CO₂ fertilization does not affect biomass production and nutritive value of a C₄ tropical grass in short timeframe

Abstract

Increased atmospheric carbon dioxide (CO 2 ) is a consequence of recent anthropogenic environmental changes, and few studies have evaluated its effects on tropical grasses used in Brazilian pastures, the main feed source for major part of ruminant livestock.This study evaluated forage production, chemical composition, in vitro total gas production and organic matter degradability of Brachiaria brizantha under contrasting CO 2 atmospheric conditions in a free air carbon dioxide enrichment (FACE) facility.The forage plants were sown in each of the 12 octagonal rings of the FACE facility: six under ambient atmospheric CO 2 concentration of approximately 390 μmol/mol, hereafter referred to as control (CON) plots, and other six rings enriched with pure CO 2 flux to achieve a target CO 2 concentration of 550 μmol/mol, hereafter called elevated CO 2 (eCO 2 ) plots. Soil samples were collected to determine carbon and nitrogen concentrations. After seventy days of sowing, a standardization cutting was performed and then at regular intervals of 21 days the forage was harvested (ten harvest dates) and forwarded to laboratorial analyses. Forage above-ground biomass production (dry matter (DM): 6,143 vs. 6,554 kg/ha), as well as morphological characteristics (leaves: 71% vs. 68%; stem: 28% vs. 31%), chemical composition (crude protein: 162.9 vs. 161.8; neutral detergent fibre: 663.8 vs. 664.3; acid detergent fibre: 369.5 vs. 381; lignin: 60.1 vs. 64.1 g/kg DM; total C: 45.9 vs. 45.9; total N: 2.8 vs. 2.8; total S: 0.2% vs. 0.2%), organic matter in vitro degradability (573.5 vs. 585.3 g/kg), methane (5.7 vs. 4.3 ml/g DM) and total gas (128.3 vs. 94.5 ml/g DM) production did not differ significantly between CON and eCO 2 treatments (p > .05). The results indicated that at least under short-term enrichment, B. brizantha was not affected by eCO 2 .

Pigeon Pea Intercropped with Tropical Pasture as a Mitigation Strategy for Enteric Methane Emissions of Nellore Steers

“…In forage diets, the NDF content is one of the determinants of forage intake [ 43 ], and the DEG and REC treatments showed NDF and ADF values in line with those reported for Urochloa spp. under tropical conditions [ 39 , 44 , 45 ]. For the MIX treatment, NDF content was lower than those found for pastures intercropped with pigeon pea [ 41 ].…”

Climate change and land-use change impacts on future availability of forage grass species for Ethiopian dairy systems

“…It would also need to take account of the predicted loss of digestibility of many forage species under future climate stress conditions [84][85][86] , as shown in other crops 87,88 . Such conditions may prevail even in areas considered 'suitable' in our analysis, although timeframe will need careful consideration also 89 . There is currently significant pressure to increase the proportion of more productive exotic breeds (Fig.…”