중질소(重窒素)를 이용한 수도품종(水稻品種) 및 시용시기(施用時期)에 따른 토양 및 시비질소(施肥窒素)의 효율 -제1보(第一報). 농가포장(農家圃場)에서의 NPK 단순시험(單純試驗)-

Efficiency of Soil and Fertilizer Nitrogen in relation to Rice Variety and Application Time, Using $^{15}N$ Labelled Fertilizer -I. N.P.K. simple trials in farmers fields-

시비질소(施肥窒素)의 효율(效率)을 조사(調査)하기 위(爲)하여 삼요소(三要素) 및 황피요소(養被尿素)(SCU), 농가포장(豊家圃場)에서 2년간(年間) 통일계(統-系)(일본형(日本型), 인도형(印度型), 교잡선발(交雜選拔))와 일반장려계(一般奬勵系)를 사용(使用) 시험(試驗)하였다. 통일계(統一系)의 수량(收量)은 일반장려계일(一般奬勵系)에 비(比)하여 32개지역(個地域) 130개포장(個圃場)에서 2회분시(回分施)와 SCU를 포함한 삼요소(三要素)시험에서 저온다조(低溫多照)해에는 16%, 고온다조(高溫多照)해에는 23%의 증수(增收)를 보였다. 적정질소수준(適定室素水準)은 통일계(統一系)가 장려계(奬勵系)보다 저온(低溫)해에는 3.8kg, 고온(高溫)해에는 5.5kg이 높았으며 동일계(同一系)에서의 년차변이(年次變累)는 동년도(同年度)의 계통간(系統間)변이(變異)보다 컸다. 2회분시(回分施)는 l-2%의 일정(一定)치 않은 수량변이(收量變異)를 보였다. SCU는 20%의 시비량(施肥量) 절감(節減)에도 평균(平均) $2{\sim}4%$의 증수(增收)를 보였으며 염류답(鹽類畓)($27{\sim}39%$), 신개답(新開畓)(20%)과 미숙답(未熟畓)(10%)에서 현저한 증수효과(增收效果)를 보였다.

For the investigation of efficient use of fertilizer nitrogen NPK simple trials were carried out using newly bred Tongil line(japonica indica hybrid selection) and the leading local varieties with sulfur coated area in fields for two years. The yield of Tongil line was higher than that of leading local varieties by 16% in the cool year and 23% is warm year with high solar radiation from NPK simple trials including SCU and 2-split application which were carried in 130 fields at 32 locations. Warm year increased yield by 9% in Tongil but only 3% in the local than the cool year did. Optimum nitrogen level was higher in Tongil by 3.8㎏ in the cool year and 5.5㎏ in warm year than for the local. Yearly variation of optimum nitrogen in the carne variety was greater than varietal variation in the same Year. Two-split application resulted in 1 to 2% of inconsistent yield variation. Sulfur coated urea increased yield by average 2 to 4% even at 20% reduced rate of nitrogen. It was remarkably effective in same $(27{\sim}39%)$, virgin (20%) and unmatured (10%) soils.