长期施肥对土壤碳储量和作物固定碳的影响

利用长期定位试验研究有机肥、化肥以及有机肥和化肥混合施用对耕层土壤有机C储量变化和作物固定C的影响。处理包括化学肥料NPK不同组合。NPK、NP、NK、PK、全部施用有机肥(OM)、化学肥料氮和有机肥氮对半施用(1/20M)及不施肥(CK)七个处理。均衡施用N、P和K,显著提高土壤有机C储量,而养分缺乏的施肥,土壤有机碳大量损失。抵消N2O排放后,只有外源有机碳输入的OM和1/2OM具有净的碳固定。土壤有机碳储量变化(Y)与土壤有机碳输入量(X)符合线性方程Y=1.3231X-1942.7(r=0.9840, n=7)。作物固定碳量和可以返还到土壤的根茬和秸秆中有机碳量都以NPK、NP和1/2ON施肥处理最多。若固定于根茬和秸秆的碳返还到原施肥土壤,则这些处理的土壤有机碳储量最多。但从经济效益考虑,最佳的施肥方式为有机和化学肥料配合施用。

CARBON CONTENTS IN SOILS AND CROPS AS AFFECTED BY LONG-TERM FERTILIZATION

A long-term stationary field experiment was carried out to study the effect of application of organic manure, chemical fertilizers or their mixture on soil carbon storage and carbon fixation by plants. The experiment was designed to have 7 treatments: organic manure (OM) , half organic manure plus half fertilizer N (1/2OM), fertilizer NPK (NPK), fertilizer NP ( NP) , fertilizer NK (NK) , fertilizer PK ( PK) and control ( CK) . The treatments, supplied with balanced nutrients of N, P and K, showed a marked increase in the storage of soil organic carbon, while those deficient in nutrient supply a significant decrease. Only in Treatments OM and 1/2OM, where additional organic carbon was supplied, a net increase in organic carbon in the soil was observed. The relationship between the storage of organic carbon ( Y) and the input of organic carbon( X) can be well described by the following linear equation: Y= 1.3231 X - 1942.7 (r =0.9840, n =7) . Treatments NPK, NP and 1/20M were the highest in both crop carbon fixation and organic carbon contents in crop straws and stubbles that can be returned to the soil. So, if the fixed carbon in the straws and stubbles return to the soil, Treatments NPK, NP and 1/20M would have the biggest storage of organic carbon in the experiment. However, the combined application of chemical fertilizer and organic manure is the optimal for agricultural field based on economic consideration.