The “El Camino de Santiago” trail is known to adventurers and Christian pilgrims who traverse this path from France into north-western Spain. Along the way, one experiences the striking, semi-arid Castile y León region farmed to wheat & barley for the last 500 years. Solvita shareholder and former organic farmer, Christopher Brinton, hiked El Camino this summer and was curious about the soil quality he was observing. “The soils look appalling. I would dig with my walking stick and the large clumps are virtually impossible to break up by hand … I’d need a hammer”. He arranged for soil along the trail west of de Órbigo to be Soil Health tested. The two Solvita variables measured, CO2-Burst and SLAN, gave very low values typical of depleted soil – 15 ppm CO2-C respiration (normal values 30-80) and < 45 ppm SLAN (we think a healthy soil has > 250ppm) (see Health Tool link). These findings support the impression that these soils are biologically exhausted (see inset image).
As luck would have it, conservation tillage and no-till practices are now being tested in the Castile-León region – a result of serious concern about the future of these important soils. A recently completed 10-year study coincidentally not far from the trail, reported in Soil and Tillage Research examines alternative soil conservation methods for carbon sequestration. According to the authors, the region is characterized by continuous cereals, low returns of organic residues, virtually no cover crops and little interest in reduced tillage – yet. According to our associate, “The farmers are using very tightly-spaced grain with heavy fertilizing” – this fits the descriptions of intensive continuous cultivation in the belief that high yields support adequate crop residues. The lab tests we ran gave a Score for the Órbigo sample of only 3.3 (on a scale of 1 – 25) using the USDA-ARS . The summation of factors showed no measurable micro-aggregate structure, little soluble carbon and almost no organic nitrogen: overall, zero N for potential mineralization. These are chemically-dependent, dying soils.
The findings of the published tillage study offer a ray of hope: introducing minimum tillage practices significantly increased soil OM up to 30 cm depth by 58% (over 10 years) compared to conventional methods. By far the biggest effect was observed comparing legumes with fallow-cropping. Fallowing is an ancient practice believed to improve yields by conserving moisture, but not helping humus accumulation, according to these data. Soil respiration was reviewed but not measured in the studies but it’s likely that it would have increased in proportion to improved practices – all good speculation on a much needed soil pilgrimage.