施用高量有机物料对新垦耕地红壤有机碳积累及性态的影响

为了解新垦红壤培肥过程中有机物料用量对土壤有机碳积累、培肥效率及土壤性态的影响,选择一新垦耕地红壤,设置秸秆、秸秆加氮和猪粪等3种添加物各7个施用水平共19个处理,每种有机物料用量设0(对照)、25、50、100、150、200和250 g·kg-1等7个级别,进行了为期24个月的模拟培养试验,观察了有机物料分解率、土壤C/N、活性有机碳和养分的动态变化.结果表明,随有机物料用量的增加,土壤中活性有机碳、总有机碳含量均增加,C/N比下降,土壤有效磷、速效钾和水溶性盐分含量增加,有机物料在土壤中的分解率也随之增加.猪粪碳的矿化速率低于水稻秸秆,加氮可增加秸秆的腐殖化系数.研究发现,有机物料添加越多,培肥效率(腐殖化系数)越低.同时,高量施用猪粪容易引起土壤盐害.猪粪用量为50g·kg-1(相当于7.5t·亩-1)时土壤盐分含量超过了 2g·kg-1;高量施用水稻秸秆可引起土壤有效氮的下降,秸秆用量超过100 g·kg-1(相当于15 t·亩-1)时土壤碱解氮明显下降;秸秆加氮处理会引起土壤酸化.结果显示,为减免有机物质的过度分解,有机物料的施用量控制在50g·kg-1以下为宜.

Effects of applying high amount of organic materials on the accumulation and properties of organic carbon in newly cultivated red soil

To understand the effect of the applied amount of organic materials on the accumulation of soil organic carbon, humification coefficient and soil properties, a newly cultivated red soil was collected for treating with straw, straw plus nitrogen and pig manure, and incubated for 24 months. The applied amount for organic materials was 0 (control), 25, 50, 100, 150, 200 and 250 g·kg^-1, respectively. The dynamic changes in decomposition rate of the added organic materials, soil C/N, active organic carbon and nutrients were monitored in the simulated culture experiment. The results showed that, with increasing applied rate of the organic materials, the content of soil active organic carbon and total organic carbon increased, the C/N ratio decreased, the available P, available K and water-soluble salt increased, while the decomposition rate of the organic materials in the soil increased. The mineralization rate of organic carbon in pig manure was lower than that of rice straw, and could increase the humification coefficient of straw by adding nitrogen. It was found that the more organic materials were added, the lower the fertilization efficiency (humification coefficient). At the same time, high-level application of pig manure was easy to cause soil salt damage. When the amount of pig manure was 50 g·kg^-1(equivalent to 7.5 t·mu^-1), the soil salt content was more than 2 g·kg^-1. High-level application of rice straw could cause a decrease of soil available nitrogen. When the amount of straw was more than 100 g·kg^-1 (equivalent to 15 t·mu^-1), it obviously decreased the soil alkali-hydrolyzed nitrogen. Straw plus nitrogen treatment could cause soil acidification. It is better to control organic matter below 50 g·kg^-1 to reduce organic matter decomposition.