今月も産官学の水田勉強会。

半乾燥ケニヤでの陸稲栽培研究。過剰な窒素施肥は茎葉部を過繁茂させる。葉面積の増加で光合成能が増加するだけではなく、茎（稈と葉鞘）が光合成産物を貯蔵する能力も増大する。穂へ転流するはずの光合成産物が茎へ転流してしまい収量が低下するという興味深い現象。

イネ－ムギ－ダイズの2年3作体系をイネ－ムギ－ダイズームギ－ダイズの3年5作体系へ転換する過程で大発生したコムギ黄斑病。ムギ－ダイズームギの期間にムギ残渣で菌密度が温存されるらしい。関東以北の品種群には抵抗性があり、西日本の品種にはほとんど抵抗性がないという興味深い話も。

【内容】
関谷（国際資源植物学）
「陸稲に対する窒素過剰施用は茎葉シンク能を増加させて収量を低下させる」
渡邊様（中日本農研）
「津市安濃町草生のダイズ後コムギ圃場において多発した、葉身の褐斑・黄斑、枯れ上がり、白穂症状　・・・・・　コムギ黄斑病」

This month’s agriculture-industry-academia paddy field study group meeting.

Research on upland rice cultivation in semi-arid Kenya. Excessive nitrogen fertilization causes excessive vegetative growth of stems and leaves. Not only does the increase in leaf area increase photosynthetic capacity, but the stems (culm and leaf sheath) also have an increased ability to store photosynthetic products. An interesting phenomenon occurs where the photosynthetic products that should be translocated to the panicle are instead translocated to the stems, resulting in decreased yields.

In the process of converting the 2-year 3-crop system of rice-wheat-soybean to a 3-year 5-crop system of rice-wheat-soybean-wheat-soybean, a major outbreak of wheat yellow spot disease occurred. It seems the wheat residues during the wheat-soybean-wheat period maintain the pathogen density. The variety groups in the Kanto and northward regions have resistance, while the varieties in western Japan have almost no resistance – an interesting point.

Sekiya (Global Plant Resource Science) “Excessive nitrogen application to upland rice increases the stem and leaf sink capacity, causing a decrease in yield”
Watanabe (Central Region Agricultural Research Center) “In the wheat field after soybean in Kusawa, Tsu, severe symptoms of leaf spot, blotch, withering, and white head occurred… wheat yellow spot disease”