Nitrogen mineralization in a desert soil: Interacting effects of soil moisture and nitrogen fertilizer

TitleNitrogen mineralization in a desert soil: Interacting effects of soil moisture and nitrogen fertilizer
Publication TypeJournal Article
Year of Publication1987
AuthorsFisher F.M, Parker L.W, Anderson JP, Whitford WG
JournalSoil Science Society of America Journal
Date Published1987
Accession NumberJRN00058
Call Number00066
Keywordsarticle, articles, drought,nitrogen mineralization, journal, journals, Larrea,nitrogen mineralization, nitrogen amendment,Larrea, nitrogen mineralization,Larrea, rainfall simulation,Larrea

The responses of N mineralization to two patterns of supplemental water, N fertilizer, and a drying-wetting episode were examined on order to evaluate the effects of variation in timing and intensity of natural precipitaion on N avialability. Field plots received either 6 mm water/week or 25 mm water/month with or without 10 g N m-2. Samples were collected three times from July 1984 to March 1985 and incubated in the lab for 28 d. The effects of drought were simulated by drying soil at 35 degrees C for 28 d followed by 168-d leaching incubations. Supplemental water reduced 28-d mineralization by 22% in soil collected during dry and moderate soil moisture conditions (July 1984, October 1984) but had no effect on soils collected during a moist period (March 1985). Nitrogen fertilizer had no effect on 28-d mineralization in soils from July but increased 28-d mineralization by 58% in soils from October and March. Air-drying increased mineralization rates across all field treatments during the first 14 d of the 168-d leaching incubations. Mineralization rates were lower in soils from watered plots in both the air-dry and field-moist treatments. Air-drying interacted with both the water and N treatments by increasing watering effects and decreasing feritlizer N effects. The observed drying effects appear to be a net result of several processes that, on the whole, tend to increase N availability. Mineralization rates in both experiments were lower in 6 mm/week soils than in 25 mm/month soils which, in turn, were lower than unwatered controls. We hypothesize that increased moisture availability eventually leads to losses of minerlizable N as initially rapid mineralizaiton converts organic N to inorganic forms that are readily lost from the soil.