SYNERGISTIC EFFECT OF FERTILIZATION ON INTERANNUAL VARIATION OF SOIL CARBON AND NITROGEN CONTENTS AND SOYBEAN YIELD IN SEMIARID SOIL.

The effects of long-term fertilization on soil organic carbon (SOC), total nitrogen (TN), and soybean yield stability were studied in semiarid areas of China for optimizing soil fertilization and obtaining stable and efficient soybean yield. SOC, TN, and soybean yields in different soil layers were measured after performing nine fertilization treatments for 5 consecutive years. The results showed that CK treatment (1,264.2 kg·hm^-2) was significantly lower than other treatments. Under the combination of organic and inorganic treatments, the interannual variation of soybean yield under treatment with organic fertilizer combined with nitrogen and phosphate fertilizer was smaller, while the stability and sustainability indices were higher. The organic carbon and TN contents in surface soil (0-20 cm) showed an increasing trend with different fertilization. There was a significant positive linear correlation between SOC and TN contents in topsoil (0-20 cm) (P < 0.01; correlation coefficient = 0.947**). The yield of soybean increased with the increase of SOC and TN contents in topsoil (0-20 cm), with a significant positive correlation between them (P < 0.05). The yield of soybean increased with the increase of SOC and TN contents in surface soil (20-40 cm), although no significant positive correlation between SOC and TN contents was observed. [ABSTRACT FROM AUTHOR]