Dry Matter Productivity and Overwintering Ability of the Dwarf and Normal Napiergrasses as Affected by the Planting Density and Cutting Frequency

Abstract

The effects of planting density and cutting frequency on dry matter productivity and overwintering ability were compared in the years following establishment among dwarf varieties (early-heading, DE and late-heading, DL) and normal varieties, Wruk wona (Wr) and Merkeron (Me), in the southern part of Kyushu, Japan. The planting densities examined were high (16 plants m~2, 25 cm X 25 cm of spacing), medium (8 plants rar2,50 cm X 25 cm), and low (4 plants m~2, 50 cm X 50 cm) for Wr, DE and DL, and was only medium for Me. The cutting frequency was three times at about 60-day intervals in 1999 and two times at about 90-day intervals in 2000. Irrespective of the planting density, dwarf varieties were higher in tiller number (TN), leaf area index (LAI) and dry weight percentage of leaf blade (PLB) than normal varieties, but lower in plant height (PLH), mean tiller dry matter weight (MTW) and total dry matter weight at all planting densities in both years. With the increase in planting density, TN and annual herbage dry matter yield (HDMY) increased. The annual HDMY was higher in 2000 (cut twice) than in 1999 (cut three times), and the difference in annual HDMY between the dwarf and normal varieties was reduced by planting at a high density and cut twice. This was due to higher MTW in dwarf varieties than in normal varieties at the higher TN conditions. The percentage of overwintered plant (POP) tended to be higher in DL than in other varieties and was higher in 2000 than in 2001 for all varieties, while it tended to decrease with the increase in planting density. Even though the dry matter productivity was higher in the normal varieties than in the dwarf varieties at any planting density and cutting frequency, DL tended to show a stable productivity with high PLB irrespective of planting density and cutting frequency. In addition, it had a high overwintering ability compared with the other varieties.