Spatial Distribution of Rice Root under Long-term Chemical and Manure Fertilization in Paddy

It is well known that root distribution of rice is a crucial factor for nutrient absorbtion and affect by soil fertility management. However, the findings on root distribution are limited due to laborious and tedious work. The characteristics of root distribution were investigated in long-term fertilizer experiment plots that were established in paddy soil, a fine silty family of typic Hal-paqueps (Pyeongtaeg series) in 1967. fertilizer experiment plots of no fertilizer, compost, NPK and NPK+compost plot have been maintained consistently for the past thirty six year and Npk+silicate plot for the past twenty two years. In NPK plot, 150kg N (urea), 100kg -$\textrm{P}_2\textrm{O}_5$ (fused phosphate) and 100kg $\textrm{K}_2\textrm{O}$(potassium chloride) per hectare have been applied. For NPK+silicate plot, 500kg $\textrm{Si}\textrm{O}_2$ (silicate) was applied in addition to fertilizer in NPK plot. For the compost plot, 10,000kg rice straw compost per hectare were applied. Root samples were taken from the positions of hill-center (below hill) and mid-point of four adjacent rice hills at heading stage by cylinder monolith (CM) method. The soil cores were sampled 20cm depth from the soil surface and partitioned four into layers at an interval of 5cm. The soil particles surrounding roots were washed out with tap water, Length and weight of the roots in each soil layer were measured and root length density (RLD), root weight density (RWD), specific root length(SRL) and rooting depth index (RDI) were calculated. Total root length was measured by intersection method. Plant height, tiller and shoot dry weight were the highest in NPK+compost plot. But RLD of hill-center soil cores was the highest in no-fertilizer plots. In the soil cores from mid-point position of four adjacent hills, RLD at 15-20cm soil depth was higher in compost plot than NPK plot. RLD in compost plots showed even distribution compared to those in chemical- fertilizer plots. RWD was the highest in the NPK+compost plot. SRL was the lowest in the NPK+silicate plot. RDI was the highest in the compost plot. Also, in this experiment it was found that the distribution of roots was closely related to the physical properties of the soil as affected by fertilization management.

화학비료 및 희비 장기시용에 따른 벼 뿌리 분포 특성

무기질 비료 및 퇴비를 36년간 장기 시용한 논 토양에서 벼 뿌리의 분포양상을 구명하기 위하여 무비, 퇴비단용, 삼요소, 삼요소+퇴비, 삼요소+규산구의 벼 뿌리 관련 특성을 조사하였다. 본 시험은 평택통에 화삼벼를 주당 3본씩 손이앙 하였으며 삼요소구의 시비량은 N-$\textrm{P}_2\textrm{O}_5$-$\textrm{K}_2\textrm{O}$ kg $\textrm{ha}^{-1}$=150-100-100를 시용하였고 규산은 ha당 500kg, 퇴비는 ha당 10,000kg를 시용하였다. 근계특성 분포 특성을 요약하면 다음과 같다. 지상부의 건물중은 시비량이 많을수록 높은 경향이었다 그러나 뿌리 건물중은 삼요소구에 비하여 삼요소+퇴비에서 많았으며, 총근장은 무비에서 컸다. 뿌리 건물중은 삼요소+퇴비구에서 높았다 토심별 근장밀도(cm $\textrm{cm}^{-3}$)는 무비구의 주간하 0-5cm에서 가장 높았고 토심이 깊어질수록 적어지는 경향이었고 주하와 주간하의 차이는 심토로 갈수록 적어지는 경향이었으나 퇴비단용구는 토심 15-20cm의 주간하에서 주하와 차이가 컸다. 토심별 근중밀도(mg $\textrm{cm}^{-3}$)는 삼요소+회비구에서 가장 높았다. 비근장은 삼요소+규산구에서 가장 낮았다. 뿌리깊이 지수는 퇴비단용구가 높았으며 근장으로 계산한 지수가 근중으로 계산한 지수보다 높았다.