The Underground Network We Have Been Farming Against

A 2026 New Phytologist methods paper by Braunmiller and colleagues, reported in Eos, used synchrotron-based X-ray micro-computed tomography to image arbuscular mycorrhizal fungi, roots, soil particles and pore space together in three dimensions in intact soil. Hyphae were seen spanning air-filled pores, forming branching networks, connecting soil particles and growing toward and along roots. The method detects hyphae best in air-filled pores, because water in fine pores obscures them.

The study did not test PQNK, rice, flooding or Alternate Wetting and Drying. Its significance for PQNK is that it makes visible the living architecture that the four governing rules are meant to protect: no inundation, no soil disturbance after conversion, permanent organic cover and encouraged biodiversity. Soil structure is not merely a container for roots; it is part of the operating environment of the root-fungal partnership.

Conventional production rebuilds the field after every harvest: residue is burnt or removed and the soil is ploughed, rotavated, levelled and re-ridged, tearing hyphal networks and collapsing the pores they occupy. The same holds for SRI as commonly practised, which still ploughs and usually puddles before each transplanting. PQNK, which began in 2009 as a mechanised SRI trial on raised beds, added permanence, so the network can accumulate from crop to crop.

PQNK Soil Moisture Management keeps the root zone moist but aerated, at roughly 30 percent water to 70 percent air in the pore space. Field photographs from PQNK beds show central rows standing taller and denser than the rows beside the furrows. The paper proposes a rice study comparing continuous flooding, AWD and a moist, aerated PQNK root zone, combining micro-CT with oxygen, redox, moisture, root and yield measurements.