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Growth of Kikuyugrass ( Pennisetum clandestinum ) Under Clipping. I. Effects of Nitrogen Fertilization, Cutting Interval, and Season on Yields and Forage Characteristics 1
Author(s) -
Whitney A. S.
Publication year - 1974
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1974.00021962006600020029x
Subject(s) - forage , zoology , agronomy , grazing , human fertilization , pasture , nitrogen , biology , mathematics , chemistry , organic chemistry
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 (r 2 = .93). Above 18 C, yields increased about 16 kg/ha per day for each 100 ly/day increase in average solar radiation (r 2 = .64). Percent crude protein in the forage was inversely related to air or soil temperature and day length (multiple R 2 =.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.