尼羅草產量及品質之性狀指標探討

Index traits for forage yield and quality of nilegrass

蕭素碧(Sue-Pea Shaug) ； 許進德(Chin-Te Hsu)

《畜產研究》 37卷3期 (2004/09) Pp. 239-256

摘要

本試驗以尼羅草（Acroceras macrum）AC14、AC15、AC26及AC30等四個品系為材料，於春、夏及秋等三個季節調查，每季從生長14天開始，每週調查一次，調查農藝性狀包括鮮葉數、乾葉數、乾葉高、最上葉領高度、株高、乾葉率、劍葉長度、第二劍葉長度、乾物率、劍葉葉面積、整枝葉面積、莖徑、分蘗數、每穴擴展面積、各節節長、葉／莖及鮮草重等，並分析粗蛋白質（CP）、酸洗（ADF）及中洗（NDF）纖維及相對飼養值（RFV）等牧草品質，目的在探討上述農藝性狀何者可當產量及品質之直接指標。結果乾物產量（DMW）及品質等於不同季節、割期及品系間皆表現極顯著的差異，且同時受到季節×割期、季節×品系、割期×品系、割期×品系×季節等交感作用的影響。DMW於品系間以AC15及AC30最高，分別為5.84及5.82公噸／公頃／割次，CP以AC30最高，ADF及NDF以AC15最高，AC30居中，RFV以AC14最高，其次AC30，由上知AC30具高的DMW及CP，中等量的ADF、NDF及RFV，此結果顯示牧草選育可同時選到高產及高品質的品系。而DMW以夏季最高，CP及RFV以春季最高，ADF及NDF以春季最低，顯示春季草具較優的品質。此外，DMW隨著生長而增加，CP及RFV則隨著割期的延後而下降，ADF及NDF亦隨生長而增加，如生長56天DMW平均6.21公噸／公頃／割次，CP 9.2%，ADF 36.6%及NDF 61.3%，RFV118，但若提前到生長42天及49天採收，DMW仍低，但品質卻明顯地高，若延遲至63天後採收，DMW雖提高，CP及RFV則明顯下降，ADF及NDF明顯增加，故為維持高品質且產量合乎經濟收益，建議生長56天左右應是適合的割期。此外，農藝性狀中只有株高、最上葉領高度及第二至第九節間長等不論季節對DMW、CP、ADF、NDF及RFV等皆呈現一致且極顯著或顯著的相關。以逐步複迴歸分析全年結果，株高及植株擴展面積對DMW的貢獻量居第一及第二，ADF、NDF及RFV等品質則以最上葉領高度居主要貢獻量，其次為乾物率，至於CP則以葉／莖佔主要且顯著的貢獻量，其次為乾物率及株高，綜合上述對產量及品質的重要性狀，剔除間接性狀及考慮性狀的穩定性，建議以最上葉領高度當指標性狀，可以簡易且有效的預估尼羅草產量及品質。

關鍵字

尼羅草 ； 牧草產量 ； 品質 ； 性狀指標

並列摘要

The objective of this experiment was to study the index traits for forage yield and quality of nilegrass (Acroceras macrum stapf) , a perennial forage grass. Four lines, i. e., AC14, AC15, AC26 and AC30 were used. The following agronomic traits were determined every 7 days from the 14^(th) day after cutting (DAC) to the 91^(th) day in spring, summer and fall seasons in 2002, respectively：leaf no. per tiller, the toppest and brown leaf collar heights, plant height, dry leaf and stem weights, leaf lengths of the sword and next to the sword, dry matter percent, sword leaf area, total leaf area, stem diameter, tiller no. per plant, expanded area per plant, internode lengths, leaf/stem and fresh forage weight. The crude protein (CP), acid (ADF) and neutral (NDF) detergent fibers and the relative feeding value (RFV) were analyzed on each harvest for evaluating the forage quality of nilegrass. The results showed that highly significant differences among growth seasons, cutting stages and lines on dry matter weight (DMW), CP, ADF, NDF and RFV which were also affected by the interactions of season × cutting, season × line, line × cutting and season × cutting × line simultenously. Lines AC15 and AC30 had the highest DMW which were 5.84 and 5.82 mt/ha/cut, respectively. AC30 had the highest CP, but moderate ADF, NDF and RFV. It indicated that AC30 could be a better line with higher forage yield and quality. In addition, although DMW of nilegrass was the highest in summer, yet the highest CP and RFV were obvious and the lowest ADF and NDF were shown in spring. This means a better forage quality of nilegrass could be obtained in spring. The DMW, ADF and NDF increased with growth days advanced where the CP and RFV decreased as the cutting delayed. The nilegrass had DMW with 4.91mt/ha/cut, CP with 9.2%, ADF 36.6%, NDF with 61.3% and RFV with 118 at 56 DAC. In addition, the DMW decreased while the forage quality highly went up at 42~49 DAC. However, when harvest at 63 DAC, the DMW kept higher, but CP and RFV decreased significantly and ADF and NDF obviously increased. This suggested that nilegrass produced high DMW with better forage quality at 56 DAC. Further, it showed that coincident and highly significant correlations dexisted between plant height, the toppest leaf collar height, the second to ninth internode lengths and DMW, CP, ADF, NDF and RFV in the three growth seasons, respectively. Besides, stepwise multiple regression analysis were conducted by using DMW, CP, NDF, ADF and RFV as dependent variables. A quantitative measurement of the priority of the variables entering the equations was shown by increasing in R^2 for each independent variable. It indicated that plant height and expanded area per plant entered the equation first and second, respectively in whole year when DMW was used as dependent variable. The contributions by the order with the toppest leaf collar height first, then dry matter percent to ADF, NDF and RFV and leaf/stem first, dry matter percent second and then plant height to CP were all highly significant in the whole year. Based on the results and considering the stability of these traits, it is suggested that the toppest leaf collar height be used as an effective and convenient index trait to evaluate both forage yield and quality of nilegrass.

並列關鍵字

Nilegrass ； Forage yield ； Forage quality ； Trait index