Soybean [Glycine max (L.) Merr.) is known to produce the highest total digestible mutrients (TDN) yield among summer grain legumes in Jeju area but little is known about the effects of cultural practices on forage yield and quality. A determinate soybean cv. Baegunkong was planted on 5 June, 20 June, and 3 July and grown at four plant densities (30, 50, 70 and 90 plants m-2 in 1998 in Jeju to evaluate the effects of planting date and plant density on the yield and quality of soybean forage. Days to flowering decreased from 47 to 38 days, average plant height from 61 to 51cm and main stem diameter from 6.31 to 5.00mm as planting was delayed from 5 June to 3 July. Average plant height quadratically increased from 45 to 62cm as plant density increased from 30 to 90 plants m-2 . Planting date did not affect the average dry matter, crude protein, and TDN yields. The average dry matter and TDN yields displayed a quadratic response to plant density and the optimum plant density for both dry matter and TDN yields was estimated about 60 plants m-2 . Plant density had no effect on crude protein yield. Planting date did not significantly influence forage quality. The crude protein content was not significantly influenced by plant density. Increasing plant density slightly increased acid detergent fiber content but slightly decreased TDN content.

To obtain a basic information on the development of effective control strategies for weedy rice in direct seeding rice cultivation, occurrence patterns of weedy rice as influenced by different cultural practices such as cultivation method, water management, seeding time, and tillage were investigated in field or pot experiments. High occurrence of weedy rice was observed in a continuous direct seeding paddy field as compared to machine transplanted one. Based on the percent of weedy rice panicle over three years trial, high ridged dry seeding was highest with 36.9%, followed by wet seeding with 30.9%, water seeding with 14.6% and machine transplanting rice with 0.8%, indicating 97.8% reduction in weedy rice occurrence by machine transplanting rice as compared with high ridged dry seeding. Germination of weedy rice was promoted to 83-94 % when rice panicle was flooded from September 30 to October 10 for 6 days and 74-88% for 9 days on October 20. Weedy rice occurrence was also substantially reduced by delayed seeding on June 10 and intensive tillage. The results suggest that machine transplanting rice be more effective cultural practice than flooding treatment, delayed seeding and intensive tillage when weedy rice problem occurs in direct seeded paddy field.

This study was conducted to assess the allelopathic potentiality of Korea traditional seventy-nine rice (Oryza sativa L.) cultivars on barnyardgrass (Echinochloa crus-galli P. Beauv. var. oryzicola Ohwi) and to identify possible allelopathic compounds from selected rice cultivars, such as Seogandodobyeo, Huadobyeo and Heugbalbyeo. In the straw mixture, Seogandodobyeo showed the greatest inhibition (67.07%) on total emergence percentage. The greatest inhibition on total seedling length and dry weight of barnyardgrass occurred in Huadobyeo (58.32 %) and Heugbalbyeo (81.20%), respectively. An HPLC analysis with nine standard compounds showed that the concentrations and compositions of allelopathic compound depend upon the cultivars. Four compounds including Ο-coumaric acid in Seogandodobyeo extracts, four compounds including p-coumaric acid in Huadobyeo extracts, and seven compounds including Ο-coumaric acid in Heugbalbyeo were detected, respectively. Ο-coumaric acid (0.97 mg/g) in Seogandodobyeo, p-coumaric acid (0.92mg/g) in Huadobyeo and Ο-coumaric acid (1.02 mg/g) in Heugbalbyeo was detected as the highest amounts, respectively. The preliminary identification by HPLC analysis resulted in peaks with retention times close to those of standards which were confirmed with EI/MS. The mass spectra of p-coumaric, and Ο-coumaric acids showed molecular ions (m/z) at 164 and 164, and their base peaks (m/z) at 164 and 118, respectively.

알팔파 (Medicago sativa L.)의 예취후 재생 기간중 저장탄수화물의 이용성을 규명하기 위해 수경재배하여 개화초기에 예취한 후 재생 24일간의 뿌리내 비구조탄수화물의 함량 및 전분 분해효소의 활력을 분석한 결과는 아래와 같다. 1. 재생초기 10일간의 잎과 줄기의 재생은 매우 느리게 진행되었으며, 예취후 뿌리의 성장이 억제되었다. 2. 예취후 초기재생 10∼14일간 뿌리내 가용성 당 및 전분의 함량은 다같이 감소하였다가 이후 빠르게 회복하는 경향이었다. 3. 재생기간중 exo-amylase의 평균 활력은endo-amylase에 비해 약 400배 이상 높았다. Exo-amylase의 활력은 재생 6일차(최고수준) 까지 증가하다가 이후 감소하였다. Endo-amylase의 활력은 재생초기 4일 동안 급격히 증가하다가 이후 재생 24일차(최고수준) 까지 서서히 증가하는 경향이었다. 이상의 결과들은 알팔파의 재생초기 동안 전분 분해효소의 활력의 증가와 아울러 뿌리내 저장탄수화물은 활발히 분해되어 새로운 조직의 재생에 이 용됨을 간접적으로 제시한다.