肥効調節型被覆尿素を用いた水稲の全量基肥不耕起直播栽培 [in Japanese] Single basal application of total nitrogen fertilizer with controlled-release coated urea on non-tilled rice culture [in Japanese]
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速効性の硫安を基肥および追肥に用いる慣行栽培を対照区として, 肥効調節型被覆尿素を用いた水稲 (品種チヨホナミ) の全量基肥不耕起栽培 (LP区) を試み, 次の結果を得た. 1) LP区の水稲は生育のごく初期に対照区よりやや劣るものの, 6月初旬以降は草丈, 葉色, 茎数および乾物重のいずれにおいても対照区より優った. 2) 対照区では, 湛水直後に急激な土壌無機態窒素の消失が起こり, 稲体は窒素欠乏状態 (クロロシス) を追肥時期まで示した. これに対してLP区の水稲は, 栽培期間中正常な生育を示した. 3) LP区の玄米収量は, 登熟期が高温・多照で経過した1990年が57.1kg/a, 低温・寡照で経過した1991年が51.2kg/aで, 対照区よりもそれぞれ55%および33%優った. 対照区の低収量の原因は, 施肥窒素が湛水とともに消失し, 主としてm^2当たり穂数が少なくなり, 籾数の確保が不充分であったためと考えられる. 4) LP区の窒素吸収量は, 対照区に比べて分げつ盛期以降は著しく優り, 成熟期には対照区の1.57倍に達した. 施肥窒素の利用率は, 全量基肥区のLPが63.2%, 対照区の基肥硫安が8.5%, 幼穂形成期の追肥硫安が52.8%, 穂揃期の追肥硫安が41.5%であった. 5) 以上の結果から, 水稲の不耕起直播栽培に対する肥効調節型被覆尿素の全量基肥施用効果が大きいことが明らかになった.
Single application of total nitrogen fertilizer with controlled-release coated urea on non-tilled rice culture (LP-plot) was compared with a conventional application method using easily released nitrogen fertilizer, ammonium sulfate (AS), for both basal and top-dressing (AS-plot). The results obtained were as follows. 1) The growth of rice on LP-plot was relatively inferior to that on AS-plot in the young seedling stage, but superior in plant height, leaf color, number of tiller and dry weight after the beginning of June. 2) A drastic reduction of soil mineral nitrogen due to denitrification occurred in AS-plot just after submerging, and severe nitrogen deficiency of rice, chlorosis, lasted until the top-dressing stage, whereas rice on LP-plot showed normal growth at all times. 3) Brown rice yields of LP-plot in 1990 with a hot summer and in 1991 with a cool summer were 57.1kg/a or 155% of AS-plot and 51.2kg/a or 133% of AS-plot, respectively. The drastic reduction in grain yield of AS-plot seems to be related to decrease of numbers of ears reflecting nitrogen deficiency of plant at the vegetative growth stage. 4) Amounts of nitrogen uptake of rice plants on LP-plot were somewhat inferior to that on AS-plot in the early growth period, but were extremely superior after the active-tillering stage and reached 1.57times of that on AS-plot at the maturing stage. Recoveries of controlled-release coated urea for basal application, AS for basal application, AS applied at panicle formation stage and AS applied at full heading time were 63.2%, 8.5%, 52.8%, and 41.5%, respectively. 5) From the foregoing, we conclude that a single basal application of total nitrogen fertilizer on a non-tilled rice culture is highly effective using controlled-release coated urea.
- Jpn. J. Crop Sci.
Jpn. J. Crop Sci. 62(3), p408-413, 1993-09
The Crop Science Society of Japan