Effects of placement of elemental S and sulfate on the growth of two rice varieties under flooded conditions
1993
Samosir, S.S.R. | Blair, G.J. | Lefroy, R.D. (New England Univ., Armidale (Australia). Dept. of Agronomy and Soil Science)
A glasshouse experiment was conducted where 35S-labelled sulfate or elemental S was either broadcast onto the surface soil soon after transplanting or incorporated in the 7-21 cm soil layers 30 days before transplanting 2 rice varieties C4-63 and Pulu Bolong. Rhizosphere oxidation and root growth were factors contributing to the higher fertilizer S uptake at 42 days after transplanting (dat) in C4-63 than in Pulu Bolong. Filled grain yield was higher in C4-63 than Pulu Bolong. At 42 dat shoot yields, and at maturity straw yields, were highest in the surface sulfate (SS) treatment. There was a significant time x fertilizer placement x soil layer x variety interaction in the amount of fertilizer S recovered in the KH2PO4-extractable sulfate and sulfide soil pools at 42 dat and maturity. At maturity, 34 to 74 percent of the fertilizer S was recovered in the soil sulfate and sulfide pools and in the algae and surface water in the presence of plants, and 20 to 34 percent in the pots without plants. The data indicate that surface application results in greater utilization of fertilizer S and suggest that combined P-S fertilizer sources are likely to be more efficient than N-S sources.
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