The Illinois Soil Nitrogen Test (ISNT) was developed for this purpose, and involves estimation of gaseous ammonia liberated by heating the soil with strong alkali in a Mason jar.

After more than a month of improvement, the water-soluble salt content of the test field dropped to 0.9 grams per kilogram of soil and the pH value plummeted to 7.6. Villager Jin Tangman, 63, was ...