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。結果如次：深施區水稻之乾物產量、谷（穀）粒產量、全株氮素吸收量及谷粒氮素量均較傳統撒施區高。幼穗形成期增施穗（氮）肥35公斤／公頃明顯增加水稻生育中、後期之氮素吸收量、乾物產量、氮素收穫指數及收穫指數，故明顯提高谷粒產量。惟因深施區水稻氮素吸收效率較高，在較高氮肥用量區增加穗（氮）肥對全乾物產量及谷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含量達1.86~l.95％時，施穗（氮）肥無增產效果，此與前人之結果相近。幼穗形成期葉片葉綠素計測值與全株氮含量呈極顯著正相關，可供此時期現場診斷植株氮營養推薦穗（氮）肥用量之依據。 The response of rice yield to deep placement of fertilizer and nitrogen top-dressing during panicle initiation stage has been investigated, and a study to develop a simple scheme for diagnosing the demand of nitrogen top-dressing during panicle initiation stage also has been evaluated. The results are as follows. Deep placement of nitrogen fertilizer promoted nitrogen uptake, gram nitrogen and nitrogen harvest index, and resulted in a higher dry matter production, harvest index and consequently a higher grain yield of rice plant. Top-dressing of nitrogen at panicle initiation stage had favorable effects on the nitrogen uptake, dry matter production, nitrogen harvest index, harvest index and grain yield of rice plant. Nitrogen top-dressing at panicle initiation stage increased the efficiency of fertilizer-N absorption. The response of rice plants to panicle fertilizer were observed and were found well correlated with the nitrogen content in the plants during panicle initiation stage, i.e. the lower the nitrogen content in the plants the higher the response of the plants to the top-dressing. The critical nitrogen contents for obtaining positive yield response as observed were about 1.86-1.95 %. Since the chlorophyll-meter value had significantly positive relationships with both leaf N % and plant N % of rice plant at panicle initiation stage, chlorophyll meter may serve as a suitable tool for determining the necessity of top-dressing panicle fertilizer.