Growth of Red-leaf Lettuce and Changes in Soil Solution Chemical Properties of Coir-dust Containing Root Media Influenced by Application Rates of Pre-planting Fused-Superphosphate

This research was conducted to investigate the influence of various levels of fused superphosphate as pre-planting fertilizer on the growth of red-leaf lettuce and changes in the chemical properties of the soil solution in three root media, namely coir-dust plus expanded rice hull (8:2, v/v; CD+ERH), carbonized rice hull (6:4; CD+CRH), or ground and aged pine bark (8:2; CD+GAPB). The amounts of fused superphosphate (FSP) incorporated into the three root media during formulation were controlled from 0 to $6.0g{\cdot}L^{-1}$ in $1.5g{\cdot}L^{-1}$ increments. The root media containing fertilizers were packed into 300 mL plastic pots and seedlings of red-leaf lettuce at the 3rd leaf stage were transplanted. After transplanting, the crops were fed with a solution of neutral fertilizer ($100mg{\cdot}L^{-1}$). The growth of red-leaf lettuce was investigated 5 weeks after transplanting and soil solutions were extracted and analyzed every week for pH, EC, and concentrations of macro-nutrients. The elevation of application rates of FSP in the three root media resulted in better growth, and the crops grown in CD+ERH and CD+GRPB had greater fresh and dry weights than those in CD+CRH when compared among the treatments of equal amounts of FSP. The pH and $PO_4{^{-3}}$ concentrations in the soil solution of CD+CRH at 3 weeks after transplant were in the ranges of 4.0 to 4.8 and 20 to $100mg{\cdot}L^{-1}$, respectively. These were lower pH and higher $PO_4{^{-3}}$ concentrations than those in CD+ERH and CD+GAPB. The $K^+$ concentrations were higher in CD+CRH than those in the other two root media, and the elevation of FSP application rates resulted in higher $Ca^{+2}$, $Mg^{+2}$ and $SO_4{^{-2}}$ concentrations in soil solution of the three root media. The $NO_3$-N concentrations in soil solution rose continuously during crop cultivation, implying that the leaching percentage was elevated. The soil solution EC varied, showing the same tendencies as the $NO_3$-N concentrations. The above results indicated that the CD+ERH and CD+GRPB media performed better than CD+CRH, and optimum application rates of FSP in the three root media were 4.5 to $6.0g{\cdot}L^{-1}$ for pot cultivation of red-leaf lettuce.

코이어 더스트 혼합상토에 용과린의 시비수준에 의한 적축면 상추의 생장과 근권부 화학성 변화

코이어 더스트(coir-dust, CD)와 팽연왕겨(expanded rice hull, ERH), 훈탄(carbonized rice hull, CRH), 및 분쇄수피(ground pine bark, GRPB)를 혼합하여 조제한 CD+ERH(8:2, v/v), CD+CRH(6:4) 및 CD+GRPB(6:4)의 세 종류 혼합상토에 기비로 혼합된 용과린의 시비수준이 적축면 상추의 생장과 근권부 화학성 변화에 미치는 영향을 구명하기 위하여 본 연구를 수행하였다. 용과린을 $0.0-6.0g{\cdot}L^{-1}$까지 $1.5g{\cdot}L^{-1}$씩 시비수준의 차이를 두어 상토에 혼합한 후 본엽 3매인 적축면 상추를 정식하고 5주간 태양광 병용형 식물공장에서 재배하였다. 매주 1회 중성비료를 $100mg{\cdot}L^{-1}$으로 농도를 조절하여 포트당 150mL씩 공급하였고, 시비 30분 후 포트 하단부에서 토양수를 추출하여 근권부 pH, EC 및 무기이온 농도 변화를 분석하였으며, 정식 5주 후에 지상부 생장을 조사하였다. 적축면 상추는 CD+CRH 보다 CD+ERH와 CD+GRPB에서 지상부 생장량이 많았고, 각 상토에서 용과린 시비수준이 높을수록 지상부 생장량이 많은 경향이었다. 정식 3주 이후 CRH를 포함한 상토의 근권부 pH는 4.0-4.8, $PO_4{^{3-}}$ 농도는 $20-100mg{\cdot}L^{-1}$ 범위로 분석되었는데 이는 ERH와 GRPB를 포함한 혼합상토 보다 pH는 낮고 $PO_4{^{3-}}$ 농도는 높은 결과이다. 용과린의 시비수준이 높을수록 세 종류 상토의 토양용액 $Ca^{2+}$, $Mg^{2+}$, $SO_4{^{2-}}$ 농도가 높았지는 경향이었으며, CD+CRH에서 다른 혼합상토보다 $K^+$ 농도가 높았다. 재배기간이 경과함에 따라 세 종류 상토의 $NO_3$-N 농도가 높아졌으며, $NO_3$-N 농도가 높을 때 토양용액 EC도 상승하는 경향을 나타냈다. 이상의 결과를 종합하면 식물공장에서 적축면 상추를 재배하기 위해 적합한 혼합상토는 CD+ERH와 CD+GRPB 였고, 기비로 혼합되는 용과린의 적정 시비 수준은 $4.5-6.0g{\cdot}L^{-1}$의 범위라고 판단하였다.