美国北部玉米带玉米轮作的氮素利用与碳固存
Nitrogen use and carbon sequestered by corn rotations in the northern corn belt, U.S.
作者信息
Pikul J L, Schumacher T E, Vigil M
机构信息
USDA-ARS, Northern Grain Insects Research Laboratory, Brookings, SD 57006, USA.
出版信息
ScientificWorldJournal. 2001 Sep 27;1 Suppl 2:707-13. doi: 10.1100/tsw.2001.90.
Diversified crop rotation may improve production efficiency, reduce fertilizer nitrogen (N) requirements for corn (Zea mays L.), and increase soil carbon (C) storage. Objectives were to determine effect of rotation and fertilizer N on soil C sequestration and N use. An experiment was started in 1990 on a Barnes clay loam (U.S. soil taxonomy: fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, SD. Tillage systems for corn-soybean ( Glycine max [L.] Merr.) rotations were conventional tillage (CS) and ridge tillage (CSr). Rotations under conventional tillage were continuous corn (CC), and a 4-year rotation of corn-soybean-wheat ( Triticum aestivum L.) companion-seeded with alfalfa ( Medicago sativa L.)-alfalfa hay (CSWA). Additional treatments included plots of perennial warm season, cool season, and mixtures of warm and cool season grasses. N treatments for corn were corn fertilized for a grain yield of 8.5 Mg ha(-1) (highN), of 5.3 Mg ha(-1) (midN), and with no N fertilizer (noN). Total (1990-2000) corn grain yield was not different among rotations at 80.8 Mg ha(-1) under highN. Corn yield differences among rotations increased with decreased fertilizer N. Total (1990-2000) corn yields with noN fertilizer were 69 Mg ha-1 under CSWA, 53 Mg ha(-1) under CS, and 35 Mg ha(-1) under CC. Total N attributed to rotations (noN treatments) was 0.68 Mg ha(-1) under CSWA, 0.61 Mg ha(-1) under CS, and 0.28 Mg ha(-1) under CC. Plant carbon return depended on rotation and N. In the past 10 years, total C returned from above- ground biomass was 29.8 Mg ha(-1) under CC with highN, and 12.8 Mg ha(-1) under CSWA with noN. Soil C in the top 15 cm significantly increased (0.7 g kg(-1)) with perennial grass cover, remained unchanged under CSr, and decreased (1.7 g kg(-1)) under CC, CS, and CSWA. C to N ratio significantly narrowed (-0.75) with CSWA and widened (0.72) under grass. Diversified rotations have potential to increase N use efficiency and reduce fertilizer N input for corn. However, within a corn production system using conventional tillage and producing (averaged across rotation and N treatment) about 6.2-Mg ha(-1) corn grain per year, we found no gain in soil C after 10 years regardless of rotation.
多样化的作物轮作可以提高生产效率，降低玉米（Zea mays L.）对氮肥的需求，并增加土壤碳（C）储量。本研究的目的是确定轮作和氮肥对土壤碳固存和氮素利用的影响。1990年在南达科他州布鲁金斯附近的巴恩斯粘壤土（美国土壤分类：细壤质、混合型、超活性、寒冷钙质湿润淋溶土）上开展了一项试验。玉米-大豆（Glycine max [L.] Merr.）轮作的耕作系统为传统耕作（CS）和垄作（CSr）。传统耕作下的轮作为连作玉米（CC），以及玉米-大豆-小麦（Triticum aestivum L.）与苜蓿（Medicago sativa L.）伴播-苜蓿干草的4年轮作（CSWA）。其他处理包括多年生暖季草、冷季草以及暖季草和冷季草混合草的地块。玉米的氮肥处理为施氮肥使籽粒产量达到8.5 Mg ha⁻¹（高氮）、5.3 Mg ha⁻¹（中氮）和不施氮肥（无氮）。在高氮条件下，各轮作方式下玉米的总籽粒产量（1990 - 2000年）均为80.8 Mg ha⁻¹，无显著差异。随着氮肥施用量的减少，各轮作方式下玉米产量的差异增大。在无氮处理下，1990 - 2000年玉米的总产量在CSWA轮作方式下为69 Mg ha⁻¹，在CS轮作方式下为53 Mg ha⁻¹，在CC轮作方式下为35 Mg ha⁻¹。轮作（无氮处理）的总氮量在CSWA轮作方式下为0.68 Mg ha⁻¹，在CS轮作方式下为0.61 Mg ha⁻¹，在CC轮作方式下为0.28 Mg ha⁻¹。植物碳归还量取决于轮作方式和氮肥。在过去10年中，高氮条件下CC轮作方式下地上生物量的总碳归还量为29.8 Mg ha⁻¹，无氮条件下CSWA轮作方式下为12.8 Mg ha⁻¹。表层15 cm土壤中的碳含量在种植多年生草时显著增加（0.7 g kg⁻¹），在CSr耕作方式下保持不变，在CC、CS和CSWA轮作方式下减少（1.7 g kg⁻¹）。碳氮比在CSWA轮作方式下显著变窄（-0.75），在种草条件下变宽（0.72）。多样化轮作有提高氮素利用效率和减少玉米氮肥投入的潜力。然而，在一个采用传统耕作且年平均玉米籽粒产量约为6.2 Mg ha⁻¹（综合轮作和氮肥处理）的玉米生产系统中，我们发现无论采用何种轮作方式，10年后土壤碳含量均无增加。
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