Effects of long-term fertilization on weed community characteristics andcarbon, nitrogen and phosphorus stoichiometry during winter-springseason in yellow-clay paddy fields of South China

As an important agronomic measure, fertilization affects not only crop growth, but also field weeds and community composition. However, the effects of different fertilization on weed community characteristics are still not fully understood. To that end, a long-term experiment was set up in 1983 at Fujian Experimental Observatory Station, a station for the monitoring (via experi-mental plots) of long-term farmland conservation practices. The station belongs to the Ministry of Agriculture and is located at 119°04'10" E and 26°13'31" N. The soils at the station are the typical yellow-clay paddy soils originating from foot-slope deposited low-hilly red soils of mid-low-yield paddy fields. The influences of different long-term fertilization schemes on the haracteristics of field weed communities and carbon (C), nitrogen (N) and phosphorus (P) stoichiometry during winter-spring seasons were investi-gated. The main aim was to lay the scientific basis for southern paddy soil fertility improvement and weed management and utiliza-tion. The results showed that compared with the control (no fertilization, CK), Shannon uniform index (E) was 0.03~0.07 lower in the treatments of chemical fertilizer plus cattle manure (NPKM), chemical fertilizer plus straw (NPKS) and chemical fertilizer (NPK). Margalef abundant index (D_MG) also dropped in NPKM and NPKS treatments. Shannon diversity index (H′), a comprehensive indi-cator, was 0.02~0.16 lower in fertilization treatments. Compared with CK, weed biomass increased by 89.6%~214.7% in all fertiliza-tion treatments. Weed N, P and K contents increased as well, and was most significant for NPKM treatment. In terms of accumulated nutrients, the treatments rank of paddy soils was NPKM > NPKS > NPK. Furthermore, weed C/N and C/P ratios dropped in all fertilization treatments. Some significant correlations were noted among weed C/N, C/P and N/P ratios and C/N, C/P, N/P ratios of soil and biomass. Different fertilization schemes influenced weed diversity and nutrient uptake. Also weed nutrient accumulation was considerable in all fertilization treatments, with enormous fertility, C and N. To some extent, ratio among C, N, P of weeds reflected C, N and P stoichiometry of soils.