玉米乾物質生產及氮素利用與產量之關係

Abstract

玉米吐絲前的營養生長可能影響子粒產量表現，本試驗採用玉米品種臺農一號為材料，以變化栽培密度處理使植株在吐絲期具有不同營養生長量，但吐絲後具有相似生育環境，調查營養生長與子粒充實期間植株乾物質與氮素的累積與分配性狀。於1991-1993年秋作進行試驗，行距均為75cm，1991年採用株距11、22及44cm三種處理，1992及1993年採用11與22cm兩種株距，又於雄穗分化始期將部份植株株距自11cm間拔為22cm；在播種至成熟期間連續取樣，分析不同器官之乾物質與氮素累積性狀。對營養生長而言，第十二葉齡以後栽培密度對單株乾物質及氮素累積能力的影響方較明顯，在第十二葉期至吐絲期約一個月生育期間，植株所累積的乾物質量佔吐絲期總乾物量的80-92%，所累積的氮素量佔吐絲期總含氮量的69-85%在營養生長全期，乾物質累積速率與氮素累積速率的比值有逐漸上升的趨勢，但在栽培密度處理間則多無顯著差異，顯示以單位氮素為基準的乾物質累積速率，在不同生育階段雖然有異，卻不受環境因子的影響。對生殖生至長而言，玉米植株在吐絲後初期所生產的光合物質平均分配於子粒及果穗其他部位，器官間可能有競爭現象。吐絲期營養生長量較低之植株，在吐絲後0-24日及48-65日之間的單株乾物質生產量較高，有利於產量表現。在氮素累積性狀方面，吐絲期營養生長及氮素累積量較低者，於子粒充實期間反而有較高的氮素同化能力。多數處理於子粒充實全期之全株氮素累積速率低於子粒氮素累積速率，以充實中期的差異最為顯著。玉米植株氮素利用效率因密植而升高，主要受氮素吸收效率影響“如吐絲期營養生長與氮素累積量不同，而吐絲後維持相同之行株距，其氮素利用效率與多數組成因子之表現並無顯著差異，顯示臺農一號玉米品種之氮素利用對栽培密度呈現較為穩定的反應。吐絲期乾物質與氮素累積量較低之處理，植株在吐絲後具有較高的光合物質與氮素同化作用能力，對子粒產量具有明顯的補償及緩衝作用。 Information pertaining to the growth characteristics of corn during vegetative growth is limited. The purpose of this study was to investigate the pattern of dry matter and N accumulation from sowing to silking and its impact on grain yield for corn hybrid Tainung 1. Field experiments were conducted in the fall crops of 1991-1993 with a row spacing of 75 cm. Within - row spacings were 11, 22, and 44 cm, and the spacings were altered by thinning the stand at either tassel initiation or silking stage. The effects of spacing on dry matter and N accumulation were not significant until the 12- leaf stage. From the 12th leaf stage to silking, the amounts of dry matter and N accumulation by the plants accounted for 80-92% and 69-86%, respectively, of the accumulation at silking stage. The ratio between dry matter and N accumulation remained the same among plant spacing treatments, indicating the amount of dry matter production per unit of N was less affected by environmental factors. Dry matter accumulated from silking to 24 days after silking was partitionedrather evenly between kernels and other portions of the ear. Those plants with less vegetative growth at silking tended to have higher dry matter and N accumulation during kernel filling. In most treatments, the rate of N accumulation of the whole plant was lower than that of the kernels. The N use efficiency was increased by increasing the population density, presumably the result of enhanced N uptake efficiency. The performance of the components of N use efficiency was not affected significantly if the amounts of dry matter and N of corn plants were different at silking stage. Experimental results indicate that physiological activities during kernel filling of corn Tainung 1 was related to the vegetative growth condition, and the buffering capacity it exerted helped to stable kernel yield under unfavorable environmental conditions during the vegetative growth period.