Research and development for cereal crop production: Soil and fertilizers

(A) Effects of Longterm applications of ammonium sulfate on amount of Soil P: a) In BWAS: longterm application of the 6 ammonium sulphate rates did not alter quantities of total P (T-P), iron phosphates (Fe-P), aluminum phosphates (Al-P) and reductant soluble phosphates (Re-P) but highly significantly to calcium phosphates (Ca-P) and Bray II-P. Negative relationship between N rates and Ca-P and Bray II-P were clearly observed. b) In FWAS: the more (NH4)2SO4 applied the less T-P, Re-P, Ca-P and Bray II-P in soil were observed, but no effects were observed for Al-P and Fe-P. c) Fe-P was the dominant inorganic P of both locations but Ca-P was the main source of available P. (B) Response to Triple Super Phosphate of Rice: a) The P fertilizer highly significantly improved growth and yield of rice and 6 kg P2O5/rai was the optimum dose for both stations. b) P rates positively related to P content in top of rice at PI stage in both stations but at maturity this relationship could be observed only in the straw at KLGES. No effect of P rates was observed for grain P in both station. c) Increasing P rates increased P uptakes for top parts of the rice plant at both PI and maturing stages in both locations. d) Growth content and uptake of P in top at PI stage could predict grain yield of RD 23 rice in both stations. (C) Residual Effect of P on Rice: a) Newly added P promoted growth of rice at the PI stage over the residual one at 0.01 and 0.05 significant levels for the KLGES and SPRES respectively. b) No significant difference in P content of any top portions of the plant at each stage of growth except that of the straw at KLGES which the straw P content was highly significantly increased by the residual P. c) Newly added P increased P uptake at the PI stage at 0.01 and 0.05 significant levels for the KLGES and SPRES respectively.