Growth of Kikuyugrass (Pennisetum clandestinum) Under Clipping. I. Effects of Nitrogen Fertilization, Cutting Interval, and Season on Yields and Forage Characteristics¹

Abstract

Kikuyugrass (Pennisetum clandestinum Hochst. ex Chiov.) is an important pasture forage, soil cover, and weed in many parts of the subtropics. Responses to N have been reported, but the relationships among management, climate, and forage production have not been well defined. We therefore studied the regrowth of kikuyugrass under 3 N levels (22, 56, and 168 kg/ha per year), and 3 cutting intervals (2, 5, and 10 weeks) for 3 years at 2 locations (Kula and Makawao, Maui). The Kula site was at 945‐m elevation on an Eutrandept, and the Makawao site was at 660‐m elevation on a Tropohumult. Average yields ranged from 4.8 to 29.4 metric tons/ha per year at Kula and from 10.2 to 32.5 metric tons/ha per year at Makawao. Average percent N in the forage was little affected by N rate except for an increase at the highest N rate at Makawao. Cutting at 2‐week intervals reduced yields per unit time to 20 to 50% of the 10‐week yields at Kula and to less than 15% of the 10‐week yields at Makawao. Over a 3‐year period, yields of 5‐week regrowth (per unit time) were 32% of the 10‐week yields at Kula but 65% of 10‐week yields at Makawao. Crude protein levels in the forage under frequent cutting averaged 1.5 to 2.0 times that in 10‐week regrowth. Two‐week regrowth was also higher in acid‐detergent solubles and lower in fiber and cellulose than 10‐week regrowth. Ten‐week regrowth from the high N treatment was higher in fiber and lignin than similar forage from the low or moderate N levels, indicating the need for careful management of N‐fertilized kikuyugrass. Dry matter yields of 5‐week regrowth fluctuated more with season than 10‐week regrowth yields, ranging from 1.4 to over 100 kg/ha per day. Five‐week regrowth yields were reduced by 11 kg/ha per day for each degree of decrease in average minimum soil temperature below 18 C (r2 = .93). Above 18 C, yields increased about 16 kg/ha per day for each 100 ly/day increase in average solar radiation (r2 = .64). Percent crude protein in the forage was inversely related to air or soil temperature and day length (multiple R2 =.57). Residual effects of N fertilization were greater on the Tropohumult than on the Eutrandept. After 3 years of clipping, cations were severely depleted from the upper horizons of both soils.

Effects of Light Intensity on Growth of Some Tropical Forage Species. I. Interaction of Light Intensity and Nitrogen Fertilization on Six Forage Grasses1

“…Napiergrass was very high yielding, except under the 27% daylight treatment; signalgrass yields were moderately high and were not significantly affected by shading; and kikuyugrass yielded poorly at all light intensities and under both N levels. In general, yield levels in full daylight were similar to those reported elsewhere for tropical grasses (Tamimi et al, 1968;Campbell et al, 1970;Grof and Harding, 1970;Whitney, 1970Whitney, , 1974Olsen, 1972;Ng and Wong, 1976).…”

Seasonal variation in the potential herbage production and response to nitrogen by kikuyu grass (Pennisetum clandestinum)

“…This compares with a single measurement over 5 weeks of 245 kg/ha/day at Kaitaia, New Zealand, for a local kikuyu grass ecotype under irrigation (Taylor, Rowley & Hunt, 1976). These growth rates are greater than those recorded for other perennial tropical grasses grown under similar climatic conditions (Cooper, 1970) and also higher than the maxima recorded for kikuyu grass in Hawaii (Whitney, 1974) and at R. L. COLMAN AND G. H. O'NEDLL Taree, N.S.W. (Kemp, 1974(Kemp, ,1976 under apparently similar climatic conditions.…”

“…The data in this study suggest that kikuyu grass ceases growth at mean screen temperatures of 10-11 C C. When allowance is made for the gradient between screen and sward temperature, these values are similar to the critical mean daily temperature of 8 °C recorded for kikuyu grass under controlled environment (Ivory, 1976). The low (Kemp, 1976) Makawao, Hawaii (20° N) (Whitney, 1974) Kula, Hawaii (Whitney, 1974) Molo, Kenya (0°) (Morrison, 1966) Palmerston North, New Zealand (40° S) (Forde et al 1976 Potential herbage production by kikuyu grass • o: critical temperature for growth and the high growth rate at relatively low mean temperatures is clearly related to the cool tropical climate at the centre of origin of the grass in the Kenya highlands at altitudes of 1800-3000 m and supports the suggestion of Mears (1970) that kikuyu grass may not be adapted to high temperatures and hence is climatically unsuitable in the humid tropics. It also explains the excellent adaptability of the species to sub-tropical and humid temperate regions.…”

“…the seasonal variation in response to nitrogen and Seasonal variation in response by kikuyu grass to establish relationships between growth and to nitrogen fertilizer has been measured in Hawaii mean climatic variables. (Whitney, 1974) and Australia (Kemp, 1975). However, in these studies both nitrogen fertilizer MATERIALS AND METHODS and cutting treatments were repeated on the same • Present address: Biometrioal Branch, New South The experiment was conducted at the Agricul-Wales Department of Agriculture, Union Carbide House tural Research Centre, Wollongbar, New South Liverpool Street, Sydney 2000.…”

Effluent Irrigation of Para Grass: Water, Nitrogen, and Biomass Budgets1

“…There was little seasonality of para grass growth at Mililani, probably because the annual soil temperature varied only 3OC (22-25OC). In Hawaii, para grass grows at elevations from sea level to 600 m; however, high yields could not be expected at elevations above 300 m because of cold soil (Mislevy and Everett, 1981;Whitney, 1974;Whitney and Green, 1969).…”