灌溉方法对保护地土壤有机氮矿化特性的影响

EFFECT OF IRRIGATION METHODS ON MINERALIZATION OF SOIL ORGANIC NITROGEN IN PROTECTED FIELD

采用Stanford和Smith提出的长期间歇淋洗通气培养法,对连续7a采用渗灌、滴灌和沟灌灌溉,栽培番茄的保护地不同剖面层次土壤的有机氮矿化特点进行了研究。渗灌管为发汗式半软管,埋深为30cm;渗灌、滴灌和沟灌灌水方法及施肥、田间管理同当地农业生产。当20cm深处的土壤水吸力达到40kPa时开始灌水,渗灌和滴灌每次的灌水量是沟灌灌水量的1/2。试验结果表明,土壤矿化氮含量随着土层深度的增加而降低。从累积矿化氮量—时间曲线变化的趋势看,可将保护地土壤0～50cm剖面分为三个层次,其中渗灌与滴灌处理相似,为0～20cm、20～40cm和40～50cm土层,而沟灌处理则为0～30cm、30～40cm和40～50cm土层。保护地不同层次土壤有机氮的矿化可以用Twopool模型表达。比较不同灌溉处理,在0～10cm土层,易矿化有机氮含量(N1)表现为滴灌>沟灌>渗灌,易矿化有机氮矿化速率(k1)常数也以滴灌处理最大,说明滴灌更有利于表层土壤易矿化有机氮的形成。与渗灌和沟灌相比,长期使用滴灌灌溉有利于改善保护地土壤有机氮的品质。

Characteristics of nitrogen mineralization in different soil layers were studied in a seven-year-old protected tomato field irrigated in three ways, infiltration irrigation, drip irrigation and furrow irrigation, using the long-term intermittent leaching aerobic incubation method （Stanford and Smith）. In infiltration irrigation, transpiration semi-soft pipes were laid down 30 cm down in the soil. The experiment was managed in the same way as in the local farming production in irrigation, fertilization and field management. When the water suction in the soil reached 40 kPa at 20 cm in depth, irrigation began. The irrigation rate of infiltration irrigation and drip irrigation was half the rate of furrow irrigation in each event. Results show that mineralized N decreased with soil depth in content. Based on the correlation curve of cumulative amount of mineralized N and incubation time, the soil within the depth of 0 - 50 cm could be divided into three layers, i.e. 0 - 20, 20 - 40 and 40 - 50 em in both infiltration irrigation and drip irrigation, and 0 - 30, 30 - 40 and 40 - 50 cm in furrow irrigation. A two-pool model was used to fit N mineralization in different layers. Comparison between irrigation methods showed that in the 0 - 10 cm soil layer, the eontent of mineralizable N （Nt ） followed the order of drip irrigation 〉 furrow irrigation 〉 infiltration irrigation, and that drip irrigation was the highest in mineralization rate （ k1 ） of mineralizable organic N, suggesting that drip irrigation facilitates formation of mineralizable organic N in the surface layer of the soil. Compared with infiltration irrigation and furrow irrigation, long-term drip irrigation is more conducive to improving quality of soil organic nitrogen in protected fields.