Seasonal changes in soil labile organic carbon pools within a Phyllostachys praecox stand under high rate fertilization and winter mulch in subtropical China

Phyllostachys praecox is a favorite bamboo shoot species that has been widely planted in southern China. High rate of fertilization and heavy winter mulch have been a common practice to gain a good yield and better economic benefit. To get an insight into the effects of fertilization and winter mulch on soil labile organic carbon pools, a trial of different types and rates of fertilizers was conducted from May 2002 to April 2003. Soils in the mixed treatments with both mineral and organic fertilizers (treatments: 1–3) were generally more abundant in soil microbial biomass carbon (MBC) ( P < 0.05) as compared with treatments of single mineral fertilizer (treatments: 4–6), with MBC for treatments 1 and 2 generally at maximal level and for treatments 4 and 5 at minimal level. The abundance of soil MBC increased with the rate of organic fertilizers applied. Soil MBC content was measured periodically during the year, with the highest in October and December 2002, moderate in August 2002 and February 2003, and the lowest in April 2003. Soil water-soluble organic carbon (WSOC) of all treatments was higher in the August and October, decreased in the December and February, and increased again in the April. It was found that the treatments with mixed mineral and organic fertilizers had much higher WSOC ( P < 0.05), compared with the pure mineral fertilizer treatments. Soil WSOC increased with the amount of organic fertilizer applied. Winter mulch enhanced soil MBC and WSOC, and the ratios of MBC in the mulch treatments to non-mulched treatments were on average 1.60 and 1.52 in February and April 2003, respectively, while the corresponding ratios of WSOC were on average 1.39 and 1.73 in the February and April, respectively. The high rate of single mineral fertilizer application was not recommended in bamboo management. Both mineral and organic fertilizers would need to be applied for sustaining soil fertility and long-term bamboo production in subtropical China.