Effect of placement and source of sulfur in flooded and non-flooded rice cropping systems.
1994
Chaitep W. | Lefroy R.D.B. | Blair G.J.
Many rice-growing areas in developing countries are becoming S deficient. A glasshouse experiment was conducted to study the effect of water regimes in successive crops (non-flooded: non-flooded, flooded: flooded and flooded: non-flooded), surface (S) and deep (D) placement of sulfur fertilizer and S sources (elemental S (E) and sulfate S (S)) on the growth of rice. A soil of granitic origin was used and 35S-labelled sulfur fertilizers were used to investigate S uptake by plants and the dynamics of S in soils. Among the sulfur sources, surface-applied gypsum produced the highest total yield, which was 83.6 g per pot under flooded conditions. Total yields under flooded conditions were ranked in order SS greater than SE greater than DS greater than DE control. In the first crop, the highest 35S recovery in the plant was 67.8 percent from the non-flooded SE, compared with 51.7 percent in the DE treatment. Deep-placed elemental S (DE) became more effective than SS and SE for the subsequent rice crop, both in terms of plant dry-matter yield and fertilizer 35S content. The highest 35S recovery in the second crop was 29.5 percent in the previous DE treatment in the flooded: non-flooded system. This compares with 7.5 percent in the SS treatment in the same cropping system.
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