Effects of long-term fertilization on corn productivity and its sustainability in an Ultisol of southern China

Appropriate fertilization practices play a critical role in enhancing crop yields, as well as in achieving sustainable increases in crop production through improving soil quality. In the present study, we examined the effects of long-term fertilization (started in 1986) on crop yield and its sustainability under a double corn (Zea mays L.) cropping system in an Ultisol of southern China. Results showed that although corn yields were higher in the fertilized treatments compared to the unfertilized control, inorganic fertilizer application alone (N and NPK) resulted in declining trends in both corn yields and fertilization effects (defined as the yield difference between the fertilized treatment and the control), especially in the N treatment. In contrast, significant increasing trends in both corn yields and fertilization effects were observed in the manure-applied treatments. Manure amendments significantly increased the contents of soil organic carbon and total N and the availability of soil P and K, while long-term inorganic fertilization alone accelerated soil acidification, especially in the N treatment. In addition, there was no significant correlation between the yield trend and climatic factors (weather trends) over the period of study. Thus, it is likely that the long-term sustainability of corn production under manure application is attributed mainly to the improved soil quality. Our results also suggest that manure amendments, particularly in combination with inorganic NPK, should be the recommended fertilization practice to enhance corn yields and improve soil quality in the Ultisol.