Reduction and Oxidation - The Biogeochemistry of Submerged Soils - page 124

1998 DS Fallow 1998 WS 1999 DS Fallow 1999 WS

Fallow Fallow Fallow 2000 DS

25

Early tillage,
with straw
Early tillage,
no straw

NPK plots

20

15

10

Late tillage,
with straw

Late tillage,
no straw

5

0

15

NK plots

10

5

0

Time

Figure 4.14 Changes in labile soil P (extractable with HCO 3 − -form anion exchange resin) during 3 years of wetland rice cropping as
affected by timing of tillage (early, late = start, end of fallow), incorporation of previous crop's straw, and application of P (20 kg ha − 1
in NPK plots). The overall P balances over 3 years were 7kgPha − 1

+ + −

37 and in the NPK plots with and without straw, and 90 and

115 kg P ha − 1 − in the PK plots. DS, WS, dry, wet season; DAT, days after transplanting (Bucher, 2001). Reproduced by permission