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Effect of Rainfall and Subsequent Drying on Nitrogen and Phosphorus Changes in a Dryland Fallow Loam
Author(s) -
Campbell C. A.,
Biederbeck V. O.,
Warder F. G.,
Robertson G. W.
Publication year - 1973
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1973.03615995003700060033x
Subject(s) - loam , lysimeter , water content , moisture , leaching (pedology) , agronomy , nitrification , nitrogen , chemistry , nitrate , environmental science , zoology , soil water , soil science , biology , geology , geotechnical engineering , organic chemistry
36 Chloride placed at 15‐ or 30‐cm depth in 15‐cm diameter cylinders of fallow loam was leached to at least 50 cm during and immediately following rainfall > 1.75 cm. As the soil dried following rainfall 36 Cl moved upwards. Nitrate content of leachates from a lysimeter experiment corroborated the leaching aspects of the 36 Cl expcriment. In the 0‐ to 2.5‐cm segment of a second‐year fallow loam which was sheltered from rainfall, moisture was below the wilting percentage and NO 3 −N and bacterial numbers declined as the soil gradually dried out. In the 2.5‐ to 15‐cm segment, moisture was in the available range, yet moisture and NO 3 ‐N changes were small. In unsheltered fallow loam, NO 3 ‐N production in the 0‐ to 2.5‐cm depth was primarily a function of soil moisture change: ΔNO 3 −N = −0.55 − 1.11 ΔM, ( r = −0.94**), and ΔNO 3 ‐N = −0.45 ‐ 0.56 ΔM, ( r = −0.81*) in the second‐ and first‐year fallow, respectively; (M = % moisture and Δ = daily change). The increase in NO 3 ‐N during drying seemed to be more a result of upward movement than of nitrification. There was a negative linear relationship between ΔNO 3 ‐N and Δ bacteria in the 0‐ to 2.5‐cm soil segment. Sodium bicarbonate soluble inorganic P (IP) generally exceeded NaHCO 3 soluble organic P (OP). In second‐year fallow, P was unaffected by environmental conditions. In first‐year fallow ΔIP in the 0‐ to 2.5‐cm segment was directly related to rainfall ( r = 0.98**), to ΔM ( r = 0.97**), and to Δ bacteria ( r = 0.88**), and inversely related to ΔNO 3 ‐N ( r = −0.76*).