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Crop rotation and tillage effects on phosphorus distribution in the central Great Plains

Bowman, R.A., Halvorson, A.D.
Soil Science Society of America journal 1997 v.61 no.5 pp. 1418-1422
Triticum aestivum, fallow, crop rotation, intensive cropping, continuous cropping, phosphorus, nutrient availability, tillage, no-tillage, Zea mays, Panicum miliaceum, Phaseolus vulgaris, Helianthus annuus, crop residues, biogeochemical cycles, conventional tillage, reduced tillage, Colorado
The fate and availability of soil P in the central Great Plains may become less predictable with less tillage and more intensive crop rotations that produce more crop residue and litter than conventional-till (CT) wheat (Triticum aestivum L.)-fallow (W-F). We need to evaluate these new systems relative to new P distribution patterns that may be occurring. We determined P changes in a Weld silt loam soil (fine montmorillonitic mesic aridic Paleustoll) in predetermined plots from a 5-year rotation-tillage experiment where 45 kg P ha-1 was applied in 1990, and 18 kg P ha-1 was applied to the wheat phase of the rotation thereafter. We determined changes in water-soluble P' resin-extractable P total organic P, bicarbonate-extractable P and phosphomonoesterase activity as a function of tillage and cropping intensity in soil from the 0- to 5-cm and 0- to 15-cm depths. Phosphorus concentration in wheat tops at an early stage was also determined to assess soil P availability. Generally P availability indices increased significantly in the 0- to 5-cm depth with continuous cropping treatments compared with wheat-fallow treatments. The results suggest that under more intensive cropping systems P recycling through residue and litter could be an important mechanism resulting in additional plant-available P.