Search

ABSTRACT: This study assessed the nitrogen nutrition index, morphogenic characteristics and tiller structure of Alexandergrass (Urochloaplantaginea (LINK) Hitch) pasture submitted to different nitrogen (N) levels (zero, 150 or 300 kg ha-1 of N). The experimental design was entirely randomized with repeated measures arrangement. The experimental animals were Angus heifers under rotational stocking grazing method. The number of animals was variable to keep 30±5 cm post-grazing sward height. Nitrogen nutrition index increased linearly according N levels (Ŷ = 59.8 + 0.1216N; P < 0.0001; r²=0.53). The leaf appearance rate adjusted to a positive linear regression model according the thermal sum (TS) with zero of N (Ŷ0N = 0.0077 + 0.0000087TS; P = 0.0308; r² = 0.72) and 150 kg ha-1 of N (Ŷ150N = 0.0020 + 0.000021 TS; P = 0.0022; r² = 0.92). The use of 300 kg ha-1 of N did not alter the leaf appearance rate (0.0124 leaf degree-days-1). The use of up to 300 kg ha-1 of N increases the Alexandergrass nitrogen content. The leaf appearance rate in Alexandergrass is modified using N while the morphogenic characteristics leaf expansion, stem expansion, phyllochron, leaf lifespan, leaf elongation duration and tiller structure are not altered by N utilization.

ABSTRACT: The canopy structure and morphogenesis of ryegrass (Lolium multiflorum Lam.) was investigated after it was over seeded with Tifton 85 (Cynodon spp.) and intercropped with red clover (Trifolium pratense L.). Time intervals between cuts were determined by different thermal sums (125, 250, 375, and 500 degree-days [DD]). Cuts were conducted at a height equivalent to 50% of the average canopy height. Morphogenic and structural data were collected from July to October of 2016 and 2017, from a completely randomized block experimental design. Canopy height, extended tiller height, pseudostem length, and forage mass were fitted to linear equations according to the thermal sums. Interaction of ryegrass with red clover was the highest (12.1%) for longer cut intervals (375 and 500 DD). The leaf appearance rate (0.0080 leaf/DD), phyllochron value (128.8 DD), and senescence rate (0.10 cm/DD) of ryegrass were comparable between the different intervals. The slowest elongation rate (0.06 cm/DD) with the shortest interval duration between cuts (171.6 DD) was observed in the 125 DD interval. According to the findings from this 2-year experiment, the use of a 250 DD cut interval was recommended between grazing events, taking into account the efficiency of forage use, ryegrass leaf, stem ratio, and interactions with red clover in the canopy under rotational stocking.