Gc. Li et Rl. Mahler, EFFECT OF PLANT-MATERIAL PARAMETERS ON NITROGEN MINERALIZATION IN A MOLLISOL, Communications in soil science and plant analysis, 26(11-12), 1995, pp. 1905-1919
The introduction of plant materials into a soil can impact the nitroge
n (N) status and the fertilizer requirement for agronomic crop product
ion. Consequently, an accurate estimate of N mineralization from soil
organic matter and incorporated plant material is necessary to adequat
ely make a N fertilizer recommendation. The purpose of this study was
to evaluate the effect of plant parameters including type, size, incor
poration rate, and time after incorporation on N mineralization and to
derive localized values for parameters in a widely used potential N m
ineralization model. Soil from the Ap horizon of a Latahco silt loam w
as amended with alfalfa (Medicago saliva L.), spring pea (Pisum sativu
m L.), and winter wheat (Triticum aestivum L.) plant materials sized t
o either <1, 1 to 2, or > 2 mm at rates of 0, 2, 4, and 6%. The soils
were incubated at 35 degrees C for 20 weeks. The inorganic N in soils
was removed by leaching with 100 mt 0.001M CaCl2 in 5- to 10-mt interv
als followed by 25 mt of a nutrient solution devoid of N (0.002M CaSO4
; 0.002M MgSO4; 0.005M Ca(H2PO4)2; and 0.0025M K2SO4) at 0, 2,4, 6, 8,
12, 16, and 20 weeks. The main effects of plant material type (PM), s
ize (S), incorporation rate (R), and incubation time (T) and many 2-,
3-, and 4-factor interactions on N mineralization were statistically s
ignificant at P=0.05. Based on w(2), incubation time (T), and incorpor
ation rate (R) were the two most important factors affecting N mineral
ization. The amount of N mineralized increased exponentially with incr
easing time and linearly with the incorporation rate. In addition, the
incorporation of plant material not only increased potentially minera
lizable N by as much as 5.1 times bur also accelerated N mineralizatio
n in soil by increasing the N mineralization rate constant 75%.