土壤特性對稻米品質之影響(三)土壤理化性質對米飯品質之影響

Abstract

本試驗目的在探討土壤各種理化性質對米飯品質的影響，據以作為良質米栽培管理的參考。於1989-1991年調查本省中部地區90處稻田土壤物理化學性質及米飯品質。土壤化學性質調查項目有土壤pH、游離鐵、易還原錳、氧化還原電位。土壤物理性質則調查滲漏速率、穿刺阻力及灰斑層深度。同時也調查土壤各種元素的比值及水稻根活性。米飯品質測定項目為食味品評及米飯物理性質。結果顯示pH較低，易還原猛含量較低及氧化還原電 位下降速率較慢之土壤，米飯食味總評及均衡度有較佳之趨勢。生產之稻米食味及均衡度 較佳的土壤，其曬田後穿刺阻力有較大的趨勢。曬田常在最適分蘗後行之，曬田程度高者，土壤通氣獲得改善，米質可能因而獲得改進，但使得土壤穿刺阻力亦随之昇高。土壤剖面灰斑層深度、水田滲漏速率及稻根活性在米質優劣區對比下均無明顯之差異。土壤Ca/ Mg比值較高及Mg/K比值較低者，米質食味總評及均衡度亦有較佳之趨勢。 This experiment aimed to investigate the effects of soil physical and chemical characteristics on rice qualities. Totally 90 field experiments were conducted at central Taiwan from 1989 to 1991. Soil properties including soil pH, free iron, reducible manganese, redox potential, percolation rate, penetration resistance, depth to gray layer, and ratios among soil nutrient elements were surveyed. Eating quality and balance of cooked rice were also tested by panel evaluation and texturometer, respectively. Experimental results showed that paddy soils with a lower pH, reducible manganese, and slower declined rate of redox potential, produced higher quality rice with good eating quality and balance. Soils produced rice with better eating quality and balance showed a higher penetration resistance after soil-drying, which is always practiced after optimum tiller number reached, and accompanied by improvement of soil aeration and increase of soil penetration resistance. Thus a higher penetration resistance implied a higher degree of soil-drying and thus a better soil aeration which resulted in production of high quality rice. Soil with a higher Ca/Mg, and lower Mg/K also tended to produce good quality rice. On the other hand， there are no significant differences of depth to gray layer, percolation rates, and root activity of rice, between producing good and poor quality of rice.