Departmental Bulletin Paper 東北地域における多収性水稲品種「いわいだわら」の収量と玄米タンパク質含有率に及ぼす豚ぷん堆肥施用と窒素施用法の影響

大平, 陽一  ,  西田, 瑞彦  ,  福重, 直輝  ,  持田, 秀之  ,  石川, 洋  ,  勝部, 忠志  ,  斎藤, 真二  ,  菊池, 公一  ,  小野, 洋  ,  白土, 宏之  ,  伊藤, 景子

(120)  , pp.47 - 66 , 2018-03 , 国立研究開発法人 農業・食品産業技術総合研究機構 , National Agriculture and Food Research Organization (NARO)
東北中南部の飼料用米生産に適した多収性水稲品種として「いわいだわら」が育成された。本研究では、耕畜連携によって豚ぷん堆肥(以下、堆肥)を活用する場面において、堆肥の肥効と、「いわいだわら」の収量・玄米タンパク質含有率を効果的に高める窒素施用法を検討した。「いわいだわら」と既存の多収品種「ふくひびき」を秋田県大仙市で5月下旬~6月上旬に移植栽培すると、4月下旬施用した堆肥の肥効が移植後1カ月過ぎから水稲の生育に現れ、幼穂形成期にかけて茎数、草丈、葉色を高めた。「いわいだわら」では、堆肥0.8~1.6t 10a−1施用により、粗玄米重が堆肥・窒素無施用処理よりも176~245kg 10a−1高くなった。また、基肥窒素を施用しなくても、生育中期からの堆肥の肥効および窒素施用によりシンク容量が「ふくひびき」より高まりやすく、穂揃い期の窒素追肥(実肥)で登熟歩合や粗玄米重が向上した。一方、「ふくひびき」は、堆肥施用の有無にかかわらず基肥窒素量を高 めないと収量が高まらない傾向にあり、また、実肥は粗玄米重の増加に寄与しなかった。「いわいだわ ら」では、玄米タンパク質含有率(乾物)は堆肥0.8t 10a−1を施用しても無施用との差はほとんどなく、1.6t 10a−1施用で0.6~1.2ポイント増加した。「いわいだわら」では、「堆肥+実肥」あるいは「堆肥+穂肥+実肥」の体系により、堆肥無施用で「基肥+穂肥」の慣行窒素施用体系と同等以上の粗玄米重(737~905kg 10a−1)および慣行より高い玄米タンパク質含有率(7.8~9.3%)の両立が可能であった。豚ぷん堆肥はリン酸の含有率が高いことから、今後は土壌養分維持の観点も含めた最適な堆肥施用量と窒素施用量の判断技術が必要と考えられた。"Iwaidawara" is a recently developed high-yielding rice cultivar suitable for rice feed grain bred in the middle and southern parts of the Tohoku region. In order to fully demonstrate the potential of "Iwaidawara" when utilizing swine compost in cooperation with livestock farmers, we examined the fertilizing effect of swine compost and the nitrogen fertilizer application method, which effectively provides high yield and protein content of rice grain. When "Iwaidawara" and "Fukuhibiki"(a high-yielding cultivar been popular in cold regions)were transplanted in late May to early June in Daisen City, Akita Prefecture, the fertilizing effect of swine compost began to appear more than a month after transplanting and increased the number of stems, plant height, and leaf color through the panicle formation stage. The grain yields of "Iwaidawara" under the application of 0.8 to 1.6 t 10a−1 of swine compost increased 176 to 245 kg 10a−1 compared to "Iwaidawara" without swine compost and nitrogen application. In "Iwaidawara", the fertilizing effect of swine compost and/or a topdressing of nitrogen fertilization from the middle growth stage was found to provide larger sink capacity than that of "Fukuhibiki" without basal nitrogen fertilization. In addition, nitrogen application at the full heading stage(NAF)increased the percentage of ripened grains in addition to grain yield. On the other hand, in "Fukuhibiki", grain yield tended to be low except under high basal nitrogen fertilization, regardless of the application of swine compost. In addition, NAF did not contribute to any increase in grain weight. The protein content of rice grain under the 0.8 t 10a−1 swine compost treatment did not differ from that under no swine compost treatment in either cultivar, while that in rice grain under the 1.6 t 10a− 1 swine compost treatment was increased 0.6 to 1.2 points compared to that under no swine compost treatment. In "Iwaidawara", under "swine compost + NAF" or "swine compost + nitrogen application at the panicle formation stage(NAP)+ NAF", it was possible to obtain high grain yields(737 to 905 kg 10a−1)equal to or greater than those obtained under the traditional system(no swine compost, basal nitrogen fertilization + NAP), as well as higher protein content in rice grain(7.8 to 9.3%)than that under the traditional system. Given the high content of phosphoric acid in swine compost, the optimal amount of swine compost and nitrogen must be determined in the near future with an eye to maintaining appropriate soil nutrients.

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