Long-Term Fertilization Effect on Fertility of Salt-Affected Soils

摘要

The long-term effects of annual fertilizer applications on the fertility of salt-affected soils under the rotation system of wheat (Triticum aestivum L.) and maize (Zea mays L.) are not well documented. In 1984, research plots were established to test the effects of annual applications of different rates of nitrogen (N) and phosphorus (P) fertilizers on the fertility of a salt-affected soil (Typic Ustochrept) at the Quzhou Experimental Station, Quzhou County, Hebei Province, China. In October 2001, composite soil samples (0-20 and 20-40 cm) were collected from each plot and analyzed for soil fertility indices. Seventeen years of N and P fertilizer applications increased the soil organic matter (SOM) in the surface layer. With combined N, 270 (N_1) and 540 (N_2) kg N ha~(-1) year~(-1), and P, 67.5 (P_1) and 135 (P_2) kg P_2O_5 ha~(-1) year~(-1), fertilizer applications, total soil N mostly significantly decreased (P < 0.05). Soil total P in the 0-20 cm layer of the P_2 treatment significantly (P < 0.05) increased as compared to those of the other treatments. Rapidly available P (RP) in the 0-20 cm layer of the N_1P_2 treatment was significantly higher than those in the other treatments except the P_2 treatment; and RP in the 0-20 cm layer of the P_2 treatment significantly increased as compared to those of the other treatments except the P_1 and N_1P_2 treatments. RP in the subsurface soil layer (20-40 cm) of the P_2 treatment (4.2 mg P kg~(-1)) was significantly (P < 0.05) higher than those in the other treatments. Nevertheless, long-term N fertilization did not significantly increase the alkali-hydrolyzable N in the soil. However, in the salt-affected surface soils the application of combined N and P fertilizers over 17 years significantly (P < 0.05) decreased rapidly available potassium (K). The results suggested that while under long-term fertilizer applications some soil fertility parameters could be maintained or enhanced, careful monitoring of soil fertility was necessary as other nutrients such as K could become depleted.