Abstract
An attempt to determine the optimum levels of P and K fertilizers application for Tong-il lines (indica${\times}$Japonica) was made with the data obtained from the farm fields during 1976 to 1979. The detailed interpretation to obtains relationships between fertilizer recommendation of P and K with their balance with Ca and Mg contents in soil were made using yield data obtained in 1977. The results were summarized as follows : 1. The optimum rates of P and K fertilizer application varied with the kinds of paddy soils showing the ranges of 6.6-11.4 kg/10a for P (as $P_2O_5$) and 7.0-11.3 kg/10a for K (as $K_2O$). The amounts of optimum fertilizers increased in the order of unmatured soil, normal soil, sandy soil, saline soil, poorly drained soil for P, and unmatured soil, poorly drained soil, sandy soil, normal soil, saline soil for K. 2. The yield increment at the optimum levels of P and K in comparison with no fertilizer application were 3,5-7.5% for P and 2.1-9.1% for K. The effectiveness of P was greatest in the unmatured soils and that of K was greatest in the poorly drained soils, and in the saline soil, that of P and K was relatively high. 3. According to relationship between relative yield index and soil testing value, the critical $P_2O_5$ contents which showed the yield response in soil were about 100 ppm for normal soil and 200ppm for sandy soil. That of exchangeable K/Ka+Mg ratio in soil were about 0.08 for normal paddy soil and over 0.08 for sandy soil, and those for poorly drained soils were not obtained in the ranged below 0.08. 4. The regression equations of fertilizer recommendation for different soils were obtained between the available $P_2O_5$ in soil or ratio of K to base including Ca and Mg in soil (x) and the amount (Y) of P and K fertilizers applied. The equations for phosphorus recommendation were Y=11.27C-0.048x for normal paddy soil and Y=13.383-0.061x for sandy soil, and those for potassium recommendation were Y=9.526-0.569x for normal paddy soil, Y=11.727-1.004x for sandy soil, and Y=12.574-0.558x for poorly drained soil, respectively.
농가포장에서 실시한 '76~'79년의 비료 시험성적으로부터 수도의 통일계 품종에 대한 인산 및 칼리의 시비효과와 시비적량을 토양의 물리적 특성을 달리하는 답유형별로 검토하였으며, 이 중 '77년의 시험성적을 집중적으로 분석하여 토양화학 검정치에 따른 시비적량의 산출기준을 설정하였는 바, 그 결과를 요약하면 다음과 같다. 1. 답유형별로 산출한 인산의 시비적량 6.6-11.4kg/10a범위에서 미숙답>보통답>사질답>염해답${\fallingdotseq}$습답의 순이었고, 칼리의 시비적량은 7.0-11.3kg/10a범위에서 미숙답>습답>사질답>보통답${\fallingdotseq}$염해답의 순이었다. 2. 답유형별로 산출된 적정시비량은 사용하였을 때 각각의 무요소구에 대한 증수효과는 인산의 경우 3.5-7.5%, 칼리의 경우 2.2-91%의 범위에서 답유형별로 차이가 있었다. 인산의 효과는 미숙답에서, 칼리의 효과는 습답에서 가장 컸으며, 염해답에서는 인산과 칼리의 효과가 모두 비교적 높았다. 3. 답토양의 필지별 화학성분 검정치와 상대수량 지수의 관계에서 시비효과의 한계점인 토양중 유효인산의 임계함량은 보통답 약 100ppm, 사질답 약 200ppm이었고, 치환성 칼리 염기비(K/Ca+Mg${\times}100$)임계점은 보통답 약 8, 사질답 8이상이며, 습답에서는 나타나지 않았다. 4. 토양검정치(x)에 따른 시비적량(y) 산출식은 인산에 있어서는 보통답 y=11.270-0.048x, 사질답 y=13.383-0.061x이고 칼리에 있어서는 보통답 y=9.526-0.569x, 사질답 y=11.727-1.004x, 습답 y=12.574-0.558x이었다.