USDA-ARS National Soil Dynamics Lab., Auburn, AL 36832, USA.
J Environ Qual. 2010 Feb 19;39(2):596-608. doi: 10.2134/jeq2009.0181. Print 2010 Mar-Apr.
Increasing atmospheric CO(2) concentration has led to concerns about potential effects on production agriculture. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional tillage and no-tillage) to elevated CO(2). The study used a split-plot design replicated three times with two management systems as main plots and two atmospheric CO(2) levels (ambient and twice ambient) as split plots using open-top chambers on a Decatur silt loam soil (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation with winter fallow and spring tillage practices. In the no-tillage system, sorghum and soybean were rotated, and three cover crops were used [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)]. Over multiple growing seasons, the effect of management and CO(2) concentration on leaf-level gas exchange during row crop (soybean in 1999, 2001, and 2003; sorghum in 2000, 2002, and 2004) reproductive growth were evaluated. Treatment effects were fairly consistent across years. In general, higher photosynthetic rates were observed under CO(2) enrichment (more so with soybean) regardless of residue management practice. Elevated CO(2) led to decreases in stomatal conductance and transpiration, which resulted in increased water use efficiency. The effects of management system on gas exchange measurements were infrequently significant, as were interactions of CO(2) and management. These results suggest that better soil moisture conservation and high rates of photosynthesis can occur in both tillage systems in CO(2)-enriched environments during reproductive growth.
大气中二氧化碳浓度的增加引起了人们对其可能对农业生产产生影响的担忧。1997 年秋季，开展了一项研究，以比较两种作物管理系统（常规耕作和免耕）对高浓度二氧化碳的反应。该研究采用裂区设计，三次重复，两个管理系统为主区，两个大气二氧化碳水平（环境和环境的两倍）为裂区，在德卡特伊利诺伊州粉质壤土（粘质、高龄土、热罗迪克古土壤）上使用开顶式气室。常规系统是高粱[高粱（L.）莫恩]和大豆[大豆（L.）梅勒]轮作，冬季休耕，春季耕作。在免耕系统中，高粱和大豆轮作，使用三种覆盖作物[红三叶草（L.）、黄麻（L.）和小麦（T. aestivum L.）]。在多个生长季节，管理和二氧化碳浓度对作物（1999 年、2001 年和 2003 年为大豆；2000 年、2002 年和 2004 年为高粱）生殖生长期间叶片水平气体交换的影响进行了评估。处理效应在各年较为一致。一般来说，无论残茬管理实践如何，在 CO2 富集条件下观察到更高的光合速率（大豆更为明显）。高浓度 CO2 导致气孔导度和蒸腾作用降低，从而导致水分利用效率提高。管理系统对气体交换测量的影响并不经常显著，CO2 和管理的相互作用也是如此。这些结果表明，在 CO2 富集环境下的生殖生长期间，两种耕作系统都可以更好地保持土壤水分和保持高光合作用率。
