臺東地區木爪缺硼臨界濃度之測定與其土壤中含硼狀況之研究

Abstract

臺東地區之木瓜栽培常見果實缺硼，影響果農收益，本試驗乃研討木瓜缺硼之葉片與土壤診斷方法，並探討該地區土壤熱水可溶性硼含量分佈與土壤母質及有機質含量等之關係。茲摘述其結果如下。 以剛成熟葉（葉片已完全展開且葉柄剛由綠轉紅褐者）為第一葉，採取其第10 葉葉身（不含葉柄）作為缺硼診斷之取樣部位，可顯著反應果園間硼含量之差異。缺硼木瓜第10 葉葉身之硼含量均在20 ppm 以下，而正常果園則在25-155 ppm 間。 果實缺硼之木瓜園土壤熱水可溶性硼含量，在黑色土類均低於0.28 ppm ，其他土類土壤則低於0.15 ppm 。黑色土類臨界濃度較高之原因或為其有機質含量較高之故，仍待查證。 土壤熱水可溶性硼含量受母質、灌溉水質、淋溶時間之久暫、及有機質含量等之影響。臺東縣境耕地土壤之硼含量在0.01-0.84 ppm 間，以紅壤含量最低，平均0.07 ppm ；粕板岩老沖積土次之，平均0.15 ppm ，但其土層深厚且排水不良之水田土壤（豐樂系）則硼含量高，平均0.39 ppm ，推測為灌溉水含硼之故；再次為粘板岩新沖積土，平均0.21 ppm ；而黑色土及東岸火成岩混合砂頁岩沖積土則硼含量較高，平均0.28 ppm （但其中採自都蘭至信義里間者則硼含量低，平均僅0.16 ppm )。東部地區之坡地土壤，以片岩、粘板岩、及砂岩母質者硼含量低，而泥岩及火成岩母質者較高。 表土之有機質含量高於底土，硼含量亦如是。粘板岩及片岩母質之土壤其硼含量與有機質之相關常達顯著水準，顯示此類土壤母質硼含量低，有機質含量乃為決定其硼含量多寡之主要因子。而含火成岩母質之土壤，其有機質與含量均為各類土壤中最高者，但兩者之相關卻極低。 Papaya fruits with rugged surface and latex secretion occurred commonly in Taitung area. The symptom was observed primaryly in western Taiwan in 1975 and had been proved to be boron deficiency, but its diagnostic technique was not established then. The purpose of this study was attempted to find out the diagnostic criteria, including soil and leaf analyses to pinpoint papaya’s boron need and the relationship between boron status and soil categories of Taitung area. The leaf sampling method for diagnosis was studied. The 10th leaf blade (without petiole) from the 1st leaf (recently matured leaf, its blade had just fully developed and with brownish color on petiole) was chosen as the sample since it can effectively reflect the variation of boron content amoung different orchards. The boron content of the 10 th leaf blade of papaya tree with deformed fruits was always lower than 20 ppm, while that of the normal tree was generally 25-l55ppm. The critical level of soil hot water soluble boron (HWSB) concerning with the boron deficiency of papaya was found to be 0.28 ppm for soils classified as black soil (derived from igneous rock and rich in organic matter) and 0.15 ppm for other groups of soils. The difference may be due to the higher organic matter content found in black soil. This needs further experiment to verify. The level of HWSB is affected by kinds of parent material, organic matter content, duration of leaching and irrigation water. The HWSB content of the cultivated lands of Taitung area ranged from 0.01 to 0.84ppm. The boron content of soils classified as latosol was the lowest (mean value: 0.07 ppm), old slate alluvial soil was the next (0.15 ppm), then recent slate alluvial(0 .21 ppm), and that of black soil was the highest (0.28 ppm). The old slate alluvial soil of upland with shallow soil depth and rain-fed only had lower content of HWSB (0.09 ppm) than that of the paddy with deep soil depth and ill drainage (0.39 ppm). The higher HWSB found in the latter was thought to be due to the boron contained in irrigation water. Boron deficiency of papaya occurred commonly in latosol and old slate alluvial soil of upland condition. The hillside leads of eastern Taiwan derived from slate and shist also had lower HWSB content than those derived from mudstone and igneous rock. The organic matter content of surface soil was higher than that of subsoil. It is the same with HWSB. The correlation coefficient between organic matter and HWSB content was significant for soils derived from slate and shist and insignificant for soils derived from mudstone and igneous rock.