in a long-term crop rotation.

Purpose of the Study:

• To evaluate the long-term impacts of CA (tillage and residue management) and varying N rates on labile, moderately labile, and non-labile P fractions.
• To determine optimal CA and N management strategies for balanced P dynamics.
• To assess the synergistic effects of CA components and N fertilization on soil P pools.

Main Methods:

• Field experiment using a split-split plot design over 36 crop cycles.
• Investigated two tillage systems: conventional tillage (CT) and strip tillage (ST).
• Evaluated two residue levels: lower residue (LR) and higher residue (HR).
• Applied six nitrogen (N) rates (N0 to N140) relative to the recommended dose.
• Analyzed various soil P fractions (labile, moderately labile, non-labile inorganic and organic P).

Main Results:

• Strip tillage (ST) and higher residue (HR) significantly enhanced labile P availability (e.g., soluble P, NaHCO3-Po).
• Higher N rates (>N100) reduced labile inorganic P (labile-Pi) by up to 45%, indicating potential P deficiency for plants.
• The NaHCO3-Pi fraction was higher under HR with lower N rates (≤N100), while moderately labile P increased with higher N rates under ST-HR.
• Acid-P increased under ST, with complex interactions; it was higher in ST-HR with lower N rates (≤N100).
• Interactions among tillage, residue, and N were significant for most P pools.

Conclusions:

• Strip tillage combined with higher residue (ST-HR) optimizes P availability and minimizes non-labile P accumulation.
• An optimal N rate (around N100) under CA is crucial for balancing P fractions and improving soil fertility.
• The findings highlight synergistic effects of CA components and N management for sustainable crop production and soil health.