肥料深施及穗肥對水稻產量之效應及診斷研究

Abstract

本研究探討肥料深施及穗（氮）肥施用對水稻生育的影響及穗（氮）肥施用必需性判定之基準。結果如下：深施區水稻之乾物產量、穀粒產量、全株氮吸收量及穀粒氮量均較傳統撒施區高。幼穗形成期增施穗（氮）肥35kg/ha明顯增加水稻生育中、後期之氮吸收量、乾物產景、氮收穫指數及收穫指數，故明顯提高殺粒產量。惟因深施區水稻氮吸收效率較高，在較高氮肥用量區增加穗（氮）肥對全乾物產量及穀粒產量反而有不利影響。施穗（氮）肥可以提高氮肥之吸收率。水稻幼穗形成期全株氮濃度達18.6-19.5 g/kg時，施穗（氮）肥無增產效果。幼穗形成期葉片葉綠素計測值與全株氮濃度呈極顯著正相關，可供此時期現場診斷植株氮營養，推薦穗（氮）肥用量之依據。 Field experiments were conducted to examine the effect of deep placement of fertilizer and nitrogen top dressing on rice yield and to develop a simple method for diagnosing the level of nitrogen (N)top-dressing during panicle initiation stage. The results showed that deep placement of nitrogen fertilizer promoted nitrogen uptake, grain nitrogen and nitrogen harvest index, resulted in a higher dry matter production, harvest index, and a higher grain yield of rice plant as compared with conventional nitrogen application. Similarly, top-dressing of nitrogen at panicle initiation stage also increased nitrogen uptake, dry matter production, nitrogen harvest index, harvest index, and grain yield of rice plant. Furthermore, nitrogen top-dressing at the stage significantly increased the efficiency of fertilizer-N absorption. Analyses of canonical correlations of rice response to panicle fertilizer revealed that nitrogen concentration of rice plant and panicle fertilizer dosage were highly correlated i.e. the lower nitrogen concentration in the plant, the higher response of the plant to the top-dressing. The critical nitrogen concentration of rice plant were under 18.6-19.5 g/kg for positive response of rice yield. The chlorophyll-meter value was significantly positively associated with both leaf N conecetration and rice plant N concentration at panicle initiation stage. Consequently, detection of chlorophll concentration using chlorophyll-meter would be a good tool for determining the essential dosage of top-dressing panicle fertilizer.