保护性耕作下蚕豆田土壤呼吸及碳平衡特性

土壤呼吸是碳循环的重要环节,为探讨垄作和覆盖对旱三熟蚕豆田土壤呼吸的影响,测定了平作(T)、垄作(R)、平作+半量覆盖(TS₁)、垄作+半量覆盖(RS₁)、平作+全量覆盖(TS₂)、垄作+全量覆盖(RS₂)6种处理下的西南紫色土丘陵区蚕豆/玉米/甘薯旱三熟体系中蚕豆生长季节的土壤呼吸变化,分析了蚕豆田碳平衡特性。结果表明,蚕豆生长季节农田土壤呼吸随作物生长一致,呈先增加后减弱的变化趋势,变化范围为0.885~10.213 μmol/(m²·s)。全生育期平均土壤呼吸速率差异显著,表现为TS₂>RS₂>RS₁ >TS₁>T>R;分别为4.096,3.780,3.441,3.104,2.850,2.439 μmol/(m²·s),较平作不覆盖处理增加了43.7%,32.6%,20.7%,8.9%,-14.4%。垄作显著降低了蚕豆农田土壤呼吸速率,而秸秆覆盖显著提高土壤呼吸速率,且随着覆盖量的增加而增加。不同生育阶段土壤呼吸总量存在差异,表现为成熟期<苗期<鼓粒期<分枝现蕾期<开花结荚期,其中开花结荚期约占50%;利用根排除法测得蚕豆田根系呼吸占土壤呼吸比例变幅为19.49%~54.23%,利用回归分析法测得结果为37.02%~60.64%,二者均值分别为38.62%和49.12%。不同耕作和覆盖处理下蚕豆田整个生长季均表现为碳汇,净碳汇为857.26~2236.25 kg/hm²。与平作不覆盖相比, RS₂、TS₂、RS₁、TS₁、R分别较平作不覆盖处理T高出160.86%,101.44%,30.78%,47.63%,110.41%,差异达显著水平。试验结果表明垄作和秸秆覆盖有利于蚕豆田生态系统的碳汇,以垄作+全量覆盖的效果最好。

Soil respiration and carbon balance in fava bean farmland under conservation tillage

Soil respiration is an important process in carbon cycling.This study investigated effects of two till-age practices (ridge tillage and traditional tillage)and straw mulching at 0,3750,or 7500 kg straw dry matter/ha on soil respiration of fava bean farmland.Six treatments applied were:traditional tillage without straw mulching (T),ridge tillage without straw mulching (R),traditional tillage+straw mulching at 3750 kg/ha (TS1 ),ridge tillage+straw mulching at 3750 kg/ha (RS1 ),traditional tillage+straw mulching at 7500 kg/ha (TS2 ),and ridge tillage+straw mulching at 7500 kg/ha (RS2 ).Soil respiration properties and carbon balance in dry-cropped farmland with a triple intercropping system of fava bean,maize,and sweet tomato were evalua-ted during the crop growth period,in a region of southwest China known as the purple hilly region.This study identified seasonal changes in soil respiration rate reflecting crop growth,with a peak in the middle of the fava bean growth cycle,and with a range from 0.885 -10.213 μmol/(m2 ·s)in cropped soils,respectively.The soil respiration rates of the different treatments ranked TS2 >RS2 >RS1 >TS1 >T>R [4.096,3.780,3.441, 3.104,2.850,2.439 μmol/(m2 ·s),respectively].Ridge tillage reduced soil respiration in fava bean farm-land,whereas straw mulching treatment resulted in increased respiration corresponding to straw mulching lev-els.In soil planted with fava bean,the respiration rate at different crop growth stages ranked ripening