Research and development for cereal crop production : soil and fertilizer

A) Influence of longterm application of ammonium sulfate on forms of soil N : Results of this experiment could be summarized. 1. An increase in rates of (NH4)2SO4 successively applied brought about : (a) increase in total N, hydrolyzable N, amino acid N and amino sugar N at highly significant level in both soil groups; (b) highly significant decrease in unidentified N in both soil groups; (c) highly significant and significant increases in nonhydrolizable N in BWAS and FWAS respectively; and (d) significant increase in NH4+ -N only in BWAS but no significant difference in FWAS. 2. Amount of total N in BWAS was higher than that of FWAS by 16.6 %. 3. Orders of N forms in both soil groups were slightly different. 4. Total N highly significantly and positively correlated to all forms of soil N in both BWAS and FWAS except NH4-N which had no correlation, but negatively correlated at highly significant level, to unidentified N and only in FWAS. B) Influence of longterm application of ammonium sulfate on growth and yield of rice in present cropping season : Results could be summarized in the following. 1. The influence of longterm (NH4)2SO4 trial brought about : (a) no influence on height and dry matter of root; (b) highly significant and positive increase in tillering and dry matter of the rice top in all physiological stages in both soil groups except at tillering stage in BWAS which was not statistically different; (c) highly significant and positive increase in yield and number of panicles per hill in both soils but only significant and positive increase in 100 grain weight in only FWAS while for number of grain per panicle no statistical difference was observed in both soils. 2. Increase in N rates still highly significantly increased plant N content but the difference was more pronounced in the earlier stage as well as that of the uptake. 3) Dry matter of top at primordia initiation stage could be a good yield indicator in both BWAS and FWAS but the latter was better. C. Influence of longterm application of ammonium sulfate an "available" forms of N in submerged soil : (Results in details).