[Effects of reduced chemical fertilizer with organic fertilizer application on soil microbial biomass, enzyme activity and cotton yield]. / åŒ–è‚¥å‡é‡é æ–½æœ‰æœºè‚¥å¯¹æ£‰ç”°åœŸå£¤å¾®ç”Ÿç‰©ç”Ÿç‰©é‡ã€é ¶æ´»æ€§å’Œæ£‰èŠ±äº§é‡çš„å½±å“.

The effects of 20%-40% fertilizer reduction and different organic fertilizers on soil microbial biomass, enzyme activity and cotton yield were examined for three consecutive years in Hexi area of Gansu, Northwest China. The results showed that compared with single chemical fertilizer application, the abundance of soil bacteria and actinomycetes were significantly increased while that of fungi were decreased with chemical fertilizer reduction combined with organic fertilizer. The abundance of soil bacteria was maximum under the treatment of chemical fertilizer reduction combined with common organic fertilizer and bio-organic fertilizer (COBF2), which was 84.6%, 57.1% and 43.5% higher than that under single application of chemical fertilizer (CF) in the bud stage, boll stage and boll open stage, while the abundance of actinomycetes was maximum under the chemical fertilizer reduction combined with common bio-organic fertilizer (CBF2), which was 28.2%, 32.7% and 32.2% higher than CF. The abundance of fungi was the lowest in the CBF2 treatment, which was 35.8%, 29.3%and 13.4% lower than CF treatment in three periods. The ratios of bacteria to fungi, actinomycetes to fungi and the activity of soil urease, catalase, sucrase and alkaline phosphatase were increased by the chemical fertilizer reduction combined with organic fertilizer. COBF2 was the most effective way to improve enzyme activity. Fertilizer reduction combined with the application of organic fertilizer increased boll number per individual of cotton plant, promoted cotton growth and dry matter accumulation in the ground to a certain extent. The cotton yield under COBF2 treatment was the highest, which showed an significant increase of 14.2% and 10.9% respectively in seed and lint cotton yield than CF. Our results showed that COBF2, with 60% reduction of chemical fertilizer combined with 1800 kg·hm-2 ordinary organic fertilizer and 600 kg·hm-2 biological organic fertilizer, had the best fertilization effect.