通过调节土壤氮素转化提高有机物料对红壤酸度的改良效果

通过培养试验，比较研究了油菜秸秆、稻草、香樟叶和豌豆秸秆单独施用以及油菜秸秆、稻草和香樟叶与豌豆秸秆混合施用对红壤酸度的改良效果。结果表明，在60天培养期内，添加4种物料均提高了土壤pH。培养试验结束时香樟叶、油菜秸秆、豌豆秸秆和稻草分别使土壤pH相对对照增加0.53、0.42、0.30和0.26。对于灰化碱含量很高的非豆科物料如香樟，其对土壤酸度的改良效果主要来源于物料所含碱性物质和物料对土壤硝化反应的抑制，但对灰化碱含量较低的非豆科物料如油菜秸秆和稻草，其改良效果主要来源于后者。豆科类豌豆秸秆主要通过所含碱性物质和有机氮矿化提高土壤pH，但培养试验后期铵态氮硝化反应释放的质子抵消了其部分改良效果。将油菜秸秆、稻草和香樟叶与豌豆秸秆配合施用，使硝化反应受到一定程度的抑制，提高了物料对土壤酸度的改良效果。培养试验结束时，香樟叶、稻草和油菜秸秆与豌豆秸秆配合施用比豌豆秸秆单独施用土壤pH分别高0.25、0.18和0.12。研究发现，香樟叶灰化碱含量很高，无论单独施用，还是与豌豆秸秆配合施用均有很好的改良效果，因此在南方地区推广种植香樟可以通过其凋落物修复酸化的森林土壤。

Increase in ameliorating effects of crop residues on an acidic red soil through adjustment of nitrogen transformation

The amelioration effects of black locust leaves, straws of canola, rice and pea on acidity of a red soil from Anhui Province were investigated with incubation experiments. The results showed that the addition of the plant materials increased soil pH to some extent compared with control during 60-day incubation. At the end of incubation, soil pH increased by 0.53, 0.42, 0.30 and 0.26 units as a result of the incorporation of black locust leaves, and straws of canola, pea and rice. The increased extent of soil pH was consistent with the amount of ash alkalinity in the plant materials. The black locust leaves increased soil pH to greatest extent among these organic materials due to the greater ash alkalinity of the plant materials and nitrification inhibiting. Straws of rice and canola increased soil pH mainly through nitrification inhibiting in the soil. Pea straw increased soil pH through ash alkalinity and mineralization of organic N in the plant material. While in the later stage of incubation, the nitrification of NH4+-N from the mineralization of organic N released H+ and decreased soil pH, which reduced the final amelioration of the material on soil acidity. The incorporation of black locust leaves and straws of rice and canola together with pea straw, the amelioration effect of plant materials on the acid soil increased due to the inhibiting of nitrification. Soil pH increased respectively by 0.25, 0.18 and 0.12 units as a result of incorporation of black locust leaves and straws of rice and canola together with pea straw compared with single incorporation of pea straw. We found that incorporation of black locust leaves singly or together with pea straw had greater amelioration effect on acid soils. Thus bio-remediation method can be developed with black locust to ameliorate acidic forest soils in south of China.