Effect of Free Air Carbon dioxide Enrichment (FACE) on the chemical composition and nutritive value of wheat grain and straw

详细信息    查看全文

• 作者：F. Porteaus ; J. Hill ; A.S. Ball ; P.J. Pinter ; B.A. Kimball ; G.W. Wall ; F.J. Adamsen ; D.J. Hunsaker ; R.L. LaMorte ; S.W. Leavitt ; T.L. Thompson ; A.D. Matthias ; T.J. Brooks ; C.F. Morris
• 关键词：FACE ; Elevated CO₂ ; Wheat ; Grain ; Straw ; Nutritive value ; Nitrogen
• 刊名：Animal Feed Science and Technology
• 出版年：2009
• 出版时间：16 March 2009
• 年：2009
• 卷：149
• 期：3-4
• 页码：322-332
• 全文大小：214 K

文摘

The global impact of an increased concentration of CO₂ in the atmosphere on plants has been studied extensively, but little information has been published on the effect of enrichment of atmospheric CO₂ on the nutritive value of grain and straw used as ruminant feeds. This paper reports the chemical composition and nutritive value of grain and straw harvested from the drought tolerant hard red spring wheat (Triticum aestivum L.) variety Yecora Rojo managed with two carbon dioxide regimes (ambient, 350 μl/l and elevated, 550 μl/l), two rates of nitrogen application (low N: 53 kg N/ha and high N: 393 kg N/ha) grown under a water-fed (i.e., no deficit) regime. Accumulation of carbon in straw did not differ among crops grown under elevated CO₂ and low N supplementation and crops grown under ambient CO₂ with low levels of N supplementation. Increased N application increased sequestration of C (P<0.05) compared to straw from crops grown under ambient CO₂ concentration. Low levels of N application and elevated CO₂ led to straw containing similar concentrations of N to those grown under ambient CO₂ conditions. Increasing N application to crops grown under ambient concentrations of CO₂ elevated the concentration of N (P<0.01) whereas crops at elevated concentrations of CO₂ did not accumulate N to the same extent. Differences in the non-structural carbohydrate and cell wall content reflected the patterns for total C. No effect of increasing the concentration of CO₂ on WSC, aNDF_om, ADF_om, hemicellulose, cellulose and lignin (sa) occurred. There was a small decline (−26 g/kg; P<0.05) in the concentration of aNDF_om in straw from crops that had received high N input. The ratio of lignin to total N was higher in straw harvested from plots with elevated CO₂ (33.5:1) compared with ambient CO₂ (24.6:1). No changes in the total C content occurred for grain samples in response to CO₂ concentration or supplemental N fertiliser. No interaction between supply of N and CO₂ concentration occurred. Changes in the total N content of grain in response to treatments were similar to the changes observed in the straw fraction. The increases in concentration of N incorporated into grain were higher from crops grown under enriched concentrations of CO₂ (i.e., +8.6 g/kg; P<0.01) than for crops grown under ambient supply of CO₂ (+3.5 g/kg; P<0.05). Differences in concentration of starch in the grain with increasing supply of N from fertiliser occurred under FACE conditions (P<0.05), but not for grain harvested from those grown under ambient CO₂ levels. No effect of changing concentrations of CO₂ were observed for ADF_om, lignin (sa), cellulose and neutral detergent cellulose digestibility but concentrations of aNDF_om (P<0.05) and hemicellulose (P<0.05) were higher in grain grown under ambient concentrations of CO₂ irrespective of supply of N to the crop. Although effects of elevated concentrations of CO₂ on grain and straw quality were expected, this poses concerns for livestock production in systems that use lower levels of agronomic inputs. Elevated concentrations of CO₂ in the ambient environment were beneficial for development of above ground biomass and grain yield as measured by thousand-grain weight. However, straw and grain quality, in terms of crude protein and the crude protein to energy ratio will be affected by increasing concentrations of CO₂ in the atmosphere, and this may lead to a reduction in the total supply of crude protein in crops used by livestock.